Theory Research And Virtual Optimization On Aero Engine Blisk Welding Distortion

Aiming at the project on welding distortion of aero engine blisk, careful studies and analysis are made on both important parts, including the theory investigation and optimization. The theory research mainly centered around bone of contention issue in welding field, namely the compressive plastic strain or the tensile plastic strain presents in weld when the welding process is completed, finite element method is employed to calculate welding distortion during the welding process. Focusing on the analysis whether the compressive plastic strain is changed by the melting phenomenon, The study reveals melting phenomenon can't change the solid metal constraint around molten pool, So far as longitudinal dimension is concerned, longitudinal dimension of metal melted keeps the same one as before being melted, it should be regarded as a kind of equivalent form which compressive plastic strain is kept down, moreover, at large analyzing transient change of different points in the heat affected zone(HAZ), the calculation results show that the tensile plastic strain of the points in HAZ lag slightly behind weld centre and the lagging time gets longer with the distance away from the weld centre, and it keeps compressive plastic strain all the time, this makes important contributions to the compressive plastic strain in weld, through above analysis , the viewpoint which the tensile plastic strain presents in the weld is denied, the theory research is applied to the aero engine blisk optimization design, providing the theory and numerical evidence.In addition, modifying Dieter Radaj principle sketch map of welding thermal stress–strain, the elastic strain and plastic strain distribution are analyzed during the welding process,respectively. The results show the elastic strain and plastic strain distribution are very complex. If the zone is only carved up four sections: compressive plastic strain zone, tensile plastic strain zone, elastic upload zone and molten pool. Which can't accurately express the elastic strain and plastic strain distribution characteristic. According to the finite element analysis results, the tensile plastic strain zone should be modified, new thermal elastic-plastic principle sketch map of welding thermal stress–strain consists of elastic loss zone, compressive plastic distortion zone, molten pool , tensile plastic distortion zone, elastic resuming zone and tensile elastic distortion zone. Based on the ideas, Dynamically Controlled Heat Cycling Removing Stress (DC-HCRS) welding technology which the following heat source is loaded in the elastic distortion zone is put forward to removing welding residual stress, this method has many advantages, including the brief operation, easy implement, preferably eliminating stress and raising productivity. The welding process of aero engine blisk is very complex, so it is difficult to get a highly qualified blisk using normal welding ways. Despite the results of the residual stress and strain obtained by experiment are accurate, it needs lots of money, for the reasons above, in virtue of finite element method, the large project software Msc.marc is used to make analysis on residual stress and distortion among different optimizations, The electron beam welding(EBW) is different from other welding methods, depth-to-width ratio is very large, which can't be performed by general heat source. Though some literates deduce many equations of welding heat source, but these heat sources can not express the characteristic of EBW heat source, aero engine blisk has very strict demands to the welding distortion, if the ideal calculation results are obtained, a nicely heat source has to be made up, therefore, double-ellipse attenuation volume heat source is deduced, it can denote not only penetration effect but also different energy distribution from front to rear molten pool. and through changing the parameter of equation , it can be transformed into the column heat source, similar double-ellipsoidal volumetric heat source and plane heat source.The follow optimization cases are adopted during the welding of blisk. First, as the depth of the bead is different, reducing heat input by changing of the power with weld depth is put forward to controlling the welding residual stress and distortion of blisk, approximately reducing the relationship between the power and penetration is linearity relation. Comparing two different power, the calculation results show that the welding residual stress and distortion of the aero engine blisk can be controlled by reducing heat input on the conditions of meeting the demand of weld penetration and guaranteeing the quality of the welding; Second, the weld tabs play rigid constraint and distortion diversion role in the welding process, The critical value of weld tabs is calculated according to different long weld tabs, impending the critical value method is adopted gradually to confirm critical length of weld tabs, according to the calculation results of different length weld tabs, the critical length weld tabs are obtained; Third, influence of welding sequence is analyzed, several typical welding sequences are calculated by means of conforming with minor temperature influence among diverse welds, the relatively reasonable welding sequence is obtained; Finally, the reverse remelting and heating method is performed to solve the welding distortion when the turntable and integral leaf joints are welded together.