超声椭圆振动高效磨削SiC陶瓷的去除机理与损伤控制研究

As one of the hard and brittle material, the silicon carbide (SiC) ceramic is typically difficult to cut with disadvantages of low efficiency and serious damage in conventional grinding. Thus, it is rather difficult to achieve the high efficiency and low damage machining, which has seriously limited the application of this kind of material. This project puts forward to conduct the research on the removal mechanism and the damage controlling in elliptical ultrasonic assisted high efficiency grinding of SiC ceramic using multilayer metallic bond diamond wheels. Following is the innovative thinking: On the base of measuring, reconstructing and characterizing the multilayer diamond wheel topology, the model of undeformed chip thickness distribution is developed by coupling the elliptical ultrasonic assisted grinding parameter and the grinding wheel status; Then, the material removal behavior, and the changing rule and formation mechanism of machining damage are investigated; On this basis, the strategy to realize low damage grinding is proposed with designed wheel status and machining parameters. The main contents in this project are as follows: modeling of undeformed chip thickness in elliptical ultrasonic assisted grinding using multilayer metallic bond diamond wheels; the material removal mechanism and the surface/subsurface damage in elliptical ultrasonic assisted grinding of SiC ceramic; the controlling strategy and the experimental verification in elliptical ultrasonic assisted grinding of SiC ceramic. The obtained research fruits can provide the base for high efficiency and precision grinding of SiC ceramic, which has important theoretical significances and practical values.

碳化硅（SiC）陶瓷作为典型的硬脆难加工材料，普通磨削过程中存在效率低、损伤严重的突出问题，难以实现高效低损伤加工，严重制约了该类材料的应用推广。本项目提出采用多层金属结合剂金刚石砂轮开展超声椭圆振动高效磨削SiC陶瓷的去除机理与损伤控制研究，创新思路在于：测量、重构和表征多层金刚石砂轮工作面状态，建立超声椭圆振动参数、磨削用量与砂轮状态耦合作用的磨粒切厚分布特征模型；在此基础上，探明工件超声椭圆振动条件下磨削弧区的材料去除行为和加工损伤变化规律与形成机制，由此提出基于砂轮状态、磨削用量与超声椭圆振动参数耦合设计的高效磨削损伤控制策略。研究内容主要包括：多层金刚石砂轮超声椭圆振动磨削的磨粒切厚分布描述、SiC陶瓷超声椭圆振动磨削的材料去除与损伤形成机制、SiC陶瓷超声椭圆振动磨削损伤控制策略与试验验证。项目成果可为高效低损伤磨削加工SiC陶瓷奠定基础，具有重要理论意义和实用价值。

针对以SiC陶瓷为代表的硬脆材料加工过程存在磨削效率低、表面/亚表面损伤严重等问题，项目基于多层金属结合剂金刚石砂轮工作面实际状态、超声椭圆振动参数和磨削用量的耦合作用，计算砂轮工作面上磨粒的运动轨迹，阐明了磨粒切厚分布特征，揭示了超声椭圆振动磨削SiC陶瓷的磨粒切厚分布特征对材料去除和加工损伤的影响规律，提出了SiC陶瓷高效低损伤加工策略并进行了验证。主要工作包括：.（1）基于超声振动辅助磨削的磨粒运动轨迹方程及相邻磨粒运动轨迹干涉理论，采用等分线法求解磨粒在完整接触弧区的单颗磨粒切厚值。在测量多层金刚石砂轮局部地貌的基础上，采用Johnson变换及其反变换重构砂轮整体地貌，求解砂轮磨削的磨粒切厚分布特征，分析了磨粒表征参数、超声振动参数和磨削加工参数对磨粒切厚分布及其特征的影响规律，发现超声振幅、砂轮转速、磨削深度是影响磨粒切厚分布范围和特征值的主要因素。.（2）开展了单颗磨粒超声椭圆振动磨削SiC陶瓷试验，发现超声椭圆振动磨削能够显著降低磨削力和磨削比能、提高材料延性去除率。基于超声椭圆振动运动学，建立了磨削力模型，并验证了模型的准确性。磨削力与单颗磨粒切厚呈正比关系，随磨削速度的增大呈现先增大、后降低、再增大的趋势。磨削比能随着单颗磨粒切厚的增大而降低，随着磨削速度的提高而增大。磨削速度越高、单颗磨粒切厚越小，划痕边界破碎越少、损伤越低。.（3）开展了超声椭圆振动和轴向振动磨削SiC陶瓷的试验。当振幅小于0.2 μm时，工件材料在塑性域被去除，导致工件表面小平面增加。而当振幅大于0.2 μm时，发生脆性去除，导致加工表面的大块和凹坑增加。随着超声振幅的增大，表面粗糙度呈现下降、上升和稳定3个变化阶段，在振幅为0.216 μm时达到最小值0.04 μm。当振幅在临界切屑厚度附近时，脆性加工表面占比下降到最小值8%。采用提高磨削速度、超声振幅接近脆塑性转变临界切厚的磨削加工策略，获得了表面粗糙度低于0.025 μm的低损伤SiC陶瓷表面，损伤降低70%，效率提高60%。