Yang Nan, Maoling Yue, Haodong Fan, Fei Du, L. Wen, Chao Xu
Composite materials have been widely used in aerospace manufacturing because of their low mass, high specific strength, high specific stiffness and good fatigue resistance. However, composite structures are susceptible to damage such as debonding and delamination due to various impacts, vibrations and other external loads. Therefore, it is crucial to regularly monitor composite structures in real-time during spacecraft service to ensure the safety and reliability of the structures. Ultrasonic guided wave is an effective means of monitoring the health of composite plate structures. Delamination, debonding and other damages of composite materials can be imaged and localized using ultrasonic guided wave signals and probabilistic imaging methods. However, due to the large damping of composite materials, the traditional probabilistic imaging method has the problem of low accuracy in damage localization. Therefore, in this paper, we propose a probabilistic imaging method based on a modified time reversal for damage localization and imaging of delamination damage. The proposed method was experimentally validated using a composite plate as a test piece and compared with the conventional method. A fully automated falling hammer impact tester was used to create low-velocity impact damage on specimens to compare the localization accuracy of the time-free reverse method and the modified time reversal method for delamination damage. The results show that the modified time reversal method can better localize and image the delamination damage of composite structures with higher localization accuracy and more sensitive to damage, which verifies the feasibility and accuracy of the method in the localization of debonding damage of composite structures.
{"title":"A Modified Time Reversal Based Probabilistic Imaging Method for Composite Plate Delamination Detection","authors":"Yang Nan, Maoling Yue, Haodong Fan, Fei Du, L. Wen, Chao Xu","doi":"10.1115/imece2022-94805","DOIUrl":"https://doi.org/10.1115/imece2022-94805","url":null,"abstract":"\u0000 Composite materials have been widely used in aerospace manufacturing because of their low mass, high specific strength, high specific stiffness and good fatigue resistance. However, composite structures are susceptible to damage such as debonding and delamination due to various impacts, vibrations and other external loads. Therefore, it is crucial to regularly monitor composite structures in real-time during spacecraft service to ensure the safety and reliability of the structures. Ultrasonic guided wave is an effective means of monitoring the health of composite plate structures. Delamination, debonding and other damages of composite materials can be imaged and localized using ultrasonic guided wave signals and probabilistic imaging methods. However, due to the large damping of composite materials, the traditional probabilistic imaging method has the problem of low accuracy in damage localization. Therefore, in this paper, we propose a probabilistic imaging method based on a modified time reversal for damage localization and imaging of delamination damage. The proposed method was experimentally validated using a composite plate as a test piece and compared with the conventional method. A fully automated falling hammer impact tester was used to create low-velocity impact damage on specimens to compare the localization accuracy of the time-free reverse method and the modified time reversal method for delamination damage. The results show that the modified time reversal method can better localize and image the delamination damage of composite structures with higher localization accuracy and more sensitive to damage, which verifies the feasibility and accuracy of the method in the localization of debonding damage of composite structures.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88114455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Helium recovery systems require multiple compressors, fans, valves and other mechanical components which are likely to radiate considerable sound to the outdoor environment. To assure compliance with a local residential noise ordinance prior to installation, sound propagation effects were investigated at the future site of a helium recovery system in State College, PA. Sound pressure spectra from a baffled acoustic source were measured at distances of 1 meter to 50 meters away from the planned installation location, and the pressure spectra were found to collapse reasonably well with distance using simple spherical spreading principles. This scaling was then applied to sound pressure spectra acquired from a representative helium recovery system located at the manufacturer’s plant in Box Elder, South Dakota. The overall sound pressure level (OASPL) from the dominant noise source on the representative system (i.e. the compressor exhaust) was measured at 1 meter and scaled to the residential property line located approximately 50 meters away from the future State College, PA site. The predicted OASPL for the new system at the residential property line was 61 dBA, which is 6 dBA above the local township noise ordinance requirement of 55 dBA. Noise control efforts are currently being considered and include the installation of an acoustic attenuator at the compressor exhaust location to reduce the overall noise level.
{"title":"Cold Spray Helium Recovery System Noise Study","authors":"S. Young, T. Brungart, Michael L. Jonson","doi":"10.1115/imece2022-95767","DOIUrl":"https://doi.org/10.1115/imece2022-95767","url":null,"abstract":"\u0000 Helium recovery systems require multiple compressors, fans, valves and other mechanical components which are likely to radiate considerable sound to the outdoor environment. To assure compliance with a local residential noise ordinance prior to installation, sound propagation effects were investigated at the future site of a helium recovery system in State College, PA. Sound pressure spectra from a baffled acoustic source were measured at distances of 1 meter to 50 meters away from the planned installation location, and the pressure spectra were found to collapse reasonably well with distance using simple spherical spreading principles. This scaling was then applied to sound pressure spectra acquired from a representative helium recovery system located at the manufacturer’s plant in Box Elder, South Dakota. The overall sound pressure level (OASPL) from the dominant noise source on the representative system (i.e. the compressor exhaust) was measured at 1 meter and scaled to the residential property line located approximately 50 meters away from the future State College, PA site. The predicted OASPL for the new system at the residential property line was 61 dBA, which is 6 dBA above the local township noise ordinance requirement of 55 dBA. Noise control efforts are currently being considered and include the installation of an acoustic attenuator at the compressor exhaust location to reduce the overall noise level.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84291067","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Several techniques are currently used for the noncontact thickness mapping of thin-walled structures, which include laser contour mapping and electrical capacitance measurement, but very few methods are available when one side of the structure is not accessible. A popular technique when only one side of the structure is accessible is the use of ultrasonics in either a resonance approach or a through transmission approach. This study will focus on the use of the through transition approach using ultrasonic guided waves transmitted and received by Electro Magnetic Acoustic Transducers (EMATs) in thin aluminum and steel plates. To validate results a Fourier analysis was preformed verifying thickness resonant frequencies predicted by dispersion curves. Because the medium is a thin plate, symmetric and antisymmetric Lamb waves as well as shear horizontal waves are the candidates for analysis in the thickness measurements. The EMATs are used for both transmission and reception of guided waves of different types. The major challenge with this type of transducers is power requirement which is achieved with the high-power ultrasonic pulse generator and a transformer circuit. The temporal difference in transmitted and received signals of various wave types were used to calculate the average ultrasonic speed of propagation in several regions of the plates. The speed of propagation is a function of plate thickness as well as several physical parameters, allowing an average thickness to be calculated over the path of the guided waves. These values can then used to produce a map of the thickness over the entire structure as a precursor to the identification and localization of damage in thin-walled structures such as large scratches, corrosion pitting, and holes. If further quantization of plate thickness is desirable, the guided waves can be explored in several orientations allowing for a finer map of sound speeds over the plate to be created. Guided wave thickness calculations where preformed on both steel and aluminum plates proving the validity of the approach to both ferrous and non-ferrous metals while providing accuracy and precision values for the methodology and hardware used. This is in preparation for future work detecting both uniform and pitting type corrosion using similar techniques.
{"title":"Characterization of Aluminum and Steel Thin Plates Using Electromagnetic Acoustic Transducers","authors":"Lukas Peterson, Andrei N. Zagrai","doi":"10.1115/imece2022-96395","DOIUrl":"https://doi.org/10.1115/imece2022-96395","url":null,"abstract":"Several techniques are currently used for the noncontact thickness mapping of thin-walled structures, which include laser contour mapping and electrical capacitance measurement, but very few methods are available when one side of the structure is not accessible. A popular technique when only one side of the structure is accessible is the use of ultrasonics in either a resonance approach or a through transmission approach. This study will focus on the use of the through transition approach using ultrasonic guided waves transmitted and received by Electro Magnetic Acoustic Transducers (EMATs) in thin aluminum and steel plates. To validate results a Fourier analysis was preformed verifying thickness resonant frequencies predicted by dispersion curves. Because the medium is a thin plate, symmetric and antisymmetric Lamb waves as well as shear horizontal waves are the candidates for analysis in the thickness measurements. The EMATs are used for both transmission and reception of guided waves of different types. The major challenge with this type of transducers is power requirement which is achieved with the high-power ultrasonic pulse generator and a transformer circuit. The temporal difference in transmitted and received signals of various wave types were used to calculate the average ultrasonic speed of propagation in several regions of the plates. The speed of propagation is a function of plate thickness as well as several physical parameters, allowing an average thickness to be calculated over the path of the guided waves. These values can then used to produce a map of the thickness over the entire structure as a precursor to the identification and localization of damage in thin-walled structures such as large scratches, corrosion pitting, and holes. If further quantization of plate thickness is desirable, the guided waves can be explored in several orientations allowing for a finer map of sound speeds over the plate to be created. Guided wave thickness calculations where preformed on both steel and aluminum plates proving the validity of the approach to both ferrous and non-ferrous metals while providing accuracy and precision values for the methodology and hardware used. This is in preparation for future work detecting both uniform and pitting type corrosion using similar techniques.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79173118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a systematic numerical research on ultrasonic phased array reverse time migration technique for damage evaluation in bulk materials. In this study, a thick aluminum bulk is used as the target structure to be tested, and an ultrasonic phased array composed of piezoelectric elements and damping blocks is prosed as the transducers for generating and receiving elastic waves. Firstly, a Finite Element Model (FEM) of a pair of transducers is established to study the wave generation and reception performance. In particular, the suppression effect of different backing material parameters (damping ratio, thickness, implementation details) on the piezo-elements to absorb excessive resonant vibrations is investigated, in order to send out and receive spatially squeezed mechanical pulses into the target medium. Then, a full-scale FEM is established with the complete probe set and typical structural damage types to understand the wave propagation and its interaction with damage. Both longitudinal (L) and shear (S) waves are studied, while they interact with a hole and cracks with different orientations with respect to the incident wave direction. Finally, the reverse time migration algorithm is further developed by considering the spatial wave characteristics. The amplitude variation along the propagation distance is taken into account to form a time/space-gain compensation function to improve the damage imaging quality and sensitivity, especially for far field damage sites. At the same time, the imaging algorithm is tested for the single L-wave, the single S-wave, and the fused LS-wave scenarios. It was found that the combination of L-mode and S-mode can significantly improve the damage imaging results. This numerical investigation may lay a solid foundation for the development of ultrasonic phased array technique for non-destructive evaluation (NDE) of bulky materials. This paper ends with a summary, concluding remarks, and suggestions for future work.
{"title":"Numerical Investigation of Ultrasonic Phased Array Reverse Time Migration Technique Considering Spatial Wave Characteristics","authors":"Shulong Zhou, Yanfeng Shen","doi":"10.1115/imece2022-94931","DOIUrl":"https://doi.org/10.1115/imece2022-94931","url":null,"abstract":"\u0000 This paper presents a systematic numerical research on ultrasonic phased array reverse time migration technique for damage evaluation in bulk materials. In this study, a thick aluminum bulk is used as the target structure to be tested, and an ultrasonic phased array composed of piezoelectric elements and damping blocks is prosed as the transducers for generating and receiving elastic waves. Firstly, a Finite Element Model (FEM) of a pair of transducers is established to study the wave generation and reception performance. In particular, the suppression effect of different backing material parameters (damping ratio, thickness, implementation details) on the piezo-elements to absorb excessive resonant vibrations is investigated, in order to send out and receive spatially squeezed mechanical pulses into the target medium. Then, a full-scale FEM is established with the complete probe set and typical structural damage types to understand the wave propagation and its interaction with damage. Both longitudinal (L) and shear (S) waves are studied, while they interact with a hole and cracks with different orientations with respect to the incident wave direction. Finally, the reverse time migration algorithm is further developed by considering the spatial wave characteristics. The amplitude variation along the propagation distance is taken into account to form a time/space-gain compensation function to improve the damage imaging quality and sensitivity, especially for far field damage sites. At the same time, the imaging algorithm is tested for the single L-wave, the single S-wave, and the fused LS-wave scenarios. It was found that the combination of L-mode and S-mode can significantly improve the damage imaging results. This numerical investigation may lay a solid foundation for the development of ultrasonic phased array technique for non-destructive evaluation (NDE) of bulky materials. This paper ends with a summary, concluding remarks, and suggestions for future work.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89492668","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Junkai Tong, Min Lin, Jian Li, Xiaocen Wang, Guoan Chu, Yang Liu
Quantitatively measuring the health status of mechanical structures is a long-standing challenge in industrial fields. For plate structure inspection in tank and pressure vessels, traditional techniques using point by point scan with probes are tedious and time-consuming. Although algorithms like full waveform inversion (FWI) and diffraction tomography (DT) provide solutions to the problems, those methods are slow and suffer from convergence problems. In this article, we provided an effective damage imaging technique using dispersive A0 mode Lamb guided wave and an inversion algorithm called DLIS. The proposed algorithm adopts convolutional neural network (CNN) as first iteration to provide a fast and low-resolution background, and further optimizes the inversion results with descent direction matrix. In this way, the nonlinearity of the problem is effectively decomposed and yields better results. To test the robustness of the proposed method, we generated 1000 samples consists of corrosion defects with various sizes and shapes using 2D acoustic wave modeling. The inversion results prove the feasibility of our approach in plate heath monitoring and inspections. Note that this method also has full potential to be applied in the fast inspection of plates made of composite materials, pipes, geophysical prospecting and medical imaging because all these inverse problems share similar physics.
{"title":"Fast and Robust Damage Imaging With a Cascaded Deep Learning Technique","authors":"Junkai Tong, Min Lin, Jian Li, Xiaocen Wang, Guoan Chu, Yang Liu","doi":"10.1115/imece2022-96652","DOIUrl":"https://doi.org/10.1115/imece2022-96652","url":null,"abstract":"\u0000 Quantitatively measuring the health status of mechanical structures is a long-standing challenge in industrial fields. For plate structure inspection in tank and pressure vessels, traditional techniques using point by point scan with probes are tedious and time-consuming. Although algorithms like full waveform inversion (FWI) and diffraction tomography (DT) provide solutions to the problems, those methods are slow and suffer from convergence problems. In this article, we provided an effective damage imaging technique using dispersive A0 mode Lamb guided wave and an inversion algorithm called DLIS. The proposed algorithm adopts convolutional neural network (CNN) as first iteration to provide a fast and low-resolution background, and further optimizes the inversion results with descent direction matrix. In this way, the nonlinearity of the problem is effectively decomposed and yields better results. To test the robustness of the proposed method, we generated 1000 samples consists of corrosion defects with various sizes and shapes using 2D acoustic wave modeling. The inversion results prove the feasibility of our approach in plate heath monitoring and inspections. Note that this method also has full potential to be applied in the fast inspection of plates made of composite materials, pipes, geophysical prospecting and medical imaging because all these inverse problems share similar physics.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81023075","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yilin Yuan, G. Shen, F. Xie, Junjiao Zhang, Pengcheng Gan, Yongna Shen, Kuan Su
It is a challenging task to understand the damage and failure of ring glass-epoxy composites after ultraviolet aging in practical application. In this paper, acoustic emission (AE) and X-ray computed tomography techniques are employed to study its damage and failure behavior under circumferential tensile loading. The results show that the additional bending effect can’t be overcome when the specimen is stretched, so the strength test is only an apparent result. With the increase of aging time, the number of AE events gradually decreases, but the accumulated acoustic energy increases, which indicates that the longer the aging time, the more severe the damage during loading. The distribution of failure modes caused by circumferential mechanical properties test of specimens can be characterized by X-ray computed technology. In addition, the two complementary nondestructive testing techniques can effectively monitor the damage process inside and outside the specimen, which can provide the basis for the health monitoring of composite structures.
{"title":"Acoustic Emission Detection of Circumferential UV-Mechanical Failure of Glass Epoxy Composites","authors":"Yilin Yuan, G. Shen, F. Xie, Junjiao Zhang, Pengcheng Gan, Yongna Shen, Kuan Su","doi":"10.1115/imece2022-95365","DOIUrl":"https://doi.org/10.1115/imece2022-95365","url":null,"abstract":"\u0000 It is a challenging task to understand the damage and failure of ring glass-epoxy composites after ultraviolet aging in practical application. In this paper, acoustic emission (AE) and X-ray computed tomography techniques are employed to study its damage and failure behavior under circumferential tensile loading. The results show that the additional bending effect can’t be overcome when the specimen is stretched, so the strength test is only an apparent result. With the increase of aging time, the number of AE events gradually decreases, but the accumulated acoustic energy increases, which indicates that the longer the aging time, the more severe the damage during loading. The distribution of failure modes caused by circumferential mechanical properties test of specimens can be characterized by X-ray computed technology. In addition, the two complementary nondestructive testing techniques can effectively monitor the damage process inside and outside the specimen, which can provide the basis for the health monitoring of composite structures.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81940387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Aktharuzzaman, Shoaib Anwar, D. Borisov, J. Rao, Jiaze He
Adequate knowledge of the materials through characterization during the development, production, and processing of the material is required for quality assurance and in-service safety. Material characterization involves the evaluation of properties such as elastic coefficients, material microstructures, morphological features, and associated mechanical properties. Ultrasonic signals are sensitive to useful acoustic properties, including wave speeds, attenuation, diffusion backscattering, variations in microstructure, and elastic properties (e.g., elastic modulus, hardness, etc.). To obtain a quantitative estimation of the material properties, an emerging imaging technique known as ultrasound computed tomography (USCT) can be utilized. This paper proposes to map the wave speeds (i.e., longitudinal and shear) inside elastic parts employing a wave-based methodology (known as full waveform inversion (FWI)) for USCT. FWI is a partial differential equation-constraint, nonlinear optimization technique. It is based on full wavefield modeling and inversion to extract material parameter distribution using wave equations. FWI consequently produces high-resolution images by iteratively determining and minimizing a waveform residual, which is the difference between the modeled and the observed signals. The performance of FWI based ultrasound tomography in material property reconstruction in numerical studies has been presented. The results show its application potential in nondestructive material characterization.
{"title":"2D Numerical Ultrasound Computed Tomography for Elastic Material Properties in Metals","authors":"M. Aktharuzzaman, Shoaib Anwar, D. Borisov, J. Rao, Jiaze He","doi":"10.1115/imece2022-90232","DOIUrl":"https://doi.org/10.1115/imece2022-90232","url":null,"abstract":"\u0000 Adequate knowledge of the materials through characterization during the development, production, and processing of the material is required for quality assurance and in-service safety. Material characterization involves the evaluation of properties such as elastic coefficients, material microstructures, morphological features, and associated mechanical properties. Ultrasonic signals are sensitive to useful acoustic properties, including wave speeds, attenuation, diffusion backscattering, variations in microstructure, and elastic properties (e.g., elastic modulus, hardness, etc.). To obtain a quantitative estimation of the material properties, an emerging imaging technique known as ultrasound computed tomography (USCT) can be utilized. This paper proposes to map the wave speeds (i.e., longitudinal and shear) inside elastic parts employing a wave-based methodology (known as full waveform inversion (FWI)) for USCT. FWI is a partial differential equation-constraint, nonlinear optimization technique. It is based on full wavefield modeling and inversion to extract material parameter distribution using wave equations. FWI consequently produces high-resolution images by iteratively determining and minimizing a waveform residual, which is the difference between the modeled and the observed signals. The performance of FWI based ultrasound tomography in material property reconstruction in numerical studies has been presented. The results show its application potential in nondestructive material characterization.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80884318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A method for adapting least-squares reverse time migration (LSRTM) for ultrasonic guided wave imaging of composite laminates is proposed in this paper. As composites become more widely used in fields such as the aerospace industry, the need for high resolution imaging in structural health monitoring (SHM) and nondestructive evaluation (NDE) is also growing. For instance, delamination is a common problem in composite laminates, which has led to a certain degree of apprehension in the use of composite materials for load-bearing structures. Although the solver-based imaging techniques using conventional reverse time migration (RTM) methods illuminate damage with a wide range of damage-scattering effects, the resulted images do not fully define the damage regions due to the limited data acquisition aperture, sensor density, frequencies/wavelengths, and incompleteness of adjoint reconstruction. Previously, we have derived the LSRTM theory and benchmarked its high-resolution damage imaging performance for isotropic plates. To improve damage imaging in composite laminates, this paper proposes to create an ultrasonic guided wave-based LSRTM method for anisotropic materials. The derivation of the forward modeling operator and the adjoint operator is presented. Numerical case studies were conducted to show the improvement of LSRTM over RTM in mapping damage in composite plates. Multiple damage sites or damage with a complex shape were created in the numerical studies based on Born approximation-based modeling.
{"title":"Guided Wave Damage Imaging of Composite Laminates With Least-Squares Reverse-Time Migration (LSRTM)","authors":"Jiaze He, A. Schwarberg","doi":"10.1115/imece2022-90231","DOIUrl":"https://doi.org/10.1115/imece2022-90231","url":null,"abstract":"\u0000 A method for adapting least-squares reverse time migration (LSRTM) for ultrasonic guided wave imaging of composite laminates is proposed in this paper. As composites become more widely used in fields such as the aerospace industry, the need for high resolution imaging in structural health monitoring (SHM) and nondestructive evaluation (NDE) is also growing. For instance, delamination is a common problem in composite laminates, which has led to a certain degree of apprehension in the use of composite materials for load-bearing structures. Although the solver-based imaging techniques using conventional reverse time migration (RTM) methods illuminate damage with a wide range of damage-scattering effects, the resulted images do not fully define the damage regions due to the limited data acquisition aperture, sensor density, frequencies/wavelengths, and incompleteness of adjoint reconstruction. Previously, we have derived the LSRTM theory and benchmarked its high-resolution damage imaging performance for isotropic plates. To improve damage imaging in composite laminates, this paper proposes to create an ultrasonic guided wave-based LSRTM method for anisotropic materials. The derivation of the forward modeling operator and the adjoint operator is presented. Numerical case studies were conducted to show the improvement of LSRTM over RTM in mapping damage in composite plates. Multiple damage sites or damage with a complex shape were created in the numerical studies based on Born approximation-based modeling.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78746015","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study proposes a novel general-purpose 3D continuously scanning laser Doppler vibrometer (CSLDV) system to measure 3D full-field vibration of a structure with a curved surface in a non-contact and fast way. The proposed 3D CSLDV system consists of three CSLDVs, a profile scanner, and an external controller, and is experimentally validated by measuring 3D full-field vibration of a turbine blade with a curved surface under sinusoidal excitation and identifying its operating deflection shapes (ODSs). A 3D zig-zag scan path is proposed for scanning the curved surface of the blade based on results from the profile scanner, and 6scan angles of mirrors in CSLDVs are adjusted based on relations among their laser beams to focus three laser spots at one location, and direct them to continuously and synchronously scan the proposed 3D scan path. A signal processing method that is referred to as the demodulation method is used to identify 3D ODSs of the blade. The first six ODSs from 3D CSLDV measurement have good agreement with those from a commercial 3D SLDV system with modal assurance criterion values larger than 95%. In the experiment, it took the 3D SLDV system about 900 seconds to scan 85 measurement points, and the 3D CSLDV system 115.5 seconds to scan 132,000 points, indicating that the 3D CSLDV system proposed in this study is much more efficient than the 3D SLDV system for measuring 3D full-field vibration of a structure with a curved surface.
{"title":"Full-Field Operating Deflection Shape Measurement of a Structure With a Curved Surface Using a Three-Dimensional Continuously Scanning Laser Doppler Vibrometer System","authors":"K. Yuan, Wei-dong Zhu","doi":"10.1115/imece2022-94706","DOIUrl":"https://doi.org/10.1115/imece2022-94706","url":null,"abstract":"\u0000 This study proposes a novel general-purpose 3D continuously scanning laser Doppler vibrometer (CSLDV) system to measure 3D full-field vibration of a structure with a curved surface in a non-contact and fast way. The proposed 3D CSLDV system consists of three CSLDVs, a profile scanner, and an external controller, and is experimentally validated by measuring 3D full-field vibration of a turbine blade with a curved surface under sinusoidal excitation and identifying its operating deflection shapes (ODSs). A 3D zig-zag scan path is proposed for scanning the curved surface of the blade based on results from the profile scanner, and 6scan angles of mirrors in CSLDVs are adjusted based on relations among their laser beams to focus three laser spots at one location, and direct them to continuously and synchronously scan the proposed 3D scan path. A signal processing method that is referred to as the demodulation method is used to identify 3D ODSs of the blade. The first six ODSs from 3D CSLDV measurement have good agreement with those from a commercial 3D SLDV system with modal assurance criterion values larger than 95%. In the experiment, it took the 3D SLDV system about 900 seconds to scan 85 measurement points, and the 3D CSLDV system 115.5 seconds to scan 132,000 points, indicating that the 3D CSLDV system proposed in this study is much more efficient than the 3D SLDV system for measuring 3D full-field vibration of a structure with a curved surface.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89338684","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A combustion oscillation experiment showed combustion oscillation frequencies of around 350 Hz when only natural gas was used as fuel and approximately 200 and 400 Hz when a hydrogen–natural gas mixture was used. To analyze the resonant frequency, two- and four-region models considering unburned and burned regions of the combustor were developed. The experimental frequencies of the 100% natural gas condition were successfully predicted. Conversely, the experimentally observed frequencies under the hydrogen–natural gas condition were not accurately predicted. A swirler-combustor model was then constructed to get closer to the actual configuration and shape of the experimental setup. However, the model could not reproduce the experimental value under the hydrogen–natural gas condition. A whole piping model was then developed by adding a casing and an air supply pipe to the combustor. The resonant frequencies under both the 100% natural gas and hydrogen–natural gas conditions were successfully calculated. The model reproduced the range and change tendency of the experimentally measured oscillation frequency.
{"title":"Examination of Resonant Frequencies Generated by Combustion Oscillation in a Combustor Fueled by a Hydrogen-Natural Gas Mixture and an Upstream Pipe","authors":"A. Uemichi, Yifan Lyu, Jin Kusaka, S. Kaneko","doi":"10.1115/imece2021-68521","DOIUrl":"https://doi.org/10.1115/imece2021-68521","url":null,"abstract":"\u0000 A combustion oscillation experiment showed combustion oscillation frequencies of around 350 Hz when only natural gas was used as fuel and approximately 200 and 400 Hz when a hydrogen–natural gas mixture was used. To analyze the resonant frequency, two- and four-region models considering unburned and burned regions of the combustor were developed. The experimental frequencies of the 100% natural gas condition were successfully predicted. Conversely, the experimentally observed frequencies under the hydrogen–natural gas condition were not accurately predicted. A swirler-combustor model was then constructed to get closer to the actual configuration and shape of the experimental setup. However, the model could not reproduce the experimental value under the hydrogen–natural gas condition. A whole piping model was then developed by adding a casing and an air supply pipe to the combustor. The resonant frequencies under both the 100% natural gas and hydrogen–natural gas conditions were successfully calculated. The model reproduced the range and change tendency of the experimentally measured oscillation frequency.","PeriodicalId":23648,"journal":{"name":"Volume 1: Acoustics, Vibration, and Phononics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75195704","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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