Method for Describing Fatigue Processes in Structural Materials

Abstract

The article studies one of the methods for phenomenological description of fatigue processes in structurally-inhomogeneous structural materials. The initial statement about the interrelationship between the static and cyclic material properties is investigated using the complete stress-strain curves or diagrams method (CSSD). Based on the analysis of the mathematic modeling results, the interrelationship is predicted to exist between the highly-localized fatigue process in a structurally-inhomogeneous material and the degradation of a static CSSD for a macroscopic specimen. It is noted that the conditions under which the specimen fails in a testing machine are similar to the ones for the material in a construction. Then the results are given for the direct experimental testing of the model predictions, illustrated with the examples of cyclic degradation of several structural materials. The tests on multiple-cycle fatigued specimens reveal degradation of several mechanical properties. The justification for the selection of the available plasticity of a material as a parameter representative of the fatigue process is given. The authors describe a few examples of building one-parameter cyclic degradation models for steels and some prospects of using the complete strain-stress diagrams for various purposes.