Load frequency effect on fatigue crack propagation in titanium at elevated in titanium at elevated temperature

At elevated temperature, both cycle-dependent and time-dependent aspects in fatigue crack propagation may be important. The present paper examines the influence of load frequency on crack growth rate in titanium at elevated temperature and attempts to analyze this effect theoretically. An elasto/visco-plastic theory is utilized to establish the constitutive equation of the material first. By using the finite element approach incorporating with the constitutive equation proposed, the visco-plastic strain and the J-integral are then evaluated and used to correlate crack growth rate under different load frequencies. It is found that these two parameters can account for the load frequency dependence very well in all the cases investigated.