Research On Improvement Of Forging Process And Fatigue Life Of Torsion Bar Spring

Torsion bar spring has a considerable application prospect in modern vehicle suspension system.Compared with traditional leaf spring and coil spring,torsion bar springs has obvious advantages,such as compact structure,light weight,large energy storage,easy installation,etc.However,due to the high processing costs,processing difficulties and other factors,torsion bar spring is still not widely used.The research on the service performance and fatigue life of torsion bar spring has been quite sufficient,fatigue fracture of torsion bar spring usually occurs in the arc neck region near the ends of both sides.In order to solve practical engineering problems,the research on the combination of upsetting process and fatigue life analysis of torsion bar spring end is relatively scarce.In this paper,the upsetting process of torsion bar spring produced in a factory was simulated by finite element analysis software.The effects of die shape,initial forging temperature and feed speed of hammer head on forging efficiency and quality were analyzed.Finally,the fatigue life of three groups of upsetting forgings was calculated and compared.The optimum processing scheme for upsetting process of torsion bar spring in this factory was finally put forward.Firstly,the finite element simulation model of upsetting process of torsion bar spring has been established.The upsetting process of the cylindrical inner die bore die and the optimized die with large angle transition arc inner die bore has been compared and analyzed under the actual processing conditions of the initial forging temperature of 1200? and the feed speed of the hammer head of 1mm/s press.The advantages and disadvantages of two kinds of dies in forming effect,metal material utilization efficiency,forming difficulty,die wear,equivalent stress field,equivalent strain field and surface damage of forming bar were studied.After comparison,it was found that the optimized die has better performance in all aspects and the optimized die model was used for subsequent analysis and research.Subsequently,this paper analyzed the selection principle of the initial forging temperature and the final forging temperature of the metal material in detail,and determined the initial forging temperature range value by theoretical calculation.Using the optimized upsetting mold and the 1mm/s press hammer feed speed,respectively simulating the seven sets of different initial forging temperature values in the temperature range of 1125?~ 1275? for the torsion bar spring metal bar upsetting effect influences.Compared the advantages and disadvantages of each component rod in forming difficulty,equivalent stress field,equivalent strain field,final forging temperature and surface damage of formed bar.Finally,this paper increased the initial forging temperature suitable for actual processing from 1200? to 1225?,and it was applied to the comparison of the feed rate of the hammer of the subsequent press.Then,the feed rate of a total of eight sets of press hammers were set between 0.5mm/s and 4.0mm/s,compared the relationship between the feed rate of the hammer of the press and the rough forming effect of the torsion bar spring.In this paper,the eight-shaped rods were compared and analyzed from the five aspects of forming difficulty,mold wear,equivalent stress field,equivalent strain field and surface damage of formed bar,and obtained the optimal range of the feed rate value of the press hammer.Combined with the static strength analysis of the torsion bar spring,the fatigue life calculations of the three sets of bars formed in the optimal feed speed range were carried out.The results show that the fatigue life of the upset member was best when the feed rate of the hammer was 2 mm/s,so the feed speed of the press hammer was optimized from 1 mm/s to 2 mm/s.Finally,this paper proposes an optimized process scheme,at a starting temperature of 1225?,which use a mold with a large angle transition arc inner mold,upset the end of the torsion bar spring metal bar with 2mm/s press hammer feed speed.This set of optimization schemes for the roughing process has a positive guiding significance for improving the production efficiency of the factory,ensuring the production quality and reducing the production cost,and provides a reliable research idea and theoretical basis for solving the practical problems of the project.