It's an important task that choosing appropriate fracture parameters and predicting the fatigue crack growth rate accurately considering the different degrees of plastic deformation at the crack tip.The relation between crack tip fracture parameters and a fatigue crack growth rate was investigated by theoretical calculation and experimental analysis under four different fatigue loading conditions.Finally

a suitable model for predicting a fatigue crack growth rate was provided by formulas and the parameter fitting.The results indicate that ΔK representing a fatigue crack growth rate loses its rationality and effectiveness gradually with increases of the load ratio and the load amplitude.At the early stage of the crack propagation

the crack propagation resistance of high load ratio is higher than low load ratio.At the later stage of the crack propagation

the gap between high and low load ratios and the crack growth resistance decreases. ΔJ'ac is the suitable fracture parameter for the fatigue crack propagation of the industrial pure titanium among all of the fracture parameters discussed.On this basis

the corresponding prediction model of the fatigue crack growth rate was proposed.