Research On Aluminum Alloy Sheet Forming Based On Variable Holder Force-Variable Punch Speed

Because of the light weight,low density,corrosion resistance,high specific strength and high specific strength,aluminum alloy is widely used in white body.The manufacturing accuracy of the white body affects the assembly accuracy,NVH,driving experience and car lifetime.The selection of stamping process parameters will significantly affect the forming performance of aluminum alloy,because stamping process is one of the important processes.Holder force-stamping speed formability window was proposed by the base of holder force formability window,because of the strain rate sensitivity of aluminium alloy.Similar to the holder force window,the holder force-stamping speed formability window can prevent the wrinkle and crinkle of rectangle part.Besides,the best holder force-stamping speed curve can inhibite the springback of parts.At first,the holder force-stamping speed window was proposed.And the basic form and the construction method of the holder force-stamping speed windows were put forward.Secondly,the necessary material mechanics test and the basic process performance test were carried out.The effects of strain rate on elongation,the strain ratio of width and thickness and anisotropy were studied by uniaxial tensile test in different strain rates.Besides,the mathematical model of true stress-true strain was also proposed.The FLC and maximum drawing depth of different stamping speed was measured by rigid die swell test.Friction coefficient and the surface friction quality were carried out by the friction experiments which were carried out under different load and sliding speed.Furthermore,the finite element model was based on the mechanical parameters and the friction coefficient.Through the MATLAB spline interpolation method,the critical wrinkling holder force-stamping speed curved surface was fitted.Similar method was used to establish the critical crinkle holder force-stamping speed curved surface.Then the two forming surface were combined into the holder force – stamping speed forming window.Finally,the general rule of springback was analyzed based on the phenomenon of uniaxial tension test.And the optimal springback control curve of holder force-stamping speed was designed.Besides,the optimal springback control curve of holder force-stamping speed can inhibit the springback of aluminum alloy forming.