| With the rapid economic development,the domestic car ownership continues to increase,and the resulting environmental pollution and energy shortage problems are becoming more and more serious.Automobile lightweighting is one of the effective methods to achieve energy saving,emission reduction and sustainable development,which has become the development trend of the automotive industry.Aluminum alloy materials are more and more widely used in the fields of automobiles,aerospace,etc,duing to their small density,high specific strength and corrosion resistance.However,compared with traditional steel plate materials,aluminum alloys have poor formability at room temperature,it is difficult to process parts with complex shapes and large degrees of deformation,and the parts have low forming accuracy,and are prone to wrinkle,crack and springback defects.Generally,the warm forming process is used to process the aluminum alloy material to improve the forming performance of the aluminum alloy plate.The warm forming process improves the forming performance of aluminum alloy plates,reduces the deformation resistance and springback,thereby improving the forming accuracy and quality of parts.Aluminum alloy plate warm forming is a highly complex nonlinear process involving multiple physical couplings of heat,force,micro,etc.Using numerical simulation to replace the traditional "trial and error method" can shorten the product development cycle and reduce development costs.In this paper,the 6111 aluminum alloy is taken as the research object,and the combination of experimental research and numerical simulation is used to study the effect of different process parameters on the aluminum alloy friction coefficient under warm forming conditions,and further study the effect of different friction coefficients on the aluminum alloy forming quality influences.The main research contents of this article are as follows:(1)Using the CFT-? friction test machine,the influence of the initial temperature of the sheet,the sliding speed and the normal load on the friction coefficient of the 6111 aluminum alloy was studied under boundary lubrication conditions;The surface micro-morphology of the sample was observed,and the aluminum alloy surface quality at 200 ° C was obtained through analysis,and it was determined as the temperature condition studied in this article;the hardness of the aluminum alloy at different temperatures was measured,and the results showed that the hardness of the aluminum alloy sample did not change much;according to the test measurement results,the variable friction coefficient models about sliding speed and normal load were established respectively.(2)Using Dynaform software to establish a U-shaped finite element analysis model,using a single factor control variable method to study the impact of stamping speed,blank holder force and friction coefficient on the forming quality of aluminum alloy,the results show that: with the increase of stamping speed,blank holder force and friction coefficient,the overall thickness distribution of the sheet decreases;increasing the blank holder force and friction coefficient can effectively reduce the springback of the sheet.(3)The method of combining orthogonal test design and numerical simulation is adopted,the maximum thinning rate is used as the test index,and the simulation results are analyzed using the range and variance analysis methods to obtain the optimized process parameter combination;Using the optimal parameter combination as the simulation parameter,the established variable friction coefficient models are input into the software,and two sets of comparative simulations are established.The thickness distribution of the sheet material obtained through the simulation is compared with the actual test measurement,and further verification is carried out through the amount of springback.The results show that the thickness distribution and springback of the sheet obtained by the variable friction coefficient model are closer to the actual measurement,which verifies the reliability and accuracy of the variable friction coefficient model. |
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