Two tools for the science of material effort

This paper discusses the science of material effort from the historical viewpoint.Two general scientific tools: the geometrical descriptive method of Mohr, and the energetic method of Huber are compared and evaluated from the very beginning.Three appropriate stress invariants are taken into account: stress intensity, stress triaxiality and stress shearness.Especially, much attention is devoted to explanation of the stress shearness invariant, which aims at describing the Lode parameter in a more analytical manner.Two different tools of finding a proper yield surface which contains the above mentioned three stress invariants are discussed in the literature perspective.In particular, the three-parameter yield surface, called the Burzyski-Pcherski hypothesis is researched and explained from this new point of view.