NOTCH EFFECT ON TWO-LEVEL CUMULATIVE LOW-CYCLE FATIGUE LIFE UNDER DIFFERENT BIAXIAL LOADING MODE SEQUENCES

Abstract Two-level cumulative low-cycle fatigue lives of AISI 316 stainless steel notched specimens with different biaxial loading mode sequences were experimentally analyzed in this paper. Forty-eight cases were conducted in the experimental program by considering the loading level sequence effect, the biaxiality of two levels and the cycle ratios. Results show that interlock effect caused by the characteristic fracture surfaces of the different biaxial states is beneficial to the cumulative fatigue lives. On the other hand, the tensile loading of the second level will accelerate the opening of cracks and decrease fatigue strength. Miner's rule predicts most fatigue lives within 30% error bands, and the loading level sequence effect was not found in this research involving complex fracture modes. Fractography of specimens in the cumulative fatigue tests is reported and discussed in this paper.