Abstract
Mechanical structures of transport machineries may be damaged by non-proportional loadings, while they are in service. Loading amplitude and direction are varying in time domain under non-proportional loadings. Non-proportional loading brings a drastic degradation in fatigue life. In this study, the method for prediction of fatigue life considered with life degradation by non-proportional loading was investigated. The method was defined with equivalent stress considered with path loading calculated by principal stress amplitude and direction. In the verification test of established method, two type specimens made of SS400 were used. One was with protrusion pillar. The other was flat shaped. The fatigue tests under non-proportional loading were conducted with two type distribution in frequency domain. One had double resonance. The other was white noise. Planar tri-axial fatigue testing machine which could emulate any stress was employed. It was found that predicted fatigue lives by established method were within factor of 3 against experimental results.
