Abstract: This paper deals with the path-independent integrals in nonlinear three-dimensional fracture dynamics. Both the nonlinear elastic case and the elastic-plastic case are considered, and some path-independent integrals have been worked out.For explaining the physical meaning of these integrals, a specimen with plane notch is considered, and the relation between the integral and dynamical crack extension force is established. Thus, such integrals may serve as a fracture criterion in nonlinear fracture dynamics.

Key words: ordered space, supremum and infimum, increasing operator and fixed point, singular boundary problem