| Electric pallet forklift is a kind of logistics handling equipment,which has the advantages of simple operation and can adapt to complex environment.It is widely used in stations,ports,production workshops,airports and modern Internet logistics companies.The welding of the rear frame of the electric pallet forklift is an important part in the manufacturing process of the electric pallet forklift.Its welding quality and welding shape variables have a significant impact on the assembly and use of the forklift.Therefore,it is of great significance to study the welding deformation of the rear frame of electric pallet forklift.This paper simulates the whole welding process of the rear frame of the electric pallet forklift,studies and analyzes the influence of the welding process on the welding deformation of the rear frame of the electric pallet forklift,which is helpful to control the welding deformation of the electric pallet forklift.The main contents of this paper are as follows:(1)The finite element model of temperature field in welding process is established,and the mechanical model of welding process is established based on the incremental elastic-plastic principle.The model considers the influence of convection,phase transformation and other factors on welding,which lays a theoretical foundation for the follow-up finite element simulation analysis of electric pallet truck welding.(2)The MIG welding finite element model of the rear frame of the electric pallet forklift is established.The visual mesh software is used to optimize the model and mesh,and the welding materials are selected,and the constraints are specified in combination with the fixture clamping situation.At the same time,the Gauss heat source model is also used.According to the actual production situation,the welding sequence in the finite element model is planned,and the corresponding welding process parameters are set.(3)The temperature field,equivalent force field and deformation field of weldment as well as its changing trend with time are studied.By analyzing the simulation results,it is found that the highest welding temperature is 2216 ℃,which occurs in the weld between the side plate and the outer shroud.The welding equivalent residual stress is mainly concentrated in the weld area between the rear vertical plate and the two side plates and between the outer shroud and the U-shaped support.The maximum welding residual stress is about 716 mpa,which is located at the upper end of the weld between the rear vertical plate and the side plate.After the workpiece is cooled for 1h,the welding deformation is mainly concentrated on the two side plates and the top right angle position of the U-shaped groove of the cowl panel.The maximum welding deformation is 1.57 mm.(4)In order to verify the correctness of the welding finite element simulation model,with the help of cooperative enterprises,a welding test platform was built and the welding experiment was completed.By comparing the simulation welding deformation results,the relative error was controlled within 14%,which verified the reliability of the simulation model.The influence factors of welding deformation are analyzed.Taking the rear frame welding of electric pallet forklift as the research object,the influence rules of welding speed,welding sequence and welding energy on the welding deformation of the rear frame are studied and analyzed.According to the welding sequence,two kinds of optimization schemes are given,and the optimization scheme is compared through simulation analysis,so as to obtain the optimal scheme,and the maximum welding deformation is greater than the original one The scheme is reduced by 12.2%. |
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