Influence of Loading Waveform on the Fatigue Life of 34CrNi3MoVA Steel

Abstract

Mechanical components often experience fatigue loading from various waveform conditions during their operational lifespan. However, the underlying mechanisms through which variations in loading waveform affect the fatigue life of components remain unclear. Thus, this study conducted tension–compression fatigue experiments on 34CrNi3MoVA steel specimens under the same stress amplitude with different waveforms (cosine, triangular, sawtooth, and reverse sawtooth) to investigate the effects of loading waveform variations on the cyclic strain hardening behaviors, the fatigue fracture failure, and the fatigue life. The results indicated that specimens under different waveforms all exhibited cyclic strain hardening. The fatigue cyclic hardening level progressively increased in the order of cosine, triangular, and sawtooth waveforms, resulting in a continuous increase in cyclic saturation strain amplitude. The analysis of fatigue fractures demonstrated a consistent increase in both the initiation and propagation zone areas in the order of cosine, triangular, and sawtooth waveforms, and the boundary between the propagation and final fracture zones gradually shifted from a straight to a curved shape. The influence mechanisms of cyclic loading waveforms on the fatigue life of specimens were analyzed based on the energy dissipation, leading to the development of a universal fatigue life prediction model applicable to different waveform conditions, the model was then verified with the reverse sawtooth wave specimens and resulted in a prediction error less than 15%. The study is expected to serve as a significant guide for predicting and evaluating the fatigue life of mechanical components under various fatigue loading conditions.