A Study On Numerical Simulation Of ZS125-70 Motorcycle Rear Fork Welding Process

The motorcycle rear fork belongs to the suspension device of motorcycle, which mainly consists of left and right rear fork side tubes, axle tubes, connector tube, stiffener plates, installing linings and other parts. The forming method of the motorcycle rear fork is mostly welding assembly process, which has the characteristics as follows: complicate welding process, dense welds, large residual stress and deformation after welding in welding structure, hard to ensure quality and structure sizes. These can not only reduce the carrying capacity of rear fork structure, but also affect vehicle assembly and vehicle performance. Therefore, it is very necessary to study and master the distribution rules of welding residual stresses and welding deformation in motorcycle rear fork, and control or reduce the welding residual stresses and distortion.In this paper, ZS125-70 motorcycle rear fork was simplified and split into the assembly of axle tube and side tube, the assembly of connector tube, stiffener plate and side tubes, and the assembly of installing linings and side tube. Firstly, based on structural characteristics of assemblies, their mesh models were built by using Pro-E 3D modeling software and Visual Mesh software. According as welding process characteristics and the actual welding process parameters, their own welding heat source model, constraints, solver parameters and numerical simulation programs were suitably made.Secondly, based on the finite element analysis theory of welding thermal process, and taking into account the material properties with temperature and the heat transfer boundary conditions such as convection and radiation. Their respective transient temperature fields were simulated by using the welding special finite element analysis software SYSWELD. In this paper, their temperature evolutions and thermal cycles nearby welding beads were given, and the temperature field distributions were quantificationally analyzed. Meanwhile, their own thermal cycles nearby welding beads were measured by using the welding thermal cycle test system, which were almost consistent with the simulation results. Therefore, the welding temperature field simulations were credible.Finally, based on the welding thermo-elastic-plastic finite element analysis theory, taking into account the material mechanical properties with temperature, constraints which were consistent with the real clamping conditions, and on the premise of that the welding temperature field simulations had been verified, their own welding residual stress fields and the welding deformation of rear fork structure were simulated by using SYSWELD. In this paper, each welding residual stress fields and the welding deformation simulation result of the rear fork structure were given and quantitatively analyzed. Meanwhile, the calculated deformation of the rear fork structure was applied as the welding pre-deformation to the actual production process, in which qualified products were produced.The quantitative analyses of the welding temperature fields, residual stresses and distortion provided a theoretical guidance for controlling and reducing the welding residual stresses and welding distortion,and laid the theoretical foundation for solving practical problems. This article puts forward a study method which is scientific, new and short period for using new materials and developing new products in welding structure.