A method using the conventional finite elements and a finite domain energy integral,Ĵ, was applied to determining the dynamic stress intensity factors for rapidly propagating cracks not only in linear elastic but also in viscoelastic bodies. In order to simulate crack propagation, a node release technique was employed in which the nodal force near the crack tip was gradually reduced to zero according to the prescribed scheme. Several schemes were tested and the most satisfactory result was found to be obtained by the linear relaxation scheme. The dynamic stress intensity factors were determined by evaluating theĴintegral. Three seemingly different representations ofĴ-integral were used and each result for linear elastic problems was in good agreement with the analytical solutions and other available numerical results. The dynamic stress intensity factors for viscoelastic problems were also determined by using a proper representation ofĴ-integ
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