Probability of detection (POD) evaluation is a widely accepted practice for quantifying the reliability of a nondestructive testing (NDT) technique. Inspections are often conceptualized and developed in laboratory environments, where factors affecting the inspection are highly controlled. However, when implemented in practice, NDT inspections suffer from many sources of variability, including changes from nominal geometry of the test piece, sensor variability, differences between operators, environmental effects on the sensor response including thermal and electromagnetic interference, and a myriad of other factors that are not present in the lab. Thus, to transition the NDT from the lab to production environments, engineers must have a quantified understanding of uncertainties. This is especially true for NDT systems that are implemented for safety-critical structures, where the life of the component may be managed with NDT. A fundamental question that must be answered in this context is: What is the largest discontinuity that could be missed when this NDT technique is implemented?
{"title":"What Is Probability of Detection?","authors":"M. Cherry, Christine E. Knott","doi":"10.32548/2022.me-04324","DOIUrl":"https://doi.org/10.32548/2022.me-04324","url":null,"abstract":"Probability of detection (POD) evaluation is a widely accepted practice for quantifying the reliability of a nondestructive testing (NDT) technique. Inspections are often conceptualized and developed in laboratory environments, where factors affecting the inspection are highly controlled. However, when implemented in practice, NDT inspections suffer from many sources of variability, including changes from nominal geometry of the test piece, sensor variability, differences between operators, environmental effects on the sensor response including thermal and electromagnetic interference, and a myriad of other factors that are not present in the lab. Thus, to transition the NDT from the lab to production environments, engineers must have a quantified understanding of uncertainties. This is especially true for NDT systems that are implemented for safety-critical structures, where the life of the component may be managed with NDT. A fundamental question that must be answered in this context is: What is the largest discontinuity that could be missed when this NDT technique is implemented?","PeriodicalId":49876,"journal":{"name":"Materials Evaluation","volume":"1 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41454340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Siyuan Fang, Xiaowan Zheng, Bicheng Guo, Danielle Zen, Lianxiang Yang
Composite materials are widely used in engineering because of their high strength, high modulus, and corrosion resistance. Accurately obtaining the mechanical properties of composites is helpful for their further development. However, in a uniaxial tensile test, the strain distribution between the front and back of the composite sheet sample may differ due to its heterogeneity, and its stress-strain curve depends on which side the strain is measured. To report the stress-strain curve more accurately, a multicamera digital image correlation (DIC) system was employed to measure the double-sided strain in this work. Two sets of 3D digital image correlation (3D-DIC) systems were placed in front of and behind the specimen to record the tensile process of the specimen, and a double-sided calibration technique was implemented to connect the two sets of 3D-DIC systems into a unified coordinate system. Young’s modulus, percent bending, and local strain history are analyzed based on the measurements of strain on both sides. The results show that the strain on both sides of the composite is not exactly same, especially in the strain concentration area. As a comparison, the strain distribution on both sides of the metal material is almost identical.
{"title":"Experimental Investigation of Double-Sided Strain of Composites in Tensile Testing Using MultiCamera DIC","authors":"Siyuan Fang, Xiaowan Zheng, Bicheng Guo, Danielle Zen, Lianxiang Yang","doi":"10.32548/2022.me-04283","DOIUrl":"https://doi.org/10.32548/2022.me-04283","url":null,"abstract":"Composite materials are widely used in engineering because of their high strength, high modulus, and corrosion resistance. Accurately obtaining the mechanical properties of composites is helpful for their further development. However, in a uniaxial tensile test, the strain distribution between the front and back of the composite sheet sample may differ due to its heterogeneity, and its stress-strain curve depends on which side the strain is measured. To report the stress-strain curve more accurately, a multicamera digital image correlation (DIC) system was employed to measure the double-sided strain in this work. Two sets of 3D digital image correlation (3D-DIC) systems were placed in front of and behind the specimen to record the tensile process of the specimen, and a double-sided calibration technique was implemented to connect the two sets of 3D-DIC systems into a unified coordinate system. Young’s modulus, percent bending, and local strain history are analyzed based on the measurements of strain on both sides. The results show that the strain on both sides of the composite is not exactly same, especially in the strain concentration area. As a comparison, the strain distribution on both sides of the metal material is almost identical.","PeriodicalId":49876,"journal":{"name":"Materials Evaluation","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46524726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Environmental barrier coatings (EBCs) are used as a coating material on fiber-reinforced ceramic matrix composites (CMC) for various aerospace and turbine engines applications. In order to validate physics-based analytical models for predicting the spallation life of EBCs, the fracture strength of the EBC and the kinetics of crack growth in EBC layers need to be experimentally determined under engine operating conditions. In this study, a coating layer of barium strontium aluminum silicate (BSAS)–based melt-infiltrated silicon carbide fiber-reinforced silicon carbide matrix composite (MI SiC/SiC) is applied on a CMC specimen and tensile tested at room temperature. Multiple tests are performed on a single specimen with increasing predetermined stress levels until final failure. Damage progression due to the load applied is monitored using a digital image correlation (DIC) system. After unloading from the predetermined stress levels, the specimen is evaluated by optical microscopy and computed tomography (CT). The inspection forms the imaging which implied that primary and secondary cracks developed during tensile loading until failure. DIC showed formation of a primary crack at ~50% of the ultimate tensile strength, and this crack grew with increasing stress and eventually led to final failure of the specimen.
{"title":"Damage Monitoring of Ceramic Matrix Composites Under Tension Loading Via NDE-based DIC Approach","authors":"A. Abdul-Aziz","doi":"10.32548/2022.me-04296","DOIUrl":"https://doi.org/10.32548/2022.me-04296","url":null,"abstract":"Environmental barrier coatings (EBCs) are used as a coating material on fiber-reinforced ceramic matrix composites (CMC) for various aerospace and turbine engines applications. In order to validate physics-based analytical models for predicting the spallation life of EBCs, the fracture strength of the EBC and the kinetics of crack growth in EBC layers need to be experimentally determined under engine operating conditions. In this study, a coating layer of barium strontium aluminum silicate (BSAS)–based melt-infiltrated silicon carbide fiber-reinforced silicon carbide matrix composite (MI SiC/SiC) is applied on a CMC specimen and tensile tested at room temperature. Multiple tests are performed on a single specimen with increasing predetermined stress levels until final failure. Damage progression due to the load applied is monitored using a digital image correlation (DIC) system. After unloading from the predetermined stress levels, the specimen is evaluated by optical microscopy and computed tomography (CT). The inspection forms the imaging which implied that primary and secondary cracks developed during tensile loading until failure. DIC showed formation of a primary crack at ~50% of the ultimate tensile strength, and this crack grew with increasing stress and eventually led to final failure of the specimen.","PeriodicalId":49876,"journal":{"name":"Materials Evaluation","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43791443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A cluster-approach-based three-camera digital image correlation (DIC) system is introduced for full-field 3D shape and motion measurement. In this system, three cameras are employed to measure the same specimen area at different viewing angles. Data points within the region of interest can be evaluated by arbitrary camera pairs as a stereo DIC system so that data points with the smallest 3D residuum are selected and mapped into one common coordinate system. Two stationary shape measurements and one out-of-plane motion measurement were carried out with the three-camera DIC system. Test results were analyzed based on the same image series, projection calibration, and correlation parameters, but compared using different camera combinations (i.e., three-camera and two-camera data). Three-camera test results show not only an improved surface coverage due to the additional camera viewing angle for uneven specimen surfaces, but also a smaller and more homogenous distributed measurement uncertainty compared to the two-camera test results. The selection of data points with the smallest 3D residuum evaluated from any arbitrary camera pairs enables a better tolerance of the three-camera DIC system against various measurement error sources such as limited depth of field, lens distortion, and speckle pattern distortion due to tilted camera viewing angles.
{"title":"A Three-Camera Digital Image Correlation System For Full-Field 3D Shape and Motion Measurement","authors":"L. Luan, Liam Crosbie","doi":"10.32548/2022.me-04293","DOIUrl":"https://doi.org/10.32548/2022.me-04293","url":null,"abstract":"A cluster-approach-based three-camera digital image correlation (DIC) system is introduced for full-field 3D shape and motion measurement. In this system, three cameras are employed to measure the same specimen area at different viewing angles. Data points within the region of interest can be evaluated by arbitrary camera pairs as a stereo DIC system so that data points with the smallest 3D residuum are selected and mapped into one common coordinate system. Two stationary shape measurements and one out-of-plane motion measurement were carried out with the three-camera DIC system. Test results were analyzed based on the same image series, projection calibration, and correlation parameters, but compared using different camera combinations (i.e., three-camera and two-camera data). Three-camera test results show not only an improved surface coverage due to the additional camera viewing angle for uneven specimen surfaces, but also a smaller and more homogenous distributed measurement uncertainty compared to the two-camera test results. The selection of data points with the smallest 3D residuum evaluated from any arbitrary camera pairs enables a better tolerance of the three-camera DIC system against various measurement error sources such as limited depth of field, lens distortion, and speckle pattern distortion due to tilted camera viewing angles.","PeriodicalId":49876,"journal":{"name":"Materials Evaluation","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44061797","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Advancements in nondestructive evaluation (NDE) have represented a continuous process of technology achievements moving toward easier approaches, a wider range of applications, and better results outcomes. Materials and component characterization is done in many instances using destructive testing, which is effective but time-consuming, costly, and difficult to obtain feedback during manufacturing. Today, new, efficient, and noninvasive materials characterization technologies are becoming standard in industry, offering cost-effective applicability and quality benefits. In addition, newer inventions, state-of-the-art methodologies and instrumentations in NDE, and characterization technologies are offering ample support to industry to advance work and operations.
{"title":"Digital Image Correlation and Its Role in NDE","authors":"A. Abdul-Aziz","doi":"10.32548/2022.me-04306","DOIUrl":"https://doi.org/10.32548/2022.me-04306","url":null,"abstract":"Advancements in nondestructive evaluation (NDE) have represented a continuous process of technology achievements moving toward easier approaches, a wider range of applications, and better results outcomes. Materials and component characterization is done in many instances using destructive testing, which is effective but time-consuming, costly, and difficult to obtain feedback during manufacturing. Today, new, efficient, and noninvasive materials characterization technologies are becoming standard in industry, offering cost-effective applicability and quality benefits. In addition, newer inventions, state-of-the-art methodologies and instrumentations in NDE, and characterization technologies are offering ample support to industry to advance work and operations.","PeriodicalId":49876,"journal":{"name":"Materials Evaluation","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49164064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Traditional nondestructive evaluation (NDE) methods present significant challenges to detecting and characterizing kissing or weak bonds in adhesively bonded structures. These kissing or weak bonds also cannot transmit shear stresses or handle complex loading modes and, if not detected, can present a significant threat to the structural integrity of the components or systems. This paper demonstrates the digital image correlation (DIC) technique for evaluating adhesively bonded dissimilar materials joints subjected to kissing or weak bonds. The study employed four adhesively bonded carbon fiber reinforced plastics and aluminum (CFRP-Al) lap-shear test coupons with varied bond quality (i.e., with no contamination and three simulated kissing bond defects). The novelty of the approach presented in this paper was that this technique could detect and demonstrate changes in the normal strain (εyy) contour map of the contaminated specimens at relatively lower load levels. This load level corresponds to 15% of the failure load for the silicone and hydraulic oil contaminated sample and around 30% for the polyvinyl alcohol (PVA) contaminated sample. In addition, higher compressive strains along the overlap edges were observed in the strain map for the single lap joints due to the higher peeling stresses of the adherend and the stress concentration at the edges of an adhesively bonded joint.
{"title":"Assessment of Composite Aluminum Adhesive Joints Using Digital Image Correlation","authors":"Anish Poudel, T. Chu","doi":"10.32548/2022.me-04281","DOIUrl":"https://doi.org/10.32548/2022.me-04281","url":null,"abstract":"Traditional nondestructive evaluation (NDE) methods present significant challenges to detecting and characterizing kissing or weak bonds in adhesively bonded structures. These kissing or weak bonds also cannot transmit shear stresses or handle complex loading modes and, if not detected, can present a significant threat to the structural integrity of the components or systems. This paper demonstrates the digital image correlation (DIC) technique for evaluating adhesively bonded dissimilar materials joints subjected to kissing or weak bonds. The study employed four adhesively bonded carbon fiber reinforced plastics and aluminum (CFRP-Al) lap-shear test coupons with varied bond quality (i.e., with no contamination and three simulated kissing bond defects). The novelty of the approach presented in this paper was that this technique could detect and demonstrate changes in the normal strain (εyy) contour map of the contaminated specimens at relatively lower load levels. This load level corresponds to 15% of the failure load for the silicone and hydraulic oil contaminated sample and around 30% for the polyvinyl alcohol (PVA) contaminated sample. In addition, higher compressive strains along the overlap edges were observed in the strain map for the single lap joints due to the higher peeling stresses of the adherend and the stress concentration at the edges of an adhesively bonded joint.","PeriodicalId":49876,"journal":{"name":"Materials Evaluation","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48149871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
It is often stated that no two engineers will set up an industrial X-ray computed tomography (CT) scan with the same parameters. In this article, an orderly set of steps is presented that will lead to an acceptable CT scan result for typical cone beam (volumetric) systems with application to denser and/or larger objects. This approach can be applied when using minifocus, mesofocus, and microfocus X-ray tubes. The strategy covers preparation and general considerations, selection of the proper tube and detector, methods to determine the proper magnification, setting X-ray tube and detector parameters, considerations to achieve good image quality, and common mistakes to avoid.
{"title":"Industrial Computed Tomography Technique Development for Industrial Volumetric X-Ray CT","authors":"D. Roth","doi":"10.32548/2022.me-04291","DOIUrl":"https://doi.org/10.32548/2022.me-04291","url":null,"abstract":"It is often stated that no two engineers will set up an industrial X-ray computed tomography (CT) scan with the same parameters. In this article, an orderly set of steps is presented that will lead to an acceptable CT scan result for typical cone beam (volumetric) systems with application to denser and/or larger objects. This approach can be applied when using minifocus, mesofocus, and microfocus X-ray tubes. The strategy covers preparation and general considerations, selection of the proper tube and detector, methods to determine the proper magnification, setting X-ray tube and detector parameters, considerations to achieve good image quality, and common mistakes to avoid.","PeriodicalId":49876,"journal":{"name":"Materials Evaluation","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46146688","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sina Mehdinia, K. S. T. Chopperla, A. Hafiz, T. Schumacher, J. Ideker
Alkali-silica reaction (ASR) is a deleterious reaction in concrete that leads to the expansion and cracking of concrete. Laboratory approaches to monitor concrete for ASR activity are often lengthy and depend on an operator for regular measurements. The aim of this research is to develop an automated and reliable monitoring approach based on ultrasonic coda (or diffuse) wavefields, which are highly sensitive to minute and slowly occurring changes in a material—ideal for ASR. In this paper, the proposed approachis introduced along with an experimental study that compares ultrasonic coda wave monitoring data with traditional expansion measurements following ASTM C1293. A simple, fast, and robust algorithm to track a selected coda wave feature is proposed and evaluated and was applied to the recorded data. The monitored concrete prisms were designed to have three different levels of ASR activity by varying the lithium admixture dosage. The proposed approach was found to be promising. The process is automated and the monitoring of the specimens using coda wavefields was able to clearly differentiate the mixtures with varying ASR expansions.
{"title":"Ultrasonic Coda Wave Monitoring of Alkali-Silica Reactivity in Concrete Laboratory Prisms","authors":"Sina Mehdinia, K. S. T. Chopperla, A. Hafiz, T. Schumacher, J. Ideker","doi":"10.32548/2022.me-04248","DOIUrl":"https://doi.org/10.32548/2022.me-04248","url":null,"abstract":"Alkali-silica reaction (ASR) is a deleterious reaction in concrete that leads to the expansion and cracking of concrete. Laboratory approaches to monitor concrete for ASR activity are often lengthy and depend on an operator for regular measurements. The aim of this research is to develop an automated and reliable monitoring approach based on ultrasonic coda (or diffuse) wavefields, which are highly sensitive to minute and slowly occurring changes in a material—ideal for ASR. In this paper, the proposed approachis introduced along with an experimental study that compares ultrasonic coda wave monitoring data with traditional expansion measurements following ASTM C1293. A simple, fast, and robust algorithm to track a selected coda wave feature is proposed and evaluated and was applied to the recorded data. The monitored concrete prisms were designed to have three different levels of ASR activity by varying the lithium admixture dosage. The proposed approach was found to be promising. The process is automated and the monitoring of the specimens using coda wavefields was able to clearly differentiate the mixtures with varying ASR expansions.","PeriodicalId":49876,"journal":{"name":"Materials Evaluation","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42719440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G. Zheng, Ze Li, Songfeng Liu, Hao Dong, Feng Hao, Feng Hu, Yuanchao Bao
In this paper, a cylindrical aluminum specimen with an eccentric circular hole is prepared and ultrasonic measurements are carried out by experimental means. The measurement area is restricted to the plane perpendicular to the axis of the cylindrical component. The measured wave data are fed into the approximate correction method formula—the Born inversion procedure—and cross-sectional images are obtained. Next, a 3D shape reconstruction of the defect in the aluminum specimen is performed by stacking the cross-sectional images. After correcting the defect’s echo amplitude, the defect reconstruction effect of the 2D section and 3D defect reconstruction effect improves remarkably.
{"title":"Born-Inversion Procedure for Shape Reconstruction of Eccentric Defects in Cylindrical Components","authors":"G. Zheng, Ze Li, Songfeng Liu, Hao Dong, Feng Hao, Feng Hu, Yuanchao Bao","doi":"10.32548/2022.me-04280","DOIUrl":"https://doi.org/10.32548/2022.me-04280","url":null,"abstract":"In this paper, a cylindrical aluminum specimen with an eccentric circular hole is prepared and ultrasonic measurements are carried out by experimental means. The measurement area is restricted to the plane perpendicular to the axis of the cylindrical component. The measured wave data are fed into the approximate correction method formula—the Born inversion procedure—and cross-sectional images are obtained. Next, a 3D shape reconstruction of the defect in the aluminum specimen is performed by stacking the cross-sectional images. After correcting the defect’s echo amplitude, the defect reconstruction effect of the 2D section and 3D defect reconstruction effect improves remarkably.","PeriodicalId":49876,"journal":{"name":"Materials Evaluation","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48987982","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-09-01DOI: 10.32548/10.32548/2022.me-04282
Zenghua Liu, Runxin Man, Kexin Wang, Yuheng Wu
Structural coatings are widely used because of their excellent mechanical and thermal properties. To evaluate defects and uniformity in coatings, both qualitatively and quantitatively, a terahertz time-domain spectroscopy (THz-TDS) detection technique is proposed. The thermal barrier coating is selected as a typical single-layer coating structure for quantitative defect detection. A wavelet noise reduction method is used on the acquired raw signals to eliminate noise while retaining detailed information. The peak value of the preprocessed signal is used as a feature parameter for imaging, and the automatic binarization threshold segmentation technique is used to describe the defects quantitatively. The automotive coating is selected as a typical multilayer coating structure for uniformity detection. The time-frequency characteristics of a strongly superimposed signal are analyzed; the peak-to-peak value is used as a feature parameter for imaging, and the peak-to-peak 3D imaging is then used to characterize the coating uniformity, enabling fast and intuitive acquisition of the coating state. The statistical characteristics of the standard deviation and range are used to evaluate the uniformity of each layer of the automotive coating. The results show that the uniformity of the clean coating is optimal. The results of a subsequent thickness inspection using an eddy current gauge are consistent with those of the terahertz technique. The results demonstrate that THz-TDS can effectively detect defects and uniformity in coatings.
{"title":"Nondestructive Evaluation of Coating Defects and Uniformity Based on Terahertz Time-Domain Spectroscopy","authors":"Zenghua Liu, Runxin Man, Kexin Wang, Yuheng Wu","doi":"10.32548/10.32548/2022.me-04282","DOIUrl":"https://doi.org/10.32548/10.32548/2022.me-04282","url":null,"abstract":"Structural coatings are widely used because of their excellent mechanical and thermal properties. To evaluate defects and uniformity in coatings, both qualitatively and quantitatively, a terahertz time-domain spectroscopy (THz-TDS) detection technique is proposed. The thermal barrier coating is selected as a typical single-layer coating structure for quantitative defect detection. A wavelet noise reduction method is used on the acquired raw signals to eliminate noise while retaining detailed information. The peak value of the preprocessed signal is used as a feature parameter for imaging, and the automatic binarization threshold segmentation technique is used to describe the defects quantitatively. The automotive coating is selected as a typical multilayer coating structure for uniformity detection. The time-frequency characteristics of a strongly superimposed signal are analyzed; the peak-to-peak value is used as a feature parameter for imaging, and the peak-to-peak 3D imaging is then used to characterize the coating uniformity, enabling fast and intuitive acquisition of the coating state. The statistical characteristics of the standard deviation and range are used to evaluate the uniformity of each layer of the automotive coating. The results show that the uniformity of the clean coating is optimal. The results of a subsequent thickness inspection using an eddy current gauge are consistent with those of the terahertz technique. The results demonstrate that THz-TDS can effectively detect defects and uniformity in coatings.","PeriodicalId":49876,"journal":{"name":"Materials Evaluation","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46211085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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