押込み試験結果の感度解析と弾塑性特性の逆推定

抄録

Sensitivity analysis of an indentation test was performed to confirm the effectiveness of inverse estimation using a single indent. Mechanical properties such as a stress-strain curve play an important role in product design and evaluation. Many studies have been addressed to develop inverse estimation techniques to obtain mechanical properties using indentation tests instead of a tensile test, most of which require plural load-displacement curves using indenters of different apex angles, that is, plural indentation tests due to the uniqueness problem. However, plural tests are time-consuming and does not give local properties on a specific point of interest. In this work, the authors investigated the dependency of indentation results on the elastoplastic properties, in particular, on yield stress and strain hardening exponent. Finite element analyses were performed to simulate an indentation test with a Berkovich indenter, with changing yield stress and strain hardening exponent. Two parameters of a coefficient of a loading curve, C and a maximum pile-up height, Z_max/h_max showed different dependencies on the elastoplastic properties, which indicates that the yield stress and strain hardening exponent are uniquely determined from C and Z_max/h_max obtained from a single indentation test. This technique can estimate the elastoplastic properties with higher reliability at lower strain hardening exponent, because Z_max/h_max had higher sensitivity in the region.