Effect of hydrostatic pressure on the yield and fracture of polyethylene in torsion

摘要: Yield and fracture of polyethylene have been studied in torsion tests under superposed hydrostatic pressures. Two ductile-to-brittle transitions observed. At high strain rates pressures, a conventional transition was found with increasing rate pressure. A second observed at low decreasing rate. The yield stress showed region low, relatively constant, dependence rates, temperatures pressures higher strain-rate In contrast, the throughout to constant intermediate value between those obtained for stress. These features confirmed that failure can be considered as competition processes. became lower than both where brittle observed, fully ductile behaviour resulting conditions exceeded pressure, temperature well described by two Eyring processes acting parallel, being pressure dependent.