An incremental indentation energy method in predicting uniaxial tensile properties of ferritic-austenitic dissimilar metal welds from spherical indentation tests

Based on the expanding cavity model and energy analysis, an analytical derivation was first conducted to develop a correlation between the increment of elastic and plastic portions of external work and the von Mises stress -strain increment, yielding an incremental indentation energy method (IIEM) to determine the stress-strain relationship from spherical indentation tests (SITs). The IIEM has two potential approaches in determining the proportional limit, one from indentation plastic zone radius rp measurements and the other from trial-and-error. Through an application of digital image correlation on the various zones of ferritic (SA508Gr.3Cl.1) to austenitic stainless steel (316L) dissimilar metal welds (DMWs), it was found that the rp measurements is capable for the two bases, but failed in the other six zones due to the inhomogeneous characteristic of DMWs. In this case, the mean strain development of indentation plastic zone was extensively investigated through systematic finite element analysis to establish an IIEM independent of rp measurements. Solidarity of the IIEM was verified through experiments on the eight representative zones of DMWs, and compared with its previous counterpart (the empirically concluded Kwon method). It was found that the IIEM can restrain errors caused by the compensation effect in reverse predictions, leading to more accurate strength predictions (with a maximum error 9.85%). This study is expected to provide a convenient and reliable approach for predicting the uniaxial tensile properties from SITs, especially when the rp measurement is not applicable.