Evaluation of creep properties considering the friction effect of the small punch test

Abstract

In contrast to the Uniaxial Creep Test (UCT), where each stress produces a corresponding strain, the Small Punch Creep Test (SPCT) generates displacement in response to applied loads. Therefore, for the direct application of SPCT in creep damage assessment, it becomes imperative to convert the displacement and load data into the strain and stress parameters observed in the UCT. Unlike the UCT, which applies the load directly to the specimen, the SPCT indirectly imposes the load on the specimen through a punch ball. This divergence in loading methods introduces friction between the specimen and the punch ball during the SPCT. This study delves into the analysis of the friction coefficient between the specimen and punch ball using the Finite Element Method (FEM). Additionally, we explore the relationship between the specimen's minimum thickness and the friction coefficient. In conclusion, we propose a correlation between the creep properties of the two test methods, with the objective of accurately capturing the influence of friction between the specimen and punch ball in the SPCT.