Fracture mechanics parameter of controlling crack propagation for 20 g steel at high temperature

The crack growth experiments of the 20 g steel CT speciments, loaded with constant displacement speed at loading point, were done at high temperature. The crack length was measured by unloading compliance method. The experimental data of crack growth were measured. The crack growth rate da/dt relates to the net section stress, stress intensity factor K. The stress intensity factor, crack growth rates and, the relation between net section stress and crack growth rates are affected by the loading rates (or the load level) and temperature. The relation between the creep crack growth rates and C* parameter for 20 g steel is different at 400°C and 500°C. C* integral is appropriate parameters for controlling 20 g steel crack growth. The governing equation of crack growth speed da/dt of 20 g steel was built, i.e. the relation of crack growth speed da/dt C* integral.