Numerical Simulation Of Welding Deformation For Automobile Engine Exhaust Manifold Based On SYSWELD

Exhaust manifold is an important part of engine can exhaust waste gas though thecylinders when the automobile is working, and also can decided to whether the enginecan work stability. At present, the automobile exhaust manifolds were produced by thetechnology of welding. Large welding deformation and residual stress was producedby the process of welding, which due to the dense welds and they are mostly alongintersecting line of the component. Because the system of automobile require all partscan work stability, as Exhaust manifold need high assembly accuracy and sealingperformance, so welding deformation of automobile exhaust manifold control thatmake an important effect on the real situation.In this thesis, a typical local structure which has a T type welded pipe choosefrom exhaust manifold was researched by the finite element analysis softwareSYSWELD, at same time which was adopted by welding thermal elastic-plastic finiteelement theory, and also added to consider the material thermal physical propertieswith the temperature change and thermal boundary conditions. The thermal actionfeatures of409ferrite stainless steel’s MAG welding was described, a new type ofcomposite heat source was based on a single double ellipsoid heat source and3dgaussian heat source are combined, and a additional volume heat source wasconsidered for molten drop, accordingly. The obtained weld pool shape by simulationis similar to the shape in experiment. The simulated results of local model’s weldingtemperature field and stress strain field show that:（1）For the welding of a structurewhich contains multiple sets of T type welded pipe, the technology of interval jumpwelding was adapt,it means that can effectively avoid the high residual deformationand stress, which exist due to superposition heating effect among adjacent welds.（2）The welds, located on interval area between stand pipe and horizontal pipe, shouldprocessed by position welding before welding. In order to prevent the difficultassembly which caused by the large displacement after completed the pipe’s weldingon one side at the ends of the vertical tube before welding the pipe on the other side.The analysis process of simulation results of local model was adopt in thissimulation, the finite element model of the automobile engine exhaust manifold’s complete structure is to analysis the welding temperature field and stress strain field,which was applied by the finite element analysis software SYSWELD. In this paper, itstudied the influence of welding sequence, heat input and the change of fixtureconstraints on the whole component’s welding deformation. The results show that:(1)Optimizing the welding sequence and using symmetry interval skip weldingtechnology, from the middle of components to the bilateral region, can effectivelycontrol the overall deformation;(2) The welding process parameter’s set up shouldguarantee the heat input in a reasonable scope, to reduce the welding residualdeformation;(3) Elastic constraint conditions can control the post welding deformationand welding residual stress more efficient than rigid constraint.This paper’s results provide a theoretical guidance to control the welding residualdeformation of automobile engine exhaust manifold and the components have the samestructural characteristics in the actual production.