Low-Cycle Fatigue under Varying Strain Conditions : Effects of the Mean Plastic Strain and the Stress Factor

抄録

In order to study the effects of the mean plastic strain and the stress factor on the cumulative damage rule, low-cycle fatigue tests were carried out on 0.38 % C steel, austenitic stainless steel and heavily cold-drawn copper. It was found that the fatigue life under arbitrarily varying plastic strain conditions could be estimated by combination of the linear cumulative damage rule in terms of the plastic strain range-- pair and the effect of the reduction of the fracture ductility caused by the mean plastic strain. Even if the above mentioned effect of mean plastic strain was considered, measurable deviations from the linear damage rule were observed, particularly on the materials which tend to work-harden or -soften to a high degree. However, such deviations were found to be reduced by allowing for the difference in the stress behavior between variable and constant plastic strain amplitude tests.