NUMERICAL INVESTIGATIONS ON THE SIGNIFICANCE OF J FOR LARGE STABLE CRACK-GROWTH

Stable crack growth under incremental theory of plasticity, small deformation and both plane strain and plane stress conditions was investigated by the finite element method simulating experimental tests on compact tension specimens. In order to validate the numerical calculations, the sensitivity of the results to the mesh and crack extension increment as well as the effect of crack growth controlling parameters have been studied. The J contour integral was evaluated in the far as well as in the near field which appeared to be strongly path-dependent immediately after initiation with a limit of zero if the area within the integration contour tends to zero. Under this aspect, the possibility of using near field integrals like those proposed by S.N. Atluri et al. in an elastic-plastic solid is discussed. The far field J value calculated from the contour integral is compared with the common formulas used to evaluate J from experimental load-displacement curves.