Bending Fatigue Strength and the Effect of Assembling Stress on Fillet Welded Joints of Catalyst Muffler Flange Pipes

Abstract

Fatigue strength is affected by assembling stress at flanges. Using samples of exhibiting different degrees of flange surface flatness, local stress was measured with strain gauges, and the effect of assembling strain and stress on fatigue strength was verified through fatigue strength examinations. Bending fatigue strengths were inversely proportional to static assembling stress which was proportional to the degree of flange flatness. Factors causing fatigue to failure, such as welding bead shape, metal structure, and crack state were identified through microscope observations and SEM-EDS chemical composition analyses, while assembling deformation and stress concentration were analyzed through FEM computer simulation.