Simultaneous dual directional strain measurement using spatial phase-shift digital shearography. (December 2016)

• Record Type: Journal Article
• Authors: Wang, Yonghong; Gao, Xinya; Xie, Xin; Wu, Sijing; Liu, Yingxue; Yang, Lianxiang
• Is Part Of: Optics and lasers in engineering. Volume 87(2016)
• Page Start: 197
• Page End: 203
• Publication Date: 2016-12
• Subjects: Dual Directional Shearography -- Spatial Phase Shift -- Dynamic measurement -- Non-destructive testing; Lasers in engineering -- Periodicals; Optical measurements -- Periodicals; Optics -- Periodicals; Lasers en ingénierie -- Périodiques; Mesures optiques -- Périodiques; Optique -- Périodiques; 621.36605
• DOI: 10.1016/j.optlaseng.2015.12.009
• Languages: English
• ISSNs: 0143-8166

Abstract

Abstract: This paper presents a Dual Directional Sheared Spatial Phase-Shift Digital Shearography (DDS-SPS-DS) system for simultaneous measurement of strains/displacement derivative in two directions. Two Michelson Interferometers are used as the shearing device to create two shearograms, one in the x -shearing direction and one in the y -shearing direction, which are recorded by a single CCD camera. Two lasers with different wavelengths are used for illumination, and corresponding band pass filters are applied in front of each Michelson Interferometer to avoid cross-interference between the two shearing direction channels. Two perpendicular shearing directions in the two measurement channels introduce two different spatial frequency carriers whose spectrums are orientated in different directions after Fourier Transform. Phase maps of the recorded two shearograms can be obtained by applying a windowed inverse Fourier transform, which enables simultaneous measurement of dual directional strains/displacement derivatives. The new system is well suited for nondestructive testing and strain measurement with a continuous or dynamic load. The capability of the dual directional spatial phase-shift digital shearography system is described by theoretical discussions as well as experiments. Highlights: A spatial phase-shift shearography for two directional NDT is reported. Two shearograms in two directions can be evaluated simultaneously by this system. Experimental results under static & dynamic loading are shown. This system works well for detecting directional distributed defects.