激光背向隐聚焦与电化学放电的多效应协同机理及微裂蚀研究

A new micro-machining technology compounded laser irradiation and electromachining for non-conductive brittle hard materials, such as glass, is presented to fabricate the corrosion resistant and high hardness microparts. Firstly, the laser beam transferred from below to above is focused on multi-points and then cause the highly stress concentration within the glass material. The electrochemical discharge machining system is located above the glass workpiece, so that the photo-thermal impact induced by multi-focus laser and the thermal shock produced by electrodischarge would be composited to produce multiple synergistic effects. The glass material would be removed through the micro-fields controlled crack method, and the processing quality and the surface appearance can be improved. Based on the principle of thermodynamics, the composite micromachining mechanism, including the laser-thermal effect, laser-force effect, thermal-etch effect and thermal-force effect, would be investigated. While the stress concentration within the glass is induced to release by electrodischarge, micro fracture would grow at the spark points. Based on the brittle fracture theory, the fracture propagation mechanism and condition were analyzed. Finally, the local field enhancement mechanism of the spark discharge to laser energy would be studied through FDTD (Finite Difference Time Domain). This investigation will illustrate the multiple synergistic effects of laser irradiation and electrochemical discharge, and the mechanism of the micro-fields controlled crack method will be illuminated. The problem of the glass material processing manufacturability will be solved. Its application is very important in the micro-manufacture field of aeronautics and astronautics, precision instrument, IC produce, etc. The investigation can provide the theoretical direction and feasible method for the compound micro-fabrication of the non-conductive brittle hard materials.

针对以玻璃为代表的绝缘硬脆类材料的微细加工需求，提出利用玻璃的透光特性将激光束由下方入射，在其内部多点隐聚焦产生高度应力集中，与玻璃上方的电化学放电加工相复合，使激光的非线性光热作用与火花放电产生的热力冲击作用交互协同，提高加工质量和获得较好的表面形貌，实现绝缘硬脆类材料的光电复合微区可控裂蚀加工。根据热力学原理，分析加工区域产生的光力效应、光电效应、热蚀效应和热力效应，研究光电复合能量的加工机理；根据脆性断裂理论研究激光产生的应力集中被火花放电诱导释放时，放电点处的裂纹模型及扩展方向；采用时域有限差分法，研究火花放电对激光能量的局域场增强机制。项目预期将揭示激光热力效应与电化学放电效应的交互协同作用，解决玻璃类材料加工工艺性差的问题，实现高硬度、耐腐蚀的微小零件制造技术，可用于航空航天、精密仪器以及IC产品等领域的微细加工，为绝缘硬脆材料的复合微制造提供理论指导和可行方案。

本项目针对以玻璃为代表的绝缘硬脆类材料的微细加工需求，提出利用玻璃的透光特性将激光束入射到玻璃内部，通过激光的多点隐聚焦产生高度应力集中，与工具电极的电化学放电效应相复合，使激光的非线性光热作用与火花放电产生的热力冲击作用交互协同，提高加工质量和获得较好的表面形貌，实现绝缘硬脆类材料的光电复合微区可控裂蚀加工。根据激光背向刻蚀和电化学放电加工的特点，构建了激光隐聚焦与电化学放电复合的微加工试验系统，实现了脉冲激光与火花放电从两个方向的协同复合加工，并实时检测和控制加工过程中的特征信号。根据热力学原理，分析加工区域产生的光热效应、光力效应、热蚀效应和热力效应，研究光电能量复合的加工机理。根据脆性材料断裂力学机理，分析了激光在脆性材料中的传输特性，研究了加工部位在多点聚焦激光作用下的温度梯度效应和隐性应力集中效应。根据电化学放电的热力冲击机理，分析了火花放电诱导应力集中释放产生的裂纹形式，研究了放电点处的材料裂蚀模型和条件。根据多能场的耦合机理，分析了激光产生的隐性材质缺陷和应力集中对火花放电的影响，研究了火花放电对激光能量的局域场增强效应。利用所构建的微加工系统中，实现了硬脆玻璃材料的脉冲激光辐照与电化学放电复合微细加工，并将该技术应用于半导体单晶硅的加工中。项目研究揭示了激光热力效应与电化学放电效应的交互协同作用，提高了玻璃类材料的加工精度和表面质量，实现了三维复杂微细结构的复合制造技术，可用于航空航天、精密仪器以及IC产品等领域的微细加工，为绝缘硬脆材料的复合微制造提供了理论指导和可行方案。