Abstract
Rotating bending fatigue tests were performed on three high tensile-strength aluminum alloys, i. e. ZK41-T6 extruded, 2024-T6 extruded, and drawn Al alloy in various environments in order to investigate cup and cone fatigue fracture. Cup and cone fracture was only observed on ZK41-T6 extruded Al alloy tested in the environments of argon gas, nitrogen gas, or mineral oil. It is thus concluded that environment is one of the factors that control the cup and cone fracture of high tensil-strength Al alloys.
In argon or nitrogen gas, fatigue strength was smaller than in air, due to the occurrance of cup and cone fracture. In the oil environment, fatigue strength also decreased below that in air, because oil wedge action against fatigue crack growth cannot be expected for cup and cone fracture. From the air-oil two stage fatigue tests, it was observed that the mechanism of rupture changed from tear to sliding rupture when the environment was changed, and that small cup and cone fracture appeared. However, the fatigue life increased as compared with that calculated from Miner's law.
