| According to the automotive market analysis report,the current car ownership in my country is close to 400 million,and the exhaust of the car has caused serious pollution to the environment,which is called a mobile pollution source.Reducing emissions and reducing pollution has become a top priority in the development of the automotive industry.Lightweight vehicles can effectively improve fuel efficiency and reduce pollutant emissions.Gears,as an important part of automobiles,account for a large proportion of automobile quality.Lightweight gears can effectively reduce the quality of the entire vehicle.The density of aluminum alloy is only one-third of that of steel.For gears with less load,aluminum alloy can be used as gear material instead of steel.However,the contact fatigue strength of the tooth surface of the aluminum alloy gear is low.To improve the reliability of the aluminum alloy gear,the fatigue strength of the tooth surface needs to be further improved.For this,this paper proposes to use bimetal to make gears.that is,steel parts that are prone to failure are made of steel.and aluminum alloys are used in the parts of the gear teeth.When the gear reaches a certain strength,Achieve its lightweight.If bimetal gears are formed using the conventional gear cutting method,not only is there a serious waste of materials,but also the processing efficiency is low.The cold precision forging process is used to form the bimetal gear,which can save materials and improve production efficiency.At the same time,the bimetal is tightly engaged through plastic deformation to improve the mechanical performance of the gear.In this paper,by combining numerical simulation and process test,the formability of the bimetal gear cold precision forging process is studied.The main work is as follows:(1)45 steel and 6061 aluminum alloy had been choosed as the bimetallic material.Proposed the combination method of steel ring sleeve aluminum alloy bar material,and 5 different thickness steel rings and corresponding size aluminum alloy bar materials,which were matched with each other into 5 kinds of blank solutions,which was convenient for comparative analysis of the deformation of bimetal under different blank solutions.According to the shape of the target gear,the unidirectional extrusion forming process plan of the bimetal gear was designed.(2)Deform-3D was used to simulate the process plan,and analyze the bimetal deformation in the simulation results and the metal velocity field.strain field,forming load and other contents in the deformation process(3)Combined the simulation results,processed and manufactured the mold,and prepared the bimetal blank at the same time.The five schemes were tested separately.The final shaped gear is full and filled,and the bimetals at the upper and lower end surfaces bite each other in the form of "wavy lines",and there are no gaps or holes.(4)Observed and analyzed the specific deformation size of the bimetal at various positions,the bonding state of the tooth top and root position,and the metallographic deformation of the longitudinal and transverse sections of the steel ring.Through observation,the thinner the thickness of the steel ring blank,the deeper the bimetallic bite,When the thickness of the steel ring were too thin,the bimetal cannot completely fit at the position of the tooth tip.Based on the bimetallic bite and combination,the billet 4 with a steel ring thickness of 4.5mm and an aluminum alloy bar diameter of 30.5mm can ensure high-strength natural bite of bimetal parts.Through calculation,this scheme can reduce the weight of the gear by about 30%.Through numerical simulation and process test,the formability of the cold precision forging process of bimetal straight tooth cylindrical gears was studied.The results show that it is feasible to form the bimetal gear by cold precision forging process.This research result has certain practical significance for the lightweight research of gears and the development of bimetal forging process. |
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