Establishment of the Fatigue Curve Model Based on Stress Ratio

Stress ratio has important effect on fatigue performance. For the influence of stress ratio o fatigue life, fatigue tests of Titanium alloy produced by rapid manufacturing(Ti alloy by RM) samples were carried out under three kinds of stress ratio( R 、 =0.5 R 、 =0.06 R=-1), to draw three fatigue limits and 3 S-N curves of "stress amplitude life model ". Based on the integral relationship of the crack growth rate and fatigue life, considering both of mathematical models of fatigue life, a systematic investigation of the relationship between stress ratio (R) and fatigue life curve (S-N) was performed to build the fatigue life mathematical mode (R-S-N). According to the modified formula proposed in this paper, the establishment of R-S-N mathematical models, applicable for Ti alloy by RM materials. The result showed that "stress amplitude" model can accurately predict moderate fatigue life. The predictive value of proposed R-S-N mathematical models were in better agreement with the experimental values, it can accurately predict the fatigue curve under any stress ratio in engineering.