Fatigue crack growth tests using LZ50 steel compact tensile specimens were performed under three different loading waveforms, i.e. triangular wave, sinusoidal wave and square wave. The characteristics of fatigue fracture were observed by scanning electron microscopy, and the effects of different loading waveforms on crack size increment and crack growth rate were analyzed based on the experimental data. The results show that the sensitivity of fatigue crack growth behavior to the waveform is relatively low and the fracture morphology of specimens is basically the same at high loading frequency. The influence of waveform on the fatigue crack growth behavior increases and the fracture morphology of specimens is different at low loading frequency. Meanwhile, the main mechanism in critical crack propagation region is fatigue striations, and the spacing of fatigue striations under triangular wave is significantly smaller than that under the other two waves. The main morphology in unstable propagation region is dimple, the shape of which is smaller and shallower under triangular wave than that under the other two waves. Stress intensity factor under the three different loading modes was calculated and analyzed based on simulation using LS-DYNA software and the node displacement extrapolation method. The results demonstrate that the influence mechanism of the loading waveforms on fatigue crack growth behavior obtained by simulation analysis is essentially consistent with the experimental results. © 2020, Department of Journal of the China Railway Society. All right reserved.
