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.

中文翻译：

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利用屈服强度和极限强度估算含或不含Luder应变的材料的真实Ramberg-Osgood曲线参数

金属材料的工程拉伸应力-应变曲线通常显示出两种不同的行为，即具有Luder应变和没有Luder应变的行为。Luder的应变在延性材料中更为常见，而高强度钢会在没有Luder应变的情况下变形。通常，韧性钢的应力-应变曲线表现出极限载荷，开始出现颈缩。另一方面，具有低延展性的钢表现出所施加载荷的单调增加，直至失效而不发生颈缩。最近，Kamaya提出了一种基于常规屈服强度和极限强度估算真实应力-应变曲线的Ramberg-Osgood关系参数的方法。这种方法对于表现出Luder应变的易延展材料可能不够准确。因此，对于具有Luder应变的材料，提出了更通用的程序。此外，建议使用一种相反的方法来评估延展性低（由于淬火或渗碳）的材料的“表观极限拉伸应力”（类似于零斜率点的韧性材料的极限应力）。