Research on the Controlling Parameters of Creep-Thermal Fatigue Crack

الملخص EN

The opening process of creep-thermal fatigue crack (CTFC) is studied by finite element method, considering the bilinear kinematic hardening and creep characteristic of the material.

The crack is closed under the compressive thermal stress during the heating and insulating processes.

The tensile stress during the late cooling process, which is normal to the crack face, makes the crack gradually open.

At this time, the temperature of material around the crack has become lower than the creep temperature; therefore, the creep fracture mechanism parameter C* is not applicable.

The CTFC is quite shallow, and comparatively the plastic zone is rather large; thus, the method of stress intensity factor is restricted.

A modified J-integral method is put forward according to the stress analysis of CTFC, which has been proved to be path independent and valid.

The method is used for not only the CTFC but also any unloading crack or the crack in the residual compressive plastic strain field.

Experimental results show that the modified J-integral can be used as the controlling parameter of the CTFC propagation.