A MULTIAXIAL FATIGUE ANALYSIS METHOD FOR DUCTILE, SEMI-DUCTILE, AND BRITTLE MATERIALS

In mechanical engineering fatigue assessment of components, where complex non-proportional loads are acting on, plays an important role to identify critical spots and to predict the lifetime till crack initiation. Today’s fatigue life prediction software has to deal with stress results of huge finite element models consisting of several hundred thousands or even millions of nodes and elements. Therefore, efficient algorithms for fatigue assessment are necessary to reduce development time and costs. Nevertheless, such methods should be able to deal with randomly and non- proportionally loaded components made of ductile, semi-ductile or brittle materials. Both cyclic tension/compression (or bending) and torsion loading and their combinations should be predicted correctly. In this contribution a new method for high cycle fatigue is presented, which covers both infinite and finite life region, and which is based on a critical plane approach combined with rainflow cycle counting and linear damage accumulation. Comparisons with test results of combined in-phase bending and torsion loaded specimens show an excellent agreement. The working method for out-of-phase loading is demonstrated as well as a practical example.