Fundamentals of static loading of structural components

Structural components, made of ductile materials, with static loading may fail in different ways. The two most important cases are failure because of yielding and failure because of fracture. There the load in cases of yielding is less than the load in cases of fracture. Fracture leads to more severe damage than yielding. Therefore the safety against yielding may be smaller than the safety against fracture. Failure because of yielding is usually explained by the maximum-distortion-energy theory. That theory says that the energy of shape distortion is the reason for yielding. This paper is showing that in special cases of stress, when yielding is impossible, other criteria may be considered; for instance a formulation based on the energy of form distortion. Unidirectional tensile tests with a flat body of ductile material show that such bodies will break under an angle which is different to rectangular. This angle of fracture is not systematically observed until now. The evaluation of this angle of fracture leads to an alternative theory. A more accurate investigation of the equivalent stress of three axially loaded bodies may show the variation of the equivalent stress in different plains of examination. This will lead to a varied intensity by direction of equivalent stress and also to an additional security factor. A prospect of further investigations to verify the new theories is additionally given.