Shearography is a non-destructive testing technique that provides full-field surface strain characterization. Previous inspection of flat objects or simple geometric shapes has been reported. However, real-life objects especially in aerospace, transport, or cultural heritage are not flat, but their inspection with shearography is of interest for both hidden defect detection and material characterization. Accurate strain measurement of a highly curved or free-form surface needs to be performed by combining in-line object shape measuring and processing of the shearography data in 3D. Previous research has not provided a general solution for that. This paper presents a new approach of 3D shape shearography which is based on the integration of a structured light projector for in-line shape measuring with 3D shearography. For the experimental part, a 3D shape shearography system prototype was developed and its performance was evaluated with a cylinder specimen loaded by internal pressure and compared with strain gauges.
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This Letter communicates a new, to the best of our knowledge, designing framework of shearography. The three elementary functional parts of quantitative shearography, namely imaging, shearing, and phase shifting, are integrated into a single diffractive optical element (DOE), named a 3-in-1 phase mask. The idea breaks through the conventional designing routine of shearography, and converts it from the combination of individual optical elements to the spatial manipulation of phase.
View Article and Find Full Text PDFPerformance of Damage Identification Based on Directional Wavelet Transforms and Entopic Weights Using Experimental Shearographic Testing Results.
Sensors (Basel)
January 2021
Department of Fundamentals of Machinery Design, Faculty of Mechanical Engineering, Silesian University of Technology, 44-100 Gliwice, Poland.
The paper aims to analyze the performance of the damage identification algorithms using the directional wavelet transforms, which reveal higher sensitivity for various orientations of spatial damage together with lower susceptibility to noise. In this study, the algorithms based on the dual-tree, the double-density, and the dual-tree double-density wavelet transforms were considered and compared to the algorithm based on the discrete wavelet transform. The performed analyses are based on shearographic experimental tests of a composite plate with artificially introduced damage at various orientations.
View Article and Find Full Text PDFThis paper presents a numerical-experimental procedure to characterize through-holes with arbitrary shapes present on metallic substrates under composite material sleeves using pulsed laser shearography and dynamic excitation combined to the finite element method. The so-called fitting process consists of matching experimental and numerical results in order to determine the shape and dimensions of the holes under the composite repair, or even quantify defects between layers of the composite laminate. The results show that the technique is capable of characterizing, in the worst case, the geometry of a hole with 83% accuracy and its respective area with a maximum error of approximately 20%.
View Article and Find Full Text PDFThe inspection of face sheet bonding, through optical interferometry techniques like holography and shearography, in potted-insert honeycomb-cored sandwich panels is different from the inspection of panels without inserts due to their complex response toward thermal and vibration stressing. In this paper, the dynamic responses of metallic honeycomb-cored sandwich structures with bonded and debonded inserts are studied using time-averaged digital holography and illustrated. At high frequencies, the face sheet regions at perfectly bonded inserts act as hard points, and regions across a debonded insert locally resonate in the sensitivity range of interferometry.
View Article and Find Full Text PDFShearography is a non-destructive testing technique that provides full-field surface strain characterization. Previous inspection of flat objects or simple geometric shapes has been reported. However, real-life objects especially in aerospace, transport, or cultural heritage are not flat, but their inspection with shearography is of interest for both hidden defect detection and material characterization.
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