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。