铝合金复杂汽车零部件热成形-淬火一体化工艺参数优化

Optimization of hot forming-quenching integrated process parameters for complex aluminum alloy automotive components

摘要:

铝合金热成形-淬火一体化工艺将成形和热处理结合,能同时实现零件尺寸精度和性能的控制,是实现汽车轻量化的主要途径之一。但是在冲压成形尺寸相对较大形状相对较复杂的铝合金板件时,依然存在各工艺参数难调试的问题。建立了AA6061铝合金的热变形统一黏塑性损伤本构模型,将其用于铝合金汽车B柱热冲压成形模拟,采用BP神经网络构建了工艺参数(板料成形温度,冲压速度,模具间隙)与成形性(最大减薄率,最大增厚率)之间的关系并结合遗传算法实现多目标优化,得到了AA6061铝合金热冲压的最佳成形工艺参数。优化之后,B柱的最大减薄率和最大增厚率分别从56.5%和14.2%降到了13.0%和10.0%,通过优化之后的工艺参数,制得了成形性良好、尺寸精度高的零件。结果证明了基于神经网络和遗传算法的热成形工艺优化方法的可行性和有效性。

关键词:热冲压;统一黏塑性损伤本构模型; BP神经网络;多目标优化

Abstract:

Hot forming-quenching integrating process of aluminum alloy sheet has been developed to improve formability and overcome thermal distortion by integrating hot stamping and quenching in one operation, which is significantly beneficial for the application of aluminum alloy components in vehicle lightweight industry. In this novel technology, processing parameters are interrelated and interacted. To obtain appropriate forming parameters, thermo-mechanical finite element (FE) model using a unified viscoplastic damage model is set up to predict the formability of a complex-designed 6xxx aluminum alloy B-pillar. A Back Propagation (BP) neural-network combined with multi-objective genetic algorithm (GA) method is adopted to optimize the key process variables including blank temperature, stamping speed and die clearance during hot stamping process. After optimization, the thinning and thickening are reduced to 13.0% and 10.0% by comparing with the initial 56.5% and 14.2%, respectively. In addition, a successful hot stamping B-pillar with satisfactory mechanical performance and excellent forming accuracy is achieved experimentally by using the optimized parameters. It indicates that the finite element model can simulate the hot stamping process accurately and that the optimization method utilized in this paper is feasible and effective.

Key words:hot stamping; Unified viscoplastic damage constitutive equation; BP artificial neural network; Multi-objective optimization