Abstract
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.
Highlights
In recent years, the increased demand coupled with the concurrent need for high strength and an acceptable stiffness/weight ratio (E/ρ) of aluminum alloys has revealed a gradual decrease due to the development and emergence of composite materials as technologically viable and economically affordable alternatives for the purpose of selection and use in the emerging and newer generation of aircraft
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
The presence of corrosion-induced products both at and along the edges of the bolt hole provides a clear indication of the extent and severity of damage due to the conjoint influence of exposure to an aggressive aqueous environment followed by cyclic loading
Summary
The increased demand coupled with the concurrent need for high strength and an acceptable stiffness/weight ratio (E/ρ) of aluminum alloys has revealed a gradual decrease due to the development and emergence of composite materials as technologically viable and economically affordable alternatives for the purpose of selection and use in the emerging and newer generation of aircraft. Liu et al. in their independent research study designed a periodical accelerated corrosion test to simulate the alternate exposure of an aircraft structure to both rain and sun that often occurs at a typical airport in the coastal region.11 An environment, such as the ocean atmosphere, contains all the ingredients that favor chloride-induced damage due to corrosion, ultraviolet radiation, and the resultant influence on damage. It becomes meaningful to carry out life prediction calculations for a structure that is under the influence of a cyclic load immediately following exposure to an aggressive aqueous environment and the resultant environment-induced damage or corrosion. The damage experienced by the bolted joints of a high strength aluminum alloy under the alternate influence of exposure to an aggressive environment followed by cyclic loading was studied. The influence of the environment on the fatigue life of the structure containing bolted joints was studied using the approaches of both the experiment and simulation
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