Experimental Research And Finite Element Analysis On Friction Characteristics Of 5052 Aluminum Alloy Sheet Stemping

Under the boundary lubrication and dry friction condition respectively,the effect of sliding velocity,normal loads and sliding stroke on the friction coefficient between 5052 aluminum alloy and SKD11 was studied by using MPX-2000 disc-pin friction tester.Using the Matlab software to analyze the experimental data and obtain the law of friction coefficient,and a variable friction model based on different sliding velocity and normal loads was established under the boundary lubrication.The micro topography observations and analysis on the 5052 aluminum alloy specimens under different experimental conditions were performed to obtain the mechanism of the influence of various factors on the friction coefficient.On the basis of further analysis of micro topography of 5052 aluminum alloy,the law of surface roughness of 5052 aluminum alloy after grinding with SKD11 with sliding velocity and normal load was obtained.Finally the model established in this paper is used to simulate the thickness distribution and Springback of U-shape parts.Comparison of the predicted results with(i)the variable friction model based on different sliding velocity and normal loads,(ii)three group of constant friction coefficient,and the measured value of the actual stamping parts.The results show that: under the boundary lubrication,the friction coefficient values between 5052 aluminum alloy and SKD11 generally decrease with increasing of the sliding velocity and normal loads,and the decreasing tendency slows down in the higher sliding velocity and normal load range;under the dry friction,with the increase of sliding velocity,the friction coefficient will decrease,with the increase of normal loads,the friction coefficient will increase firstly and then decrease.the variation of friction coefficients with sliding stroke under the both condition exist two distinctively characterized stages:i)increasing stage,ii)stable stage;under the condition of the same sliding velocity and normal loads,the friction coefficient under dry friction condition is much higher than the frictioncoefficient under the boundary lubrication condition.The furrows wear and adhesive wear is the main wear mechanism with a slight sticking wear under the boundary lubrication;the severer adhesive wear take place under the dry friction condition.under the boundary lubrication,the surface roughness of the 5052 aluminum alloy after grinding with SKD11 generally increase with increasing of the normal loads and decreasing of the sliding velocity;under the same sliding velocity and normal load conditions,and the surface roughness of dry friction is 10 times higher than the boundary lubrication.The predicted results of the thickness distribution of the constant friction coefficient 0.1 and the variable friction coefficient model are more consistent with the actual measured values,but the predicted results of Springback and the predicted of stress distribution show great differences;with the same blank holder force and forming speed,the predicted values of Springback for the model with constant coefficient of friction were 8.4 and 6.3 respectively,and the errors from the actual measured values were-25% and-19.2%;the predicted Springback values of the variable friction model were 12.1 and8.3 respectively,and the errors from the actual measured values were 8%and 6.4%;the above result indicates significant improvement of Springback prediction with the variable friction coefficient model established in this paper.