Conjoint influence of environment and load on fatigue life of a bolted aluminum alloy structure

In this paper, an attempt is made to describe the decline in fatigue life of an aluminum alloy structure containing bolted joints under the conjoint influence of an aggressive aqueous environment and loading that is essentially cyclic in nature. In an attempt to project the real situation experienced by an aluminum alloy structure containing bolted joints while in service, an alternate cycle test method was used to essentially include the damage caused by the environment and cyclic loading. A chloride-containing solution was used to simulate the damage caused to the bolted structure upon exposure of the aluminum alloy structure containing a joint to the environment. The nature of fatigue loading was essentially cyclic tension. It was found that following an observable amount of environment-induced damage caused by exposure to a wet–dry environment followed by cyclic loading, the fracture position revealed a noticeable shift from the centerline of the bolt hole to the loading end. This can be attributed to the occurrence of fretting-related damage at the fine microscopic level. Based on an assumption of an average fracture line, a life prediction model was established. Compared with experimental results, the prediction method considering the fracture position to shift from the centerline of the bolt hole does provide results with a reasonably high degree of accuracy. The method proposed in this study does provide a convincing approach for reliable estimation of life, or endurance, of an aluminum alloy structure containing joints.