Design And Fem Analysis Of Mg Framework Of Electric Bicycle

As a lighter, more energy-efficient and environment-friendly personal transportation means, electric bicycle has gained a tremendous development in recent years. Meanwhile, energy conservation and performance improvement have become an inevitable development trend in transportation industry. Framework, as the most essential part of an electric bicycle, its weight can be greatly reduced by using weight-saving materials, such as magnesium, to save electricity and to improve driving performance.This research is devoted to redesign of a magnesium framework of an electric bicycle from the traditional steel one provided by Light Metal Co. Ltd., in order to lay a sound base for magnesium alloy application in this field.To do so, a new idea featured by its composite structure consisting of extrusion profile and die-cast jointing parts was forged out to take the advantages of fatigue behaviour of both component structures. Based upon this guideline, the new 3-D model was designed in compliance with the requirements of original human body engineering sizes, assembly requirements and its shape forming processing. Then, its mechanical model for Finite Elemental Analysis was created, and the stress/strain distribution, fatigue life were analysed followed by service structure optimization. Finally, its processing structure was optimized in accordance with the casting process requirements for processing quality.Main conclusions are as follows:â‘ According to the original size and assembly requirements, combined with casting performance, the new 3-D framework was created by CATIA, which consisted of magnesium profile and castings.â‘¡The FEM model was established, and the stress, strain and fatigue life were analyzed according to material properties. The results have shown that the max stress of the optimized framework is less than 40 MPa, and fatigue life is more than 100,000 times, and the stiffness meets safety driving requirement.â‘¢The modal analysis was also investigated based on FEM model. The results have suggested that the optimized framework will not occur resonance, for the lowest natural frequency of the optimized framework is 122.4 Hz, higher than the excited frequency activated by normal driving. â‘£The structual optimization was conducted on the basis of previous anlysis and process quality requirements. As a result, the optimized framework is approximately 1.8 kg, 4 kg lighter than the original steel framework.