Research On V-notched Brittle Fracture

Based on the basic equations of the elasticity plane problem and the two Airy stress functions in the thesis, stress singularity eigenequations and displacement fields as well as singular stress fields near the V-notch tip and the crack tip for homogeneous materials are obtained. Numerical methods to determine the stress intensity factors for single and double stress singularity problems are presented and a pathway is provided to select nodes for improving the accuracy of the stress intensity factor. By utilizing the above methods and the results of the finite element program named MSC/Nastran, the paper carries through specific calculations corresponding to the single stress singularity and the double stress singularity issues, which consist of the cracks for Mode I , Mode II, the mixed mode crack of mode I and II and many V-notched problems. The calculations show that the numerical methods advanced in the paper have the advantages of simplicity, applicability and high accuracy, so that they are perfectly applied for the projects.Based on the theory of Fracture Mechanics, the relation between the critical stress intensity factors for V-notch Kc and the plane strain crack toughness K10c and the brittle fracture criterion of the maximum circumferential stress for single and double stress singularity with the V-notch problems are proposed. Experiments were carried out using two kinds of V-notched specimens made out of plexiglas to verify this brittle fracture criterion. It is indicated that the maximum circumferential stress criterion coincides with the experimental results.