Numerical analysis of strength mismatch effect on stress field in Charpy specimen

The influence of strength mismatch adjacent to the V-notch in Charpy specimen on stress field has been numerically analyzed with a 3D finite element method. It is found that the softer material adjacent to the V-notch provides a “shielding effect” from high-speed straining introduced by impact loading. As this leads to reduction in flow stress ahead of the V-notch, lower opening stress compared with homogeneous specimen is found in the case of the V-notch within the harder material in heterogeneous specimen. By contrast, in the case of the V-notch within the softer material, plastic strain is concentrated near the V-notch and the opening stress is elevated by constraint due to hard material adjacent to the V-notch. The Charpy impact test was conducted with the Charpy specimen extracted from the clad steel consisted of low- and high-strength steels in order to investigate the strength mismatch effect Charpy absorbed energy KV. It is found that KV value is affected by strength mismatch adjacent to the V-notch and the Weibull stress criterion can be applied to the quantitative evaluation of the strength mismatch effect on KV.