Physical interpretation of the J2 integral by identifying the associated crack translation

The physical interpretation of the J integral (i.e., J₁ integral) is clear. J₁ integral is the energy release rate associated with crack extension(i.e., translation of the crack in the x₁ direction). However, the physical interpretation of the J₂ integral remains unclear. In this study, different crack translations in the x₂ direction were selected and tested by calculating the energy release rates associated with the crack translations and comparing them with the theoretical value of the J₂ integral.