In this paper, we discuss J-integrals near models Ⅰ and Ⅱ crack tips for the plates of linear-elastic isotropic homogeneous material and orthotropic composite material, using the theories of complex function and calculus, and obtain the result as follows:(1) The various J-integrals are transformed into standard form of line integrals with respect to coordinates: J=∫rp(x,y)dx+Q(x,y)dy (2) Independence of path of the various J-integrals is proved.(3) Computing formulae of J-integrals are derived.
Rice,J.R.,A path-independent integral and the approximate analysis of strain concentrations by notches and cracks,J.Applied Mechanics,35,2(1968).379-386.