A new incremental formulation in the time domain for crack initiation in an orthotropic linearly viscoelastic solid

The problem of predicting the crack growth initiation in a linearly viscoelastic material is investigated. A new incremental fracture equations relating viscoelastic stress intensity factors (VSIFs) to viscoelastic opening displacement intensity factors (VODIFs) are established. Crack growth initiation is studied in detail by means of a computational approach based on a modified path independent integral. It is found that the mechanical and kinematical fields around the crack tip can be determined using an incremental formulation based on a discrete spectrum representation of the viscoelastic compliance functions; thus the difficulty of computer storage requirements is avoided. Numerical results are obtained for predicting the time at which propagation initiates and these are compared with the analytical solution.