樹脂管の急速破壊伝ぱに対する抵抗性評価への落錘衝撃試験の適用

Abstract

Brittle fracture behavior of medium and high density polyethylene pipes has been investigated. The drop weight tear test (DWTT) was applied as a simple evaluation method to solve the rapid crack propagation problem of polyethylene pipes. Since the critical ductility index of fracture surface of plastic pipes is needed to evaluate the crack propagation/arrest temperature, the crack propagation velocity in DWTT specimens was measured and the relation between the velocity and the ductility was investigated. As a result, velocity decreased with increasing ductility to 100m/s at about 30% ductility. Data analysis was performed by Mimura's method which takes the competing velocities of gas decompression and crack propagation into consideration. From this analysis, it was concluded that the critical ductility index for plastic pipes, such as polyethylene pipes, should be less than that for steel line pipes, because the crack propagation velocity of polyethylene is less than that of steel.