Conditions and assumptions of strength criteria

The equivalent stress concept (Sect. 1.2) is an engineering tool. There are no physical principles (e.g., balance equations in Continuum Mechanics, Altenbach, Kontinuumsmechanik: Einführung in die materialunabhängigen und materialabhängigen Gleichungen, Springer, Berlin, 2015, [1]; Altenbach and Altenbach, Einführung in die Kontinuumsmechanik, Teubner, Stuttgart, 1994, [2]) underlying such a formulation. This chapter summarizes the necessary conditions and the most important plausibility assumptions providing reliable criteria for the real-life applications. In particular, recent developments of criteria are discussed as well as the need of a generalized hypothesis.