Evaluation on micro-tomographic diagnosing method of residual stress around resin interface by laser welding

Abstract

This paper presents Optical Coherence Stressgraphy (OCSE) based on PS-OCT, which can obtain stress tomography from low coherence interference fringe patterns caused by photo-elastic effect at a cross-section. OCSE can visualize the difference between the secondary principal stress as fringe patterns by photo-elastic effect using PS-OCT. The stress distribution can be obtained by finding the spatial frequency of photo-elastic low-coherence interference fringes shown in the stokes parameter tomographic map S_a(x, z)/S₀(x, z) . In this experiment, OCSE was applied to laser welded material of PAR and PBT/PC alloy material. As a result, this system can offer the tomographic retardation map S3 which was verified to be depth-resolved and be dependent on the residual stress by laser welding. It was found that there is a correlation between the maximum stress by OCSE and the number of chemical cracks. Consequently, it was suggested that the proposed OCSE can visualize non-destructively and micro-tomographically the residual stress even for nontransparent.