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A Semiempirical Approach to the Extension of Stress Cracking in Polymeric Materials under Creep Conditions

The aim of this work is to derive a semiempirical equation for the crack-extension rate of stressed polymers. This is achieved by using the Dugdale model and assuming that an imaginary crack jerks and transfigures itself into a true crack when a plastic strain near the crack-tip reaches a critical value. The overall rate of plastic deformation is shown to play an important role in determining the rate of steady crack-extension. Finally, the life time is written as a function of the distribution of dislocation density, applied stress, the Newton viscosity, temperature, the stress sensitivity (or the activation volume) and some material constants. This formulation of the life time can be reduced to the so-called the Holland—Turner’s equation and to the Zhurkov—Narsulaev’s equation for the region of low-and high-stress applied, respectively.