Dynamic elastic-plsstic Crack Curving Phenomenon

탄소성 동적 균열전파의 만곡현상

The elastic dynamic crack curving could be obtained by controlling the loading rate, the initial crack-tip blunting to store much energy before crack initiation and the magnitude of reflected wave from finite boundaries. However there is no theoretical and experimental elastic-plastic dynamic curving study. This paper proposes a specimen geometryfor a study of dynamic elastic-plastic crack curving and presents a preliminary result. The specimen has a blunt physical crack tip on a side, and a round notch tip on the other side. From the experiment using this specimen, it is found that the narrow plastic zone ahead of the round notch tip produces the change of load direction and anti-symmetricity of the dynamic isochromatics, and each result causes the crack curving phenomenon. After a certain time, as the elastic-plastic crack gets close to the round notch tip near, the degree of the crack curving get larger. The elastic reack curving propagates more sensitively to the surround of crack tip than the plastic crack curving does. The cynamic elastic-plastic crack curving is found to be proportional to the CTOA(the crack tip opening angle). The dynamic elastic-plastic crack may propagate in the direction perpendicular to the loading. An apparant strip yield zone which is similar to the Dugdale strip yield zone is noted ahead of the physical crack tip.