論文ID: 17-00151
In turbomachinery, such as turbine, pump, and valve, components damage caused by collapsing cavitation bubbles has been a critical issue that needs a proper solution. For this reason, investigation on the cavitation erosion behavior of materials as well as the life prediction techniques has been extensively conducted. Moreover, a number of repairing techniques, such as by a surface coating of polymeric materials, has been established. However, in real operation, cavitation is actually not the only load acquired by the components. Other external loads, such as centrifugal force and hydraulic pressure, may also affect the generation of damage. Therefore, its effect on the lifetime needs to be considered carefully. In this paper, the behavior of cavitation damage of epoxy resin specimens subjected to uniaxial tensile loading is reported. A self-developed testing device was used to conduct a cavitation test based on ASTM G32 while at the same time exerting a constant uniaxial tensile load to the specimen. Using this device, various levels of tensile stress effect on the cavitation damage was examined. As a result, besides erosion damage, we revealed that the specimens demonstrated fracture when a certain tensile load was applied. Furthermore, as the tensile load was increased, the time to fracture was shortened significantly, indicating the pronounced effect of tensile stress on the damage formation. The crack growth mechanism was then analyzed by fractography. The result indicated that the crack propagation under a mixed condition of cavitation and tensile loads was most likely driven by the combination of creep deformation and fatigue-like crack growth. Finally, a mathematical relationship between tensile stress and cavitation damage life was proposed. The relationship is important to enhancing the existing theory of cavitation damage evaluation in e.g. turbomachinery application.
