A numerical scheme, incorporated with the finite element method, is developed for calculation of the J(2)-integral for 2-D cracks appearing in rubbery fields under large deformation. The scheme is formulated based on the concept of the generalized version of the domain integral method. Due to the nature of J(2), the method is shown to be "patch-independent" in a modified sense, and so the near-tip region is always included in the calculation. The proposed technique is therefore particularly addressed to appropriate modeling of the near-tip singular mechanical behavior in order to circumvent the unavoidable imprecision associated with the finite element approximations in the vicinity of the crack tip. The numerical results show that no a priori information on the asymptotic singular behavior is required in order to achieve an acceptable value of J(2). The computation procedure is generally feasible for different rubbery material models. (C) 1998 Elsevier Science Ltd. All rights reserved.
