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. Photoviscoelas tic technique is employed for the evaluation of the time-dependent stress s tate around a crack tip. For the fringe pattern analysis, a new technique u sing an elliptically polarized white light, which can determine isochromati c and isoclinic parameters simultaneously from a colored image obtained by a single acquisition, is applied. The time-dependent stress intensity facto r 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-I*(C) may be considered as a characteristic pr operty of the material under monotonically increasing load.