Bridge Motoring Utilizing Smart Portable Sensors

Presenting author(s): Mr Ahmed Elhattab »

Co-Authors: Mr Nasim Uddin

Room: Seminole B | 9:00 AM Tuesday, March 27, 2018

Natural Frequencies of structures is an elegant intrinsic property that is essential for many Civil Structural applications, as Structural Health Monitoring and Simulation Modeling. The physically tangible relation between the frequency of the structures and its dynamic characteristics was the impetus for using different time/frequency based methods to quantify this fundamental property. Unfortunately, the disruption effect of noise requires incorporating advanced sensors, that provide signals with a low noise-intensity, to accurately identify the fundamental frequencies of the structure. This article solves this bottleneck via exploiting the Stochastic Resonance (SR) phenomena to extract the fundamental frequencies of a bridge using an acceleration recorded by a conventional portable sensor as the sensor implemented in small portable accelerometer. The portable accelerometer device has an M9 motion coprocessor designed mainly for tracking human activities. Human activities have an exaggerated amplitude when it is compared to the structural responses. Therefore, if an iPhone device is used to record the response of the structure (for example a bridge) the structure response will be swamped by severe surrounding noise because of its small amplitude. Therefore, in this vein, the SR phenomena has been employed to use rather than suppress the noise to magnify the feeble bridge response in the recorded acceleration and hence identify the corresponding frequency. The fidelity of the proposed approach has been verified using the data of a field experiment. The bridge frequencies are identified first using conventional vibration analysis, thereafter, the portable accelerometer has been attached to the bridge rail to record the bridge vibration under the passing traffic. The recorded data has been processed using a new Developed Underdamped Pinning Stochastic Resonance (DUPSR) technique to quantify the bridge frequency.

Print this page

Real-Time Ultrasonic Monitoring of Laser Powder Bed Melting

Presenting author(s): Dr Christopher Michael Kube

Co-Authors: Mr Brandon McWilliams, Mr Jian Yu, Mr Daniel Galles, Mr William H Green

Room: Seminole A | 9:00 AM Tuesday, March 27, 2018

Additive manufacturing (AM) appears to be set to disrupt, innovate, and advance a number of industries that rely on expedient manufacturing capabilities along with high material performance demands. A number of incremental advances in the AM process need to be accomplished before AM will be in a position to achieve the desired industry wide breakthroughs. Specific problems in quality control and microstructural characterization, which are both inherently related to mechanical properties, are particularly amenable to solutions in nondestructive evaluation. In this presentation, ultrasonic methods for real-time microstructural sensitive measurements of AM parts will be discussed. The primary focus will be on a fundamental study that utilizes ultrasound to monitor the evolution of single spot meltpools consisting of a single layer of powder resting on an underlying substrate (build plate). The ultrasonic method for monitoring the meltpools makes use of a number of ultrasonic immersion transducers located under the substrate. The plurality of transducers permits the analysis of single-mode pulse-echo and pitch-catch mode converted scattering from features of the meltpool. The results will be presented with respect to potentially measureable parameters including meltpool geometry, melting/solidification rates, pore formation, and others. Lastly, the transition of the described method into commercially available AM systems will be updated and discussed.

Print this page

Processing GPR Signals to Estimate Thin AC Overlay Thickness and Density using Non-linear Optimization

Presenting author(s): Dr Imad L Al-Qadi »

Co-Authors:

Room: Seminole B | 9:20 AM Tuesday, March 27, 2018

Processing of ground penetration radar (GPR) signals collected from thin asphalt concrete (AC) overlay is challenging due to the limitation of GPR signal resolution. In this study, a gradient descent based non-linear optimization approach was developed to analyze GPR signals collected from thin AC overlays to estimate their thickness and density. Both finite difference time domain (FDTD) simulation and field tests were conducted to validate the proposed algorithm. It was found from the simulation study that the accuracy of dielectric constant estimation increased after the non-linear method was applied, and the thickness estimation error was less than 1 mm. The field test was conducted on US Route 45, IL. The results showed that the average AC overlay thickness and density estimation errors are 3 mm and 1.81%, respectively. This study demonstrates that the non-linear algorithm is an effective approach for estimating thin AC overlay thickness and density from GPR data.

Print this page

Nondestructive Evaluation of Additively Manufactured Metal Components with an Eddy Current Technique

Presenting author(s): Mr Benjamin Schneider »

Co-Authors: Mr Mohammad Rashid Bin Mohammad Shoaib, Mr Hossein Taheri, Mr Lucas Koester, Mr Timothy Bigelow, Dr Leonard J Bond

Room: Seminole A | 9:20 AM Tuesday, March 27, 2018

The ability of Additive Manufacturing (AM) processes to ensure delivery of high quality metal based components is somewhat limited by insufficient inspection capabilities. The inspection of AM parts presents particular challenges due to the design flexibility that the fabrication method affords. The nondestructive evaluation (NDE) methods employed need to be selected based on the material properties, type of possible defects and geometry of the parts. Electromagnetic, in particular Eddy Current (EC)) is proposed for the inspections. This evaluation of EC inspection considers surface and near-surface defects in a stainless steel (SS) 17 4 PH additively manufactured sample and a SS 17 4 PH annealed plates manufactured conventionally (reference sample). Surface of the samples were polished using 1 micron polishing Alumina grit to achieve a mirror like surface finish. 1.02 mm (0.04”), 0.508 mm (0.02”) and 0.203 mm (0.008”) deep Electronic Discharge Machining (EDM) notches were created on the polished surface of the samples. Lift off and defect responses for both additive and reference sample were obtained using a VMec -1 commercial instrument and a 500 kHz absolute probe. The inspection results as well as conductivity assessments for the AM sample in terms of the impedance plane signature were compared to response of similar features in the reference sample. Direct measurement of electromagnetic properties of the AM samples is required for precise inspection of the parts. Results show that quantitative comparison of the AM and conventional materials help for the development of EC technology for inspection of additively manufactured metal parts.

Print this page

Opportunities for the Use of Electronic Distance Measurement Instruments in Nondestructive Testing and Structural Health Monitoring and Implications for ASNT

Presenting author(s): Mr David H Parker »

Co-Authors:

Room: Seminole B | 9:40 AM Tuesday, March 27, 2018

The state-of-the-art for commercially available electronic distance measurement instruments (EDM), commonly known as laser trackers, advanced by quantum leaps in 2004 and 2010. It is now practical to measure 3-D coordinates of targets attached to cardinal points on large-scale structures with an absolute accuracy (traceable to NIST) of the order of one part-per-million, and relative dynamic movements, such as vibrations, typically 10 times better. For example, absolute 3-D coordinates of a structure within a 100 meter cube can be measured within a volume of a 0.1 mm cube (the thickness of a sheet of standard printer paper), and vibrations within a 0.01 mm cube. While this technology has been widely exploited in the manufacturing and aerospace industries, a literature search confirms that it has not yet been generally adopted by the nondestructive testing (NDT) industry. However, due to the unprecedented measurement accuracy, this technology presents opportunities for new methods for NDT. For example, instead of looking for defects as indicators of reduced performance of a structure, one could simply measure the performance of the structure under various loading conditions, and compare the measured performance to finite element models (FEM), or look for salient characteristics such as; linearity, hysteresis, creep, symmetry, damping coefficient, and the like. Moreover, the measurements can be repeated over the life of the structure in a trend analysis. The manufacturing and aerospace industries have adopted the technology from a quality control perspective, i.e., comparing the measured coordinates to the drawings—not from a failure mode perspective. The experience resources of the ASNT Membership are needed to adopt these new methods to NDT.

Print this page

Characterization of Additively Manufactured Metals

Presenting author(s): Mr Madison Parks

Co-Authors: Ms Janelle Chambers

Room: Seminole A | 9:40 AM Tuesday, March 27, 2018

Additive manufactured metal parts offer significant promise for the materials community but as yet, characterization of defects and the impact of those defects on material properties is difficult. Significant defects may include both coarse and fine porosity, poorly bonded or melted material as well as a plethora of other phenomenon that would likely cause dissimilar properties to the surrounding material. Recently, Southern Research (SR) has performed a study comparing wrought samples to additively manufactured samples. The initial results of the study show promise in detecting localized strain differences using Digital Image Correlation (DIC) during nondestructive modulus mechanical testing at room temperature and elevated temperatures.

Print this page

NDT Methods Applicable to Health Monitoring of ABC Closure Joints

Presenting author(s): Mr Saman Farhangdoust »

Co-Authors: Mr Armin Mehrabi, Mr Sayed Firas Al Mosawi

Room: Seminole B | 10:00 AM Tuesday, March 27, 2018

Accelerated Bridge Construction (ABC) promises to reduce on-site construction time and mobility impact in bridge construction and rehabilitation projects by the use of special design and construction methods. Generally, it comprises of precast elements of the bridge fabricated on site or away, moved to the bridge location and installed in place. Regardless of the fabrication and installation of precast-prefabricated elements, connections need to be established on site and in place. These connections, Closure Joints, are expected to provide continuity between adjoining elements for the purpose they are designed for. Therefore, normally, they contain reinforcing bars and enclosures of various shapes that in some cases create congestion within the joint. To provide shear connectivity, some of these joints are designed with cavities within the precast elements. UHPC, SCC, and other high- and normal-strength, fast-setting concrete mixes are normally used to fill the closure joints. In all, the specific nature of the joint application, in-situ casting, curing, material incompatibility, cavities and steel congestion contribute to create potential for leaving defects and anomalies in the closure joints. This, in turn, results in a higher potential for exposure and other detrimental effects with possible degradation in time, and therefore reducing the strength and serviceability of the joint and the structure. The long-term deflections and environmental loading will only exacerbate the situation. A variety of Non-Destructive Testing (NDT) methods have been utilized for evaluation and structural health monitoring of bridges including those with closure joints. However, a concerted attempt for categorization of these methods, comparison of capabilities, and selection of methods most applicable to closure joints is lacking. As a part of the ABC-UTC program at the Florida International University, a comprehensive study is being undertaken to investigate and identify the defects and problems associated with closure joints, review and evaluation of available NDT methods for applicability to closure joints, and finally selection and verification of the most promising methods. This paper summarizes the results of the ongoing study to date.

Print this page

X-ray Computed Tomography of Additively Manufactured Metal Parts

Presenting author(s): Mr William H Green

Co-Authors:

Room: Seminole A | 10:00 AM Tuesday, March 27, 2018

There has been a strong interest recently in the nondestructive testing/evaluation (NDT/E) of additively manufactured (AM) parts. The AM community has expressed the need for NDT/E methods for part inspection, analysis, and certification. There is also the need for NDT/E methods for research purposes and process optimization in parallel with development of new AM methods and materials in order to facilitate the fundamental understanding and control of the microstructure. X-ray computed tomography (XCT) has shown some potential in these areas, especially for void analysis and part tolerance quantification, given its capability to sufficiently map and represent three-dimensional volumes. Part certification and qualification is also very important to the additive manufacturing community and while laser-based methods can provide a quick scan of the outer surface, XCT is advantageous for more complex geometries that have internal channels or chambers that a laser would be unable to reach. The Army Research Laboratory (ARL) has recently been using XCT for inspection, evaluation, and analysis of internal AM test parts in a variety of areas, which is currently a focus of ARL’s major AM program. Examples of application of XCT to AM metal parts and their respective results will be discussed.

Print this page

Common Operating Platform for Employing UAVs in Infrastructure Monitoring

Presenting author(s): Mr Niranjan Rao Krishnan »

Co-Authors: Mr Arjun Chiddarwar, Mr Chandrasekar Venkatesh, Mr Mehdi Norouzi, Mr Victor J Hunt, Mr Arthur J Helmicki, Mr Fred Judson

Room: Seminole B | 10:20 AM Tuesday, March 27, 2018

The advancement in Unmanned Aerial Vehicle (UAV) technology over the past years has created many opportunities and possible applications in the transportation industry. UAVs are being used in monitoring and evaluation of construction sites, important construction events, documenting traffic patterns, etc. Due to the nature of infrastructure monitoring missions. In this paper, a common operating platform that is being developed for Ohio Department of Transportation to collect and process data from different unmanned aerial systems will be reviewed. The platform would allow visual observers and inspectors to have and independent control over the sensors while the pilot controls the flight in tight spaces or over roadways. The platform also allows the user to stream video real-time during a mission, share data amongst off-site and on-site personnel, and post process data using a centralized database. Through an interface, users can review the processed data; interact with 3D point cloud rendering system through computer or an augmented reality goggles. First, the overall characteristics of the common operating platform will be introduced. The back-end processing engines as well as the front-end interface will be detailed. Second, onsite processing algorithms including real-time image processing methodologies as well as off-site modeling algorithms will be discussed. Finally, the results of the preliminary version of the developed common operation platform and its performance will be presented.

Print this page

Ultrasonic Grain Scattering for Advancing Additive Manufacturing Techniques

Presenting author(s): Ms Andrea Arguelles

Co-Authors:

Room: Seminole A | 10:20 AM Tuesday, March 27, 2018

Additive manufacturing (AM) processes are desirable for components that require high quality and limited production basis. Current inspection methods to maintain production speed and efficiency are lacking. In this presentation, an ultrasonic approach to accurately characterize the microstructure and condition of AM components is described. This ultrasonic scattering technique provides detailed information about the material microstructure which can assist in the determination of an AM part’s suitability for service. As an ultrasonic wave propagates, reflects and scatters through the microstructure of the AM part, the resulting signals contain encoded information about internal features. Analytical models and advanced signal processing algorithms can be used to translate ultrasonic scattering data to spatial maps of microstructural parameters such as grain size, modulus, presence of heterogeneities (including porosity), and residual stress. Preliminary scattering measurements on a Ti-6Al-4V sample that evidence the difference between forged and additive manufactured sections are presented. Lastly, the potential of this technique for in-situ monitoring is discussed.

Print this page

Efficient Euler-Bernoulli Beam Impairment Localization and Quantification Using Deformation Influence Line: Case Study of an Application

Presenting author(s): Mr Yasha Zeinali

Co-Authors: Mr Jase Sitton

Room: Seminole B | 10:40 AM Tuesday, March 27, 2018

An unavoidable part of a structure’s service life is its degradation. Detecting structural impairments and assessing their nature is a significant challenge, which may help engineers to adequately rate the bridge condition. Degradations reduce structural system stiffness and subsequently affect system deformations. An effective structural health index is able to capture these changes in deformation and relate them to a structural system stiffness. This paper presents a utilization of deformation influence lines for estimating the flexural rigidity of bridge systems represented by Euler Bernoulli beams. In the proposed technique, the relationship between the second derivative of the deformation influence line and the flexural rigidity for both statically determinate and indeterminate beam structures is presented. This technique provides an estimate of flexural rigidity over the entire span based on a single measurement location and estimates both the location and severity of impairments regardless of the measurement locations or the damaged zones. The proposed methodology is demonstrated under laboratory conditions and is applied on a real-world continuous bridge. In the application, fusion of data from multiple sensors increases the resolution of influence lines and provides increased robustness.

Print this page

Fast Ultrasonic Imaging with Total Focusing Method (TFM) for Inspection of Additively Manufactured Polymer Composite Component

Presenting author(s): Mr Hossein Taheri »

Co-Authors: Mr Timothy Bigelow, Dr Leonard J Bond, Dr Dominique Braconnier, Mr Ewen Carcreff, Mr Gavin Dao, Mr Alan Caulder, Dr Ahmed Arabi Hassen

Room: Seminole A | 10:40 AM Tuesday, March 27, 2018

Ultrasonic adaptive imaging based on the phased-array technology and the synthetic focusing algorithm Total Focusing Method (TFM) is proposed for fast ultrasonic nondestructive evaluation of additively manufactured composite materials. Nondestructive evaluation and inspection of additively manufactured parts and components are necessary for quality assurance of the materials. Effective detection of defects and anomalies in manufactured parts prevents extra cost and production time. However, there are several limitations encountered when using conventional methods of nondestructive inspection for as built additively manufactured parts due to surface conditions and geometrical complexity. Extra machining is usually needed to be able to detect the possible defects such as layer disband, micro-cracks and voids in the composite parts. The capability of aperture focusing in phased array ultrasonic methods provides the opportunity for the adjustment of the delay laws in ultrasonic beams and reduces the noise and beam distortion for better imaging. An additively manufactured carbon fiber reinforced Acrylonitrile Butadiene Styrene (ABS) composite sample having artificial side and bottom drilled holes with different sizes, used to represent defects, were successfully inspected using the Total Focusing Method (TFM). Unlike conventional ultrasonic techniques, results show a promising way to provide inspection for as built additively manufactured composite parts with rough surface finish conditions. The proposed method helps to decrease the inspection time and eliminate extra machining and preparation costs.

Print this page

Total Focusing Method (TFM) Development for Lamb Wave based Structural Health Monitoring

Presenting author(s): Mr Mehrdad Ghyabi

Co-Authors: Mr Rigo M Salazar, Dr Ehsan Dehghan Niri

Room: Seminole B | 2:00 PM Tuesday, March 27, 2018

This paper presents a Lamb wave based Total Focusing Method (TFM) and a multi-cluster sensor network approach for detection and imaging of oriented cracks in plate-like structures. Ultrasound based imaging has been used for years as an advanced industrial and medical diagnostic method. Phased array technology, that relies on phased array transducer and time delay laws, is now a mature technique in the industrial and medical imaging and has many different diagnostics applications. Recently, to improve the imaging quality, Total Focusing Method (TFM) have been developed. TFM has significantly improved the imaging capabilities of the ultrasound imaging especially in detection and imaging of oriented cracks. Despite the advancement of this technique for crack detection and imaging using bulk ultrasound waves, it has not been fully developed for crack detection using Lamb waves in plate-like structures. In this research a Lamb wave based TFM algorithm is developed for structural health monitoring (SHM) of plate-like structures. A multi-cluster sensor network is proposed to enhance the network coverage for variety of crack orientations. To evaluate the developed SHM system in detecting and imaging oriented cracks in an aluminum plate, two clusters consisting of seven embedded piezoelectric discs are used. The experimental results show that the sensor network coverage using multi-cluster network is substantially enhanced. Cracks with different orientations are detected and imaged using the proposed multi-cluster network and developed TFM algorithm.

Print this page

Overview of NDE Techniques for Additive Manufacturing

Presenting author(s): Mr Ryan J Spencer

Co-Authors: Dr Ahmed Arabi Hassen, Dr Uday Vaidya

Room: Seminole A | 2:00 PM Tuesday, March 27, 2018

Additive manufacturing has quickly developed into a viable solution for constructing complex geometry parts. Unlike traditional subtractive techniques for complicated applications, additive manufacturing is a practical alternative with improved lead time and cost savings. There is great evidence additive manufacturing can bring superior solutions, but the technique is still in its infancy. Even with the exponential growth of the technology, there has been limited research on the quality assurance of the processes. This overview summarizes the different NDT techniques applied to the various additive manufacturing systems. Both metal and polymer additive manufacturing techniques will be reviewed along with their key associated defects and corresponding NDT solutions identified. There is great potential to revolutionize the manufacturing world from traditional ways. But a strong understanding of quality assurance is necessary to produce defect-free components. NDT techniques will pave the path to build confidence in the AM process.

Print this page

Wireless Structural Health Monitoring System Based on a Piezoelectric Fatigue Fuse

Presenting author(s): Dr Carlos Gamez »

Co-Authors: Mr Kyle Weztlar, Ms Marybeth N Miceli

Room: Seminole B | 2:20 PM Tuesday, March 27, 2018

A major issue facing the world’s inventory of aging steel bridges is cracking associated with fatigue damage. The primary method used to check these cracks is visual inspection. However, visual inspection is labor intensive, misidentifies cracks and may have insufficient inspection intervals. To provide a more reliable way to monitor fatigue, a Fatigue Fuse (FF) system is proposed that integrates a piezoelectric status monitor, an energy harvester, and a wireless communication link. The FF is a highly calibrated metal analog sensor made of the same material as the host structure. It is designed with several pre-notched ligaments that fracture after specific number of load cycles have been accumulated. Our steel FFs are undergoing qualification to bring them to a technology readiness level of 6. Currently, the fuses require visual inspection, but it can also be self-powered and interrogated remotely by incorporating a piezoelectric pitch-catch circuits and kinetic energy harvesting system. The pitch piezoelectric excites a fundamental acoustic mode in the FF and the catch piezoelectric senses the vibration. When the crack propagates across the fuse, the resulting catch electrical signal changes along with the mechanical stiffness of the fuse. This mechanical information is stored in the fuse and the fatigue status then needs to be interrogated and sent across a wireless network. As a result, the electronics for remote sensing can remain in a low power dormant mode. This fatigue monitoring system provides a convenient method to assess the useful life of steel infrastructure and prevent catastrophic failures.

Print this page

Non-Destructive Characterization of 3D-Printed Turbine Components Featuring Engineered Porosity

Presenting author(s): Mr Ilya Mingareev

Co-Authors: Luisana Calderon, Jayanta Kapat, Martin Richardson

Room: Seminole A | 2:20 PM Tuesday, March 27, 2018

X-ray computed tomography was adopted to characterize turbine parts produced from Inconel superalloys using Selective Laser Melting (SLM). SLM is a unique 3D-fabrication technology that uses high-power laser light to melt and fuse metal powders layer by layer, and create complex part geometries that are not possible with conventional manufacturing methods such as casting. The leading edge of a prospective turbine blade featuring (1) internal surface containing jet orifices for leading edge internal impingement, and (2) porous  sections near leading edge for transpiration cooling to replace showerhead cooling, both aimed at increased cooling efficiency was designed and fabricated using SLM. After a heat-treatment, the part was extensively examined for manufacturing accuracy, uniformity of periodic design features, and overall fabrication tolerances. Variance distribution between the design and the 3D-printed part was determined for several key design elements responsible for enhanced performance of the prospective turbine blade. X-ray CT analysis of the part was performed with the overall resolution of 60 microns, and provided a volume reconstruction of the internal shape including micro-scale features.

Print this page

Improvement of Resolution in Frequency Selective Surface-Based Sensors

Presenting author(s): Ms Mahboobeh Mahmoodi »

Co-Authors: Dr Kristen Donnell

Room: Seminole B | 2:40 PM Tuesday, March 27, 2018

Frequency selective surfaces (FSSs) are periodic arrays of conductive elements located on a dielectric substrate. When FSSs are illuminated by electromagnetic energy, they have a specific reflection/transmission response which is sensitive to element geometry, spacing and substrate properties. As such, FSS-based sensors have recently shown potential in structural health monitoring. An important aspect of FSS sensing is sensor resolution. If the sensor is illuminated in its entirety, the resultant (measured) frequency response is related to the entire sensor geometry and the measurement resolution is low (i.e., the size of the sensor). Thus, in order to improve the sensor resolution such that the sensor can be utilized for localized measurements, the sensor must be illuminated with a narrow beam that is subsequently scanned over the full sensing area. In this way, localized sensing may be accomplished. To this end, FSS sensors can be considered to consist of many sensor cells, each of which are illuminated individually and their response measured. Therefore, it is important to understand the effect of illumination, cell size, and number of elements within a cell. More specifically, as it relates to the illumination pattern, ideally a uniform illumination is used. However, realistic patterns vary spatially. Thus, a given antenna with a specific antenna pattern can affect the sensor response differently as the distance between the antenna and sensor is altered (as this also alters the illuminating pattern). Therefore, the distance from the illuminating antenna has direct bearing on the sensor cell dimensions and thus the resolution. Similarly, the number of elements within a cell directly affects the performance of the cell itself. Thus, while fewer elements (and smaller cells) improves sensor resolution, the performance is also degraded and hence a tradeoff exists. This limitation can be reduced, however, by implementing FSS miniaturization techniques in order to increase in the number of elements within a specific cell dimension. In addition, miniaturization will also reduce the sensitivity of the cell to non-uniform illumination. This work will quantitatively study the effect of illumination pattern, cell size, and number of elements on FSS sensor resolution and provide guidelines for sensor cell design.

Print this page

Using A Novel Ultrasonic Spectroscopy Technique for Additive Manufacturing (AM) In-Situ Monitoring

Presenting author(s): Ms Janelle Chambers

Co-Authors:

Room: Seminole A | 2:40 PM Tuesday, March 27, 2018

A new method is proposed that uses a combination of swept-frequency spectrum signatures, resonance behavior and time responses to evaluate build layers during the additive manufacturing process.  The ultrasonic spectroscopy technique provides a customizable broad range of frequencies with a robust signal-to-noise (SNR) ratio up to 25 MHz with ranges as broad as 10 MHz.  Using single-sided pitch-catch mode, the method measures the changing resonance behaviors of the structure as well as overall wavelength interaction with defects.  Initial results will be presented along with discussion regarding potential use of the technique for feedback during AM builds.

Print this page

A New Simple Impulse Response Testing Method Evaluated on a Large-Scale Laboratory Reinforced Concrete Girder

Presenting author(s): Mr Ali Hafiz

Co-Authors: Dr Thomas Schumacher

Room: Seminole B | 3:00 PM Tuesday, March 27, 2018

A number of nondestructive evaluation (NDE) methods are available to detect cracks and damage in reinforced concrete structures. Some methods like ultrasonic, impact echo, or X-ray testing have high resolution but are time consuming to perform and therefore only used locally. Since the early 1970s, researchers have also studied the vibration characteristics of a structure for damage detection and identification. The problem with this approach is that it has limited sensitivity to small cracks and difficulties in locating them. In this study, an instrumented hammer used for impulse response testing and a single accelerometer at a fixed location were used to estimate the natural frequencies and modes of a large-scale laboratory concrete girder. This method is easier to apply than the conventional approach that requires a large number of accelerometers measuring simultaneously. The girder was preloaded beyond the cracking moment at the mid-span and quarter-span locations to introduce deterioration in form of cracking. The test procedure was performed before loading the girder, after loading it at mid-span, and then again after loading it at the quarter-span. The frequency response function (FRF) was used to normalize the acceleration response with the impulse force since each impulse location has a different force amplitude. The mode shapes were extracted successfully for the first six modes. The results show that the flexibility of the supports play a critical role in that they affect the natural frequencies for the lower modes (up to the fifth) and introduce additional modes. The frequency shifts of the higher modes were found to be highly sensitive to cracking.

Print this page

Process Monitoring and Predictive Analytics for Additive Manufacturing Using Machine Learning

Presenting author(s): Dazhong Wu

Co-Authors:

Room: Seminole A | 3:00 PM Tuesday, March 27, 2018

To realize high quality, additively manufactured parts, real-time process monitoring and advanced predictive modeling tools are crucial for accelerating quality assurance in additive manufacturing. While previous research has demonstrated the effectiveness of physics- and model-based diagnosis and prognosis for additive manufacturing, very little research has been reported on real-time monitoring and predictive modeling of surface roughness in fused deposition modeling (FDM), also known as fused filament fabrication (FFF). This paper presents a data-driven approach to surface roughness prediction in FDM using predictive models trained by machine learning algorithms. A real-time monitoring system is developed to monitor the health condition of an additive manufacturing machine and FDM processes in real-time using multiple sensors. The data-driven predictive modeling approach is demonstrated through an example problem. Experimental results have shown that the predictive models built by machine learning algorithms can predict surface roughness with very high accuracy.

Print this page

Acoustic Emission Monitoring of a Nuclear Containment Structure during Post-Tensioning: Data Mining and Knowledge Discovery

Presenting author(s): Mr Arvin Ebrahimkhanlou »

Co-Authors: Mr Jongkwon Choi, Mr Trevor Hrynyk, Dr Salvatore Salamone, Mr Oguzhan Bayrak

Room: Seminole B | 3:40 PM Tuesday, March 27, 2018

Containment structures are cylindrical post-tensioned concrete structures that are essential to the safety of nuclear power plants. These structures are the last passive barrier against contaminating radioactive materials that may spread in the environment. In the curved walls of such structures, hidden delamination defects may develop. These defects are due to the radial through-thickness tensile stresses that the post-tensioning introduces in concrete. If remain undetected, such defects may lead to the brittle and without warning failure of the containment structure. In this study, we used acoustic emission (AE) technology to monitor a curved concrete wall during post-tensioning. In this large-scale test, the post-tensioning forces were monotonically increased until the wall failed due to delamination. Eight AE sensors were mounted on the outer surface of the wall to collect AE signals during the test, which were later post-processed in MATLAB. During the post-processing, advanced data mining techniques were used to recognize common patterns in the AE signals. Specifically, AE signals were clustered using K-Mean clustering, and their sequence was modeled with a hidden Markov model. In order to select the optimal number of clusters, a nonlinear dimensionality reduction technique (Isomp) and a silhouette analysis were performed. The physical meaning of each cluster was interpreted through a comprehensive analysis based on the mechanics of the wall and the traditional AE plots commonly used for concrete, including cumulative AE curves, average frequency versus rise time plots, and localization results. This modeling allowed a knowledge discovering on the mechanics of the process that delaminates the wall. In addition, it enabled us to accurately identify the onset of delamination and find a common pattern in the AE signal associated with the progression of this defect. These observations were confirmed via accurate through-thickness expansion measurements performed during the post-tensioning of the wall. These results prove that this modeling can provide an in-time alarm to take remedial and preventive actions against delamination defects in nuclear containment structures.

Print this page

High-speed Rail Inspection by Passive Non-contact Ultrasonic Technique

Presenting author(s): Mr Albert Liang

Co-Authors: Mr Simone Sternini, Ms Margherita Capriotti, Mr Xuan Zhu, Dr Francesco Lanza di Scalea, Mr Robert Wilson

Room: Seminole A | 3:40 PM Tuesday, March 27, 2018

Ultrasonic rail inspection is the most commonly implemented method for detecting internal rail defects. While the conventional ultrasound wheel probe (Rolling Search Unit– RSU) has gained its popularity within rail maintenance community, it suffers from limited test speeds (25-30 mph at most). This paper discusses the development of an inspection technique that can be carried out at regular train speeds (60 mph and beyond), potentially enabling a new maintenance practice with no traffic disruption and with an increased opportunity for redundancy given the multiple train passes on the same track. This approach utilizes non-contact receivers and the natural wheel excitation of the rail. A special signal processing routine has been developed to eliminate the role of the random and unknown wheel excitation so as to extract a stable ultrasonic transfer function between two points of the rail. Changes in this passively-extracted transfer function are then related to rail discontinuities, including joints, welds and defects. This concept was tested for the first time at the Transportation Technology Center (TTC) in Pueblo, CO. The focus of these tests was the extraction of a stable ultrasonic transfer function of the rail from the random wheel excitation at speeds up to 80 mph. Results from these tests will be presented. A second field test, aimed at assessing the flaw detection performance of the system, is being planned.

Print this page

Field Verification for the B-WIM System Using Wireless Sensors

Presenting author(s): Mr Yahya Mohammed Mohammed »

Co-Authors: Mr Nasim Uddin

Room: Seminole B | 4:00 PM Tuesday, March 27, 2018

Bridge Weigh-in-Motion (B-WIM) is the concept of using measured strains on a bridge to calculate the static weights of passing traffic loads as they pass overhead at full highway speed. This paper describes the experimental testing of the B-WIM system based on moving force identification (MFI) theory. The bridge was instrumented by wireless accelerometers and strain gages on the girders to measure the dynamics response when the calibrated trucks pass the bridge. LS-Dyna finite element program is used to imitate the 3-D bridge model, which validated utilizing the acceleration data, which collected from the field. Then the measurements from the wireless strain sensors are utilized to run the (MFI) algorithm and calculate the truck weight. Since the 3-D model has a large number of DOFs, the Moving force identification time reduction technique is employed to reduce the time needed to obtain the truck weight.

Print this page

Metallurgical and Nondestructive Testing Developments of Rail from the 1800’s to 2017

Presenting author(s): Mr Gregory A Garcia

Co-Authors:

Room: Seminole A | 4:00 PM Tuesday, March 27, 2018

It’s not a railroad if it doesn’t have rail! That statement holds an inherent truth regarding the importance of not only the need for rail to build a railroad track, but to assure that the rail is structurally sound in order to meet the service requirements of the railroad industry. The weight and speed of trains have continuously increased over the years driving improvements in rail metallurgy and inspection to assure safety and efficiency in railroad operations. Chemical and mechanical properties of rail have been researched, evaluated and fine-tuned providing desired material characteristics to address rail strength, fatigue resistance, and wear. As material characteristics are changed manufacturing and service flaw characteristics and types are also changed, or at least influenced, identifying the need for continuous improvements in inspection approaches and technology. This presentation/paper provides an overview of metallurgical and nondestructive testing advances in North America from the late 1800’s to present day.

Print this page

I-235 Bridge Load Test Combined with Acoustic Emission Monitoring

Presenting author(s): Mr Hang Zeng »

Co-Authors: Ms Julie Ann Hartell, Mr Robert Emerson, Mr Bruce Russell

Room: Seminole B | 4:20 PM Tuesday, March 27, 2018

In the past decade, FHWA required the DOTs to inspect their posted tensioned grouted tendons due to a history of problems associated with grouting materials leading to material deficiencies. Upon inspection of a section of I-235 Bridge, construction and distress features were observed, voids within the ducts and corrosion products respectively. Following findings, repairs were undertaken by filling the voids with thixotropic grouts; however, the strands were not replaced nor cleaned of superficial corrosion products. In this project, an array of nondestructive tests including live load testing, strain monitoring and acoustic emission monitoring were conducted to assess the performance of repairs by comparing between locations where ungrouted tendons were repaired and similar known locations which were originally deemed structurally sound. The structure’s strain response at critical positions, such as midspan and supports of tested span, were recorded during the bridge live load test. In addition to strain monitoring, acoustic emission (AE) monitoring was used as a supplement test method to the standard load/deformation analysis. This study demonstrates results which indicate an elastic behavior of the tested bridge span under three different load levels utilizing strain response combined with acoustic emission parameters.

Print this page

Ultrasonic Imaging of Rail Defects using SAFT and Wave Mode Compounding

Presenting author(s): Mr Albert Liang

Co-Authors: Mr Simone Sternini, Dr Francesco Lanza di Scalea, Mr Robert Wilson

Room: Seminole A | 4:20 PM Tuesday, March 27, 2018

Current rail ultrasonic inspection methodology utilizes a Roller Search Unit with fluid filled ultrasonic wheels for initial defect detection, followed by hand verification with an ultrasonic probe. Hand verification is performed through an A-scan or B-scan which heavily relies on operator judgement and interpretation of the waveforms to determine a defect’s shape and size. Instead, with ultrasonic imaging, quantification becomes less objective by removing the variability associated with interpreting raw waveforms. Traditionally, ultrasonic imaging uses the Synthetic Aperture Focus Technique (SAFT) which sums time delayed waveforms across array elements to generate an intensity pixel based off the geometry of the problem at each location. In this paper, three major improvements to the SAFT algorithm are discussed. First, weights in reception can be applied based off the physics of the propagating wave modes received by the array (i.e. longitudinal or shear waves in the bulk of the material). Second, image compounding over different wave modes in solids for transmission and reception is used to improve image sharpness. Third, wedge imaging is implemented through ray tracing to increase the reflected energy in defects oriented nearly perpendicular to the surface. Results from experimental tests on both natural and man-made defects in rail sections belonging to the FRA Rail Defect Library hosted by the Transportation Technology Center (TTC) in Pueblo, CO will be shown.

Print this page

Influence of Temperature in Vibration-Based Structural Health Monitoring of a Vertical Lift Bridge

Presenting author(s): Ms Maryam Mashayekhizadeh

Co-Authors: Ms Erin S Bell

Room: Seminole B | 4:40 PM Tuesday, March 27, 2018

The structural health monitoring for in-service infrastructure systems such as bridges promises for increased durability, safety, and service life. Measuring the changes in structural response through structural health monitoring provides the ability to detect and quantify the change in structural performance which could prevent decreased durability and in the worst case, unexpected failures. Bridges are subject to multiple operational and environmental demand variations during their service life which may mistakenly be treated as deviant structural response induced by the change in performance or damage. With a proper definition of the vibration response threshold for different demand category variations, one can separate out the deviance response due to damage. This paper inspired by multiple statistical methods addresses the influence of ambient temperature as one of the major sources of variations on the modal properties of a vertical lift bridge, the Memorial Bridge, Portsmouth, NH. The objective is to study the influence of ambient temperature on the vibrations induced by lift operation and traffic excitations. In addition, a threshold is defined for the vibration response of the bridge due to the ambient temperature. This study will use a database, created through the use of a long-term monitoring program of the Memorial Bridge that contains a significant amount of variations on the vibration response due to seasonal effects. The defined thresholds can be incorporated into the bridge management and maintenance procedure to be used to quantify the changes in performance potentially due to damage, more efficiently which can increase the effectiveness of visual inspections.

Print this page

Crack Propagation Identification in Concrete Bearers in Railway Switches and Crossing using Acoustic Emission

Presenting author(s): Dr Sakdirat Kaewunruen »

Co-Authors: Mr Rim Janeliukstis, Mr Andrew Clark

Room: Seminole A | 4:40 PM Tuesday, March 27, 2018

Prestressed concrete turnout bearers in railway switches and crossings (or turnout systems) are safety-critical elements that distribute the dynamic wheel loads from the rails to the track support system. At the turnout area, wheels often generate detrimental dynamic loading conditions to the bearers. These loads often cause cracks and damage on the bearer components. Often, cracks on the bearers develop and propagate under cycling loading. These cracks can cause broken bearers and sometimes damage the fastenings and baseplate too. Such components failure can cause widening gauge and possible train derailments. This paper is the world first to present an application of non-destructive acoustic emission technology for crack propagation in railway concrete turnout bearers. It presents experimental investigations in order to demonstrate the use of acoustic energy to identify crack propagations in the component. Experimental laboratory testing involves three-point bending tests of four concrete sleepers. Three-point bending tests correspond to a real failure mode, when the loads are not transferred uniformly to the ballast support. It is observed that AE sensing provides an accurate means for detecting the location and magnitude of cracks. Cycling load test is also highlighted in the paper to demonstrate the capability for crack propagation identification of acoustic emission technology.

Print this page

Wave Propagation in Damaged Composite Materials

Presenting author(s): Dr John C Duke, Jr »

Co-Authors: Mr Ryan Lane, Mr Arnab Gupta

Room: Seminole B | 9:00 AM Wednesday, March 28, 2018

In 1989 one of the authors used the term “microstructural acoustics” to describe the study of the details of wave propagation in composite laminates with damage from both mechanical loading and projectile impact. That study used the acousto-ultrasonic method and limited consideration to effects on the energy transmission caused by the damage including anisotropic influences. More recently the DSML has studied the details of plate modes which are caused by either actual or simulated acoustic emission (AE) events. This work takes on added importance in light of the USAF funding of research to “…nondestructively quantify the degraded elastic modulus and Poisson’s ratio in an impacted Polymer Matrix Composite (PMC) with a spatial accuracy of 0.01 in. and estimated properties NTE ±5% of those found via traditional mechanical testing.” Observations of ultrasound interaction with various types of damage in laminate composite materials will be described. In particular work done to characterize the wave speeds as well as scattering and attenuation of various plate modes will be discussed. A procedure for extracting the arrival times of symmetric and antisymmetric modes has been developed and used for situations where the wave modes overlap at the point of detection. The nature of the observations is counter intuitive and is driving further research.

Print this page

Quantitative Phase-Space Nonlinear Ultrasound (PSNU)

Presenting author(s): Dr Ehsan Dehghan Niri »

Co-Authors:

Room: Seminole A | 9:00 AM Wednesday, March 28, 2018

This paper presents a new technique based on Phase-Space analysis of nonlinear ultrasound waveforms. Nondestructive evaluation techniques based on acoustic nonlinearity have shown promising results in detection and characterization of discontinuities in materials. They have successfully been used in applications where traditional linear ultrasound techniques were incapable of characterizing defects.  An example of nonlinear ultrasound application is to characterize surface and subsurface defects that exhibit loaded interfaces such as fatigue cracks in metallic structures, and kissing bonds between laminar polymers. The current nonlinear ultrasound techniques and models, however, are based on evaluating and quantifying sub and/or super harmonics generation in frequency domain that make them incapable of classifying different physical phenomenon that cause similar spectral nonlinearity effect. As a result, the current nonlinear techniques are very prone to false alarm. In this paper the phase-space topography of ultrasound waveform is constructed numerically. Quantitative features extracted from Poincaré map of the constructed phase-space portrait then will be used to analyze and characterize defects. The Phase-Space Nonlinear Ultrasound (PSNU) provides a powerful diagnostic tool for development of reliable material evaluation and effective structural health monitoring methods. Experimental results show that the PSNU provides a unique detection and classification capability.

Print this page

Unravelling the Complex Ultrasonic Pulse-Echo Response from a Composite Laminate – A Phononic Superlattice

Presenting author(s): Dr Robert A Smith »

Co-Authors:

Room: Seminole B | 9:20 AM Wednesday, March 28, 2018

Designers and manufacturers are keen to be provided with detailed information about the internal microstructure of as-manufactured composites. Whilst X-ray Micro-CT is capable of high-resolution 3D imaging, there is a trade-off between resolution and component size which makes pulse-echo ultrasound the favored method for components larger than standard test coupons. The potential for ultrasonic 3D-characterisation of the internal structure of composites is being gradually revealed through modelling studies of the analytic-signal response of these regular one-dimensional layered materials. Using new ultrasonic parameters of instantaneous amplitude, instantaneous phase and instantaneous frequency, it has been possible to track plies in three dimensions and characterize and classify features such wrinkling (marceling), ply drops, tape gaps and tape overlaps [1]. The success of these methods is noticeably reduced in composites containing thick resin layers between plies due to thermoplastic-particle toughening. Recent modelling work has shown the cause to be the laminate behaving as a phononic superlattice with characteristic resonances and transmission band gaps [2]. This latest piece of the jigsaw puzzle explains why local zeros in amplitude (phase singularities) appear at certain times (depths) in the ultrasonic response and why these times are not consistent across a component. As a result, the complex response of these structures is at last being understood in a way that should make it possible to create a comprehensive inversion algorithm to convert the response into the full information about the microstructure. The modelling results will be used to explain experimentally observed phenomena in terms of the analytic-signal response of a phononic superlattice.

Print this page

Brush-on Ultrasonic Coatings for Applications up to 1300

Presenting author(s): Dr Bernhard R Tittmann »

Co-Authors: Mr Yamankumar Trivedi

Room: Seminole A | 9:20 AM Wednesday, March 28, 2018

In-place sensing of large pipes in high-temperature environments such as power plants faces several limitations: commercial transducers are not rated for such high-temperatures, gel couplants will evaporate, and measurements cannot be made in-situ. To solve this, we have furthered the work of Ledford in applying a practical transducer in liquid form which hardens and air dries directly onto the substrate. The transducer material is a piezoceramic film composed of bismuth titanate and a high-temperature binding agent, Ceramabind 830. The effects of several fabrication conditions were studied to optimize transducer performance and ensure repeatability. These fabrication conditions include humidity, binder ratio, water ratio, substrate roughness, and film thickness. The final product is stable for both reactive and non-reactive substrates, has a quick fabrication time, and has an operating temperature up to the Curie temperature of BIT, 650oC, well beyond the safe operating temperature of PZT (150°C).

Print this page

Combining Inspection Data, Modeling and Optimization Techniques to Identify the Elastic Constants of a Woven Fiber Reinforced Laminated Composite

Presenting author(s): Dr Sarah L Stair »

Co-Authors: Mr David G Moore, Dr Byron P Newberry

Room: Seminole B | 9:40 AM Wednesday, March 28, 2018

Fiber reinforced laminated composites provide engineering benefits, such as high strength low weight alternative to metals, but these complex materials also pose challenges with respect to identifying material properties and quality assurance inspections. Laminated composites are manufactured using fibers and a binding matrix material. The surrounding matrix material is a viscoelastic material whose properties change with time and are a function of operating environment and damage to the part. Thus, a nondestructive inspection method for identifying the elastic constants of a fiber reinforced laminated composite is important for maintaining quality assurance throughout its lifetime. Although inspection methods have been developed for identifying the elastic constants of unidirectional composites, the present work focuses on woven fiber reinforced laminated composites. The composites in this study were inspected with an oblique incidence through transmission ultrasound technique, which allowed the inspector to observe how the ultrasound wave scattered as it propagated through the laminate thickness. The inspection data was then compared to results obtained from a model of the ultrasound wave propagation, which used an estimate of the laminate’s elastic constants. If the inspection data and the model results did not compare well with one another, the analysis entered an optimization loop. The elastic constants in the model were updated, the new model results were compared with the inspection data, and the iterative process continued until the model and inspection results correlated. The results from the optimization process were compared with the elastic constants that were obtained through mechanical experiments.

Print this page

Advanced Volumetric Phased Array Inspection for Un-Bored Steam Turbine Rotors

Presenting author(s): Mr Robert W Bergman »

Co-Authors:

Room: Seminole A | 9:40 AM Wednesday, March 28, 2018

As the power industry continues to change to meet new demand cycles, the daily operational profile of the steam turbine is leading to new system safety and reliability challenges.  One of the most highly stressed components in the steam turbine is the rotor.  During operation, the stress on the rotor is highest in the vicinity of the first stage turbine wheel of the high pressure and intermediate pressure steam turbine rotor.  Additionally, the last stage of a low pressure steam turbine experiences very high levels of stress.  Many steam turbine rotors manufactured over 15 years ago contain a bore machined at the centerline where it is suitable to conduct a bore ultrasonic inspection.  New generations of steam turbines do not contain a machined bore.  These new generation rotors still experience significant stress under the wheels and require periodic ultrasonic inspection to determine the condition of the rotor in these highly stressed regions.  This paper is an introduction to a new patented inspection offering by the General Electric Company which will provide inspection coverage in the highest stressed areas of steam turbine rotors.  The GE technique is a new and unique use of phased array ultrasound to provide complete volumetric inspection in the highest stressed and often the most difficult volume of material to inspect. The result of using the GE Unbored Rotor Ultrasonic System (URIS™) is a composite view of the rotor volume inspection results and an inspection report highlighting potential areas of concern.

Print this page

Multi-Sensor Data-fusion for Improved Diagnosis and Prognosis of Delamination in Composites

Presenting author(s): Ms Portia Banerjee

Co-Authors: Mr Rajendra Prasath Palanisamy, Dr Mahmoodul Haq, Dr Lalita Udpa, Dr Yiming Deng

Room: Seminole B | 10:00 AM Wednesday, March 28, 2018

One of the recent advancements in non-destructive evaluation (NDE) is the use of multiple sensors for inspection of industrial structures. Inspection signal from different NDE techniques such as optical, electromagnetic or acoustic methods may vary from each other due to differences in their operating principles or measurement noise. Incorrect evaluation of damage level from one sensor data at an observation time leads to incorrect prediction of the structural health in future. Hence, fusion of data from multiple sensors has become a critical task in modern NDE systems. Combining information effectively can improve damage detection and prediction of system’s remaining useful life (RUL). In this study, we focus on monitoring growth and prognosis of fatigue induced delamination in glass fibre reinforced polymers (GFRP). GFRP structures, used in several industries ranging from automotives to construction, are often vulnerable to flaws during fabrication or service which compromises their performance and residual lifetime. Multiple NDE techniques including optical transmission, guided waves, near-field microwaves and capacitive coils are therefore used to detect cracks and delaminations in GFRP. In this paper, a data fusion technique integrated with particle-filtering framework is presented based on Bayesian updating of joint likelihood of multi-variate data. Measurement noise from individual sensors and correlation of data from multiple sensors are incorporated into the proposed prognosis approach. Experimental data from run-to-failure fatigue tests on Mode 1 GFRP sample followed by periodic inspection using multiple NDE techniques will be used to predict the failure threshold and RUL. Prognosis results demonstrating benefit of the proposed fused data over individual sensor signals will be presented in the full paper.

Print this page

Embedded Speckle Adhesive Joint Defect Detection using Ultrasonic Digital Image Correlation (UT-DIC)

Presenting author(s): Mr Eric Lim »

Co-Authors: Mr Seyed Fouad Karimian, Dr Tsuchin Philip Chu

Room: Seminole A | 10:00 AM Wednesday, March 28, 2018

The accelerated development of industries such as aerospace, automotive and renewable energy has generated an increased demand to implement composite materials to produce lighter, stronger and more reliable components. Non-Destructive Evaluation (NDE) methods should be used to reliably inspect the integrity of adhesive joints which are commonly used to combine composite materials. A combination of Ultrasonic testing (UT) and Digital Image Correlation (DIC) has shown promising potential to evaluate strain within adhesive bonds. The objective of this paper was to evaluate the use of Ultrasonic Digital Image Correlation (UT-DIC) to analyze the strain map within an adhesive joint with an embedded speckle pattern on Acrylic glass samples. This NDE approach utilizes ultrasonic C-scan results, which are converted into images for DIC analysis using Ncorr, an open source 2D digital image correlation MATLAB program. Speckle patterns within the adhesive joint were created using 0.5 grams of metal shavings. This experiment would identify the limits of this NDE method by introducing defects of varying shapes and sizes in samples. The strain mapping results obtained from the acrylic glass samples were verified with results obtained from the optical DIC method.

Print this page

Microscale Flexible Sensors for NDI of Curved Surfaces in Turbofan Component

Presenting author(s): Mr Evan Weststrate »

Co-Authors:

Room: Seminole B | 10:20 AM Wednesday, March 28, 2018

The inspection of turbofan components is becoming increasingly complex as new designs contain more curved surfaces requiring periodic non-destructive evaluation. This complicates the need to efficiently perform rapid inspections and provide reliable indications of threshold sized cracks in low conductivity metals such as titanium or nickel alloys. RMD has developed a membrane style coil sensor array that conforms to complex surfaces and has enough sensitivity to reliably detect 250 micron flaws at high speed. This is a widely applicable sensor technology that can be used for surface inspection of small flaws on complex contours. The microFlex Ribbon sensor is an array of reflective coil based eddy current elements that have predictable flaw signatures and can be arranged to be less sensitive to edges. This is possible because of the non-concentric, orthogonally oriented sense coils, which give the sensors a uniquely directional response to flaws. We have shown that the sensors can be formed to tight curvatures, with radii down to 2mm, and will still perform well. This is because the sensor elements are small and do not begin to fold back onto themselves until they are curved very tightly. Arrangements of sensors can be in series for high speed single channel applications, and in parallel for wide swath, low noise scans, and they can be printed in any orientation. The sensors are currently being integrated into US Air Force propulsion maintenance inspections as replacements for traditional wound-coil based ECT sensors.

Print this page

Phased Array Probes for Non-contact Air-coupled Ultrasonic Testing

Presenting author(s): Mr Andreas Mueck »

Co-Authors: Mr Manuel Lucas

Room: Seminole A | 10:20 AM Wednesday, March 28, 2018

The non-contact ultrasonic testing using air-borne ultrasound has grown in importance during the last years especially due to the application of new composite materials. The main advantage of waiving couplants like water is set against the disadvantage of high coupling losses, which make the interpretation of testing results more complicated. Therefore improvements in the testing system and its components are necessary. A promising approach is the application of the phased array technique to the contact-free ultrasonic testing. Using probes with multiple elements and a multi-channel instrument it is possible to adapt the ultrasonic soundfield to the application and to improve the testing process. This technique is introduced and has proved its performance in industry and medicine since decades. However only a few systems are available for the use for non-contact testing. One reason is, that the design of non-contact probes differs from conventional probes. An adaption of the concepts of phased array probes to the design of such probes is necessary. In the presentation a novel phased array probe for non-contact testing is introduced. By detailed measurements the ultrasonic properties have been investigated. On the basis of these results phased array concepts like electronic focussing will be applied and the performance compared with conventional single-element probes. Finally the capability of the new equipment will be demonstrated by means of application examples.

Print this page

Acquiring New Talent for NDT; Utilizing Innovative and Effective Techniques to Attract and Train Qualified Technicians

Presenting author(s): Ms Marybeth N Miceli

Co-Authors: Mr John A Stewart, Mr Shane Walker

Room: Seminole B | 10:40 AM Wednesday, March 28, 2018

The NDT industry is facing a void of qualified technicians and inspectors as most of the legacy service providers enter retirement. This problem is well known yet solutions have been limited in scope, too expensive, or isolated to a specific company, industry or region. Based on new research conducted on behalf of the American Aerospace Technical Academy (AATA), this presentation provides specific details on the looming talent void and discusses innovative techniques that the AATA is implementing to solve the problem. The new research provides a unique perspective on the global market for service providers, with insight on how many new technicians and inspectors will be needed over the next decade. This presentation pairs the market research with recent success stories from the AATA, highlighting how effective techniques are being implemented to attract and train new talent into the NDT industry. The scope of the research includes analysis by industry (aerospace, automotive, construction, defense, infrastructure, laboratories, oil and gas, shipbuilding, steel and foundry, power, others), individuals employed (full-time, contractors), compensation by certification (Level I, Level II, Level III, API Inspector, CWI Inspector), rate of retirement, individuals in training, forecast of future demand for certified technicians, compliance; ISO 9712, SNT-TC-1A. About the AATA: The American Aerospace Technical Academy (AATA) is a Los Angeles-based 501c3 nonprofit. AATA's mission is to bring high quality basic and advanced NDT training to the industry at a price that is affordable; so that everyone, especially veterans, women and disenfranchised individuals can take advantage of the great opportunities offered in Non-Destructive Testing. AATA students receive Level 1 and Level 2 training in Radiography, Magnetic Particle, Penetrant, Ultrasonic Testing, UT Phased Array and Visual Testing, in addition to training in Computed Radiography and Radiation Safety. AATA now offers Online Training for those who cannot travel.

Print this page

Non-contact Surface Wave Testing Inversion by Neural Network

Presenting author(s): Mrs Hiba Al-Adhami »

Co-Authors: Dr Nenad Gucunski

Room: Seminole A | 10:40 AM Wednesday, March 28, 2018

The non-contact SASW test is considered an extension of the traditional SASW test. It has the same test procedures, but the ground sensors are replaced by noncontact sensors to collect the data (i.e. Leaky surface waves instead of ground vibration) during the first phase of the test. Thus, the advantage of noncontact sensing, air-coupled transducers provide an opportunity for quick scanning and imaging of large civil engineering structures. The objective of the test is to determine the Leaky Rayleigh wave dispersion curve, i.e. velocity of a Leaky Rayleigh waves as a function of frequency, and then through a process of inversion to estimate the elastic modulus profile. Significant efforts have been devoted to develop a general automated inversion procedure The neural network is considered one of the successful tools in many civil engineering applications. This paper presents development and application of neural networks for an automated inversion of Non-contact SASW test data. Anumerical simulation of air-coupled SASW test was conducted using finite elements. Several hundred finite element models of various pavement configurations were used to develop an extensive database of surface wave dispersion curves. The developed automated system has been validated by using experimental data and it shows a good performance to predict the pavement profiles.

Print this page

Construction Site Evaluation Employing 3D Models From UAV Imagery

Presenting author(s): Mr Aswin Balasubramaniam »

Co-Authors: Mr Chandrasekar Venkatesh, Mr Rumit Kumar, Mr Bryan Brown, Mr Mehdi Norouzi, Mr Victor J Hunt, Mr Arthur J Helmicki, Mr Kelly Cohen, Mr Manish Kumar, Mr Fred Judson

Room: Seminole B | 2:00 PM Wednesday, March 28, 2018

Continuous monitoring of a construction progress using traditional methods such as survey measurement is a labor-intensive process. With the advancement in Unmanned Aerial Vehicles (UAV) and image processing techniques, such evaluation can be improved. This study reviews the current state of the art technology and demonstrates the abilities of construction surveying using UAV imagery. First, various flight parameters, mission planning applications and cameras for capturing aerial images will be compared. Second, the procedure for post-processing aerial images to create 3D models and orthomosaics will be reviewed including the impact of different ground sampling distances on the quality of the 3D models. The quality of image geolocation will also be compared using Real time kinematics (RTK) based position correction and its effect on the 3D models. Optimized 3D models will be analyzed further to achieve accurate measurements (length measurement and volume measurement). Finally, the effects of inclusion of manually surveyed ground control points on the final measurements will be reviewed and the accuracy of the measurements will be compared against manual and survey measurements.

Print this page

Laser Ultrasonics for Remote Detection of Stress Corrosion Cracking in Harsh Environments

Presenting author(s): Mr Mostafa Hasanian »

Co-Authors: Sungho Choi, Dr Cliff J Lissenden

Room: Seminole A | 2:00 PM Wednesday, March 28, 2018

Structural components susceptible to degradation in harsh environments with limited accessibility require distinctive nondestructive testing methods. Rayleigh surface waves generated and received using laser ultrasonics are capable of characterizing surface degradation and are most suitable for robotic delivery systems because of the noncontact transduction. Stress corrosion cracking in austenitic stainless steel is the primary concern in the present research. Specifically, the stainless steel canisters used within dry storage casks for spent nuclear fuel provide a challenging application due to the elevated temperature (up to 350oF) and gamma radiation (up to 27 krad/hr) environment as well as the extremely limited access. Chloride induced stress corrosion cracking in the heat affected zone of full penetration welds is a concern. Nondestructive inspection provides information on the structural integrity of the canister that could be used to re-certify the dry storage facility. A Q-switched pulsed laser provides a noncontact method to actuate a surface wave that can, in turn, be received by a laser interferometer. Laser pulses to the canister and received signals from the canister can be delivered by fiber optics or a system of mirrors. A pitch-catch inspection method is proposal whereby a surface wave having high directivity is generated that interacts with stress corrosion cracks and is scattered and reflected back to the location where the laser interferometer beam measures the out of plane wave motion. In this way, the laser interferometer receives both the incident wave and the wave reflected by any surface cracks. In addition to the environment and access challenges, the generation of surface waves having high directivity and laser interferometer based reception of wave motion from a rough surface are addressed in this research. A slit mask is used to illuminate a specific pattern on the surface that creates a directional wave as opposed to the omnidirectional wave generated by a point source. Slits that are straight, a diverging arc, and a converging arc are analyzed using finite element simulation as well as laboratory experiments. The primary feature of merit is the wave amplitude at a prescribed distance from the source. However, the amplitude is greatly dependent upon the surface roughness at the location where the wave motion is detected by the laser interferometer. Thus, the effects of surface roughness on the signal-to-noise ratio are characterized and signal processing methods to improve the signal quality are explored. This research was conducted as part of an ASNT Fellowship Award.

Print this page

Applications of Eddy Current Simulation Model in Steam Generator Tube Inspection

Presenting author(s): Mr Anton Efremov

Co-Authors: Mr Saptarshi Mukherjee, Mr Anders Rossell, Dr Lalita Udpa, Mr Vivek Rathod, Mr James Benson, Mr Nathan Driessen

Room: Seminole B | 2:20 PM Wednesday, March 28, 2018

Three-dimensional (3-D) simulation of eddy current testing (ECT) of steam generator tubing (SGT) in nuclear power plants is highly desirable for the training and performance demonstration of both manual and automated data analysis processes and can be beneficial for studying the basic ECT field/flaw interactions in order to obtain a fuller understanding of the ECT method. Simulation models based on solving integral equations are, in general, efficient. However, these methods can only model very simple geometries. Finite element (FE) method is widely used in modeling realistic eddy current problems. However, FE models are computation intensive and take long execution times, particularly when array coil and rotating probe techniques are involved. This paper presents an interactive software package, for simulating ECT of SGT that is easy-to-use, flexible, and accurate. The method includes innovative modifications of the basic FE model which allows modeling of probe motion without the need for re-meshing the probe coil at each position. The model can serve many important needs such as simulating complex defect geometries, generating training data, performing probe optimization, training inspectors and determining probability of detection (POD) for various degradation mechanisms.

Print this page

Robotic Crawler ILI of Unpiggable 10” Natural Gas Pipeline

Presenting author(s): Mr Steven Trevino

Co-Authors: Mr Aaron Huber

Room: Seminole A | 2:20 PM Wednesday, March 28, 2018

Diakont Advanced Technologies was commissioned to assess the integrity of a natural gas pipeline that was partially buried under an urban area on a major North American pipeline. The company used a reduced size robotic crawler to successfully navigate a 10 in. pipe. The size of this pipe has previously been a limitation, making it ‘unpiggable’ using other ILI methods. Designated as a high consequence area (HCA) due to being located in a densely populated area, this section of pipeline had never been inspected. Low flow, its narrow 10 in. internal diameter (ID), and its characteristics (tight bends, plug valves etc.) made the pipe unsuitable for traditional smart pigging. However, the United States’ federal Pipeline and Hazardous Materials Safety Administration (PHMSA) regulations require specific integrity management programs in HCAs. The pipeline’s inspection challenges could have forced its operator to replace an entire quarter of a mile length of pipe if they could not inspect the line effectively and on schedule. The technology gap between the inspection requirements and the available tooling forced the industry work with pipeline service vendors to develop a suitable solution. New Technology: Reduced Size and Self Propelled The new robotic crawler tooling traverses challenging pipeline geometries using a ruggedized multiple track system, which allows for navigation across horizontal surfaces. Moreover, the tool can extend the tracks to the pipe wall for stabilization. This arrangement provides the traction that is necessary to hold the tool rigidly in place while inspecting difficult-to access pipeline applications (such as inclines and vertical sections), where conventional ILI tools may not be feasible. This Sprinter system moves at a deliberate pace to provide accurate mapping of anomaly locations within the pipeline. Being self-propelled and bidirectional, the Sprinter can also be deployed and retrieved from a single access point, which was another key feature in its selection for this inspection program. This presentation will provide details on the NDT tooling along with a case study for inspecting the unpiggable natural gas pipeline.

Print this page

A New Nondestructive Method Based On Propagation and Detection of Highly Nonlinear Solitary Waves to Assess the Internal Pressure of Thin-Walled Pressure Vessels

Presenting author(s): Mr Amir Nasrollahi »

Co-Authors: Dr Piervincenzo Rizzo

Room: Seminole B | 2:40 PM Wednesday, March 28, 2018

This paper discusses the dynamic interaction between a monoatomic chain of solid spheres and a thin-walled spherical pressure vessel. The objective is to find a relationship between the highly nonlinear solitary waves (HNSWs) propagating within the chain and the internal pressure of the vessel. The study introduces first a general finite element model to predict the abovementioned interaction, and then a specific application to tennis balls. The scope is to demonstrate a new nondestructive testing method to infer the internal pressure of thin-walled pressure vessels. The overarching idea is that a mechanically induced solitary pulse propagating within the chain interacts with the thin-walled vessel to be probed. At the chain-vessel interface, the acoustic pulse is partially reflected back to the chain and partially deforms the material giving rise to secondary pulses. The research hypothesis is that one or more features of the reflected waves are monotonically dependent on the internal pressure. The model is validated experimentally by testing commercial tennis balls of different characteristics. Both numerical and experimental results demonstrate a monotonic relationship between the time-of-flight of the solitary waves and the internal pressure of the tennis balls. In addition, the pressure inferred nondestructively with the HNSWs matches very well the pressure measured destructively with an ad-hoc pressure gauge needle. In the future, the results presented in this study could be used to develop a portable device to infer anytime anywhere the internal pressure of deformable systems for which conventional pressure gages cannot be used noninvasively.

Print this page

Smart Sound Processing for Residual Thickness Estimation using Guided Lamb Waves generated by EMAT

Presenting author(s): Dr Roberto Gil-Pita »

Co-Authors: Mr Joaquin Garcia-Gomez, Ms Marta Bautista-Duran, Mr Antonio Romero-Camacho, Mr Jesus Antonio Jimenez-Garrido, Mr Victor Garcia-Benavides

Room: Seminole A | 2:40 PM Wednesday, March 28, 2018

EMAT sensors generate lamb waves which allow fast in field evaluations of residual thickness in metallic pipes through the estimation of the size and position of defects. Traditionally, amplitude and echo analysis have been applied in this sense, but there exist difficulties in the estimation of the residual thickness, mainly caused by variations in the behavior of the defects in function of their shape. Smooth defects usually reflect less energy than abrupt ones, independently of the residual thickness of the pipe caused by the defect. In a different approach, the thickness reduction may also cause changes in both the phase and group velocity of a given propagation mode, these changes depending on the frequency of the wave. Thus, changes in these speeds are reflected in the waveform of the received signal once the lamb wave has traveled along the pipe. The objective of this paper is to establish smart sound processing tools for estimating the group and the phase velocity of a given mode in guided lamb waves, with the objective of analyzing the best configuration for determining the depth of a given defect in a metallic pipe. Correlation of the size of the damages with all the extracted parameters are then used to propose estimators of the residual thickness, considering amplitude and phase information. Results demonstrate the suitability of the proposal, improving the estimation of the residual thickness.

Print this page

Quantitative Ultrasonic Beam Profiles of Conventional Single-Element Probes

Presenting author(s): Dr Myles Dunlap »

Co-Authors: Dr George D Connolly, Mr Mark A Dennis

Room: Seminole B | 3:00 PM Wednesday, March 28, 2018

The objective of this study was to quantitatively compare experimental and simulated ultrasonic beam profiles. Beam profiles can be produced through careful experimental measurements or ultrasonic modeling and simulation software. Test cases are presented in this study and were developed to cover various test parameters such as probe frequency and diameter. Experimental data were collected for each test case and are quantitatively compared to modeling and simulation results using commercial NDE software. Additionally, conclusions are drawn from this study, and future research opportunities are suggested.

Print this page

Applications of a Compact NDT Shearography System Specially Designed For the Petroleum and Gas Industry

Presenting author(s): Mr Daniel Pedro Willemann »

Co-Authors: Ms Analucia Vieira Fantin, Mr Mauro Eduardo Benedet, Mr Fabio Aparecido Alves da Silva, Mr Armando Albertazzi, Mr Sergio Damasceno Soares, Mrs Fabiana D F Martins

Room: Seminole A | 3:00 PM Wednesday, March 28, 2018

The increasing use of composite materials keeps happening in several industrial sectors, including the oil and gas industry. The use of fiber reinforced plastic pipes and fittings as well as the use of composite materials to protect and/or repair corroded metal structures are currently the most widespread applications in this sector. In the oil and gas industry, defects in composite materials can arise during the application of the repairs in the field or the pipe assembly stage. It leads to the development of equipment and methods to inspect these composite structures in order to prevent accidents with people and environmental disasters. Shearography is an optical method which uses laser interferometry to measure deformation gradients at the surface of a structure. Speckle patterns produced with the composite structure in stressed and unstressed states are subtracted and a resulting image containing a fringe pattern reveals changes in the deformation gradient of the surface. Basically, anomalies in a regular fringe pattern indicate the locations of the damaged regions in the composite repairs. This work presents a very compact shearography system specially designed to the inspection of pipelines in the oil and gas industry. Different inspection results with in the petroleum industry applications achieved in laboratory and in the field are also shown. The current status of this nondestructive inspection technique, its challenges and the next steps in its development are discussed.

Print this page

Defect Evaluation in Active Microwave Thermography Inspections

Presenting author(s): Mr Ali Mirala

Co-Authors: Dr Mohammad Tayeb Ghasr, Dr Kristen Donnell

Room: Seminole B | 3:40 PM Wednesday, March 28, 2018

Estimation of dimensions and location of defects is important in many nondestructive testing and evaluation (NDT&E) techniques as it relates to the assessment of structural integrity of materials. Active Microwave Thermography (AMT) is a relatively new technique that utilizes a microwave heat excitation and subsequent thermal monitoring via a thermal camera. This technique has many advantages including short inspection times for relatively large areas, non-contact interrogation and inspection, and easy-to-interpret results. AMT has recently shown promise for inspection of materials/structures relevant to the aerospace and infrastructure industries such as detection of debonding in carbon-fiber reinforced polymer (CFRP) composites used to rehabilitate cement-based structures, presence of corrosion on steel reinforcing bars, presence of air voids (flat bottom holes) in CFRP structures, and presence of water that has ingressed into rubber transport pipes (indicating a reduction of the integrity of the pipe itself). However, much of the success exhibited by AMT thus far has focused on defect detection rather than evaluation. As such, this work focuses on the efficacy of AMT for evaluation of such defects (i.e. cross-sectional location and depth). To this end, spatial and temporal variations of temperature in thermal images captured by a thermal camera will be monitored and processed to provide a 3D estimation of the position of the defects mentioned above in a structure. Simulation and measurement results demonstrate strong potential for AMT as an NDT&E tool capable of defect evaluation (rather than just detection).

Print this page

SHM POD and POT

Presenting author(s): Dr John C Duke, Jr »

Co-Authors: Mr Marshal H McCord, Mr Ryan Lane

Room: Seminole A | 3:40 PM Wednesday, March 28, 2018

The issue of determining the probability of detection (POD) of structural health monitoring (SHM) is of great interest. However, upon careful consideration the specific details depend greatly on how the term SHM is defined. The USAF defines “Structural health monitoring is a nondestructive inspection process or technique that uses in-situ sensing devices to detect damage.” While the ASNT Aerospace Handbook includes the following definition “A process which typically involves technology-based monitoring of a structure in order to identify the operational loads and environment, deterioration caused by service, the rate of development of deterioration during service, and the effects of the deterioration and its rate of development on the future serviceability of the structure.” Other definitions may be used as well, further complicating the pursuit of SHM POD. This presentation will discuss the issues and propose a process for assessing the POD, as well as the probability of tracking (POT), for situations referred to as “hotspot monitoring.” The proposed approach offers a tangible means of assessing the “ideal” POD as well as to offer a means of validating modelling being proposed as an alternative to experimental POD assessment. Using the ideal SHM POD and POT actual in-situ sensing procedure implementation can be used with appropriate knock-down factors if the approach meets the needs of the full SHM process being used for management of a particular asset. Preliminary test results indicate that under ideal conditions an ultrasonic pitch-catch procedure can be used to monitor crack initiation and subsequent growth in 7075 T6 Al subjected to cyclic loading (28200 cycles of loading) exhibiting ~50% signal amplitude reduction for total crack growth of 2.4 mm (0.094 in) before the precrack development process was terminated.

Print this page

Infrared and High-definition Image-based Bridge Scanning using UAVs without Traffic Control

Presenting author(s): Dr Shuhei Hiasa »

Co-Authors: Dr Fikret Necati Catbas, Mr Enes Karaaslan

Room: Seminole B | 4:00 PM Wednesday, March 28, 2018

In order to prevent impending deterioration of these bridges, more effective and reliable periodic inspections than current routine and/or in-depth inspections with less cost and traffic disturbance are indispensable for proper assessment and maintenance of bridges. Under such circumstances, several non-destructive evaluation (NDE) methods have been developed. Among these technologies, this study focuses on high-definition (HD) imaging and infrared thermography (IRT) using with unmanned aerial vehicles (UAVs). As for bridge decks, these image-based technologies have been utilized with vehicles while driving the car at normal driving speed without lane closures. However, other bridge components such as underside of decks and substructures are still inspected visually at a distance or manual hammer sounding method using special vehicles such as snooper trucks with traffic control. This study explores the capabilities and limitations of these image-based technologies using with a drone to inspect whole bridge components. Regarding HD imaging, this study explores the detectability of minimum crack width. As for IRT application with UAVs, the effect of vibration caused by the drone is investigated. By clarifying the capabilities and limitations of image-based technologies using with UAVs in accordance with current bridge inspection requirements, this study investigates the potential to use these techniques for real bridges.

Print this page

FELLOWSHIP AWARD WINNER: Microwave NDE System with Metamaterial Sensor for High Resolution Imaging of Composites

Presenting author(s): Mr Saptarshi Mukherjee

Co-Authors: Dr Lalita Udpa, Dr Yiming Deng, Dr Mahmoodul Haq, Dr Satish S Udpa, Dr Antonello Tamburrino, Mr Premjeet Chahal

Room: Seminole A | 4:00 PM Wednesday, March 28, 2018

In the past few decades, the usage and application of composite materials have expanded in the aerospace, automobile and civil industries, to replace metals fully or partially. However, defects in the form of disbonds, voids and delaminations caused during manufacturing or with use can affect their overall strength and performance [1]. This has boosted research efforts in non-destructive inspection (NDI) of composite materials during manufacturing and maintenance stages. Microwave NDE techniques offer several advantages in comparison to other NDE techniques such as ultrasonic, X-ray, visual, thermography and other methods [2]. Some of the recent applications of Microwave NDE are corrosion detection in painted aluminum and steel substrates, flaw detection in Sprayed on Foam Insulation (SOFI) of space shuttles, disbond detection in CFRP strengthened cement based structures [3]. The demands for finer resolution, higher detection probability and better imaging have led to the development of novel microwave sensor systems, lens and probes for tackling these challenges. This contribution focuses on the development of a novel, hybrid electromagnetic imaging system (HEMIS) for NDE of composites that combines benefits of both near field and far field electromagnetic systems. First, a far field system, coupled with an efficient time reversal imaging system is set up for rapid detection of defect regions in large areas of composites. Next, a novel near field metamaterial inspired sensor is developed to scan the localized regions to accurately image the defects with high resolution. Introduced by Veselago in 1968, metamaterials are artificially designed materials having simultaneously negative permittivity and permeability [4], that can be exploited to provide resolution beyond diffraction limits. A built in calibration system, integration of multiple sensors (high and low frequencies) and high Q factor are some of the benefits of the sensor. Specifically, the sensor’s super resolution capability for detection of sub-wavelength defects inside the composite materials will be investigated. The sensor design, experimental results and demonstration of the overall system will be presented to demonstrate its feasibility for practical NDE applications. [1] J. Denney and S. Mall, Engineering Fracture Mechanics 57, no. 5 (1997): 507-525. [2] S. Kharkovsky and R. Zoughi, IEEE Instruments & Measurement Magazine, 10 (2), 26-38, 2007. [3] V.G. Veselago, Soviet physics uspekhi, 10(4), p.509, 1968.

Print this page

Thermographic Characterization of Subsurface Defects

Presenting author(s): Dr Steven M Shepard »

Co-Authors:

Room: Seminole B | 4:20 PM Wednesday, March 28, 2018

In its most basic form, active thermography using a simple heat source (e.g. lamp or hot air gun) and an infrared camera can be used to detect subsurface defects such as voids or inclusions in an opaque solid. The presence of a void causes a region of retarded cooling at the surface, which appears as a hot spot in the infrared image sequence. "Strong" defects that can be detected this way (e.g. voids or trapped water) are generally spatially finite (they are smaller than the camera field of view, so that they can be compared to a flaw free surrounding areas), have large diameter to depth ratio and their thermal conductivities are significantly different than the host material. Many defects that occur in aerospace NDT do not meet these criteria, and require that excitation, infrared image acquisition and post processing are appropriately configured. "Weak" defects do not cause a detectable hot spot to appear at the surface, due to either their size or composition. In such cases, the defect can be detected indirectly, as it causes a delay in the transit time required for heat to travel from the front to back wall of the sample. Additional considerations apply when the defect is spatially extended (e.g. an entire sheet of backing material embedded in a composite), since there are no contrast cues or edges to view. We will demonstrate how weak defects can be detected using the Thermographic Signal Reconstruction (TSR) method.

Print this page

A Proposal to Enhance the Importance of Reliability in the Application of NDE and SHM

Presenting author(s): Mr David J Gilbert »

Co-Authors: Mr Bernard McGrath

Room: Seminole A | 4:20 PM Wednesday, March 28, 2018

In the early 1990s, the European PISC programme undertook research in to the Human Factors of NDE. The first European American Workshop on NDE reliability took place in Berlin in 1997, the same year that the first PANI project was initiated in the UK. Since then the NDE Reliability knowledge base has expanded, a lot of good work has been undertaken and reported and various initiatives have been adopted in different industry sectors and by individual companies and operators. However, there has not been a consistent uptake within the NDE community. Steps to ensure reliability are perceived in a negative light and as an unessential expense. NDE is inexorably linked with Quality Assurance, but the relationship has been inconsistent: some aspects of QA are fully adopted; others are adopted in some industry sectors and not others; yet others are stubbornly avoided. This paper presents a comparison of NDE Reliability topics with recent issues of Quality Assurance International Standards and proposes that this synergy could be used to promote the wider, positive adoption of Reliability across the NDE and SHM profession. The British Institute of NDT manages the International Association of Quality Practitioners (IAQP), which currently provides an information service to practitioners in the fields of quality assurance, quality control, inspection, measurement and testing. This paper will illustrate how, subject to consultation and agreement, the IAQP could be used as a vehicle to support and implement the above proposal.

Print this page

Thermal Methods, Mixed Reality Applications and Decision-making

Presenting author(s): Dr Fikret Necati Catbas

Co-Authors: Dr Shuhei Hiasa, Mr Enes Karaaslan

Room: Seminole B | 4:40 PM Wednesday, March 28, 2018

Print this page

Characterization of Bonding Agent Durability in Fatigue Monitoring Applications Utilized in NDT

Presenting author(s): Mr Ryan Lane »

Co-Authors: Dr John C Duke, Jr

Room: Seminole A | 4:40 PM Wednesday, March 28, 2018

Choosing the appropriate bonding agent for fatigue monitoring applications is critical considering bond reliability is an important aspect for reliably detecting signals over time and in fatigue structural health monitoring applications. The purpose of this study was to characterize several bonding techniques used in the laboratory and industrial environment to better understand the durability of various bonding agents. A Krouse testing machine was used with a triangular beam specimen designed to provide constant stress/strain throughout the beam when deflected. Piezoelectric sensors were bonded by various methods to the specimens and cycled. An ultrasonic C scan and pencil lead break were performed before the test began. Pencil lead breaks were done at intervals of 100,000 cycles up to a total of 500,000 cycles to track the deterioration of the bond. After fatigue testing was completed, a final ultrasonic C scan was performed. The attenuation of the recorded pencil lead break waveforms was the main characteristic used for evaluation in this study. The results indicated that across all the bonding agents there is an observable difference in the attenuation of the signal between the initial pencil lead break at 0 cycles and 100,000 cycles. The signal’s attenuation remains somewhat constant after the first 100,000 cycles to 500,000 cycles. However, the effect on the attenuation was different across bonding agents and varying amplification would be needed for the waveform to be distinguishable. The results from this study demonstrate that not only is it important to pick a bonding agent that demonstrates good attenuation for signals, but also one that performs well after long periods of fatigue.

Print this page

Evaluating New Technology for UT & DFT Non-Destructive Testing

Presenting author(s): Mr Jeff McCutcheon

Co-Authors:

Room: Seminole B | 9:00 AM Thursday, March 29, 2018

A number of companies are racing to provide robotic applications to perform non-destructive testing of above ground storage tanks. While the new technology shows great promise, no studies exist to establish the overall efficacy of the technology compared to existing human conduct. This paper looks at the practical ramifications of using aerial robots (drones) for performing ultrasonic (UT) wall thickness testing and Dry-File Thickness (DFT) testing. The paper reviews side-by-side comparisons of aerial robots and traditional employees testing the sides and roof of an above-ground storage tank (AST). Comparisons include safety, validity of test results, and performance/cost. Specifically, the author uses actual data where an aerial robot is used to perform tests concurrent with the traditional human method. The study looks at NDT performance in terms of man-hours required to perform the inspection, statistical validity of test results, comparable equipment costs, asset utilization and insurance & other indirect savings. The study is performed on a field-erected AST following the API 653 UTT in-service inspection of shell and roof and a SSPC PA-2 inspection of paint thickness. The study addresses only the comparison of data obtained through hand-held sampling by a human compared to data obtained from a drone performing a similar task. The purpose of this study is to establish the validity of drone-obtained UT wall thickness and DFT measurements compared to existing methods, and the general viability of the technology in 5-year external inspections. The paper concludes with high confidence that there is no measurable difference between robot-performed NDT and traditional practices, although robots have the capacity to perform the tests far faster, at a lower cost, and with far greater employee safety.

Print this page

Machine Learning Techniques for Industrial Material Classification Applications with Color CT Datasets

Presenting author(s): Mr Srivathsan Koundinyan »

Co-Authors: Ms Noelle M Collins, Ms Adriana Stohn, Mr Ryan Goodner, Dr Edward Jimenez, Mr Kyle R Thompson

Room: Seminole A | 9:00 AM Thursday, March 29, 2018

Sandia National Laboratories has recently acquired a Multix multi-channel linear array detector calibrated for obtaining sinogram data up to 300 keV across 128 channels per pixel. This works aims to examine the utility of this color CT system for materials classification and identification purposes, with a focus on materials critical to industrial and security applications; namely, oils, water, plastics, copper, lead, and aluminum. Machine learning algorithms such as naïve Bayes, support vector machines, and random forests will be investigated for distinguishing different materials of interest with similar absorption properties. Methods to properly adapt the aforementioned schemes for multichannel datasets, as well as possible reasons for an algorithms’ lessened ability to label materials, will be highlighted. In addition, ensemble schemes like bagging and boosting will be explored to improve the robustness of the classification tasks. Collectively, this work will determine the optimal strategy for industrial material identification in the context of color CT datasets. This work could have tremendous impact on many applications within the Non-destructive Evaluation community including quality assurance, anomaly detection, and verification and validation applications. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Print this page

2D Imaging of Resistance Spots Welds of Dissimilar Thickness Material

Presenting author(s): Mr Andrew L Ouellette

Co-Authors: Dr Andriy M Chertov, Dr Roman Gr Maev

Room: Seminole B | 9:20 AM Thursday, March 29, 2018

The resistance spot weld is a commonly employed joining technique in the automotive industry and others. This technique makes use of copper electrodes to pass current through a stack of metallic sheets, heating and melting the sheets together at a point. The highly-automated process present in modern assembly can often result in deviations from design parameters and the failure of the process to form an adequate joint. In the automotive industry, the average vehicle contains thousands of spot welds, resulting in cost and time prohibitive manual inspection. To overcome the cost associated with inspection, along with associated repairs or scrapping of failed parts, an inline ultrasonic monitoring process was developed. This process makes use of a transducer built into the welding electrode which, with repeated pulse echo sampling can form a weld-quality image through the monitoring of both solid- solid and solid-liquid boundaries during welding. This system has shown an excellent correlation in numerous cases, but difficulties present in the fact that the monitoring must assume an axial-symmetric arrangement. For this reason, the development of a 1D linear array was performed, with the potential for examining processes along the lateral dimension of the weld. This system has been used to examine a difficult monitoring situation of the joining process of dissimilar thickness plates, where the thermodynamics result in the presence of phase transitions in addition to the melting process. The results of this monitoring, alongside a comparison to the single element process, will be presented.

Print this page

Iterative NDE X-Ray CT Image Reconstruction and Beam-Hardening Correction

Presenting author(s): Mr Zhan Zhang

Co-Authors: Mr Anindya Das, Mr Aleksandar Dogandzic

Room: Seminole A | 9:20 AM Thursday, March 29, 2018

The beam hardening effects in traditional CT reconstruction methods cause cupping and streaking artifacts, which obstruct the diagnosis in medical CT and defect inspection in industrial CT. Most existing beam-hardening correction methods rely on empirical knowledge, or known incident energy spectra, or known object material composition. The beam-hardening artifacts are caused by treating polychromatic X-ray sources as monochromatic during reconstruction. We proposed a new model parameterization that allows for blind correction of these artifacts and then developed iterative reconstruction algorithms based on this parameterization. Here, blind correction means that incident photon energy spectrum and object materials (attenuation coefficients) are unknown. We developed a novel iterative reconstruction algorithm for beam-hardening correction based on this parameterization. Our iterative algorithm is the first physical-model-based method for simultaneous blind sparse image reconstruction and mass-attenuation spectrum estimation from polychromatic measurements.Testing with multiple sets of Micro-CT data with different materials confirms the effectiveness of this method to remove the cupping artifacts and reduce streaking artifacts. The concept-proof code is now only implemented for 2D reconstruction on Matlab with single material object. Future work will generalize this method to allow for 3D reconstruction: here, we will also explore suboptimal low-complexity approaches, such as linearized FDK algorithms.

Print this page

In-line Ultrasonic Quality Control Monitoring of Aluminum-Steel Joining Fabricated by Cold Spray & Resistance Spot Welding Processes

Presenting author(s): Dr Roman Gr Maev »

Co-Authors: Dr Andriy M Chertov, Mr Volf Leshchynsky, Mr Waldo Perez Regalado

Room: Seminole B | 9:40 AM Thursday, March 29, 2018

Print this page

Increased Process Safety and Efficiently Through Automated Defect Recognition (ADR) In X-Ray Inspection

Presenting author(s): Mr Lennart Schulenburg »

Co-Authors:

Room: Seminole A | 9:40 AM Thursday, March 29, 2018

Especially automotive manufacturers with a very high production volume need interaction free in-line systems with Automated Defect Recognition (ADR). This reduces personnel costs and lowers the chance of human errors during the inspection process. Automated inspection systems have to comply to international quality standards like ASTM, VDI, EN etc. and the demanding company standards of VW, BMW, Porsche etc. As the production process of such parts is already completely automated, systems have to be designed for 24/7 operation without human interaction. Additionally, offline inspection stations are used to train the inspection sequences or review the results. This leads to a completely decoupled procedure for 100% system uptime. Typical ADR applications are the detection of porosities, inclusions or cracks in casting parts. It is possible to define certain ROIs and check defect metrics like defect density, defect distance, defect size, defects per area and many more. Thresholds can be defined dynamically. Training of the system does not require any programming skills and can be done through level II or III personnel. This drives down production costs and reduces the inspection bottleneck, while increasing the reliability and process safety. An integration to Industry 4.0 factory solutions allows full traceability of the inspection process down to single part level. More demanding tasks like automated measurement, completeness or density checks can be performed through the unique VAIP (VisiConsult Automated Image Processing) module. Complex test sequences can be performed on static images or in real time. Example applications: The behavior of heat pumps under different temperatures and completeness checks of valves.

Print this page

Qualitative Assessment of Structural Damage to Composite Avionic Materials by Acoustic and Thermographic NDE Methods

Presenting author(s): Dr Roman Gr Maev »

Co-Authors: Mr Dimitriy Gavrilov, Mr Inna Seviaryna

Room: Seminole B | 10:00 AM Thursday, March 29, 2018

Pre-flight inspection of critical aircraft components and systems is key to maintaining flight safety. In order to provide high quality testing and avoid interference with the flight schedule such an inspection must be prompt yet reliable. This work is the pilot stage of a study conducted on a Bombardier C-series wing material with the aid of acoustic microscopy and principal components thermography. Both methods were applied to composite samples subject to quasi-static loading, and defects were visualized and compared. The methods are discussed for applicability as part of possible pre- and post-flight inspection routine.

Print this page

FELLOWSHIP AWARD WINNER: Large-Area Electrical Resistance Tomography Based Sensing Skin

Presenting author(s): Dr Reza Rashetnia

Co-Authors:

Room: Seminole A | 10:00 AM Thursday, March 29, 2018

Recently, there has been a growing interest in the development of large-area sensors for Structural Health Monitoring (SHM). These sensors have a wide range of applications in monitoring civil and mechanical structures. Commonly referred sensing skins are one type of these sensors consist of a thin layer of electrically conductive materials, e.g., electrically-conductive paints or films. These sensors can be installed on the surface of the structure or embedded within materials. Damage to the structure is detected based on local conductivity change in the sensing skins using the Electrical Resistance Tomography (ERT). The sensing skin technology has been successful in detecting, localization, and quantification of damages in terms of conductivity change in small sizes, in the order of a several inches. In this paper, using experimental ERT and difference imaging method, we show the feasibility of detection damages by the sensing skin on large-area surfaces.

Print this page

Ultrasonic Full-Waveforms Comparison Technique to Detect Changes in the Applied Stress on Concrete

Presenting author(s): Mr Ali Hafiz

Co-Authors: Dr Thomas Schumacher

Room: Seminole B | 10:20 AM Thursday, March 29, 2018

Monitoring the performance of reinforced concrete structures has experienced increasing interest over the last decade, especially for bridges. Many types of sensors have been utilized for this purpose such as strain gages, accelerometers, displacement sensors, etc. Typically, these sensors are attached to the concrete surface and can thus detect only the changes on the surface. In contrast, ultrasonic waves propagate through the thickness of a concrete member and can thus detect internal changes. This research presents the ultrasonic full-waveform comparison technique, which makes use of the highly sensitive diffuse portion of the recorded waveform. In this study, the changes in the interior stress were correlated to the changes in the ultrasonic waveforms, which were estimated using magnitude-squared coherence (MSC). This presentation discusses a comprehensive study of the ultrasonic full-waveform comparison technique by investigating all parameters that affect the relationship between the MSC and changes in the interior stress. First, six concrete cylinders were cast and tested to study the effect of maximum aggregate size. Second, two concrete prisms were used to study the effect of pulse wavelength. The sensitivity of the measurement increased with decrease in pulse wavelength and the maximum aggregate size. Finally, the proposed technique was applied during a load test on an in-service bridge. The results showed that MSC correlates well with changes in the interior stress and the new technique can be applied on exciting full-scale structures.

Print this page

Regulatory Status of Buried Pipe and Tank of Nuclear Power Plant in Korea

Presenting author(s): Dr Kyung-Cho Kim

Co-Authors: Mr Jin-Gyum Kim

Room: Seminole A | 10:20 AM Thursday, March 29, 2018

Leakage from buried and underground pipes caused by corrosion has resulted in recent ground water contamination incidents. Some of these leaks resulted in groundwater contamination incidents with associated heightened NRC and public interest. The NRC conducted inspections using TI 2515/173, “Review of the Implementation of the Industry Groundwater Protection Voluntary Initiative” to assess licensee response to these incidents and determine the extent of the industry’s voluntary groundwater protection initiative. Subsequently, the industry communicated its plan to address buried piping integrity in its November 2009 letter “Industry Initiative on Buried Piping Integrity” The scope of the first underground piping initiative only addressed piping that is directly buried in soil. However, because operating experience which revealed that leakage of tritiated water from underground piping in vaults or chases (but not in contact with soil) could also lead to groundwater contamination, the industry expanded the scope of its first initiative to include underground piping not in direct contact with the soil and selected underground tanks. Its September 2010 letter “Industry Initiative on Underground Piping and Tanks Integrity” describes its revised commitments. This second initiative contains all of the requirements and objectives from the first initiative but adds underground piping and tanks that are outside of a building and below the surface of the ground (whether or not they are in direct contact with the soil) if they are safety-related or contain licensed material or are known to be contaminated with licensed material. Also, an owner’s piping located outside the owner controlled area is considered to be within the scope of the underground piping and tanks integrity initiative if it is safety-related or contains licensed material. The industry issued a guidance document, Nuclear Energy Institute (NEI) 09-14, “Guideline for the Management of Buried Piping Integrity” to describe a licensee’s goals and required actions (commitments made by the licensee) resulting from this underground piping and tank initiative. NEI later issued NEI 09-14, Revision 1, “Guidance for the Management of Underground Piping and Tank Integrity,” on December 31, 2010. An Electric Power Research Institute (EPRI) document “Recommendations for an Effective Program to Control the Degradation of Buried and Underground Piping and Tanks” is a guidance document that provides additional details on the buried pipe and tank initiative elements and attributes to incorporate into a licensee’s buried pipes and tanks program. Alternative documents such as those produced by NACE International also provide acceptable guidance. Under the underground piping and tanks Integrity Initiative, each site is to develop and implement either site-specific or company program for buried piping and underground piping and tanks. According to NEI 0914, utility provided procedures , risk ranking , inspection plan and asset management plan These procedures , risk ranking , inspection plan and asset management plan were evaluated by USNRC according to TI 2515/173. The same evaluation and inspection should be performed according to aging degradation of Korea NPP. The purpose of this research is to develop regulatory techniques for aging management for buried and underground pipes and tank in Korean Nuclear Power Plant and to develop regulatory guideline for aging management for buried and underground pipes and tank in Korean Nuclear Plants. For this purpose, aging, direct and indirect inspection technique and regulatory technique for buried and underground pipes and tank will be evaluated and database for damage of buried and underground pipe and tank will be developed. From these techniques and database information, in-service inspection guideline and review guideline for aging management will be developed.

Print this page

TBA-Radiography/Digital Imaging

Presenting author(s):

Co-Authors:

Room: Seminole A | 10:40 AM Thursday, March 29, 2018

Print this page

Passenger Vehicle Effect on the Truck Weight Calculations using B-WIM System

Presenting author(s): Mr Yahya Mohammed Mohammed »

Co-Authors: Mr Nasim Uddin

Room: Seminole B | 1:00 PM Thursday, March 29, 2018

The Bridge Weight-In-Motion (B-WIM) system has been developed in the last few decades to prevent the overload trucks from passing on the bridges. The truck's weight calculations must have a high level of accuracy to stop the correct overload one. As a result of higher vehicle numbers, the Moving Force Identification (MFI) technique faces a new challenge to calculate the truck weight especially when another vehicle crosses over the bridge at the same time. It is not important to calculate the passenger vehicle weight because its weight is not significant enough to damage the bridge, but it is necessary to know its effect on the truck weight. This paper focuses on showing this effect on the MFI algorithm results by simulating a case study using 3D finite element models. Also, it proposes a solution for this problem by creating the first error chart which helps to determinate the most accurate truck weight. An experiment was done on a Pre-stressed concrete bridge to validate the analytical results which done consider US-78 bridge and 5-axles truck.

Print this page

Past, Present, and Future of Nonlinear Solitary Waves in NDT

Presenting author(s): Mr Amir Nasrollahi »

Co-Authors: Dr Piervincenzo Rizzo

Room: Seminole A | 1:00 PM Thursday, March 29, 2018

In the last two decades it has been demonstrated that highly nonlinear solitary waves (HNSWs) propagating in chains of granular particles can be used in many physics and engineering applications, including acoustic lenses, impurity detectors, and nondestructive testing (NDT). HNSWs are compact nondispersive waves that propagate in nonlinear medium such as 1D chains of spherical particles. In this paper a brief history about the use of HNSWs in NDT at the University of Pittsburgh is given. A few examples of past projects regarding the non-invasive assessment of cement and concrete strength will be given. Then, the outcomes of a current study on the non-invasive measurement of internal pressure of inflatable systems will be presented. Finally, the paper will unveil possible future studies in which solitary waves can be used to detect corrosion in metallic structures.

Print this page

Structural Health Monitoring of Vertical Lift Bridge Using Vibration Data

Presenting author(s): Mr Vahid Shahsavari »

Co-Authors: Milad Mehrkash, Ms Erin S Bell

Room: Seminole B | 1:20 PM Thursday, March 29, 2018

An objective decision-making criterion is developed for condition assessment of the new Memorial Bridge connecting Portsmouth, New Hampshire to Kittery, Main, United States. The analysis is based on the energy of acceleration signals obtained from a series of accelerometers permanently deployed along the bridge. In the present paper, a Wavelet Packet Transform (WPT) is used as a means to decompose the measured signals with an arbitrary time-frequency resolution. A unique aspect of this approach is the coupling of various techniques in an effort to enhance the discrimination between vibration-based data recorded from different states of the structure. Firstly, the wavelet packet component that represents the most dominant patterns of variation of the signal properties is determined through wavelet analysis. Secondly, the wavelet packet component energy is computed for each sensor. Finally, the mean energy obtained from the entire set of sensors in each day is calculated for further investigations through a control chart analysis. A statistical framework is developed to train a baseline model in the early age of the bridge when the condition is undamaged. The principal theory behind the methodology relies on assumption that the variations of the extracted features between the estimated control limits correspond mainly to normal operating conditions of the bridge. Therefore, the exceedance of future indicators from the enclosure signifies the presence of unusual sources of variability. The proposed approach is analytically verified through a Finite Element (FE) model of the bridge subjected to structural damage in one of its diagonals. Results indicate a significant distinction between undamaged and damaged responses of the bridge.

Print this page

Utilizing Water Contact Angle Measurements to Predict Surface Preparedness for Dye Penetrant Application

Presenting author(s): Ms Elizabeth Kidd »

Co-Authors: Ms Brooke Campbell

Room: Seminole A | 1:20 PM Thursday, March 29, 2018

Reliably predicting dye penetrant wettability for fluorescent crack inspections hinges on understanding surface cleanliness prior to penetrant application. Validating the efficacy of a parts washer using water contact angle measurements is a non-destructive method for quantifying surface cleanliness and can ensure complete wetting of the penetrant across a substrate. For this study, surface energies of washed and un-washed aluminum parts were characterized via water contact angle measurements and subsequently correlated with dye penetrant wettability. Penetrant was applied to the surface via cotton swab and allowed to wet the surface for 15 minutes before obtaining a visual inspection of wetting pattern; a smooth, uniform distribution of penetrant indicated sufficient wettability while a blotchy, non-uniform distribution indicated insufficient wettability. Freshly washed samples displayed low contact angles and yielded acceptable penetrant wettability while unwashed parts displayed high contact angles and displayed unacceptable penetrant wettability. Water contact angle can be used to determine surface readiness prior to penetrant application.

Print this page

Metasurface Based Surface Crack Sensor using Asymmetric Complementary Split Ring Resonator

Presenting author(s): Mr Salem Ali Al Otaibi »

Co-Authors: Dr Manos Tentzeris

Room: Seminole B | 1:40 PM Thursday, March 29, 2018

Metal surface crack detection and sizing is crucial task in petrochemical and aerospace industry. The development of precise, flexible and reliable sensor for structural health monitoring system is highly recommended to monitor crack growth and avoid sudden failure. This paper present high sensitive microwaves-based designs of surface crack sensor topologies. The presented sensors are developed by breaking symmetry of complementary split ring resonators (CSRR). This design enhances the sensors’ probability of detection (POD) by at least 50% compared to recently developed metasurface based sensors due to the presence of at least two sensing elements in each sensor. Moreover, sensor design is simple with flexible design parameters and a wide dynamic range of the sensing-related frequency which make it suitable for customized design based on inspection procedure and recommended acceptance criteria. The sensor performance has been verified using the full-wave numerical simulation package ANSYS HFSS. A proof-of- concept resonance frequency shift of hundreds of MHz was obtained for aluminium cracked samples having crack with 190-100um width and 2-0.5mm depth.

Print this page

Truncation Effects of Frequency Selective Surface-Based Sensors

Presenting author(s): Ms Mahboobeh Mahmoodi »

Co-Authors: Dr Kristen Donnell

Room: Seminole A | 1:40 PM Thursday, March 29, 2018

Frequency selective surfaces (FSSs) are periodic arrays of conductive elements located on a dielectric substrate. By illuminating an FSS with electromagnetic energy, the specific reflection/transmission response is related to element geometry, spacing and substrate properties. These features, in addition to their planar structure, ease of implementation, and wireless (remote) interrogation, open the door to a passive and wireless sensing solution for structural health monitoring. In particular, parameters such as normal and shear strain, temperature, presence of defects/damage in layered structures (disbonds and delamination), etc., may be monitored via FSS-based sensing. As it relates to practical sensor design, FSS sensors have finite dimensions and are interrogated with realistic (spatially-varying) electromagnetic field patterns. However, their analysis is based on an infinite array interrogated by a perfect plane wave. This results in a potential deviation in the frequency response of the sensor from the theoretical response. In addition, for applications that require localized strain measurements (for example), even a large FSS may need to be considered as a compound sensor made up of many (smaller) sub-FSS sensor cells. In this way, by interrogating each cell individually (with an appropriate illumination), the resolution of the strain measurement may be improved. However, this approach (effectively) truncates the dimensions of the FSS sensor, and therefore may significantly affect the frequency response. As such, in order to determine optimal cell dimensions, there is a trade-off between the desired resolution and truncation effects due to cell size (i.e., change in frequency response). Another aspect that must be considered when utilizing the sensor cell approach is the location of the sensing parameter of interest. More specifically, for example, the effect of a crack contained completely within a cell on the frequency response may differ from that of a crack that is common to two adjacent cells. This presentation will highlight the effect of practical illumination of realistic (finite) FSS sensors, as well as discuss the concept of the sensor cell approach and its associated benefits and limitations.

Print this page

Seismically Damaged Structure Assessment Under Subsequent Extreme Events

Presenting author(s): Mrs Heba Elsisi »

Co-Authors: Mr Ahmed Elhattab, Mr Nasim Uddin

Room: Seminole B | 2:00 PM Thursday, March 29, 2018

Buildings are a major investment in the United States where they touch our lives in many aspects as livelihoods, security, and safety. In the many parts of the central and eastern, tall buildings are present in regions where there is the potential for major earthquakes and high winds due to tornadoes and hurricanes. Major earthquakes cause widespread structural damage over large regions, leading to disparately damaged structures. The extent of structural damage may go undetected and unrepaired, especially when there are no clear visual damage indicators. Unaddressed seismic damage has clear implications for structural performance specifically if the earthquake event is followed by an extreme tropical storm. This paper investigates a new approach in providing a quick assessment for the structure performance and safety after extreme earthquake takes a place. In the article, the floor acceleration is utilized to identify the presence of damage via monitoring the instantaneous frequency shift of the structural elements. The damage extent is then ranked based upon the structural value of the element. Finally, the safety of the damaged structure (i.e. the ranked structure) is assessed against future extreme wind events. Wind pressure is generated using the integrated pressure modal load (IPML) technique to mimic strong tropical storms. The paper highlights both the structural safety and damage implication on inducing more structural damages to the building.

Print this page

Uncertainty Bounds on Ultrasonic Phase Velocities for Polycrystalline Media

Presenting author(s): Mr Musa Norouzian »

Co-Authors: Dr Joseph A Turner

Room: Seminole A | 2:00 PM Thursday, March 29, 2018

In most theoretical work related to the study of the effective properties of polycrystals, the media are assumed to be infinite with randomly oriented grains. Therefore, the bulk material has absolute isotropy because in each direction, an infinite number of grains exists with infinite possibilities for grain orientation. However, measurements on real samples will always include a finite number of grains such that the inspection volume will have some associated anisotropy. Therefore, bounds on the bulk properties can be expected for a given measurement. In this work, the effect of the number of grains on this anisotropy variation is studied using Dream.3D software. The effective elastic modulus tensor is derived using Voigt, Reuss, and self-consistent techniques with 1700 microstructures comprised of equiaxed cubic grains in 17 different sizes. The Bond transformation is utilized to quantify the standard deviation present in the average elastic modulus. The standard deviation is investigated for aluminum, copper, nickel, iron, gold, chromium, potassium, lithium and platinum and is shown to be inversely proportional to the square root of the number of grains. Based on the single-crystal anisotropy, a master curve is derived which relates modulus anisotropy to the number of grains for the three averaging techniques. In addition, Christoffel equation is used to study the relevant phase velocities. With appropriate normalization, a similar master curve is derived. Such results are anticipated to have an important impact on ultrasonic models associated with metals. [Research supported by AFRL under prime contract FA8650-15-D-5231].

Print this page

Neutron Generator Driven Active Nuclear Fuel Scanner

Presenting author(s): Dr Karuppanan Sekar

Co-Authors: Mrs Katie Rittenhouse

Room: Seminole A | 2:20 PM Thursday, March 29, 2018

Non-Destructive Assay has long been used for active scanning of nuclear fuel. In this method, fuel rods traverse through a scanner with an activation zone in which they are subjected to neutron radiation and fission activity is subsequently measured as the rods exit the irradiator. From this and other information, the enrichment and other characteristics of each rod and pellet are determined. Californium-252 has traditionally been used as the neutron source in the activation zone, because it is an intense neutron emitter and is readily packaged in compact, portable capsules. However, a recent shift to a full cost-recovery basis for Cf-252 has led to a more than 10 times increase in cost. This increase in cost is forcing some Cf-252 users to seek alternate neutron sources, including nuclear fuel manufacturers. A high-flux, accelerator-based neutron source has been developed as a viable alternative for applications requiring large Cf-252 sources – on the milligram-scale or larger – such as neutron radiography, nuclear fuel rod scanning, and neutron flux detector calibration. Neutron flux modeling and expected fission rates for the complete active scanning system based on the neutron generator will be presented.

Print this page

Towards New Imaging Methods for Ultrasonic Nondestructive Testing Part I

Presenting author(s): Mr Alan Caulder »

Co-Authors: Mr Leon Barton, Dr Dominique Braconnier

Room: Seminole A | 2:40 PM Thursday, March 29, 2018

The total focusing method (TFM) is becoming a standard in the nondestructive testing industry. TFM generally provides lower noise and higher lateral resolution than conventional phased array imaging. Furthermore, TFM opens doors to the development of a new generation of advanced imaging methods. In the study presented in these two papers, we compare several advanced imaging methods. First, we present Delay-and-sum (DAS) approaches where the purpose is to build each pixel by summing the contributions of each Ascan at the proper time of flight. The output image is therefore focused at every pixel. These methods generally give better image quality than conventional phased-array imaging. Next, we examine migration methods, which work within the wavenumber domain and are known to give better image quality than DAS approaches. We also present results from TFMp, a method based on an inverse problem approach. In this method, the purpose is to consider a specific structure of the piece under test, contrary to the previous approaches. We assume a sparse structure, meaning that the piece under test contains point-like reflectors. The image is obtained by minimizing a data misfit criterion including a sparse penalization term. Metrics such as lateral resolution and peak signal to noise ratio (PSNR), which defines the contrast, are used to adequately compare the methods. Migration methods give a better PSNR than DAS methods and provide similar lateral resolution. The TFMp approach can be combined with any method except migration and gives outstanding results for lateral resolution and PSNR compared to standard methods.

Print this page