Quasistatic calculation of linear response for crack propagation

Quasistatic calculation using Mushkelishvili's analytic functions is presented for the linear-response function of the mode I (opening mode) crack shape to externally applied stress in order to examine the importance of the detailed structure of the cohesive zone that has been found in the fully dynamical calculation recently done by Ching, Langer, and Nakanishi [Phys. Rev. E 53, 2864 (1996)]. It is confirmed that the result does not reduce to that of Cotterell and Rice [Int. J. Fract. 16, 155 (1980)] if the cohesive shear stress is included.