Process Optimization Of Aluminum Alloy Sheet Based On Discrete Gap Holding

Nowadays, the energy crisis is picking up and people's environmental awareness is enhancing. With them, the auto industry develops in the direction of light weight. Due to its light weight, high specific strength, high ductility and excellent corrosion resistance, aluminum alloy sheet in automobile body manufacturing in increasing. However, the big disparity on material characteristics make the traditional steel panel forming theory and tooling design and manufacture technology which apply to aluminum alloy sheet stamping forming process directly some forming defects, such as wrinkle and fracture. The present research centers in variable blank holder force technology to ameliorate the quality of stamping formability. In this way, people need to reconfigure punching machine to satisfy the requirement of volume-produce in auto industry, which costs a big budget and takes a long time.Blank holder gap is one of the important process parameter in stamping; it refers to the distance from blank holder to die. In the process of sheet metal forming process, blank holder gap directly determines blank holder force, and then impact the stamping formability. There is a big blank holder force when blank holder gap is narrow. In this case, sheet is easy fracture. While the wider blank holder gap will cause of wrinkle in the flange part, because the blank holder force is small. Given that, this paper tries to transform technology of variable blank holder force in different position into discrete blank holder gap.Combined with the experimental design method, approximate model technology, optimization algorithm and numeric al simulation to optimize the blank holder gap and other process parameters of aluminum stamping. We carried out the following major works:Firstly, introduced the using status quo of aluminum alloy sheet in car body, pointed out the shortages and main met hods in the existing research, and proposed the research content and significance.Secondly, introduced optimization design's circuit and speculative knowledge, analyzed deformation theory in aluminum alloy sheet stamping and defined the quality evaluation criteria.Thirdly, taking an inner panel of ear body made of aluminum as an example, using DYNAFORM software to establish the finite element model for numerical simulation, introducing some setting methods about process parameter and analyzing the influence on stamping formability by constant blank holder pressure and four common blank holder force curve.Fourthly, on the basis of the above work, separating the blank holder, a multi-objective mathematical model is built in which the discrete blank holder gaps, the coefficient of friction, die radius, stamping speed and blank holder force are design parameters, maximum thinning rate and maximum thickening rate are target functions. Using the Orthogonal table for screening, the Latin Hypercube experimental design and approximate model of quadratic polynomial response surface technology and obtaining a set of non-inferior solution set through the Pareto optimal solution set of the multi-objective particle swarm optimization algorithm to get the optimal combination of the stamping parameters. According to the optimization results, rebuilding the finite element model for numerical simulation and analyze the validity and practicability of this way.