Evaluation of Time-Dependent Fracture Mechanics Parameters of a Moving Crack in a Viscoelastic Strip

The present work studies time-dependent stress fields around a moving crack tip in a viscoelastic strip and crack extension resistance. Photoviscoelastic technique is employed for the evaluation of the time-dependent stress state around a crack tip. For the fringe pattern analysis, a new technique using an elliptically polarized white light, which can determine isochromatic and isoclinic parameters simultaneously from a colored image obtained by a single acquisition, is applied. The time-dependent stress intensity factor K*I which is extended for linearly viscoelastic materials is evaluated using a method based on least-squares. The results show that the proposed crack extension resistance K* may be considered as a characteristic property of the material under monotonically increasing load.