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

Zhang, Ying (2004). Numerical and experimental exploration of the contour method for residual stress evaluation. PhD thesis The Open University.



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.

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