A CONTOUR INTEGRAL METHOD FOR DYNAMIC STRESS INTENSITY FACTORS

The contour integral method previously used to determine static stress intensity factors is applied to dynamic crack problems. The required derivatives of the traction in the reference problem are obtained nume rically by the displacement discontinuity method. Stress intensity fac tors are determined by an integral around a contour which contains a c rack tip. If the contour is chosen as the outer boundary of the body, the stress intensity factor is obtained from the boundary values of tr action and displacement. The advantage of this path-independent integr al is that it yields directly both the opening-mode and sliding-mode s tress intensity factors for a straight crack. For dynamic problems, La place transforms are used and the dynamic stress intensity factors in the time domain are determined by Durbin's inversion method. An indire ct boundary element method, incorporating both displacement discontinu ity and fictitious load techniques, is used to determine the boundary or contour values of traction and displacement numerically.