Danial Ghahremani Moghadam, Khalil Farhang Doost, Ali Rastegar Mohammadabadi, Mohammad Ramezani Moghadam,
Volume 15, Issue 2 (4-2015)
Abstract
In this study, microstructure, microhardness and residual stress in the butt jointed friction stir welded aluminum alloy 2024-T351 plates with different tool’s rotational and traverse speed is studied. According to the 2024-T351 aluminum is a heat treatable alloy, Hardness test results showed that increasing rotational speed or decreasing traverse speed of the tool reduced hardness in the weld zone. Then, using standard X-ray diffraction, which is a non-destructive method, residual stress in the welded samples is determined. A thermal model of friction stir welding process is simulated by using finite element method in the ABAQUS software. Comparison of residual stress results that obtained from the numerical solution with experimental measurements show that, the numerical model can predict the residual stress fields in friction stir welding joints reasonably. The results show that, increasing rotational speed, cause to higher residual stress in the weld zone, due to generation the higher thermal gradient and also, The higher tool traverse speed will induce a greater high-stress zone with a higher stress value in the weld, because of, a lower heat input and result in the relatively harder metal in the weld zone, causes a greater resistance to the plastic extrusion.
Ali Rastegar, Danial Ghahremani Moghadam, Khalil Farhangdoost, Masoud Tahani,
Volume 16, Issue 6 (8-2016)
Abstract
Friction stir welded butt joints were performed on sheets made of AA2024-T351 aluminum alloy at tool rotational speeds of 400, 630, 800 rpm and traverse speeds of 8, 16, 25 mm/min. The fatigue crack propagation rate was investigated according to standard ASTM-E647 in CT specimens. FE simulation of FSW process was implemented for different welding conditions and next the fatigue crack propagation was simulated using XFEM method. In this analysis, to assess the damage in the joints, maximum stress criterion is used. The maximum principal stress in element was the fracture criterion. Numerical results are in good agreement with the experiments so the simulation is reliable. The obtained results show that the tool rotational and traverse speed affect the fatigues crack growth rate. For all welded specimens crack propagation rate was slower than that of the base metal for low values of ∆K (∆K≤13 Mpa) but is much faster at high values of ∆K. Furthermore fatigue properties of specimens that welded with lower speeds are better than base metal and increase in rotational or traverse speeds of the tool will increase the crack propagation rate of the welded specimens.
