The electromagnetic acoustic resonance (EMAR) method with shear wave is sensitive to boundary conditions and plate thickness. In this paper, a new noncontact ultrasonic testing method based on the electromagnetic acoustic transducer (EMAT) in the resonant mode is proposed for the bonding strength evaluation in metal-based adhesive structures. Different from the conventional pulse-echo method using short-burst excitation for bonding inspection, the attenuation coefficient feature of the resonant ultrasonic signal with long-burst excitation is applied to increase the signal-to-noise ratio (SNR) and detecting sensitivity of the EMAT for adhesive bonding strength evaluation. A theoretical model for adhesive bonding testing with EMAT signals in the resonant mode is established. To extract the signal feature representing the reflection coefficient, the time-domain signal was processed by Hilbert transformation and exponential curve fitting. Through the simulation on the received signal, the correlation between the attenuation coefficient of the exponent fitted curve and the strength on the adhesive imperfect interface were confirmed. Finally, the proposed correlation is verified by an experiment on stainless steel plates bonded with polymethyl methacrylate plates by epoxy adhesion via a permanent magnetic EMAT.
{"title":"Measurement of Adhesive Bonding Strength With an EMAT in the Resonant Mode","authors":"Tianhao Liu, Hai-qiang Zhou, C. Pei, Zhenmao Chen","doi":"10.1115/1.4044638","DOIUrl":"https://doi.org/10.1115/1.4044638","url":null,"abstract":"\u0000 The electromagnetic acoustic resonance (EMAR) method with shear wave is sensitive to boundary conditions and plate thickness. In this paper, a new noncontact ultrasonic testing method based on the electromagnetic acoustic transducer (EMAT) in the resonant mode is proposed for the bonding strength evaluation in metal-based adhesive structures. Different from the conventional pulse-echo method using short-burst excitation for bonding inspection, the attenuation coefficient feature of the resonant ultrasonic signal with long-burst excitation is applied to increase the signal-to-noise ratio (SNR) and detecting sensitivity of the EMAT for adhesive bonding strength evaluation. A theoretical model for adhesive bonding testing with EMAT signals in the resonant mode is established. To extract the signal feature representing the reflection coefficient, the time-domain signal was processed by Hilbert transformation and exponential curve fitting. Through the simulation on the received signal, the correlation between the attenuation coefficient of the exponent fitted curve and the strength on the adhesive imperfect interface were confirmed. Finally, the proposed correlation is verified by an experiment on stainless steel plates bonded with polymethyl methacrylate plates by epoxy adhesion via a permanent magnetic EMAT.","PeriodicalId":52294,"journal":{"name":"Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89253736","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}
R. James, M. Haider, V. Giurgiutiu, David Lilienthal
The manufacturing process of carbon fiber reinforced polymer (CFRP) composite structures can introduce many characteristic defects and flaws such as fiber misorientation, fiber waviness, and wrinkling. Therefore, it becomes increasingly important to detect the presence of these defects at the earliest stages of development. Eddy current testing (ECT) is a nondestructive inspection (NDI) technique that has been proven quite effective in detection of damage in metallic structures. However, NDI of composite structures has mainly relied on other methods such as ultrasonic testing (UT) and X-ray to name a few and not much on ECT. In this paper, the authors explore the possibility of using ECT in NDI of CFRP composites by conducting simulations and experiments thereafter. This research is based on the fact that the CFRP displays some low-level electrical conductivity due to the inherent conductivity of the carbon fibers. This low-level conductivity may permit eddy current pathways to cause the flow of eddy currents in the CFRP composites that can be exploited for nondestructive damage detection. An invention disclosure describing our high-frequency ECT method has also been processed. First, the multiphysics finite element method (FEM) simulation was used to simulate the detection of various types of manufacturing flaws and operational damage in CFRP composites such as fiber misorientation, waviness, wrinkling, and so on. Thereafter, ECT experiments were conducted on CFRP specimens with various manufacturing flaws using the Eddyfi Reddy eddy current array (ECA) system.
{"title":"A Simulative and Experimental Approach Toward Eddy Current Nondestructive Evaluation of Manufacturing Flaws and Operational Damage in CFRP Composites","authors":"R. James, M. Haider, V. Giurgiutiu, David Lilienthal","doi":"10.1115/1.4044722","DOIUrl":"https://doi.org/10.1115/1.4044722","url":null,"abstract":"\u0000 The manufacturing process of carbon fiber reinforced polymer (CFRP) composite structures can introduce many characteristic defects and flaws such as fiber misorientation, fiber waviness, and wrinkling. Therefore, it becomes increasingly important to detect the presence of these defects at the earliest stages of development. Eddy current testing (ECT) is a nondestructive inspection (NDI) technique that has been proven quite effective in detection of damage in metallic structures. However, NDI of composite structures has mainly relied on other methods such as ultrasonic testing (UT) and X-ray to name a few and not much on ECT. In this paper, the authors explore the possibility of using ECT in NDI of CFRP composites by conducting simulations and experiments thereafter. This research is based on the fact that the CFRP displays some low-level electrical conductivity due to the inherent conductivity of the carbon fibers. This low-level conductivity may permit eddy current pathways to cause the flow of eddy currents in the CFRP composites that can be exploited for nondestructive damage detection. An invention disclosure describing our high-frequency ECT method has also been processed. First, the multiphysics finite element method (FEM) simulation was used to simulate the detection of various types of manufacturing flaws and operational damage in CFRP composites such as fiber misorientation, waviness, wrinkling, and so on. Thereafter, ECT experiments were conducted on CFRP specimens with various manufacturing flaws using the Eddyfi Reddy eddy current array (ECA) system.","PeriodicalId":52294,"journal":{"name":"Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems","volume":"9 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2019-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84490162","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 aims to detect, localize, and assess the severity of barely visible indentation damage in a composite sandwich structure using ultrasonic guided waves. A quasistatic loading was gradually applied on a specimen of carbon fiber reinforced epoxy resulting in dents on the surface. Lamb-wave measurements, from a sensor network mounted on the panel's surface, were taken for the intact condition and three damage cases (0.2, 0.5, and 2.7-mm dents). Three approaches were adopted to define the damage indices (DIs) toward anomaly detection, namely, amplitude variation, symbolic dynamics, and root mean square deviation. Data fusion was performed between measurements from multiple excitation frequencies for single and multiple DIs, where the anomaly combination between all the frequencies and the DIs was called a total anomaly. An imaging algorithm was implemented for damage localization in conjunction with single and combined DIs. It was shown that combining the effects of different frequencies and/or different DIs increases the robustness and consistency of the damage detection and localization process. Moreover, a distance-based classification technique was applied using features from single DIs and the combined anomaly measure. Accuracies higher than 91% were attained for the majority of the cases tested.
{"title":"Robust Localization and Classification of Barely Visible Indentations in Composite Structures by Fusion of Ultrasonic Damage Indices","authors":"M. Fakih, S. Mustapha, A. Abdul-Aziz","doi":"10.1115/1.4044177","DOIUrl":"https://doi.org/10.1115/1.4044177","url":null,"abstract":"This study aims to detect, localize, and assess the severity of barely visible indentation damage in a composite sandwich structure using ultrasonic guided waves. A quasistatic loading was gradually applied on a specimen of carbon fiber reinforced epoxy resulting in dents on the surface. Lamb-wave measurements, from a sensor network mounted on the panel's surface, were taken for the intact condition and three damage cases (0.2, 0.5, and 2.7-mm dents). Three approaches were adopted to define the damage indices (DIs) toward anomaly detection, namely, amplitude variation, symbolic dynamics, and root mean square deviation. Data fusion was performed between measurements from multiple excitation frequencies for single and multiple DIs, where the anomaly combination between all the frequencies and the DIs was called a total anomaly. An imaging algorithm was implemented for damage localization in conjunction with single and combined DIs. It was shown that combining the effects of different frequencies and/or different DIs increases the robustness and consistency of the damage detection and localization process. Moreover, a distance-based classification technique was applied using features from single DIs and the combined anomaly measure. Accuracies higher than 91% were attained for the majority of the cases tested.","PeriodicalId":52294,"journal":{"name":"Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2019-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90427666","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}
Lingfeng Yang, Tonghai Wu, Kunpeng Wang, Hongkun Wu, N. Kwok
Online ferrography, because of its nondestructive and real-time capability, has been increasingly applied in monitoring machine wear states. However, online ferrography images are usually degraded as a result of undesirable image acquisition conditions, which eventually lead to inaccurate identifications. A restoration method focusing on color correction and contrast enhancement is developed to provide high-quality images for subsequent processing. Based on the formation of a degraded image, a model describing the degradation is constructed. Then, cost functions consisting of colorfulness, contrast, and information loss are formulated. An optimal restored image is obtained by minimizing the cost functions, in which parameters are properly determined using the Lagrange multiplier. Experiments are carried out on a collection of online ferrography images, and results show that the proposed method can effectively improve the image both qualitatively and quantitatively.
{"title":"Optimum Color and Contrast Enhancement for Online Ferrography Image Restoration","authors":"Lingfeng Yang, Tonghai Wu, Kunpeng Wang, Hongkun Wu, N. Kwok","doi":"10.1115/1.4044049","DOIUrl":"https://doi.org/10.1115/1.4044049","url":null,"abstract":"Online ferrography, because of its nondestructive and real-time capability, has been increasingly applied in monitoring machine wear states. However, online ferrography images are usually degraded as a result of undesirable image acquisition conditions, which eventually lead to inaccurate identifications. A restoration method focusing on color correction and contrast enhancement is developed to provide high-quality images for subsequent processing. Based on the formation of a degraded image, a model describing the degradation is constructed. Then, cost functions consisting of colorfulness, contrast, and information loss are formulated. An optimal restored image is obtained by minimizing the cost functions, in which parameters are properly determined using the Lagrange multiplier. Experiments are carried out on a collection of online ferrography images, and results show that the proposed method can effectively improve the image both qualitatively and quantitatively.","PeriodicalId":52294,"journal":{"name":"Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems","volume":"36 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2019-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73204590","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}
Max Ovenden, Qing Wang, Songling Huang, Wei Zhao, Shen Wang
Wind turbine (WT) blade structural health monitoring (SHM) is important as it allows damage or misalignment to be detected before it causes catastrophic damage such as that caused by the blade striking the tower. Both of these can be very costly and justify the expense of monitoring. This paper aims to deduce whether a SICK DT-50 laser displacement sensor (LDS) installed inside the tower and a half-bridge type II strain gauge bridge installed at the blade root are capable of detecting ice loading, misalignment, and bolt loosening while the WT is running. Blade faults were detected by the virtual instrument, which conducted a z-test at 99% and 98% significance levels for the LDS and at 99.5% and 99% significance levels for the strain gauge. The significance levels chosen correspond to typical Z-values for statistical tests. A higher significance was used for the strain gauge as it used a one-tail test as opposed to a two-tail test for the LDS. The two different tests were used to test for different sensitivities of the tests. The results show that the strain gauge was capable of detecting all the mass loading cases to 99.5% significance, and the LDS was capable of detecting misalignment, bolt loosening, and 3 out of 4 mass loading cases to 99% significance. It was able to detect the least severe mass loading case of 11 g at the root to only a 98% significance.
{"title":"Real-Time Monitoring of Wind Turbine Blade Alignment Using Laser Displacement and Strain Measurement","authors":"Max Ovenden, Qing Wang, Songling Huang, Wei Zhao, Shen Wang","doi":"10.1115/1.4043850","DOIUrl":"https://doi.org/10.1115/1.4043850","url":null,"abstract":"Wind turbine (WT) blade structural health monitoring (SHM) is important as it allows damage or misalignment to be detected before it causes catastrophic damage such as that caused by the blade striking the tower. Both of these can be very costly and justify the expense of monitoring. This paper aims to deduce whether a SICK DT-50 laser displacement sensor (LDS) installed inside the tower and a half-bridge type II strain gauge bridge installed at the blade root are capable of detecting ice loading, misalignment, and bolt loosening while the WT is running. Blade faults were detected by the virtual instrument, which conducted a z-test at 99% and 98% significance levels for the LDS and at 99.5% and 99% significance levels for the strain gauge. The significance levels chosen correspond to typical Z-values for statistical tests. A higher significance was used for the strain gauge as it used a one-tail test as opposed to a two-tail test for the LDS. The two different tests were used to test for different sensitivities of the tests. The results show that the strain gauge was capable of detecting all the mass loading cases to 99.5% significance, and the LDS was capable of detecting misalignment, bolt loosening, and 3 out of 4 mass loading cases to 99% significance. It was able to detect the least severe mass loading case of 11 g at the root to only a 98% significance.","PeriodicalId":52294,"journal":{"name":"Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems","volume":"5 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2019-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84444768","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}
Acoustic emission (AE) signals are recognized as complementary measures for detecting incipient faults and condition monitoring in rotary machinery due to their containment of sources of potential fault energy. However, determining the potential sources of faults cannot be easily realized due to the non-stationarity of AE signals. Available techniques that are capable of evoking instantaneous characteristics of a particular AE signal cannot optimally perform in a sense that there is no guarantee that these characteristics (hereinafter referred to as the “features”) remain constant when another AE signal is obtained from the system, albeit operating under the same machine condition at a different time instant. This paper provides a theoretical framework for developing a highly reliable classification and detection methodology for gas turbine condition monitoring based on AE signals. Mathematical results obtained in this paper are evaluated and validated by using actual gas turbines that are operating in power generating plants, to demonstrate the practicality and simplicity of our methodologies. Emphasis is given to acoustic emissions of similar brand and sized gas turbine turbomachinery under different health conditions and/or aging characteristics.
{"title":"Gas Turbine Condition Monitoring Using Acoustic Emission Signals","authors":"S. Shahkar, K. Khorasani","doi":"10.1115/1.4044232","DOIUrl":"https://doi.org/10.1115/1.4044232","url":null,"abstract":"Acoustic emission (AE) signals are recognized as complementary measures for detecting incipient faults and condition monitoring in rotary machinery due to their containment of sources of potential fault energy. However, determining the potential sources of faults cannot be easily realized due to the non-stationarity of AE signals. Available techniques that are capable of evoking instantaneous characteristics of a particular AE signal cannot optimally perform in a sense that there is no guarantee that these characteristics (hereinafter referred to as the “features”) remain constant when another AE signal is obtained from the system, albeit operating under the same machine condition at a different time instant. This paper provides a theoretical framework for developing a highly reliable classification and detection methodology for gas turbine condition monitoring based on AE signals. Mathematical results obtained in this paper are evaluated and validated by using actual gas turbines that are operating in power generating plants, to demonstrate the practicality and simplicity of our methodologies. Emphasis is given to acoustic emissions of similar brand and sized gas turbine turbomachinery under different health conditions and/or aging characteristics.","PeriodicalId":52294,"journal":{"name":"Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems","volume":"21 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2019-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82433290","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 article presents a numerical formulation and the experimental validation of the dynamic interaction between highly nonlinear solitary waves generated along a mono-periodic array of spherical particles and rails in a point contact with the array. A general finite element model of rails was developed and coupled to a discrete particle model able to predict the propagation of the solitary waves along a L-shaped array located perpendicular and in contact with the web of the rail. The models were validated experimentally by testing a 0.9-m long and a 2.4-m long rail segments subjected to compressive load. The scope of the study was the development of a new nondestructive evaluation technique able to estimate the stress in continuous welded rails and eventually to infer the temperature at which the longitudinal stress in the rail is zero. The numerical findings presented in this article demonstrate that certain features, such as the amplitude and time of flight, of the solitary waves are affected by the axial stress. The experimental results validated the numerical predictions and warrant the validation of the nondestructive evaluation system against real rails.
{"title":"Numerical Analysis and Experimental Validation of an Nondestructive Evaluation Method to Measure Stress in Rails","authors":"A. Nasrollahi, P. Rizzo","doi":"10.1115/1.4043949","DOIUrl":"https://doi.org/10.1115/1.4043949","url":null,"abstract":"This article presents a numerical formulation and the experimental validation of the dynamic interaction between highly nonlinear solitary waves generated along a mono-periodic array of spherical particles and rails in a point contact with the array. A general finite element model of rails was developed and coupled to a discrete particle model able to predict the propagation of the solitary waves along a L-shaped array located perpendicular and in contact with the web of the rail. The models were validated experimentally by testing a 0.9-m long and a 2.4-m long rail segments subjected to compressive load. The scope of the study was the development of a new nondestructive evaluation technique able to estimate the stress in continuous welded rails and eventually to infer the temperature at which the longitudinal stress in the rail is zero. The numerical findings presented in this article demonstrate that certain features, such as the amplitude and time of flight, of the solitary waves are affected by the axial stress. The experimental results validated the numerical predictions and warrant the validation of the nondestructive evaluation system against real rails.","PeriodicalId":52294,"journal":{"name":"Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems","volume":"11 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2019-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88602527","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}
E. Mohseni, C. Macleod, Y. Javadi, Z. Qiu, R. Vithanage, D. Lines, R. Zimermann, G. Pierce, A. Gachagan
Dual matrix transmit-receive longitudinal (TRL) arrays have been shown to provide an improved signal to noise ratio in the near field zone which makes them the most suitable array configuration for the inspection of near-surface defects. This study aims to compare the performance of different configurations for transmit-receive longitudinal matrix arrays. For this purpose, four matrix configurations of 2 × 32, 4 × 16, 4 × 32, and 8 × 16 elements are investigated using EXTENDE CIVA modeling package. The array operating frequencies investigated are either 5 MHz or 10 MHz. The effect of different natural focal depths, arrays separation distances, dynamic electronic depth focusing, and electronic beam skewing for these TRL arrays are considered in models prepared in CIVA. The inspection of a series of flat bottom holes extended up to a few millimeters under the surface using the selected TRL configurations is also investigated in the study. It is found that the performance of focusing for near-surface areas is more efficient using the 4 × 16 and 8 × 16 elements configurations as compared with the others, and the signal amplitudes of the defects located deeper in the target material are almost independent of the configuration.
{"title":"A Model-Based Study of Transmit-Receive Longitudinal Arrays for Inspection of Subsurface Defects","authors":"E. Mohseni, C. Macleod, Y. Javadi, Z. Qiu, R. Vithanage, D. Lines, R. Zimermann, G. Pierce, A. Gachagan","doi":"10.1115/1.4046718","DOIUrl":"https://doi.org/10.1115/1.4046718","url":null,"abstract":"\u0000 Dual matrix transmit-receive longitudinal (TRL) arrays have been shown to provide an improved signal to noise ratio in the near field zone which makes them the most suitable array configuration for the inspection of near-surface defects. This study aims to compare the performance of different configurations for transmit-receive longitudinal matrix arrays. For this purpose, four matrix configurations of 2 × 32, 4 × 16, 4 × 32, and 8 × 16 elements are investigated using EXTENDE CIVA modeling package. The array operating frequencies investigated are either 5 MHz or 10 MHz. The effect of different natural focal depths, arrays separation distances, dynamic electronic depth focusing, and electronic beam skewing for these TRL arrays are considered in models prepared in CIVA. The inspection of a series of flat bottom holes extended up to a few millimeters under the surface using the selected TRL configurations is also investigated in the study. It is found that the performance of focusing for near-surface areas is more efficient using the 4 × 16 and 8 × 16 elements configurations as compared with the others, and the signal amplitudes of the defects located deeper in the target material are almost independent of the configuration.","PeriodicalId":52294,"journal":{"name":"Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems","volume":"100 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2019-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80079649","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}
The current techniques in assessing the healing of a fixated fractured long bone, which include X-ray, computed tomography (CT), and manual manipulation, are qualitative and its accuracy depends on the surgeon's experience. A lack of a robust and quantitative monitoring method of fractured bone healing limits the survival of orthopedic implants and the ability to accurately predict and prevent fixation failure and complications. This paper experimentally and computationally investigates the efficacy and the potential application of a vibration-based quantitative monitoring methodology. This nonintrusive technique incorporates the cross-spectra response of externally placed sensors located remotely from the fractured region. In this study, the test specimens are composite femurs fixated with an intramedullary nail fixation system and the epoxy adhesive applied in the osteotomized region is used to simulate the healing process. Epoxies with a 30-min and 2 h gel time are used separately to investigate the sensitivity of this healing assessment technique. The findings highlight the key vibrational modes to establish the state of healing and the quantification evaluation of healing of fixated femurs based on a formulated healing index is also presented. This efficacy study seeks to verify the viability of this external measurement technique for human health monitoring and the future development of healing devices.
{"title":"Vibration-Based Healing Assessment of an Internally Fixated Femur","authors":"W. K. Chiu, B. Vien, M. Russ, M. Fitzgerald","doi":"10.1115/1.4043276","DOIUrl":"https://doi.org/10.1115/1.4043276","url":null,"abstract":"The current techniques in assessing the healing of a fixated fractured long bone, which include X-ray, computed tomography (CT), and manual manipulation, are qualitative and its accuracy depends on the surgeon's experience. A lack of a robust and quantitative monitoring method of fractured bone healing limits the survival of orthopedic implants and the ability to accurately predict and prevent fixation failure and complications. This paper experimentally and computationally investigates the efficacy and the potential application of a vibration-based quantitative monitoring methodology. This nonintrusive technique incorporates the cross-spectra response of externally placed sensors located remotely from the fractured region. In this study, the test specimens are composite femurs fixated with an intramedullary nail fixation system and the epoxy adhesive applied in the osteotomized region is used to simulate the healing process. Epoxies with a 30-min and 2 h gel time are used separately to investigate the sensitivity of this healing assessment technique. The findings highlight the key vibrational modes to establish the state of healing and the quantification evaluation of healing of fixated femurs based on a formulated healing index is also presented. This efficacy study seeks to verify the viability of this external measurement technique for human health monitoring and the future development of healing devices.","PeriodicalId":52294,"journal":{"name":"Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems","volume":"33 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2019-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74252732","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}
Elastodynamic Green's function for anisotropic solids is required for wave propagation modeling in composites. Such modeling is needed for the interpretation of experimental results generated by ultrasonic excitation or mechanical vibration-based nondestructive evaluation tests of composite structures. For isotropic materials, the elastodynamic Green’s function can be obtained analytically. However, for anisotropic solids, numerical integration is required for the elastodynamic Green's function computation. It can be expressed as a summation of two integrals—a singular integral and a nonsingular (or regular) integral. The regular integral over the surface of a unit hemisphere needs to be evaluated numerically and is responsible for the majority of the computational time for the elastodynamic Green's function calculation. In this paper, it is shown that for transversely isotropic solids, which form a major portion of anisotropic materials, the integration domain of the regular part of the elastodynamic time-harmonic Green's function can be reduced from a hemisphere to a quarter-sphere. The analysis is performed in the frequency domain by considering time-harmonic Green's function. This improvement is then applied to a numerical example where it is shown that it nearly halves the computational time. This reduction in computational effort is important for a boundary element method and a distributed point source method whose computational efficiencies heavily depend on Green's function computational time.
{"title":"An Improved Technique for Elastodynamic Green's Function Computation for Transversely Isotropic Solids","authors":"Samaneh Fooladi, T. Kundu","doi":"10.1115/1.4043605","DOIUrl":"https://doi.org/10.1115/1.4043605","url":null,"abstract":"Elastodynamic Green's function for anisotropic solids is required for wave propagation modeling in composites. Such modeling is needed for the interpretation of experimental results generated by ultrasonic excitation or mechanical vibration-based nondestructive evaluation tests of composite structures. For isotropic materials, the elastodynamic Green’s function can be obtained analytically. However, for anisotropic solids, numerical integration is required for the elastodynamic Green's function computation. It can be expressed as a summation of two integrals—a singular integral and a nonsingular (or regular) integral. The regular integral over the surface of a unit hemisphere needs to be evaluated numerically and is responsible for the majority of the computational time for the elastodynamic Green's function calculation. In this paper, it is shown that for transversely isotropic solids, which form a major portion of anisotropic materials, the integration domain of the regular part of the elastodynamic time-harmonic Green's function can be reduced from a hemisphere to a quarter-sphere. The analysis is performed in the frequency domain by considering time-harmonic Green's function. This improvement is then applied to a numerical example where it is shown that it nearly halves the computational time. This reduction in computational effort is important for a boundary element method and a distributed point source method whose computational efficiencies heavily depend on Green's function computational time.","PeriodicalId":52294,"journal":{"name":"Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2019-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82818834","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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