Research On The Impact Factors Of Fatigue Characteristics Of The Rear Axle In A Passenger Car And Structure Improvement

The rear axle is the key to the vehicle parts,It plays a role in supporting, joining,carrying.So the rear axle must have sufficient strength,stiffness and fatigue life.There aremany factors affect the fatigue strength and life of the rear axle. We can dramaticallyimprove fatigue design quality of the rear axle and raise fatigue life prediction evelthrough quantitative research on these factors.First, For simulating the welding line, We use two modeling methods to build thefinite element model of the rear axle.By contrast and analysis of the two solutions,we cansee the impact of the simulating the welding line on the finite element analysis.Secondly,On the basis of the theoretical analysis and experimental research work,thefinite element analysis are applied to the problematic rear axle under typical workingconditions to analyze the reasons of the torsion bar and find the impact factors of thefatigue property, proposing three reasonable solutions on this basis.1. From the perspectives of thickness of the rear axle, An improvement is proposed:increasing the thickness of the torsion bar appropriately on the condition that the torsionalrigidity remains constant, the fatigue performance can be improved. By calculating thestiffness and strength of the torsion bar with thickness is5mm,5.5mm and6mm and somefatigue bench tests, the improvement is proven.2. From the perspectives of outside diameters of the rear axle, An improvement isproposed: decreasing torsion bar diameter appropriately to improve the fatigueperformance. Based on the simulation platform constructed by HyperWorks,UG and nSoftsoftwares, static calculation of the before and after improving rear axle is carried out andthe calculation result is proved to be accurate by static electrometric tests. At last,Thefatigue analysis of before and improved rear axles are carried out on the basis of staticanalysis results, By contrasting the analsys results with the fatigue bench tests results, theresults from compared show that the analysis results agree fairly well with the resultswhich obtained by fatigue bench tests and the fatigue fracture problem of torsion bar hasbeen successfully solved by the improved solution.3. Looking the rear axle as a carrier, we can study the impact of the whole lifespan ofthe rear axle by means of two fatigue life prediction methods, The two techniques are S-N Analysis mechod and E-N Analysis method.The compared results can tell us whichfatigue life prediction method is more accurate method.The results show that the static analysis results is closer to those obtained from straingauge and the analysis results agree fairly well with the results which obtained by fatiguebench tests. That reflects the accuracy of the analysis results in a certain degree and alsodemonstrates the effectiveness and rationality of improved methods.By the fatigue testsand verify,the rear axle after improvement could satisfy the requirement of application.