Modeling And Analysis Of Force And Temperature Field In The Welding Zone Of Friction Stir Welding

Friction stir welding(FSW),a solid-phase joining technology,has been widely used in the welding of rocket fuel tanks,for example,and the increase in rocket diameter has also put forward higher requirements for the load-bearing capacity and welding quality of the welding equipment,while the welding force has an important impact on the quality of the welding process and is closely related to the process parameters,which is one of the main factors in the control of the welding equipment.In this paper,for the actual engineering application requirements of FSW,the modelling analysis of the force and temperature field in the FSW welding zone is carried out to study the relationship between the influence of the process parameters on the temperature and the welding force.Based on the theory of elasto-plastic mechanics,assuming that the junction of the elastic-plastic region of the welding zone meets the boundary condition continuity,in accordance with the FSW process,the establishment of the welding force model of the FSW welding zone throughout the welding process,taking into account the yield strength and friction coefficient in the model with the temperature change factor,deduced the relationship of force and temperature field of welding tool in the FSW welding zone,on this basis through fortran written Dflux subroutine of surface heat source and body heat source of welding tool into Abaqus finite element software,to get the welding force prediction model based on the temperature field of the FSW welding zone.Consider the strong coupling of the force,temperature,and the material flow during FSW process,take the modified strain-compensated Arrhenius intrinsic model as the material rheological stress,while the welding process segmentation using Coulomb and shear friction coefficient.With the help of commercial finite element software Deform-3D,establish the welding zone thermal-mechanical coupling finite element model,to verify the aforementioned welding force prediction model validity.On this basis,the force of the welding tool is predicted to vary with the welding process parameters,and the response surface model of process parameter is established to provide a theoretical basis for the development of welding equipment and welding process control.Based on the response surface model of welding process parameter,the SQP algorithm is used to optimise the process parameters for a given plate thickness in the stable welding phase.Take the temperature of welding core zone of workpiece in the optimum range and the minimum upsetting force of welding tool as the constraint,the minimum traverse resistance as the optimisation target to ensure the quality of FSW,to determine the optimum rotation speed and traverse welding speed and to provide theoretical support for the application of the new welding process.