High-accuracy compliance correction for nonlinear mechanical testing: Improving Small Punch Test characterization

Abstract Small punch test, SPT, of metallic materials is a very convenient mechanical test since it requires a small volume of material. However, SPT data from different laboratories suffer from large scatter, mainly due to the different experimental set-ups, especially when displacement is measured without an LVDT. Such uncertainty is attributed predominantly to the large effect of elastic displacement associated to the low stiffness of the device set-up, which has not been taken properly into account so far. Additionally, we show that large stiffness variations during SPT are taking place. Thus, in this study, we present a methodology for performing the elastic correction in SPT load vs. displacement curves through a load-unload cycles test, allowing the attainment of the elastic displacement and associated stiffness for each unload step as a function of increasing SPT displacement. The proposed methodology provides SPT load vs. plastic displacement curves, which offer more accurate mechanical data and more reliable comparisons among different laboratories and materials, independently on the employed SPT set-up.