采用半隐式压力关联算法,通过引进VOF函数和分段线性界面结构(PLIC)构建自由曲面,建立了微喷金属熔滴流动和传热数值模型,模拟了7075铝合金熔滴成形过程中撞击速度、熔滴间距、基板温度和熔滴尺寸等工艺参数对成形形貌的影响规律,并对模拟结果进行了实验验证.结果表明:确定合理的撞击速度和熔滴间距是获得好成形精度和质量的关键,熔滴直径为100 μm,间距为200 μm的7075铝合金熔滴在初始温度为350K的不锈钢基板上以1.5 m/s的初速度沉积成形时,可获得较好的成形效果.模拟结果与试验结果基本吻合,较好反映了实际成形过程中熔滴撞击、铺展和固化行为,为该工艺的实际应用提供了参考依据.
A numerical model of flow and heat transfer for micro-droplet deposition forming was established on 7075 aluminum alloy by semi-implicit pressure-linked equation algorithm (SIMPLE),and the volume of fluid (VOF) method with Piecewise Linear Interface Construction (PLIC) was employed to reconstruct the free surface.The influence of processing parameters including impacting velocity,relative distances between two successive molten droplets,the temperature of the substrate and droplet size on end-shapes morphology was simulated during fabricating 7075 aluminum alloy by micro-droplets,and the numerical models were validated with experimental results.The results show that the determination of reasonable impact velocity and droplet relative distances is the key to obtain a good precision and quality.Better forming effect can be obtained when molten 7075 aluminum alloy droplet with 100 μm in diameter and the distance between two successive droplets 200 μm is deposited on a stainless steel surface at 350 K with velocity 1.5 m/s.The simulation results agree well with the experimental results,which reflect better the actual process of droplet impacting,spreading and solidification behavior,and provide a reference for the practical application of the process.
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