Determining Norton creep properties from small punch creep tests by using the representative stress–strain method and inverse approach

Abstract

The small punch creep test (SPCT) emerges as an innovative technique for evaluating the creep properties of materials. Although the existing standards, such as CWA 15627 and EN 10371, establishes empirical correlations between SPCT and uniaxial creep tests (UCT), the complexity inherent to SPCT mandates an empirical approach that is both material-specific and labor-intensive for achieving precision. This paper introduces a novel methodology that synthesizes the representative stress–strain method with inverse finite element analysis to extract Norton creep properties of metallic materials directly from small punch test (SPT) and SPCT. The representative stress–strain method to SPT facilitates the determination of elasto-plastic properties at elevated temperatures, enabling a streamlined prediction of Norton creep law parameters by the inverse approach of SPCT. Notably, this methodology circumvents the need for intermediate UCT conversions, thereby providing a more efficient and accurate pathway for directly obtaining Norton creep properties from SPT and SPCT. Experimental validation conducted on P91 and P92NT steels at 600°C confirms a strong correlation between the predicted Norton creep properties and those obtained from UCT, underscoring the practicality and accuracy of the proposed approach.