High Cycle Fatigue of Structural Components Using Critical Distance Methods

This study explores the high cycle fatigue strength of crack-like discontinuities in metallic structures as well as those made from powder metals using approaches that are based on theory of critical distances (TCD). The methods used in this study consist of (a) the point method, (b) the line method, and (c) the imaginary crack method. The effective parameter for the methods (a), (b), and (c) is the distance ‘d’ from the material surface, which is a material property and the reference parameter is the fatigue limit. The imaginary crack method involves introduction of a sharp crack at the root of a notch and the length of the crack, ‘lo’ assumed a material constant. In the imaginary crack method, the effective crack length is taken as the sum of the actual crack and the material parameter ‘lo’. It is concluded that the high cycle fatigue has a volumetric character and the proposed methods introduce the volume effect in the determination of stress and strain fields as well as the fatigue life. Using the material parameters from the various approaches, the number of cycles to initiate a fatigue has been determined for a number of materials and compared with experimental results.