A 3-D APPROACH TO THE CALCULATION OF THE ENERGY-RELEASE RATE IN SOME FRACTURE PROBLEMS

A 3-D ellipsoidal flaw model is sufficiently versatile to cover a wide variety of flaw shapes: existing 2-D flaw models are special cases. T he energy release rate from an ellipsoidal flaw in an infinite medium may be calculated by both a 'strain method' and a 'displacement method '. Solution techniques for both tension and compression are presented. The results calculated by both methods are in excellent agreement wit h available explicit results. The simpler and more efficient strain me thod is preferred in the calculation of the energy release rate for va rious flaws, except for line cracks and flat cracks subject to tensile stress normal to the crack plane. The 3-D formulation has considerabl e promise for providing understanding of the effects of various parame ters on the energy release rate under triaxial stress states.