Numerical and experimental exploration of the contour method for residual stress evaluation

• Main Author: Zhang, Ying
• Published: Open University 2004
• Subjects: 620.11230287
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402270

This thesis comprehensively investigates the contour method - a newly-invented destructive technique for residual stress evaluation - in terms of its principle and application. The principle of the contour method is based on a variation of Bueckner's elastic superposition theory. A two-dimensional map of residual stress profile normal to a plane of interest can be determined in a simple, cheap and time-efficient manner. In practice,residual stress evaluation using the contour method involves the experimental measurement of the displacement formed by the stress release following a cut on the surface at issue, and then numerical calculation of the residual stress based on the experimentally measured displacement. The whole process of the contour-method measurement was simulated using a finite element method and the simulated result confirms the correctness of the novel technique. A number of different applications have been explored using the contour method to measure a cross-sectional residual stress distribution: a hole cold expansion EN8 steelplate, a hole cold expansion 7475-T7351 aluminium alloy plate, a MIG 2024-T351 aluminium alloy welded plate and a VPPA 2024-T351 aluminium alloy welded plate. Favourably good outcomes were obtained from each case. The most impressive comparison of the contour-method result was made on the VPPA 2024-T351 weld with neutron and synchrotron X-ray diffraction measurements, showing an extremely good match with deviation approximately 9 % on average. This work has proved that the contour method is a powerful novel technique to determine across-sectional residual stress profile with accuracy in many engineering components, and has great prospects to find application elsewhere.