Low-Cycle Torsional Fatigue of High Carbon Steel under Multiple Repeated Loads

Abstract

The fracture criterion of low-cycle fatigue based on variable strains, which is represented as1/C0∫N0γpadn=1 for the varying plastic strain amplitude, has been verified experimentally by carrying out the low-cycle fatigue tests under the tension-compression and rotating bending conditions. The low-cycle torsional fatigue tests under multiple repeated loads were made on the 0.84% C piano wires and the applicability of the above mentioned criterion was examined.The main results obtained are as follows:(1) The experimental values of the cumulative damage obtained from the above criterion are larger than the values calculated from the linear damage criterion, and they scatter around in the vicinity of unity.(2) The test results indicate the existence of an exponential relationship between the equivalent stress amplitude τeq and the equivalent plastic strain amplitude γp.eq.