A Study Of Aluminum Alloy Trimming Cross-section Quality

Automotive lightweight is particularly important in energy and environmental issues.The widespread use of aluminum alloys is conducive to the realization of lightweight.In the forming process of aluminum alloy,blanking,punching,trimming and other blanking processes are essential.It is inclined to generate debris,burrs and other issues.Electronic devices may be damaged,workpieces may be scratched and assembly accuracy may be reduced,which were caused by burrs.The mold and parts surface were easy to be attached by debris so that the quality of stamping parts,mold life and production line efficiency were affected.It is necessary to deeply investigated the trimming section quality of aluminum alloy.In this paper,the trimming test of AA5182 and AA6016 aluminum alloy was designed and the effects of different process parameters(blanking clearance,blanking angle,die radius),die material and pre-strain on the trimming section quality of aluminum alloy was studied.When the mold material is common SKD11,the best combination of process parameters was obtained,and four ductile fracture criteria,Rice-Tracy,Oyane,Brozzo and McClintock,were respectively used to simulate the process parameters.The causes of the debris generation were analyzed.The conclusions were obtained as follows:(1)The impact of the process parameters on the quality of the blanking section was explored when the mold material was SKD11.With the increase of blanking clearance,the bending deformation of the waste was aggravated,the length of the fillet zone was increased and the proportion of the burnished zone was decreased.The burr height and length of fillet zone was reduced with smaller fillet radius of the upper die.But the burr can not be prevented even with an infinitely sharp blade.The direction of crack propagation was changed by the blanking angle.The localized area of strain for angled blanking extends from the upper tool edge to the lower tool edge rather than extending to the initial indentation of the lower tool,and thus the possibility of burr generation was reduced.The amount of slivers and proportion values of burnished zone were comprehensively affected by trimming gap,fillet radius of upper die and trimming angle.When the blanking gap is 10% t,with the other two process parameters arbitrary combination,there was no burr generated on the aluminum alloy cross-section.(2)The effect of mold material and pre-strain on trimming surface quality was studied.The impact of die material on section quality after repeated blanking: GGG70 L was better than SKD11 and HMD5 was the worst in the amount of slivers.The burr height and cross-sectional profile were not affected.The proportion of burnished zone was affected by three kind of die material within 20 percent.Overall SKD11 was the best in the proportion of burnished zone,followed by HMD5.After pre-strain,there is still no burr under the optimal combination of process parameters,the amount of blanking debris was slightly increased and fine filaments are easily produced,the amount of slivers was not affected by the pre-strain direction.The proportion of burnished zone was decreased obviously after pre-strain.Furthermore,it was found that the proportion of the burnished zone of AA5182 and AA6016 was reduced larger under biaxial tensile pre-strain than uniaxial tensile pre-strain,which was 32.74% and 31.54%,respectively.(3)The simulation results of four kinds of ductile fracture criterion under the best process parameter were compared,and the prediction result of Brozzo fracture criterion was the closest to the experimental result.By simulating the blanking process,it was found that the debris was generated in the bright zone and fault zone.At the beginning of the upper crack initiation,filamentous slivers were produced.Before the upper and lower main cracks merge,the debris was generated in the fault zone.After the upper and lower main cracks converge,the burnished zone was formed and debris was produced.To explain the debris generated in fault zone,the microscopical morphology was further studied.For AA6016,the amount of debris was less when the size of dimple diameter was larger and the dimple density was smaller.For AA5182,there was no debris on the condition that the size of dimple diameter was 3.16,the smaller value of the dimple diameter size deviated 3.16,the less debris and the relationship of the amount of debris and dimple density was not very obvious.