Finite Element Analysis And Structure Optimization On Magnesium Frame Connected By Bolt

After the preliminary structure design of magnesium alloy electric bicycle frame, ithas light weight, energy saving, environmental protection and other advantages;however, because the original magnesium alloy electric bicycle saddle part intends touse casting molding process, and the saddle part structure is very complex, will causethe casting mould large difficulty of design, core pulling device, high cost, high manydie scrap rate; therefore, there is required improvement design for the saddle partstructure, and taking the two part saddle bolt connection way connection.This topic is cooperated with SiChuan Light-metal Magnesium TechnologyCo.,Ltd, have structure optimization on the original magnesium alloy electric bicycleframe, and foundated of frame concrete products forming.Then, in accordance with the relevant strength, fatigue design criteria, improvedesign the original magnesium alloy electric bicycle frame, and creativity use the boltson magnesium alloy connection, completed the improved structure design ofoptimization magnesium alloy electric bicycle frame; then, according to the electricbicycle frame service mechanical model, based on taking full account of the contactbetween bolt and magnesium frame, established magnesium frame finite element modeland finish element analysis; completed static analysis, modal analysis and fatigueanalysis of the new magnesium frame, which in the static analysis, focuses on the boltpretension effect of the frame and stress results; completed idle mode analysis andpre-stressed modal analysis; especially, made a more detailed analysis and calculation inthe fatigue analysis with the fatigue life changes due to the contact between stainlesssteel bolt and magnesium frame.The main conclusion of this paper has:①Based the original magnesium alloy electric bicycle frame structure, usingPro/E three-dimensional modeling software establish the new frame model with thebolts connecting structure, a frame body material is magnesium alloy, bolt material isstainless steel;②According to the service condition of electric bicycle frame and the nationalstandard, establish service mechanical model of the new structure magnesium frame, and fully consider the contact relationship between magnesium frame and bolt,analysis frame static loading by the using the finite element software ANSYS Workbench and checking standard. The calculation results show that: when the boltscrew diameter is7mm, and the bolt pretension is under5000N, the static results ofmagnesium frame and bolt connecting structure regional meet the requirements;③Based on the novel magnesium frame service mechanics model,take the modalanalysis by using ANSYS Workbench finite element analysis software. Analysis resultsindicate: the minimum order natural frequency is96.5Hz by pre-stressed modalanalysis, far higher than the normal service of electric bicycle dynamic vibrationfrequency, suggesting that magnesium frame service does not cause resonance, canguarantee the driving comfort;④The comprehensive utilization ofANSYS Workbench,ANSYS/FE-SAFE,ANSYS finite element software, finish the fatigue calculation of the new bolt-connectmagnesium frame structure model. The results show that: the overall frame fatigue lifeis more than100000times, in line with national standards.⑤The six group was established under the different conditions of bolt joint form,and test validation of each joint corrosion properties by salt solution immersion, anddiscusses the result of difference between different joint forms of corrosion.