Fatigue Test for Two-Holes Diagonally-Placed Plate at Elevated Temperature

The objective of the present study is to evaluate fatigue strength of a perforated plate at an elevated temperature of 550°C under displacement-controlled loading. Specimens having two circular holes have stress concentrations near the hole sides. The two holes in the specimen made of SUS304 stainless steel are placed at an angle of 30°, 60° and 90° measured from the loading direction. Stress concentration factors of these specimens, having the complicated stress pattern distribution, were estimated by the finite element method (FEM). Based on the stress concentration factor, the inelastic strain was estimated by the simplified equation of the Stress Redistribution Locus (SRL) method, and the estimated strain was compared to the experimental Best Fit Fatigue (BFF) curve. Crack initiation cycles were determined from graph showing the crack propagation process, which were measured by a CCD camera at a regular interval cycle. Crack initiation cycles were smaller than failure cycles of 75% load decreasing point. By using these inelastic local strain and crack initiation cycles, the experimented results were predicted well by the present complicated structures.