Two Dimensional Non-Linear Finite Element Analysis of Strain Energy Density in Cracked A-517 Steel Plates

摘要

A two-dimensional non-linear finite element analysis has been carried out to study the variation of the local strain energy density, dW/dV, in the neighborhood of a crack in A-517 steel compact tension specimens. It has been found that there exists a particular direction, theta, in which the variation of dW/dV is anomalous to its well-known general decay from a very high value close to the crack tip to a low value further away from the crack tip. This direction is considered as the probable direction of the crack propagation. This anomalous variation of the local strain energy density leads to the establishment of its two critical values, (dW/dV)min and (dW/dV)con, which are independent of the crack length and specimen geometry. It is suggested that the criticality of (dW/dV)min may signify a local instability ahead of the crack tip leading to the onset of crack initiation; in addition, the criticality of (dW/dV)con may signify a global instability leading to the catastrophic fracture or plastic collapse of the specimen. It has also been demonstrated in the present study that the failure loads can be numerically and reliably predicted for any crack length.