Welding Simulation Analysis And Deformation Control Of EMU Roof

Nowadays,high-speed EMUS have gradually become an important way for people to travel.Welding is one of the most widely used joint technologies in the production process of the roof of high-speed EMUS.The welding deformation of the structure affects the appearance of the roof and even causes hidden trouble to the safe operation of the EMUS.Therefore,it is very important to predict and control the welding deformation correctly.In this paper,the roof of a certain type of stainless steel high-speed EMUS is taken as the research object.Based on the thermoelastoplastic theory and the inherent strain method,the welding deformation of the roof containing 6 kinds of welded joints is predicted and controlled,which provides a reference for the welding process design in actual production.The main research contents of this paper are as follows:Firstly,the development history of welding simulation technology and the basic principle of finite element method of welding were introduced,and typical local joints were extracted for heat source check,proved the rationality of the selected welding parameters and heat source model,and the welding thermal cycle curve,residual stress distribution and deformation of each local joint after welding were studied.Secondly,the model of the middle part of the roof was established with SOLIDWORKS software,and the inherent strain values of typical joints were extracted.The inherent deformation values were calculated by inverse analytical method,and compared with those obtained by three-dimensional thermoelastoplastic method.Except for a few measuring points with large errors,most of the other measuring points showed good consistency,which verified the correctness of the inherent deformation.By using the inherent deformation method,the inherent strain was applied to the model of the middle part of the roof,and the welding deformation was calculated.The maximum deformation value was 4.172 mm,which occurred in the roof near the welding of the roof and the 3 mm thick longitudinal beam segment.Thirdly,by studying the influence of different welding process conditions,such as boundary conditions,welding position,welding parameters and other factors on welding deformation,and compared multiple welding simulation results,the optimal welding process conditions of the middle roof model were as follows:The constraint conditions considered four-point minimum constraints + ends translative constraints + longitudinal beam clamping constraints.The weld arrangement adopted symmetrical welding form,and the welding heat input was the minimum heat input under the condition of ensuring welding quality.Finally,based on the computational capability of the existing welding finite element simulation software,the overall model of the roof of a high-speed EMUS was properly simplified,and the rationality of the simplified scheme was verified through calculation and comparison.The optimal process conditions determined above were used for welding simulation analysis of the entire roof,and the distribution of the welding deformation of the entire roof was obtained: The roof deformation near the segmental welding between the roof and the 3 mm longitudinal beam was the largest,and the maximum deformation was about2.473 mm,and the maximum deformation was about 1.05 mm at the first and second ends of the roof.