Study On Strain And Fatigue Prediction Of Aluminum Alloy Plate Stir Friction Welding

During friction stir welding,there will be a relatively large temperature gradient in the weld zone,and the temperature field will change with the movement of the stirring head.This non-uniform heating and cooling process in time and space will cause welding residual stress and residual deformation.Welding residual stress will affect the damage tolerance and fatigue life of the structure,and residual deformation will affect the assembly of components.Therefore,it is of practical engineering value to study the residual stress distribution,residual deformation and fatigue life of friction stir welding.Although the residual state can be studied using experimental methods,it is easily affected by the surrounding environment and the time period is relatively long.Therefore,it is necessary to study the friction stir welding process using numerical methods.In this paper,the numerical simulation method was used to study the temperature field,residual stress field distribution and post-weld deformation of butt welding in flat panel,and a single variable control method was used to compare the friction welding process by changing different welding parameters.The study of the influence of residual stress of welded joints on fatigue of welded components.The chapters in this article are organized as follows:Chapter 1 summarizes the research progress of friction stir welding technology,mainly including the welding principle of friction stir welding and the main welding process parameters,the temperature field of friction stir welding components,the residual state of friction stir welding components,the microscopic view of the friction stir welding joints.The distribution of tissues and the study of fatigue performance,and summarizes the main work in this article.Chapter 2 introduces the basic theory of the thermo-mechanical coupling model of friction stir welding.In the third chapter,a sequential thermo-mechanical coupled finite element model is established,and the procedure of moving the heat source of the stirring head is programmed through the ABAQUS subroutine,and the welding process of friction stir welding is simulated and simulated.In the fourth chapter,through sequential thermo-mechanical coupling simulation analysis of friction stir welding,the distribution cloud and variation curve of welding temperature field,stress field distribution and welding residual deformation are obtained,and the general rule is obtained: the temperature field during friction stir welding is obtained.The distribution shows a semi-elliptical distribution around the stirrer head;the residual stress is mainly distributed in the weld area,mainly in the longitudinal residual stress,and appears “M” in the direction perpendicular to the weld,along the direction of the weld.A parabolic distribution is present;the welding deformation mainly shows a downward trend in the area of the weld.Chapter 5 uses a single variable control method to control the rotational speed,welding speed and shoulder radius of the stirrer's welding process parameters,and to study the influence of welding parameters on the temperature field and residual stress field of friction stir welding.Chapter 6 studies the effect of residual stress on the fatigue of welded components.It is found that the residual stress at the weld is mainly in the form of tensile residual stress,and the fatigue life of the component is reduced due to the presence of tensile residual stress.The welding stress can be reduced by changing the welding parameters to reduce the residual stress at the weld to improve the life of the components.Chapter 7 summarizes the work in this article and looks forward to the future work.