Microstructural Evolution in Sintering - Experimental, Mathematical and Numerical Study

小行星9705849 该项目研究材料科学中的一个重要过程，粉末的固态烧结。 为了理解、控制和预测烧结过程的结果，需要从微观结构的角度对该过程进行仔细的研究。 该项目旨在基于特定烧结和相关机制而不是经验统计函数进行过程模拟。 为了从机理的角度对烧结进行建模，研究人员采用了实验、数学模型和数值模拟相结合的方法。 在许多烧结机制中，研究人员选择了一种通常主导烧结过程的常见机制，即晶界扩散。 它们将表面质量输运和晶界扩散耦合起来，形成一个完整的数学体系。 该系统涉及高阶非线性偏微分方程（PDE）和移动边界。 为了解决这个系统，研究人员使用一种精确有效的数值方法来求解偏微分方程，结合区域分解和自适应/移动网格。 同时，还探讨了细粒度和粗粒度仿真算法的并行计算。 为了验证和证实模拟，该项目设计并进行了八个实验。 其中七个目标是简单的规则几何形状的粒子。 出于实验原因，在大多数实验中使用Ni涂覆的W丝。 这些实验提供了健全的比较与数学模型的基础上，个别机制。 实验结果将与数值模拟进行比较。 这些比较将验证和估计理论模型的有效性。 在基于这些简单情况的比较之后，研究人员将进行一项关于不规则颗粒簇烧结的实验，其中涉及并耦合了几种机制。 将实验结果与扩大的完整数学系统的数值模拟进行比较。 本研究为研究烧结对烧结材料微观结构演变的影响提供了有力的工具。 通过实验、数学模型和计算机模拟相结合，结果将更接近真实的世界情况，并更好地解释烧结过程中的显微组织演变。 该模拟将有助于科学家和工程师更好地了解烧结材料的性能，并优化烧结工艺。 ***

9705849 Zhang The project investigates an important process in materials science, solid state sintering of powders. In order to understand, control and predict the results of a sintering process, a close study of the process from a microstructural point of view is required. This project aims at process simulations based on specific sintering and related mechanisms rather than empirical, statistical functions. To model sintering from the mechanism point of view, the investigators employ a combination of experiments, mathematical models, and numerical simulations. Among many sintering mechanisms, the investigators have selected a common one which often dominates the sintering process, grain boundary diffusion. They couple mass transport by surface and grain boundary diffusion to form a complete mathematical system. This system involves high order nonlinear partial differential equations (PDEs) and moving boundaries. To solve this system, the investigators use an accurate and efficient numerical method for solving PDEs, combined with domain decomposition and adaptive/moving grids. A parallel computation in the simulation algorithm for both fine and coarse granularity level is also explored. To verify and corroborate the simulation, the project designs and carries out eight experiments. Seven of these target simple regular geometries of particles. For experimental reasons, Ni-coated W wires are used in most of the experiments. These experiments provide sound comparisons with the mathematical models based on individual mechanisms. The experimental results will be compared with the numerical simulations. These comparisons will verify and estimate the validity of the theoretical models. After comparisons based on these simple cases, the investigators will conduct an experiment on the sintering of an irregular cluster of particles where several mechanisms are involved and coupled. This experimental result will be compared with the numerical simulation of the enlarged complete mathematical system. %%% This investigation provides a powerful tool for studying the effects of sintering on the evolution of the microstructure of a sintering material. By combining experiments, mathematical models and computer simulations, the results will closely follow real world situations and better explain the microstructural evolution during sintering. The simulation will help scientists and engineers to understand better the properties of the sintered materials and to optimize sintering process. ***