ぜい性プラスチックス破面模様の一次き裂伝ぱによる変化 : 比較的長い中央き裂を持つ場合

抄録

We have reported that fracture surface marks in brittle plastic sheet specimens having short (≤ 5mm) and long (≥ 40mm) central primary cracks are well expressed by equations under the fracture conditions of a constant load (or stress) and a constant deflection (or strain), respectively. Here, we discuss the velocity and the marks in the specimens having an intermediate-length central crack. The crack velocity is measured and expressed by an equation where the velocity is presumed to be composed of both constant stress and strain components. In this case, a fracture starts with a constant stress condition which changes gradually to a constant strain condition as the crack propagates, and we call this a fracture in a mixed condition. This velocity expression, combined with the existing relation between crack velocity and a dynamic stress-intensity factor, gives the variations of the dynamic stress-intensity factor and a dynamic strain energy release rate both of which excellently predict the experimental variations of the fracture surface marks in those specimens such as the number of marks, the relative interference appearing distance (e/C_o2) and the relative critical distance (d/C_o2).