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 linearlyviscoelastic material is investigated. A new incremental fractureequations relating viscoelastic stress intensity factors (VSIFs) toviscoelastic opening displacement intensity factors (VODIFs) areestablished. Crack growth initiation is studied in detail by means of acomputational approach based on a modified path independent integral. Itis found that the mechanical and kinematical fields around the crack tipcan be determined using an incremental formulation based on a discretespectrum representation of the viscoelastic compliance functions; thusthe difficulty of computer storage requirements is avoided. Numericalresults are obtained for predicting the time at which propagationinitiates and these are compared with the analytical solution.