Crack-velocity due to combined tensile and impact loading

Abstract
A surface-deposited resistance grid technique has been used to measure crack-velocity versus distance curves for P.M.M.A. edge-notched specimens fractured under combined tensile and impact loading. The velocity profiles were dependent upon both the impact energy and the tensile stress. The effect of the impact was transient and the growth of the crack was mainly controlled by the pre-load stress through its affect on the crack-tip stress intensity. For appropriate loading conditions, cracks moved initially at high velocities then decelerated to a minimum velocity and accelerated again. It is suggested that the stress intensity on the crack-tip at the point of minimum velocity is the dynamic fracture toughness of the material at that velocity and data for P.M.M.A. are presented.

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