An estimation of true Ramberg‐Osgood curve parameters for materials with and without Luder's strain using yield and ultimate strengths
Daniel Kujawski, Pranav S. Patwardhan, Rajprasad A. Nalavde
Abstract
Abstract Engineering tensile stress–strain curves for metallic materials typically show two different behaviours, namely, with Luder's strain and without Luder's strain. Luder's strain is more common for ductile materials, whereas high‐strength steels deform without Luder's strain. Usually, the stress–strain curves of ductile steels exhibit ultimate load where necking starts to develop. On the other hand, steels with low ductility exhibit monotonic increase of the applied load till failure without necking. Recently, Kamaya proposed a method to estimate the Ramberg‐Osgood relationship parameters for true stress–strain curves on the basis of conventional yield and ultimate strengths. This method can be not accurate enough for ductile materials exhibiting Luder's strain. Hence, a more general procedure for the materials exhibiting Luder's strain is proposed. In addition, an inverse method for assessing an ‘apparent ultimate tensile stress’ (akin to the ultimate stress of ductile materials at point of zero slope) for materials with low ductility (due to quenching or carburizing) is suggested.