Effects of High-Rate Fracture of Brittle Materials

Abstract

One of the main problems of testing the characteristics of resistant materials in dynamics is the dependence of dynamic strength on the way that the exterior action is applied. This difficulty typically appears under conditions of high-rate loading. In this case, the strength can be interpreted as a critical value of the stress-intensity factor which corresponds to microcracking near the crack tip. The strength can also be interpreted as a dynamic local stress leading to rupture continuum. Both are intensity limits of a local stress field and the fracture occurs when these limits are reached. The dependence of dynamic strength on the method of loading is manifested as critical values during variations of action duration, of amplitude, and of rate of rise of the exterior force. In the case of macrocrack motion initiation, such values will be critical as regards the stress-intensity factor of growth of the macrocrack. During fracture of ‘intact’ solids (i. e., not containing the given macroscopic defects) the local cleavage stress is not determined by a material’s characteristics but as a complex function of loading history.