非连续增强钛基复合材料的超高速高效低损伤磨削基础研究

The discontinuously reinforced titanium matrix composites (DRTMCs) have some important merits (i.e., light weight, good heat-resistance, and high strength), which make them have broad application prospects in aviation and aerospace industry fields. However, because DRTMCs consist of titanium alloy matrix and hard and brittle reinforcements , they belong to the particular difficult-to-cut materials with both the high strength-toughness and the high hardness. During the traditional grinding process of DRTMCs, the disadvantage phenomena, including short tool life, severe surface/subsurface damage, and low machining efficiency, are also encountered, which have hindered the engineering application of DRTMCs. For this reason, in this project it has been put forward to investigate the super-high speed, high efficiency and low damage grinding of DRTMCs using the brazed CBN abrasive wheels. Firstly, the research work is conducted on the thermal damage of brazed CBN abrasives, distribution model of the undeformed chip thickness per grain, and the materials removal mechanism in grinding. On this basis, the underformed chip thickness distribution is controlled and adjusted through the coupled design of working surface status of the abrasive wheels and the grinding parameters. Accordingly, the ground DRTMCs could be removed by means of the synergistic chip formation behavior, and the grinding damage is therefore controlled and minimized. The main contents are as follows: thermal damage and control mechanism of CBN abrasives of monolayer brazed wheels; model of abrasive wheel surface and undeformed chip thickness distribution; material removal mechanism and surface/subsurface damage of DRTMCs; controlling strategy and its machining verification of DRTMCs damage produced in super-high speed grinding. The obtained research fruits could provide a reliable method and theoretical support for the high efficiency and low damage machining of DRTMCs, which has an important significance.

非连续增强钛基复合材料（DRTMCs）具有“轻质、耐热、高强”优势，在航空航天领域应用前景广阔。但DRTMCs包含物理力学特性不同的钛合金基材与硬脆增强体，属于兼具高强韧与高硬度特性的难加工材料，普通磨削加工存在工具寿命短、表层/亚表层损伤严重、生产效率低难题，制约了材料应用推广。本项目提出采用单层钎焊CBN砂轮开展DRTMCs超高速高效低损伤磨削研究，在解决CBN磨粒钎焊热损伤、单颗磨粒切厚分布描述与材料去除机制三个关键问题基础上，通过耦合设计砂轮工作面状态与超高速磨削参数以调控切厚分布，由此实现DRTMCs内部组元协同成屑去除以控制加工损伤。研究内容包括：单层钎焊CBN砂轮磨粒热损伤评价与控制机理、砂轮工作面状态与磨粒切厚分布描述、材料磨削去除机制与表层/亚表层损伤表征、超高速高效磨削损伤控制策略与加工验证。项目成果可为高效低损伤加工DRTMCs提供可靠途径和理论支持，具有重要意义。

非连续增强钛基复合材料（DRTMCs）因具有轻质、耐热、高强的特点，在航空航天领域有广泛的应用，因此开展其机械加工及质量控制研究具有重要意义。但是，此类材料中硬脆增强体与金属基材截然不同的物理力学特性使其成为典型的难加工材料，特别是在磨削加工过程中，存在工具寿命短、表层/亚表层损伤严重、加工效率低等难题。钎焊CBN超硬砂轮具有磨粒把持强度高、砂轮地貌可控的优点，在难加工材料磨削中有广阔应用前景，但是钎焊过程中磨粒热损伤限制了砂轮的磨削潜能。有鉴于此，本项目提出采用单层钎焊CBN砂轮开展非连续增强钛基复合材料的超高速高效低损伤磨削基础研究的构想。通过控制钎焊CBN砂轮磨粒热损伤以提高砂轮耐用度，控制砂轮地貌特征定量描述单颗磨粒切厚分布，揭示DRTMCs磨削材料去除机制与损伤形成机理，实现DRTMCs高效低损加工。.主要工作包括：.（1）通过试验方法研究了TiN改性钎料钎焊CBN磨粒的界面微结构和热损伤的影响因素，阐明了钎料改性作用机制，据此优化钎焊工艺，成功研制了磨削性能优越的单层钎焊CBN超硬砂轮。.（2）采用复型法和数学变换方法重构了单层钎焊CBN整个砂轮的地貌，建立了单颗磨粒切厚分布模型并通过试验验证了模型的有效性，揭示了CBN砂轮工作面状态对单颗磨粒切厚分布的影响规律。.（3）通过单颗磨粒磨削试验和有限元仿真，研究了DRTMCs磨削烧伤的影响规律，揭示了材料的去除机制，确定了DRTMCs磨削低损伤阈值，在此基础上，建立了DRTMCs磨削表层损伤程度与磨粒切厚分布的关系模型。.（4）阐明了砂轮状态与磨削参数耦合作用对DRTMCs磨削损伤程度的影响规律，基于单颗磨粒切厚分布规律建立了砂轮工作面状态与磨削参数耦合设计模型，获取了高效低损伤磨削加工参数域，提出了DRTMCs高效低损伤磨削策略，完成了DRTMCs超高速高效磨削验证。