Abstract
Recent progress in the study of dynamic fracture mechanics is reviewed. Attension is forced on the mode-I (crack opening mode) fracture from a practical viewpoint. In contrast to static fracture mechanics, both mathematical and experimental difficulties are encountered in the efforts to understand the dynamic fracture phenomena and there still remain some unanswered questions. For example, an enormously sharp increase in the impact fracture toughness KId observed at very high loading rates can be explained by assuming the existence of a fracture incubation time, but its physical background remains unknown or uncertain. For another example, the experimental data indicating the geometrical or crack-acceleration dependence of the crack propagation toughness KId raise a serious question about the extent to which the basic assumption, K(t, v) = KID (K(t, v) denotes the dynamic stress intensity factor), can be validly used. Further study is expected to answer these questions.
