1988 年 37 巻 413 号 p. 114-118
The effects of hydrostatic pressure on deformation and fracture energy at the notch bottom of single V-notch test specimens were investigated experimentally on commercial 7-3 and 4-6 brasses by means of the tension tear and three point bending tests. The specimens were soaked under hydrostatic pressures up to 200MPa for one hour before measuring at atmospheric pressure the transient behaviors of such parameters as the fracture toughness, the unit crack initiation energy (UIE) and the unit crack propagate energy (UPE).
The following conclusions were obtained:
(1) The initiation of unstable deformation was delayed by applying hydrostatic pressure.
(2) The pressure soaking treatment dispersed the dislocations piled up at the grain boundaries. This caused a temporary work-softening, and then the increase of fracture ductility and the decrease of flow stress.
(3) A remarkable influence of hydrostatic pressure was observed on the fracture toughness Kc, UIE and UPE in the tear tests. These parameters increased with increasing hydrostatic pressure. This means that both the ductility of fracture and the flow stress increase with increasing hydrostatic pressure. The same results were obtained in the three point bending tests, and they were explained well by the linear fracture mechanics.