James Blackshire - Academia.edu (original) (raw)

Papers by James Blackshire

AIP Conference Proceedings, 2016

The public reporting burden for this collection of information is estimated to average 1 hour per... more The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 11 19a. NAME OF RESPONSIBLE PERSON (Monitor) a. REPORT

AIP Conference Proceedings, 2016

The nondestructive evaluation of polycrystalline materials has been an active area of research fo... more The nondestructive evaluation of polycrystalline materials has been an active area of research for many decades, and continues to be an area of growth in recent years. Titanium alloys in particular have become a critical material system used in modern turbine engine applications, where an evaluation of the local microstructure properties of engine disk/blade components is desired for performance and remaining life assessments. Current NDE methods are often limited to estimating ensemble material properties or detecting localized voids, inclusions, or damage features within a material. Recent advances in computational NDE and material science characterization methods are providing new and unprecedented access to heterogeneous material properties, which permits microstructure-sensing interactions to be studied in detail. In the present research, Integrated Computational Materials Engineering (ICME) methods and tools are being leveraged to gain a comprehensive understanding of root-cause ultrasonic scattering processes occurring within a textured titanium aerospace material. A combination of destructive, nondestructive, and computational methods are combined within the ICME framework to collect, holistically integrate, and study complex ultrasound scattering using realistic 2-dimensional representations of the microstructure properties. Progress towards validating the computational sensing methods are discussed, along with insight into the key scattering processes occurring within the bulk microstructure, and how they manifest in pulse-echo immersion ultrasound measurements.

The nondestructive quantification of local grain properties in polycrystalline aerospace material... more The nondestructive quantification of local grain properties in polycrystalline aerospace materials is an important area of recent research, where information related to mean grain size, grain size distribution, and crystallographic orientation are needed for engineering analysis and remaining life predictions in aerospace engine components. In the present effort, a novel ultrasonic imaging method is described that provides enhanced resolution measurements and characterization opportunities for microstructure states in polycrystalline materials. The method utilizes a standard focused immersion ultrasound approach to send ultrasound into a material system, and a collinear wavefield imaging beam to sense local ultrasound fields on the opposite side of the material. By raster scanning the sample relative to the transducer and wavefield beam positions, a high resolution measurement can be generated that has enhanced sensitivity to local grain property estimation.

AIP Conference Proceedings, 2009

Terahertz imaging and dielectric property measurements were assessed as nondestructive evaluation... more Terahertz imaging and dielectric property measurements were assessed as nondestructive evaluation techniques for damage to aircraft glass fiber composites. Samples with localized heat damage showed a minimal change in refractive index or absorption coefficient; however, material blistering was detected. Voids were located by terahertz imaging using amplitude and phase techniques. Delamination depths were approximated by measuring the timing of Fabry‐Perot reflections. Evidence of bending stress damage and simulated hidden cracks was also detected with terahertz imaging.

The public reporting burden for this collection of information is estimated to average 1 hour per... more The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

Proceedings of SPIE, May 28, 2003

It is important to determine the onset of damage as well as the extent of the damage area when ma... more It is important to determine the onset of damage as well as the extent of the damage area when materials are illuminated by intense laser radiation. In this work, an optical interferometric technique was used to assess laser-induced damage in semiconductor materials based on the three-dimensional, topographic characteristics of the damage site. Both antireflection coated and uncoated materials were evaluated for variations of fluence level, focused spot size, and laser repetition rate. The interferometric technique was non-contact and nondestructive in nature, providing a high-resolution capability of assessing damage levels on the surfaces of the materials.

40TH ANNUAL REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION: Incorporating the 10th International Conference on Barkhausen Noise and Micromagnetic Testing, 2014

An ultrasonic contact technique was developed to assess the in-plane modulus of Ceramic Matrix Co... more An ultrasonic contact technique was developed to assess the in-plane modulus of Ceramic Matrix Composite (CMC) materials in the absence of multiple, distinct ultrasonic echoes within a specimen. This technique employs a dry-couplant for sending and receiving guided waves in a pitch-catch mode. The ultrasonic velocity is estimated from the zero-crossing, first-peak arrival time of a 200 kHz lowest-order symmetric mode (S0), where modulus estimations are made using standard plate-wave theory. The low-frequency asymptotic velocity characteristics of the S0 mode provide a means for estimating velocity with minimal dispersion effects and mode-overlap. Preliminary validation of the technique shows reasonable agreement with published modulus data and mechanical testing results.

40TH ANNUAL REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION: Incorporating the 10th International Conference on Barkhausen Noise and Micromagnetic Testing, 2014

An ultrasonic near-surface contact imaging technique was developed to study bond integrity variat... more An ultrasonic near-surface contact imaging technique was developed to study bond integrity variations in a foam-based hybrid composite material system. The method integrates a pair of ultrasonic wedge transducers into a traditional ultrasonic C-scan system in a pitch-catch arrangement. Unlike a conventional C-scan, the specimen is not immersed in water but uses a thin layer of water couplant between the wedges and sample surface. The use of an angled wedge system produces generalized Rayleigh-Lamb waves in the multi-layer material system, where variations in local amplitude and phase velocity of the travelling waves were mapped between bonded polymer composite laminates and ceramic foam substrates. Three categories of features were observed in the scans including: (1) near-surface thermocouple hole positions, (2) reflected wave edge effects, and (3) potential bond line integrity variations.

Nucleation and Atmospheric Aerosols, 2013

Ultrasonic assessment of the bonding integrity between a composite layer and a foam substrate in ... more Ultrasonic assessment of the bonding integrity between a composite layer and a foam substrate in foam-based hybrid composite materials was explored. The challenges of this task are: (1) the foam has air-like acoustic impedance and (2) contact surface wave generation on polymer matrix composites (PMC) is not conventional. To meet these challenges, a novel wedge made of a low velocity material was developed. The results showed that the bonding condition in these composites can be identified by monitoring the amplitude of the ultrasonic signals received.

Nucleation and Atmospheric Aerosols, 2015

A current area of intense research involves the development and use of integrated computational m... more A current area of intense research involves the development and use of integrated computational materials engineering (ICME) approaches, which promise to develop next-generation material systems with significant cost and time savings. At its core, ICME synergistically combines material-centric models related to materials development, processing, manufacturing, and property/performance assessment, where key material property information is shared between the various models to enhance process and product outcomes. The integration of computational NDE models within the ICME framework represents an additional opportunity to advance material science and engineering processes through the development of advanced material state awareness (MSA) sensing methods. In particular, nondestructive sensing methods are needed for ICME model and process validation at all stages of the material development process. Several examples of this are presented, which show model-driven sensing for in-process monitoring, microstructu...

Proceedings of SPIE, Apr 6, 2007

The public reporting burden for this collection of information is estimated to average 1 hour per... more The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

Proceedings of SPIE, Jul 24, 2003

ABSTRACT Recent advancements in small, microscopic NDE sensor technologies will revolutionize how... more ABSTRACT Recent advancements in small, microscopic NDE sensor technologies will revolutionize how aircraft maintenance is done, and will significantly improve the reliability and airworthiness of current and future aircraft systems. A variety of micro/nano systems and concepts are being developed that will enable whole new capabilities for detecting and tracking structural integrity damage. For aging aircraft systems, the impact of micro-NDE sensor technologies will be felt immediately, with dramatic reductions in labor for maintenance, and extended useable life of critical components being two of the primary benefits. For the fleet management of future aircraft systems, a comprehensive evaluation and tracking of vehicle health throughout its entire life cycle will be needed. Indeed, micro/nano NDE systems will be instrumental in realizing this futuristic vision. Several major challenges will need to be addressed, however, before micro- and nano-NDE systems can effectively be implemented, and this will require interdisciplinary research approaches, and a systematic engineering integration of the new technologies into real systems. Future research will need to emphasize systems engineering approaches for designing materials and structures with in-situ inspection and prognostic capabilities. Recent advances in 1) embedded / add-on micro-sensors, 2) computer modeling of nondestructive evaluation responses, and 3) wireless communications are important steps toward this goal, and will ultimately provide previously unimagined opportunities for realizing whole new integrated vehicle health monitoring capabilities. The future use of micro/nano NDE technologies as vehicle health monitoring tools will have profound implications, and will provide a revolutionary way of doing NDE in the near and distant future.

Springer eBooks, 2004

Two advanced nondestructive evaluation systems are developed for imaging surface-breaking cracks ... more Two advanced nondestructive evaluation systems are developed for imaging surface-breaking cracks in aerospace materials. The systems use scanning heterodyne interferometry and frequencytranslated holography principles to image ultrasonic displacement fields on material surfaces with high resolution and sensitivity. Surfacebreaking cracks are detected and characterized by visualizing near-field ultrasonic scattering processes, which in turn results in local intensification of ultrasonic displacement fields in the immediate vicinity of a crack. The local intensification permits cracks to be easily distinguished from background levels, and creates unique displacement field images that follow the contours and morphology of the cracks with microscopic precision. The interferometric and holographic imaging approaches each provide noncontact and near optical-diffraction-limited measurement capabilities that are essential for probing ultrasonic displacement fields in the immediate vicinity of cracks. Several representative crack-imaging results are provided, along with detailed descriptions of both experimental techniques, and the capabilities and limitations of each method. The resulting systems provide simple yet very powerful tools for evaluating surface-breaking cracks in detail.

arXiv (Cornell University), May 7, 2020

We introduce an optimized physics-informed neural network (PINN) trained to solve the problem of ... more We introduce an optimized physics-informed neural network (PINN) trained to solve the problem of identifying and characterizing a surface breaking crack in a metal plate. PINNs are neural networks that can combine data and physics in the learning process by adding the residuals of a system of Partial Differential Equations to the loss function. Our PINN is supervised with realistic ultrasonic surface acoustic wave data acquired at a frequency of 5 MHz. The ultrasonic surface wave data is represented as a surface deformation on the top surface of a metal plate, measured by using the method of laser vibrometry. The PINN is physically informed by the acoustic wave equation and its convergence is sped up using adaptive activation functions. The adaptive activation function uses a scalable hyperparameter in the activation function, which is optimized to achieve best performance of the network as it changes dynamically the topology of the loss function involved in the optimization process. The usage of adaptive activation function significantly improves the convergence, notably observed in the current study. We use PINNs to estimate the speed of sound of the metal plate, which we do with an error of 1%, and then, by allowing the speed of sound to be space dependent, we identify and characterize the crack as the positions where the speed of sound has decreased. Our study also shows the effect of sub-sampling of the data on the sensitivity of sound speed estimates. More broadly, the resulting model shows a promising deep neural network model for ill-posed inverse problems.

The nondestructive quantification of microstructure states in polycrystalline materials is an imp... more The nondestructive quantification of microstructure states in polycrystalline materials is an important area of recent research. Mean grain size estimates, for example, have been successfully made in a number of instances using frequency-dependent attenuation measurements and signal inversion theory based on statistically isotropic/equiaxed microstructure states and random crystallographic orientation conditions. In order to have a greater impact on engineering analysis and remaining life predictions, however, nondestructive evaluation estimates of local microstructure state variations are needed. In the present effort, forward ultrasonic models and targeted experiments are used to study and quantify the local statistical variability of microstructure states and ultrasonic signal response behaviors in synthetically generated and realistic Ti-6Al-4V titanium materials. An extension of equiaxed grain states to include extended log-normal grain size distributions is made, where local variations in the volumetric microstructure state, ultrasonic field scattering behavior, and frequency-dependent attenuation are evaluated using model-assisted studies and pulse-echo immersion ultrasound measurements.

Terahertz (THz) time domain spectroscopy (TDS) was assessed as a nondestructive evaluation techni... more Terahertz (THz) time domain spectroscopy (TDS) was assessed as a nondestructive evaluation technique for aircraft composites. Material properties of glass fiber composite were measured using both transmission and reflection configuration. The interaction of THz with a glass fiber composite was then analyzed, including the effects of scattering, absorption, and the index of refraction, as well as effective medium approximations. THz TDS, in both transmission and reflection configuration, was used to study composite damage, including voids, delaminations, mechanical damage, and heat damage. Measurement of the material properties on samples with localized heat damage showed that burning did not change the refractive index or absorption coefficient noticeably; however, material blistering was detected. Voids were located by THz TDS transmission and reflection imaging using amplitude and phase techniques. The depth of delaminations was measured via the timing of Fabry-Perot reflections after the main pulse. Evidence of bending stress damage and simulated hidden cracks was also detected with terahertz imaging. v First, I would like to thank my advisor, Lt Col Matt Bohn, for his guidance in this research, offering skillful advice with the laboratory experimental setup and providing expert scientific insight in helping me to resolve research issues. I would also like to thank Dr. Jim Blackshire of AFRL/RXLP for sponsoring this work and for providing us with representative aircraft composite samples which were essential to the research. In addition, I would like to thank Abel Nunez for his help with image processing and to Jeremy Johnson and AFRL/RXLP for the ultrasound and x-ray images. Thanks to Col Brent Richert and my parents for their encouragement to return to school and earn this degree and to my mother for helping to proofread this dissertation. I would like to thank Epiphany Lutheran Church for its spiritual support along the way. I am very grateful for the birth of my two children who have been an inspiration to me and represent promise for the future. Most of all, I would like to thank my wife for her patience and understanding during the difficult days and nights when I was studying, researching, and writing. I also thank her for her strength in enduring an uncomfortable work situation for 4 years.

Sensors and Actuators A-physical, Dec 1, 2008

Abstract Single-element interdigital transducers (IDTs) are designed, fabricated, and characteriz... more Abstract Single-element interdigital transducers (IDTs) are designed, fabricated, and characterized as a complimentary sensor approach for traditional ultrasonic transducers used in nondestructive testing (NDT). The frequency of interest is in the lower megahertz range, 2–10 MHz. In this paper, a simple five-finger paired IDT is described, where laser micro-machining techniques were used to shape the electrode patterns for an IDT resonance frequency of ∼3 MHz. Detailed characterization of the Rayleigh surface waves generated by the IDT is performed using a scanning laser interferometry system. Wave properties such as beam profile, beam divergence, energy decay, frequency response, and phase dependence are reported.

REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION: VOLUME 32, 2013

In an effort to evaluate the modulus of materials at elevated temperatures, an ultrasonic delay l... more In an effort to evaluate the modulus of materials at elevated temperatures, an ultrasonic delay line approach was developed. The setup was tested with a known material, an aluminum alloy, using delay lines at ambient temperature to examine the feasibility of this approach. Due to the low frequency used, interference occurred between multiple passes of the ultrasound through the material resulting a lower than expected measured velocity. Incorporation of a transmission coefficient in the model of the experiment corrected the expected timing of the ultrasonic signals, reconciling the model to measurements of velocity.

25th Plasmadynamics and Lasers Conference, Jun 20, 1994

AIP Conference Proceedings, 2016

The public reporting burden for this collection of information is estimated to average 1 hour per... more The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 11 19a. NAME OF RESPONSIBLE PERSON (Monitor) a. REPORT

AIP Conference Proceedings, 2016

The nondestructive evaluation of polycrystalline materials has been an active area of research fo... more The nondestructive evaluation of polycrystalline materials has been an active area of research for many decades, and continues to be an area of growth in recent years. Titanium alloys in particular have become a critical material system used in modern turbine engine applications, where an evaluation of the local microstructure properties of engine disk/blade components is desired for performance and remaining life assessments. Current NDE methods are often limited to estimating ensemble material properties or detecting localized voids, inclusions, or damage features within a material. Recent advances in computational NDE and material science characterization methods are providing new and unprecedented access to heterogeneous material properties, which permits microstructure-sensing interactions to be studied in detail. In the present research, Integrated Computational Materials Engineering (ICME) methods and tools are being leveraged to gain a comprehensive understanding of root-cause ultrasonic scattering processes occurring within a textured titanium aerospace material. A combination of destructive, nondestructive, and computational methods are combined within the ICME framework to collect, holistically integrate, and study complex ultrasound scattering using realistic 2-dimensional representations of the microstructure properties. Progress towards validating the computational sensing methods are discussed, along with insight into the key scattering processes occurring within the bulk microstructure, and how they manifest in pulse-echo immersion ultrasound measurements.

The nondestructive quantification of local grain properties in polycrystalline aerospace material... more The nondestructive quantification of local grain properties in polycrystalline aerospace materials is an important area of recent research, where information related to mean grain size, grain size distribution, and crystallographic orientation are needed for engineering analysis and remaining life predictions in aerospace engine components. In the present effort, a novel ultrasonic imaging method is described that provides enhanced resolution measurements and characterization opportunities for microstructure states in polycrystalline materials. The method utilizes a standard focused immersion ultrasound approach to send ultrasound into a material system, and a collinear wavefield imaging beam to sense local ultrasound fields on the opposite side of the material. By raster scanning the sample relative to the transducer and wavefield beam positions, a high resolution measurement can be generated that has enhanced sensitivity to local grain property estimation.

AIP Conference Proceedings, 2009

Terahertz imaging and dielectric property measurements were assessed as nondestructive evaluation... more Terahertz imaging and dielectric property measurements were assessed as nondestructive evaluation techniques for damage to aircraft glass fiber composites. Samples with localized heat damage showed a minimal change in refractive index or absorption coefficient; however, material blistering was detected. Voids were located by terahertz imaging using amplitude and phase techniques. Delamination depths were approximated by measuring the timing of Fabry‐Perot reflections. Evidence of bending stress damage and simulated hidden cracks was also detected with terahertz imaging.

The public reporting burden for this collection of information is estimated to average 1 hour per... more The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

Proceedings of SPIE, May 28, 2003

It is important to determine the onset of damage as well as the extent of the damage area when ma... more It is important to determine the onset of damage as well as the extent of the damage area when materials are illuminated by intense laser radiation. In this work, an optical interferometric technique was used to assess laser-induced damage in semiconductor materials based on the three-dimensional, topographic characteristics of the damage site. Both antireflection coated and uncoated materials were evaluated for variations of fluence level, focused spot size, and laser repetition rate. The interferometric technique was non-contact and nondestructive in nature, providing a high-resolution capability of assessing damage levels on the surfaces of the materials.

40TH ANNUAL REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION: Incorporating the 10th International Conference on Barkhausen Noise and Micromagnetic Testing, 2014

An ultrasonic contact technique was developed to assess the in-plane modulus of Ceramic Matrix Co... more An ultrasonic contact technique was developed to assess the in-plane modulus of Ceramic Matrix Composite (CMC) materials in the absence of multiple, distinct ultrasonic echoes within a specimen. This technique employs a dry-couplant for sending and receiving guided waves in a pitch-catch mode. The ultrasonic velocity is estimated from the zero-crossing, first-peak arrival time of a 200 kHz lowest-order symmetric mode (S0), where modulus estimations are made using standard plate-wave theory. The low-frequency asymptotic velocity characteristics of the S0 mode provide a means for estimating velocity with minimal dispersion effects and mode-overlap. Preliminary validation of the technique shows reasonable agreement with published modulus data and mechanical testing results.

40TH ANNUAL REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION: Incorporating the 10th International Conference on Barkhausen Noise and Micromagnetic Testing, 2014

An ultrasonic near-surface contact imaging technique was developed to study bond integrity variat... more An ultrasonic near-surface contact imaging technique was developed to study bond integrity variations in a foam-based hybrid composite material system. The method integrates a pair of ultrasonic wedge transducers into a traditional ultrasonic C-scan system in a pitch-catch arrangement. Unlike a conventional C-scan, the specimen is not immersed in water but uses a thin layer of water couplant between the wedges and sample surface. The use of an angled wedge system produces generalized Rayleigh-Lamb waves in the multi-layer material system, where variations in local amplitude and phase velocity of the travelling waves were mapped between bonded polymer composite laminates and ceramic foam substrates. Three categories of features were observed in the scans including: (1) near-surface thermocouple hole positions, (2) reflected wave edge effects, and (3) potential bond line integrity variations.

Nucleation and Atmospheric Aerosols, 2013

Ultrasonic assessment of the bonding integrity between a composite layer and a foam substrate in ... more Ultrasonic assessment of the bonding integrity between a composite layer and a foam substrate in foam-based hybrid composite materials was explored. The challenges of this task are: (1) the foam has air-like acoustic impedance and (2) contact surface wave generation on polymer matrix composites (PMC) is not conventional. To meet these challenges, a novel wedge made of a low velocity material was developed. The results showed that the bonding condition in these composites can be identified by monitoring the amplitude of the ultrasonic signals received.

Nucleation and Atmospheric Aerosols, 2015

A current area of intense research involves the development and use of integrated computational m... more A current area of intense research involves the development and use of integrated computational materials engineering (ICME) approaches, which promise to develop next-generation material systems with significant cost and time savings. At its core, ICME synergistically combines material-centric models related to materials development, processing, manufacturing, and property/performance assessment, where key material property information is shared between the various models to enhance process and product outcomes. The integration of computational NDE models within the ICME framework represents an additional opportunity to advance material science and engineering processes through the development of advanced material state awareness (MSA) sensing methods. In particular, nondestructive sensing methods are needed for ICME model and process validation at all stages of the material development process. Several examples of this are presented, which show model-driven sensing for in-process monitoring, microstructu...

Proceedings of SPIE, Apr 6, 2007

The public reporting burden for this collection of information is estimated to average 1 hour per... more The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

Proceedings of SPIE, Jul 24, 2003

ABSTRACT Recent advancements in small, microscopic NDE sensor technologies will revolutionize how... more ABSTRACT Recent advancements in small, microscopic NDE sensor technologies will revolutionize how aircraft maintenance is done, and will significantly improve the reliability and airworthiness of current and future aircraft systems. A variety of micro/nano systems and concepts are being developed that will enable whole new capabilities for detecting and tracking structural integrity damage. For aging aircraft systems, the impact of micro-NDE sensor technologies will be felt immediately, with dramatic reductions in labor for maintenance, and extended useable life of critical components being two of the primary benefits. For the fleet management of future aircraft systems, a comprehensive evaluation and tracking of vehicle health throughout its entire life cycle will be needed. Indeed, micro/nano NDE systems will be instrumental in realizing this futuristic vision. Several major challenges will need to be addressed, however, before micro- and nano-NDE systems can effectively be implemented, and this will require interdisciplinary research approaches, and a systematic engineering integration of the new technologies into real systems. Future research will need to emphasize systems engineering approaches for designing materials and structures with in-situ inspection and prognostic capabilities. Recent advances in 1) embedded / add-on micro-sensors, 2) computer modeling of nondestructive evaluation responses, and 3) wireless communications are important steps toward this goal, and will ultimately provide previously unimagined opportunities for realizing whole new integrated vehicle health monitoring capabilities. The future use of micro/nano NDE technologies as vehicle health monitoring tools will have profound implications, and will provide a revolutionary way of doing NDE in the near and distant future.

Springer eBooks, 2004

Two advanced nondestructive evaluation systems are developed for imaging surface-breaking cracks ... more Two advanced nondestructive evaluation systems are developed for imaging surface-breaking cracks in aerospace materials. The systems use scanning heterodyne interferometry and frequencytranslated holography principles to image ultrasonic displacement fields on material surfaces with high resolution and sensitivity. Surfacebreaking cracks are detected and characterized by visualizing near-field ultrasonic scattering processes, which in turn results in local intensification of ultrasonic displacement fields in the immediate vicinity of a crack. The local intensification permits cracks to be easily distinguished from background levels, and creates unique displacement field images that follow the contours and morphology of the cracks with microscopic precision. The interferometric and holographic imaging approaches each provide noncontact and near optical-diffraction-limited measurement capabilities that are essential for probing ultrasonic displacement fields in the immediate vicinity of cracks. Several representative crack-imaging results are provided, along with detailed descriptions of both experimental techniques, and the capabilities and limitations of each method. The resulting systems provide simple yet very powerful tools for evaluating surface-breaking cracks in detail.

arXiv (Cornell University), May 7, 2020

We introduce an optimized physics-informed neural network (PINN) trained to solve the problem of ... more We introduce an optimized physics-informed neural network (PINN) trained to solve the problem of identifying and characterizing a surface breaking crack in a metal plate. PINNs are neural networks that can combine data and physics in the learning process by adding the residuals of a system of Partial Differential Equations to the loss function. Our PINN is supervised with realistic ultrasonic surface acoustic wave data acquired at a frequency of 5 MHz. The ultrasonic surface wave data is represented as a surface deformation on the top surface of a metal plate, measured by using the method of laser vibrometry. The PINN is physically informed by the acoustic wave equation and its convergence is sped up using adaptive activation functions. The adaptive activation function uses a scalable hyperparameter in the activation function, which is optimized to achieve best performance of the network as it changes dynamically the topology of the loss function involved in the optimization process. The usage of adaptive activation function significantly improves the convergence, notably observed in the current study. We use PINNs to estimate the speed of sound of the metal plate, which we do with an error of 1%, and then, by allowing the speed of sound to be space dependent, we identify and characterize the crack as the positions where the speed of sound has decreased. Our study also shows the effect of sub-sampling of the data on the sensitivity of sound speed estimates. More broadly, the resulting model shows a promising deep neural network model for ill-posed inverse problems.

The nondestructive quantification of microstructure states in polycrystalline materials is an imp... more The nondestructive quantification of microstructure states in polycrystalline materials is an important area of recent research. Mean grain size estimates, for example, have been successfully made in a number of instances using frequency-dependent attenuation measurements and signal inversion theory based on statistically isotropic/equiaxed microstructure states and random crystallographic orientation conditions. In order to have a greater impact on engineering analysis and remaining life predictions, however, nondestructive evaluation estimates of local microstructure state variations are needed. In the present effort, forward ultrasonic models and targeted experiments are used to study and quantify the local statistical variability of microstructure states and ultrasonic signal response behaviors in synthetically generated and realistic Ti-6Al-4V titanium materials. An extension of equiaxed grain states to include extended log-normal grain size distributions is made, where local variations in the volumetric microstructure state, ultrasonic field scattering behavior, and frequency-dependent attenuation are evaluated using model-assisted studies and pulse-echo immersion ultrasound measurements.

Terahertz (THz) time domain spectroscopy (TDS) was assessed as a nondestructive evaluation techni... more Terahertz (THz) time domain spectroscopy (TDS) was assessed as a nondestructive evaluation technique for aircraft composites. Material properties of glass fiber composite were measured using both transmission and reflection configuration. The interaction of THz with a glass fiber composite was then analyzed, including the effects of scattering, absorption, and the index of refraction, as well as effective medium approximations. THz TDS, in both transmission and reflection configuration, was used to study composite damage, including voids, delaminations, mechanical damage, and heat damage. Measurement of the material properties on samples with localized heat damage showed that burning did not change the refractive index or absorption coefficient noticeably; however, material blistering was detected. Voids were located by THz TDS transmission and reflection imaging using amplitude and phase techniques. The depth of delaminations was measured via the timing of Fabry-Perot reflections after the main pulse. Evidence of bending stress damage and simulated hidden cracks was also detected with terahertz imaging. v First, I would like to thank my advisor, Lt Col Matt Bohn, for his guidance in this research, offering skillful advice with the laboratory experimental setup and providing expert scientific insight in helping me to resolve research issues. I would also like to thank Dr. Jim Blackshire of AFRL/RXLP for sponsoring this work and for providing us with representative aircraft composite samples which were essential to the research. In addition, I would like to thank Abel Nunez for his help with image processing and to Jeremy Johnson and AFRL/RXLP for the ultrasound and x-ray images. Thanks to Col Brent Richert and my parents for their encouragement to return to school and earn this degree and to my mother for helping to proofread this dissertation. I would like to thank Epiphany Lutheran Church for its spiritual support along the way. I am very grateful for the birth of my two children who have been an inspiration to me and represent promise for the future. Most of all, I would like to thank my wife for her patience and understanding during the difficult days and nights when I was studying, researching, and writing. I also thank her for her strength in enduring an uncomfortable work situation for 4 years.

Sensors and Actuators A-physical, Dec 1, 2008

Abstract Single-element interdigital transducers (IDTs) are designed, fabricated, and characteriz... more Abstract Single-element interdigital transducers (IDTs) are designed, fabricated, and characterized as a complimentary sensor approach for traditional ultrasonic transducers used in nondestructive testing (NDT). The frequency of interest is in the lower megahertz range, 2–10 MHz. In this paper, a simple five-finger paired IDT is described, where laser micro-machining techniques were used to shape the electrode patterns for an IDT resonance frequency of ∼3 MHz. Detailed characterization of the Rayleigh surface waves generated by the IDT is performed using a scanning laser interferometry system. Wave properties such as beam profile, beam divergence, energy decay, frequency response, and phase dependence are reported.

REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION: VOLUME 32, 2013

In an effort to evaluate the modulus of materials at elevated temperatures, an ultrasonic delay l... more In an effort to evaluate the modulus of materials at elevated temperatures, an ultrasonic delay line approach was developed. The setup was tested with a known material, an aluminum alloy, using delay lines at ambient temperature to examine the feasibility of this approach. Due to the low frequency used, interference occurred between multiple passes of the ultrasound through the material resulting a lower than expected measured velocity. Incorporation of a transmission coefficient in the model of the experiment corrected the expected timing of the ultrasonic signals, reconciling the model to measurements of velocity.

25th Plasmadynamics and Lasers Conference, Jun 20, 1994