纤维增韧陶瓷基复合材料磨削机理及其高效、低损伤磨削参数优化方法研究

The fiber reinforced ceramic matrix composite (FRCMC) is an ideal material for the high-temperature and high-impaction component in combustion of aerospace engine and nuclear reactor. The FRCMC component can endue higher burning temperature, which can the increase combustion efficiency and save a lot of fuel. However, the application of FRCMC has been severely constrained due to high wheel wear rate, low material removal rate, and surface damage in the manufacturing process. Combining with the theoretical analysis, experiment study, and application test, this project used three different material models to describe the fiber, matrix, and coating properties, separately. Through conducting the single diamond grain scratching FRCMC experiment and smoothed particles hydrodynamics (SPH) simulation, the material parameters in fiber, matrix, and coating can be inversed, which can form the constitute material model of FRCMC for the experiment and SPH simulation study. Besides, the FRCMC material micro-mechanical behavior and damage generation mechanism can be clarified. By considering effect of grinding wheel microstructure, grinding parameters, and fiber orientation on the FRCMC material removal behavior, the multi-grain grinding model for the FRCMC material removal study was built, based on grinding wheel structure (including: grain geometry, size, extrusion height, density, et al) and grinding parameters (including: wheel speed, depth of grinding, feed rate) used in the experiments. Treating the high efficiency and low damage grinding of FRCMC as constrained minimum nonlinear optimization problem, the grinding wheel structure parameters, grinding parameters, and fiber orientation of FRCMC are the variables needed to be optimized and the FRCMC damage degree is the optimization objection. Through transferring the existing experiment and theoretical results to the constrained optimization space and treating the multi-grain grinding model based on SPH as the nonlinear function between the variables and objection, the best coupling relationship and matching criteria among the fiber orientation, grinding parameters, and grinding wheel parameters was searched through iteration in FRCMC grinding simulation. The parameters optimization and adjustment strategies for the high-effective, low-damage, and low-cost grinding can also be obtained, which will promote the manufacture of the FRCMC components to the coordinated controlling of the shape and function.

纤维增韧陶瓷基复合材料（FRCMC）是航空发动机和核反应堆等高端装备的高温高冲击燃烧室构件的理想材料，可耐更高燃烧温度从而显著提升燃烧效率和节省燃料，但其制造过程中砂轮磨损快、材料去除率低和表面易产生微裂纹，已严重制约了该类材料的普及应用。本项目采用理论分析、实验研究与应用测试相结合的方法，通过分别采用单一材料模型描述纤维、基体和涂层界面材料特性，并采用单颗金刚石磨粒划擦实验结合光滑粒子动力学（SPH）仿真反演计算材料模型参数值，建立适用于实验与SPH仿真的FRCMC的材料本构模型，同时揭示材料的细观断裂行为与损伤机制；通过综合考虑砂轮微观结构与磨削工艺参数对不同纤维方向的FRCMC材料磨削去除过程的演变规律，根据实验测量的砂轮结构（包含磨粒的形状、尺寸、突出高度、密度等）和使用的工艺参数（砂轮线速度、磨削深度、工件进给速度），构建出便于实际FRCMC材料加工过程分析的多磨粒磨削模型，探寻在多磨粒断续磨削作用下的FRCMC材料的去除机理及表面损伤累积机制；将FRCMC高效低损伤磨削问题转化为限制性非线性最小化优化问题，以砂轮结构参数、磨削工艺参数和FRCMC纤维方向作为优化变量，以FRCMC的损伤程度作为优化目标，将已有磨削实验及理论计算结果转化为参数优化限制性空间，将基于SPH的多磨粒磨削模型看作优化变量与优化目标间的非线性函数关系，迭代搜索FRCMC磨削过程中纤维方向、工艺参数和砂轮参数的最佳耦合关系与匹配准则，获得有效降低磨削成本和表面损伤并大幅提升磨削效率的参数优化调控策略，促使高端FRCMC关键构件的制造朝着形性协同控制的目标发展。

本项目针对纤维增韧陶瓷基复合材料（FRCMC）加工成本高、效率低和表面损伤大的问题，以典型的FRCMC材料2.5D SiCf/SiC为研究对象，开展其磨削去除机理和高效低损伤磨削方法研究。项目分别开展了单颗金刚石磨粒划擦SiCf/SiC的实验和仿真研究，明晰了SiC基体、SiCf的材料去除和损伤机制，并构建了SiCf/SiC的材料本构模型，采用实验与仿真对比的方法对材料本构模型参数进行了校准。随后开展了SiCf/SiC砂轮磨削实验和多磨粒划擦去除的仿真，综合考虑砂轮微观结构及磨削过程中工件表面演变规律，构建出便于实际加工过程分析的多磨粒磨削模型，探寻在多磨粒断续磨削作用下的材料去除机理及表面损伤累积机制；引入限制性非线性最小化优化算法，将磨削实验及理论计算结果转化为参数优化限制性空间，寻求FRCMC磨削过程中材料结构、工艺参数和砂轮参数最佳耦合关系与匹配准则，获得磨削参数优化调控策略。结果表明SiC基体的划擦去除和损伤以裂纹、基体剥离、纤维暴露和断裂面等形式为主，尖锐磨粒还会留存少量的延性去除划痕，横向SiCf以纤维剥离为主，底部有纤维和基体断裂，去除形式以剪切断裂为主，产生一个沿划擦方向约45°的断口。纵向SiCf去除弯曲断裂去除为主，去除表面会留有较多的纤维剥离损伤。通过构建的SPH仿真模型，采用JH-2模型分别描述SiC基体和纤维，可以较好预测单颗磨粒沿不同的纤维方向划擦SiCf/SiC的力。对2.5D SiCf/SiC的磨削实验表明，沿纤维的法向去除得到的磨削力最小且表面质量更高，磨削后的砂轮表面磨损严重。而多磨粒划擦仿真表明磨粒的多次叠加损伤会加剧2.5D SiCf/SiC内部裂纹的扩展，最后导致大量材料的成块剥离，而不是单颗磨粒划擦过程中的材料粉末化剥离。最后基于构建的基于SPH的多磨粒模型，开发了基于限制性非线性最优化算法的高效低损伤工艺参数优化算法，结果表面当磨削深度为50μm，进给速度为300mm/min，砂轮转速为8500r/min 时，且沿纤维的法向磨削时，得到的材料表面粗糙度最低，表面质量最好。上述研究能促使高端FRCMC关键构件的制造朝着形性协同控制的目标发展。