| 摘要: | 研究期間：10108~10207;Aluminum alloys have many excellent properties, and welding is one of their important manufacturing processes. Therefore, welded aluminum structures have been widely used in various industries. In engineering use, fatigue is the most important failure mode of welded structures. Because the material microstructures, geometry and flaws near the welds are not easy to control, the traditional fatigue analysis method must be modified. To offer engineering applications, a number of associations developed fatigue design codes for welded structures according to the regression of fatigue failure data. They divided welded aluminum structures into several categories, and recommended the corresponding stress-life (S-N) line. But, these design codes have some shortness, such as they neglected the effects of materials type, welding method and structural thickness, etc. In addition, the validation of fatigue assessment approaches of welded aluminum structures under variable amplitude loading is lacking. This is a three-year project. The effects of several variables including materials (aluminum alloys 5052 and 6061), thicknesses (4 mm and 12 mm), joints (butt joints and T-joints), and welding methods (gas tungsten are welding and vacuum brazing) will be studied. The fatigue properties of welded aluminum structures under constant and variable amplitude loadings will be obtained, respectively. In this project, methods for the fatigue evaluation of welded aluminum structures are assessed from the view points of original design (without cracks) in the first and second years. We will examine the suitability of related design codes, and establish the best fatigue life analysis method when the welded aluminum structures are under variable amplitude cyclic loading. In the third year, we will investigate methods for the residual life estimation of existing welded aluminum structures (with cracks). Fatigue design of these two perspectives can complement each other and construct a complete fatigue design system. |
