微波烧结多物理场耦合过程的实验、建模与模拟方法研究

Microwave sintering represents the coupling effects of multi-physical fields, such as the electrol-magnatic, temperature, density and stress fields etc. By means of physical experiments, the applied project studies firstly the validation of permittivity and permeability of powder materials in the process of microwave sintering, and the validation of parameters in thermal dynamics. Hence the mechanism of microwave heating on powder materials in determined. Then based on the relevant existing theories on microwave heating, and draw lessons from sintering modeling and simulation by resistive furnace, the numerical simulation of microwave sintering will be studied and realized. Accorrding to the nature of microwave sintering, and taking into accout the non-thermal effect of microwave sintering process (such as electric arc discharge, Activation energy decrease, reduction reaction strengthen, etc.), the key governing equations is determined. A complete set of mathematical model and numerical method for simulation of the whole process of microwave sintering, from heat generating by electrol-magnatic field, to the heat transfer and to the desification process of powder material, will be proposed in this project. Finally, a reasonably user subroutine for describing the microwave sintering behavior of a particular powder material will be built. Then it will be implanted into the commercial finite element software Comsol Multiphysics to realize the coupling caculation of muti-physical fields during microwave sintering process. The project provides the theretical analysis and knoeledge on mechanism for microwave sintering process. It has the important research significance for the development of sintering materials and the optimization design of microwave sintering furnace.

微波烧结是电磁场、温度场和粉末材料内部应力场等多物理场耦合作用的结果。本项目拟采用物理实验方式研究粉末材料在微波烧结过程中介电常数、导磁系数，以及热动力学参数的变化规律，探索微波加热作用于粉末材料的机理。然后在现有微波加热相关理论的基础上，借鉴粉末材料传统电阻炉加热烧结的力学本构模型，针对微波烧结的特点，考虑微波烧结过程中存在的非热效应（例如电弧放电，活化能降低，还原反应加强等），确定关键的控制方程。完善一套从微波与粉末材料耦合生热，到热量传递，再到粉末烧结致密化全过程的数学模型和模拟方法。最后编写能够合理描述某特定粉末材料微波烧结行为的用户子程序，并植入商业有限元软件Comsol Multiphysics中进行求解计算，实现微波烧结全过程多物理场的耦合求解。该项目研究对促进微波烧结过程的机理分析，拓展可烧结材料的类型以及微波烧结设备的优化设计等有重要的研究意义。

为了获取用于微波烧结数值计算的更真实的初始密度场，本项目研究首先修正了团队前期自行研发的模拟双相流注射填充过程的有限元程序并植入了表面张力效应的评估。然后采用物理实验方式研究粉末材料在微波烧结过程中介电常数、导磁系数，以及热动力学参数的变化规律，探索微波加热作用于粉末材料的机理。基于传统电阻加热烧结过程的建模与模拟，结合电磁场、热力学以及连续介质力学原理，确定了一套从微波与粉末材料耦合生热，到热量传递，再到粉末烧结致密化全过程的数学模型和模拟方法；采用 Comsol Multiphysics软件实现了微波烧结全过程的数值模拟。该项目研究对促进微波烧结过程的机理分析，拓展可烧结材料的类型以及微波烧结设备的优化设计等有重要的研究意义。