基于激光诱导变质的陶瓷铁基凹面凸轮轴高效智能磨削机理研究

Vehicle exhaust has become an important reason why PM2.5 concentration exceeds the national standard seriously and heavy haze weather appears frequently in mid-eastern provinces and cities of China. Ceramic Fe-based concave camshaft can significantly improve the fuel economy and the exhaust emission of automobile engine. But its processing difficulty is a bottleneck for large-scale application. . On the basis of prophase research, using the reverse thinking a new method of high efficiency and intelligent grinding based on laser induced deterioration is proposed. Firstly, deterioration layer is formed in the concave cam surface by pulse optical fiber laser induction, whose thickness and distribution are controlled accurately. Then the layer is removed easily on the wet and high efficiency grinding condition. In the present work, the theory of single-pulse laser induced deterioration is investigated. The dynamic behavior characteristics and the formation mechanism of deterioration layer are revealed. The overlap effect between adjacent laser spots is analyzed by developing the process intelligent matching and reasoning system. Conducting comparative experiment, the influence rules of deterioration structure, thickness and distribution on the grinding quality, the grinding accuracy and the wheel wear are studied. It can be solved to some key scientific problems such as controlling deterioration layer thickness precisely, uniform deterioration layer formation and high efficiency grinding removal mechanism. The study can provide a new idea and theoretical basis of high efficiency machining for ceramic Fe-based concave camshaft and other difficult-to-machine materials.

汽车尾气已成为我国中东部地区PM2.5严重超标、灰霾天气大范围频频出现的重要原因。陶瓷铁基凹面凸轮轴可显著改善汽车发动机的燃油经济性和尾气排放，但加工难一直是制约其大规模应用的瓶颈。在前期预研基础上，本项目采用逆向思维，提出主动引入变质层以提高陶瓷铁基凹面凸轮轴可加工性的新方法——激光诱导变质高效磨削：拟采用脉冲光纤激光诱导凸轮表面产生变质层，变质层厚度和分布精确可控；然后在湿式磨削条件下高效磨除表面变质层。在此基础上系统建立单脉冲激光诱导变质理论，揭示脉冲激光诱导动态行为特性及变质层形成机理；构建工艺智能匹配/推理机制，分析相邻光斑之间的重叠效应；开展与传统磨削对比性实验，研究变质层组织、厚度及分布特征对磨削加工质量/精度及砂轮磨损的影响规律。解决变质层厚度精确可控、变质层均匀分布及高效磨削去除机理等关键问题。本项目将为陶瓷铁基凹面凸轮轴及其他硬脆难加工材料高效加工提供新思路和理论基础。

随着国家大力推进排放标准的提高及加大汽车产业的减排力度，对凸轮轴的加工精度及耐磨性提出了更高的要求。陶瓷铁基凹面凸轮轴能够进一步改善发动机燃油经济性和减少尾气排放，但是内凹轮廓使陶瓷铁基凸轮轴的磨削加工机理异常复杂化。本项目采用逆向思维，提出了主动引入变质层以提高陶瓷铁基凹面凸轮轴可加工性的新方法——激光诱导变质高效磨削。项目主要研究了陶瓷铁基凹面凸轮轴脉冲激光诱导变质层形成机理及分布特征，揭示了基于变质层的陶瓷铁基凹面凸轮轴高效磨削加工机理，分析了脉冲激光诱导变质高效磨削工艺智能化及工艺参数优化。研究发现脉冲激光诱导变质后的工程陶瓷表面材料发生了分解及氧化反应，原始表面的Si3N4晶体组织被Si单质结晶相、SiO2结晶相所取代。证实了变质层具有结构疏松、强度低和容易磨削去除等特点。同时，还发现凹坑具有储存磨削液的能力，材料去除方式也能够从大尺寸的脆性去除模式向小尺度脆性去除模式转变。在此基础上，构建了基于粗糙集、层次分析法及基于实例推理理论等多种智能技术集成的凸轮轴磨削工艺智能优选模型，提出了一种基于规则推理理论、遗传算法、BP神经网络等多种智能技术集成的凸轮轴数控磨削工艺智能推理模型体系结构。研究成果为工程陶瓷、光学玻璃及半导体材料等硬脆难加工材料提供了一种新的加工方法，对推动我国高效磨削加工技术的发展有重要理论意义和应用价值。