| The drive axle housing,as the installation carrier of the vehicle's main reducer,differential,half shaft,drive wheel and other transmission devices and leaf springs and other load-bearing devices,is a key part of the automobile drive assembly.The drive axle housing is not only a load-bearing part,but also a transmission part.It has to bear the braking torque and reaction force of the transmission system during the running of the vehicle,and also bear the difference between the frame and the road surface caused by the vehicle load transmitted through the leaf spring seat.The vertical force,the longitudinal force and the lateral force are acting between the vertical force,the longitudinal force and the lateral force,and the above-mentioned loads are all complex and alternating heavy loads.Therefore,the drive axle housing parts are required to have high mechanical and fatigue properties.The structure of the drive axle housing is complex,especially the existence of the pipa hole structure where the main reducer is installed,making it difficult to form and process.Traditional drive axle housings mostly use integral casting and punching and welding processes.The former is self-heavy,the material has poor tensile and impact resistance,and casting defects such as porosity and cracks are prone to occur during the production process,so the application is limited;Shells have been widely used in the production of drive axles due to their advantages of light weight,good mechanical properties,and high material utilization.However,due to the existence of the welding heat-affected zone,many welds on the press-welded bridge housing often become the source of fatigue cracks in use,thereby affecting the service life of the press-welded bridge housing.The current research on the forming of the drive axle housing is mostly focused on the overall plastic forming of steel materials,which not only uses the good mechanical properties and formability of the plastic deformation of thematerial,but also avoids the reduction of fatigue life caused by the welding heat-affected zone,internal high pressure forming,New processes for forming drive axle housings such as solid particle bulging and mechanical bulging came into being;among them,mechanical bulging drive axle housing forming combined with shaft head necking and other processes can realize the integral forming of the drive axle housing,with simple process implementation,The advantages of low equipment requirements,and in the integral forming of the heavy and thick-walled drive axle housing,have the advantages that other processes cannot replace,and have good development potential and application prospects.The new process of mechanically bulging drive axle housing is to apply mechanical load to the prefabricated long circular hole of the hot blank,so that the preformed long circular hole expands to form a pipa hole under the constraint of the mold to realize the integral formation of the drive axle housing.However,during the mechanical bulging process,due to the stress concentration and the large bulging ratio,the material at the rounded corners on both sides of the prefabricated oblong hole flows violently to both sides,causing the thickness of the triangular plate area of the drive axle housing after mechanical bulging.Severe thinning will affect the overall performance of the mechanically bulging drive axle housing.Aiming at the serious thinning of the material in the triangular plate area of the mechanically bulging drive axle housing,the thesis carried out the finite element numerical simulation study and the integral mechanical thermal expansion test and bench experiment of the axle housing.The main research work is as follows:For the material for stamping and welding axle housing SAE 1527,thermal tensile experiments at different temperatures and different speeds were carried out to obtain the best temperature and rate of thermal expansion forming of the material;the mechanical thermal expansion process plan of the integral axle housing was determined,and according to The structural characteristics and dimensions of the 510 axle housing determine the three-pass bulging process of coreless pre-bulging,radialexpansion forming,and axial shaping.The thermo-mechanical bulging of the drive axle housing blank(that is,the size of the blank section of the bulging part is the same as the section size of the leaf spring seat on both sides)of the thermo-mechanical bulging was carried out by finite element numerical simulation.The relationship between the width and length of the oblong hole,the stress field,velocity field,and wall thickness reduction during the pre-bulging,radial expansion forming and shaping process have determined that the main defect of the forming is the sharp reduction of the wall thickness in the triangular plate area of the formed part,Given the optimal prefabricated oblong hole size of the uniform cross-section blank and the die size of each pass;and then discussed the influence of the forming temperature,core mold speed,friction coefficient and other process parameters on the forming load and the wall thickness of the triangular plate area.Determined the optimal parameters.The thermal expansion forming process experiment was carried out on the equal-section tube blank with a length of 575 mm and a width of 40 mm.The axial and radial dimensions of the thermally formed part meet the design requirements,and the wall thickness of the triangular plate area is above 8mm.The numerical simulation results are verified.The axle housing bench test was further carried out,and the results showed that the vertical bending strength and rigidity requirements of the axle housing were met,but the fatigue life was less than 1 million times,which proved the need for further blank optimization to meet the performance requirements of axle housing products.Aiming at the problem that the thickness reduction of the triangular plate area after the bulging of the uniform cross-section tube blank is difficult to meet the fatigue strength requirements,the thermal expansion forming of the axle housing with the local thickened tube blank and the variable cross-section tube blank as the blank was carried out.Keeping the bulging ratio unchanged,by analyzing the influence of the size and thickness increment of the local thickening area of the blank on thethickness reduction of the triangular plate area after bulging,the blank thickening parameters that meet the thickness requirements of the triangular plate area after bulging are given;Small bulging ratio,increasing the width of the blank at the bulging part and the width of the prefabricated oblong hole,and discussing the change of the roundness size of the pipa hole of the mechanical bulging blank of the variable cross-section and the thinning rule of the triangular plate area.The results of numerical simulation,forming process test and fatigue life comparison analysis show that when the thickness of the triangular plate of the tube blank is increased to 20 mm,the thickness of the fillet area of the prefabricated hole of the formed part increases to10.2mm;the width of the prefabricated hole increases with the tube blank of variable cross section,The bulging ratio is reduced,which improves the thinning of the wall thickness in the triangular plate area during the forming process.After forming,the wall thickness of the fillet area of the prefabricated hole reaches 10.5mm.After optimization,the thickness of the triangular plate area of ??the axle housing is increased,and the fatigue life of the axle housing is greatly improved,which fully meets the performance requirements of the axle housing products. |
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