滚镀体系中随机过程及多场耦合动力学机制研究

Barrel plating is the most efficient method for finishing small workloads without manual racking or unracking. There are lots of publications on the engineering technology of barrel plating while few literatures involve the theoretical investigation. The difficulty of theoretical investigation comes from both the stochastic nature of the tumbling movement of the workloads in a rotating barrel and the complexity of the coupling of multi-field (such as electric field, fluid field, mechanical field, etc.). In this proposal, a strategy for modelling the barrel plating is proposed. On the one hand, considering the stochastic nature of the tumbling movement of the workloads, the movement will be studied in light of Markov process theory and the stochastic equations will be derived. The stochastic equations will be efficiently and reliably solved using Monte Carlo method, and the position of each workload as well as the actual total plating area of the whole workloads can be obtained. On the other hand, the multi-field coupling will be investigated step by step. First, the concentration distribution of ions and the electric field distribution in the barrel will be preciously measured experimentally. Then, combined with the experimental results and the principles of the hydrodynamics or electrics, the mass transfer equations, heat transfer equations and electrics equations will be derived. Finally, the coupling mechanism of the chemical, electric, hydrodynamic factors will be analyzed systemically. Based on the results of the two aspects above, a reasonable and reliable theoretical model for barrel plating will be proposed. With this model, the thickness values of coating on the workloads and the voltage-time curves will be predicted. For the calculated thickness and voltage values, some statistic parameters (such as the average value, variance, etc.) and the stochastic parameters (including power spectrum, fractal dimension and Lyapunov index) will be extracted. These parameters can be treated as the criteria to improve the theoretical model and to study the influence of the major factors (such as the geometric characteristics of the barrel, barrel rotation speed, workload capacity, plating temperature, plating time) on the quality of barrel plating. The achievements of this project will guide the improvement of the barrel plating technology. Moreover, this project could be regarded as a typical paradigm to promote the investigations on the complex chemical systems.

滚镀是一种应用广泛的重要电镀方式，但由于工件在滚筒内翻滚运动的随机性以及电场、流场、温度场等多场耦合的复杂性导致对其理论分析非常困难。本项目针对工件在滚筒内翻滚运动的随机性本质，将翻滚运动纳入马尔科夫过程分析的理论框架之中，采用蒙特卡罗方法模拟再现其物理图景，进而确定实际受镀工件位置、数量并计算实际受镀面积；实验测量滚筒内离子浓度分布、电场分布，并依据流体力学及电学原理，总结推导出传质、传热、电学方程。基于上述结果，剖析滚镀体系中化学、电学、流体力学、温度等多种因素的耦合作用机制，建立滚镀的理论模型并进行计算机模拟，预测镀层厚度及电压-时间曲线，提取厚度、电压变化的统计参量及随机性参量作为判别指标，定量考察滚筒特征几何参数、滚筒转速、工件装载量等因素对镀层质量的影响。本项目可为改进滚镀装置、优化滚镀工艺、拓展滚镀应用范围提供理论指导，其研究方法也可为其他复杂化学体系的研究提供借鉴思路。

滚筒电镀(简称滚镀)是将一定数量的小工件作为阴极置于转动的滚筒中进行电镀加工的过程，具有效率高、电镀质量好等优点，是一种特殊而重要的电镀方式，得到了广泛应用。但目前滚镀的改进只能基于大量烦琐的、重复性实验的经验总结。.针对当前滚镀研究的困境，本项目基于对滚筒电镀(简称滚镀)过程中粒子(工件)间相互作用、粒子同滚筒壁间相互作用、粒子与流场相互作用的分析，采用离散元法(DME)模拟工件粒子之间、工件粒子与滚筒壁之间的碰撞，采用光滑粒子流法(SPH)将液体模拟为粒子，从而实现无网格化的对固液耦合运动的模拟，建立了滚镀体系中粒子运动的多场耦合的动力学模型。基于这个模型，我们分析了滚镀工艺参数，包括滚筒形状、滚筒尺寸、滚筒旋转速度、工件装载量、镀液黏度等，对工件运动状况的影响，发现六边形滚筒相对于圆形滚筒具有不易打滑、工件混合效率高等优点，从理论上解释六边形滚筒在实际生产中得到广泛应用的原因。我们同时搭建了滚镀实验系统，结合数码摄像系统和计算机处理软件，能对部分理论模拟结果进行实验验证，表明理论模拟的合理性和可靠性。另外，我们还基于对大量理论模拟结果的统计分析，为滚镀生产中常见的概念如“混合效率”、 “受镀时间”、 “镀层均匀性”、“混合周期”等赋予了清晰、可定量计算的物理内涵。.本项目的开展，可为合理选择滚镀工艺参数、提高滚镀质量、设计新型滚镀装置提供理论指导，同时也为多场耦合的复杂动力学体系的研究提供一个典型范例。