Energy balance criteria for viscoelastic fracture (original) (raw)

An energy balance criterion of the Griffith type has been used to derive conditions that are valid, in the isothermal noninertial approximation, for the growth of cracks in viscoelastic bodies. These bodies are acted upon by general position and time-dependent load. The conditions have the same form as the instability conditions obtained for the corresponding problems in elasticity theory and, in particular, are independent of crack velocity. The analysis relies upon an exact calculation of the displacement and stress fields that is derived in the Appendix with the aid of extensions to viscoelasticity of the Kolosov-Muskhelishvili equations of elasticity theory.