Estimation of the Fatigue Lives under Actual Loads by Hereditary Method

抄録

In a fatigue test under actual load, the induced strains become rather stabilized after a certain number of cycles, and the stress-strain curves show loops according to the stress wave forms. Therefore, plastic strain ε_p is supposed to be caused by the deviatoric stress of each stress peak i from the mean stress of the wave. Then, the influence of other stress peaks for the ε_p of a peak is analogized by the static stress-strain curve in the plastic range. And the stress amplitude of an ordinary fatigue test that causes the same plastic strain as the peak i is called an equivalent stress σ_{eq, i} and its cumulative distribution curve is drawn. And then, program test or cumulative fatigue damage law according to the distribution curve is adopted for the evaluation of fatigue lives under the actual stress wave form.