A new domain-independent interaction integral for solving the stress intensity factors of the materials with complex thermo-mechanical interfaces

Thanks to the feature of being domain-independent for the interfaces with discontinuous mechanical properties, the domain-independent interaction integral (DII-integral) has become a quite effective method to solve the stress intensity factors (SIFs) of the materials with complex interfaces. However, the DII-integral loses its domain-independence feature for the interface with a discontinuous thermal expansion coefficient, which causes a great difficulty in applying the DII-integral to deal with the materials with complex thermo-mechanical interfaces under thermal loading. In order to overcome this difficulty, this paper proposes a zero-mean stress auxiliary field and employs it to establish a new DII-integral. The new DII-integral is domain-independent for the interface with discontinuous mechanical properties as well as discontinuous thermal expansion coefficient, and its expression does not contain any thermal property parameters. These features greatly facilitate its practical application in solving the SIFs of the material with complex thermo-mechanical interfaces. Finally, the DII-integral combined with the extended finite element method (XFEM) are used to solve the SIFs of adiabatic cracks in order to verify its effectiveness.