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基于LBM的铝微滴斜柱沉积水平偏移研究

A LATTICE-BOLTZMANN METHOD SIMULATION OF THE HORIZONTAL OFFSET IN OBLIQUE COLUMN DEPOSITION OF ALUMINUM DROPLETS

  • 摘要: 金属微滴沉积制造技术采用逐点堆砌方式成型, 为斜柱沉积提供无支撑制造方式, 具有高度灵活性. 本文针对铝液滴斜柱连续沉积过程, 建立格子玻尔兹曼模型进行数值模拟, 研究液滴在凝固表面上的水平偏移运动. 根据表面能充放过程, 沉积运动被划分为下落、快速扩张、慢速扩张、回弹4个阶段, 其受力状态由表面能、重力势能、动能和黏性耗散趋势得到. 液滴内部流动在扩张阶段中表现为滑动状态, 而在回弹阶段中表现为滚动状态. 液滴偏移运动的加速阶段主要发生在扩张阶段, 而偏移距离则在回弹阶段中产生. 扩张阶段的受力状态表明偏移运动的主要推动力为重力和毛细力. 随着液滴轴线距离的增大, 扩张阶段中的加速段时间缩短、速度峰值提高, 使水平偏移距离呈先增大后减小的趋势, 这种阶段化特征源于加速段时长和速度极大值的竞争关系. 不同沉积高度和固液浸润度下, 偏移距离均保持相同的演化趋势. 在相同的轴线距离下, 偏移距离随固液浸润度的增大而减小, 随沉积高度的增大而减小. 通过拟合水平偏移距离演化规律、优化扫描步距, 能够实现斜柱的均匀沉积, 并使倾角与理论结果一致.

     

    Abstract: The metal droplet deposition manufacturing technology adopts a point-by-point stacking method, which provide an unsupported manufacturing method for oblique column deposition with high flexibility. In this paper, a lattice Boltzmann model is established for simulating the continuous deposition process of the oblique column, and the horizontal displacement of the droplet on the solidification surface is studied. According to the charging and discharging process of surface energy, the deposition process is divided into four stages: falling, rapid expansion, slow expansion, and rebound. The forces on the deposited droplet are analyzed by the trend of surface energy, the gravitational potential energy, the kinetic energy, and the viscous dissipation. The internal flow of droplet is sliding in the expansion stage and rolling in the rebound stage. The internal flow of the droplet shows sliding state in the expansion stage and rolling state in the rebound stage. The acceleration of the deviation mainly occurs in the expansion stage, while the deviation distance occurs in the rebound stage. Combined with the forces in the expansion stage, it is concluded that the main driving forces of displacement are gravity and capillary force. With the increase of the droplet axial distance, the acceleration in expansion stage is shortened, and the peak of velocity is increased, so that the horizontal deviation is first increased and then decreased. This staged feature stems from the competitive relationship between the acceleration period and the maximum speed in the deviate motion. Under different deposition heights and solid-liquid wettability, the deviation distance maintains the same trend. Under a certain axial distance, the deviate distance decreases with the increasing solid-liquid wettability, or the increasing deposition height. The evolution tendency of the horizontal deviation distance is fitted, and the scanning step is optimized to realize the uniform deposition of the inclined column whose inclination angle is consistent with the theoretical result.

     

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