An integral representation of the displacement for problems of transient propagation of horizontally polarized shear waves is employed to investigate the diffraction of a plane wave by a crack of finite length. The stress intensity factors at small times are derived for an incident wave of arbitrary shape. For a step-stress wave the maximum stress intensity factors are shown to exceed the factors of the corresponding static problem by a factor 4 π. Brittle fracture is subsequently investigated by employing a balance of rate of energy. It is shown that for a step-stress wave the critical stress for brittle fracture is reduced by a factor π 4√2 as compared to the critical stress of the corresponding static problem. Ductile fracture is studied by assuming that yielding is restricted to a narrow band in the vicinity of the crack tips. The propagation velocity of the zone of yielding is computed and the location of the point of rupture is determined.
ASJC Scopus subject areas