STRAIN-ENERGY RELEASE RATE FORMULAS FOR 3D FINITE-ELEMENT

Three expressions for the strain energy release rate for three-dimensi onal singular and non-singular finite elements are derived based on Ir win's virtual crack-closure method. The strain energy release rate for the three modes of fracture mechanics can be expressed in terms of th e nodal forces ahead of the crack front and the opening displacements behind it. The material is assumed to be isotropic. The formulae are d erived for three different element types, namely, 20-node singular ele ment, eight-node and 20-node non-singular elements, The validity of th e derived formulae is checked by comparing their results to those from the literature for mode I and mixed mode I and II problems.