石英玻璃表面的磨削裂纹激光修复和去应力工艺技术研究

发布时间：2018-01-01 04:34

本文关键词：石英玻璃表面的磨削裂纹激光修复和去应力工艺技术研究　出处：《山东大学》2017年硕士论文　论文类型：学位论文

【摘要】：石英玻璃是典型的硬脆难加工材料,"缓进给精磨成型—CO2激光修复表面磨削裂纹—塑性域超精密磨削"的工艺流程可以大幅度缩短大口径非球面石英玻璃透镜的生产周期。采用CO2激光辐照石英玻璃表面可以消除石英玻璃表面的磨削裂纹,但会在石英玻璃表面产生残余拉应力。本研究以降低裂纹修复后的表面粗糙度和消除残余应力为目标,研究了石英玻璃表面磨削裂纹的激光修复工艺和修复后石英玻璃的低温加热去应力工艺。本研究构建了激光修复实验平台,该平台由激光光源和光路、三维运动平台、控制系统三部分组成。利用该实验平台成功进行了石英玻璃表面磨削裂纹的激光修复实验,结果表明,在本激光修复工艺条件下玻璃亚表面不会产生微裂纹;阐释了石英玻璃表面磨削裂纹的愈合机理。建立了激光修复石英玻璃温度场有限元模型,分析了激光修复工艺参数对修复过程中玻璃温度场的影响。结果表明,能修复石英玻璃表面磨削裂纹的工艺参数均能使石英玻璃表面温度处于2050K～2350K之间。研究了激光修复工艺参数对表面粗糙度的影响。结果表明,修复后表面粗糙度随着激光功率的增大先降低后增大,过大的功率会造成玻璃表面烧蚀;修复后表面粗糙度随着激光光斑直径的增大而降低;修复后表面粗糙度随着扫描间隔的减小而降低;在0.05m/s～0.2m/s范围内,激光扫描速度对修复后表面粗糙度影响很小。研究了激光修复石英玻璃过程中残余应力的产生原因和修复后石英玻璃表面的激光加热去应力工艺。确定了石英玻璃的粘弹性本构方程,建立了修复后的石英玻璃表面残余应力的有限元模型,获得了残余应力的分布规律;实验验证了有限元模型的正确性。揭示了激光修复后石英玻璃表面残余应力的产生原因是在石英玻璃转变温度范围内激光辐照引起了热应力的应力松弛。实验研究了激光修复工艺参数对残余应力的影响规律,残余应力随着激光光斑直径的增大而减小,随着扫描速度的减小而减小。提出了采用较大光斑直径、较小激光功率、较低扫描速度的激光加热去应力工艺,降低了激光修复过程产生的残余应力。对比实验结果和有限元分析结果表明,该去应力工艺能显著降低修复后石英玻璃的残余应力。研究了激光修复后石英玻璃的电热低温加热去应力工艺,对低温加热去应力工艺进行了有限元分析。结果表明,在800℃下保温12小时,然后以10℃/h速率降温至740℃,可以基本消除石英玻璃中的残余应力,去应力后石英玻璃的双折射光程差降低至国家标准规定的应力双折射1级要求。提出了采用微波加热作为低温加热去应力工艺的加热方式,研究了高温下微波加热介质(SiC粉)对石英玻璃表面的元素污染,结果表明高温下微波加热介质会侵入石英玻璃表面,侵入深度小于0.3μm,可通过后续磨削和抛光去除。
[Abstract]:Quartz glass is a typical hard brittle materials, the grinding process of creep feed molding CO2 laser repair grinding surface crack - plastic region of ultra precision grinding "can greatly shorten the aspheric lens of the quartz glass production cycle. By CO2 laser irradiation of quartz glass surface can eliminate grinding crack on the surface of quartz glass, but will produce residual tensile stress in the quartz glass surface. This research is to reduce the surface roughness after crack repair and removing residual stress as the goal, the low temperature heating quartz glass was studied by laser repairing technology and the crack surface of quartz glass grinding after the stress process. This study established a laser repair experiment the platform, the platform is composed of a laser source and a light path, three-dimensional motion platform control system is composed of three parts. The success of the crack surface of quartz glass grinding induced by using the experimental platform The experimental results show that light repair, in the laser repair process conditions of glass sub surface does not produce micro cracks; explains the mechanism of grinding surface of quartz glass crack healing. The laser repair of quartz glass temperature field finite element model, analyzes the influence of the laser repair process parameters on the glass temperature field in the process of repairing. The results showed that the process parameters can repair the crack surface grinding of quartz glass can make the surface temperature of quartz glass at 2050K ~ 2350K. The research of laser repair process parameters on surface roughness. The results showed that after the restoration of surface roughness increases with the laser power increases and then decreases too much power will cause the glass surface ablation; after the restoration of surface roughness increases with laser spot diameter decreased; after the restoration of surface roughness decreases with scan interval decreased from 0.05m/s to 0.2m/s; Within the range of laser scanning speed on the repair of surface roughness has little effect on the residual stress. The laser repair of quartz glass produced during laser heating of quartz glass surface causes and repair after the stress process. The viscoelastic constitutive equation of quartz glass, a finite element residual quartz glass surface repair the stress model, the distribution rules of residual stress; the finite element model is verified. Reveals the reasons of residual stress of quartz glass surface laser repaired in quartz glass transition temperature range of laser irradiation caused the thermal stress and stress relaxation. The experimental study on the effect of of laser repair process parameters on the residual stress and the residual stress decreases with the increase of laser spot diameter, and decreases with the decrease of scanning speed. The larger diameter than. Small laser power, laser heating and low scanning speed to reduce the residual stress process, laser repair process stress. Experimental results show that with the results of finite element analysis, the stress process can significantly reduce the residual stress of quartz glass after repair. Electric heating low temperature heating quartz glass laser repair after the stress process, the low-temperature heating stress process are analyzed by finite element method. The results show that the heat for 12 hours at 800 DEG C, and then to 10 DEG /h to 740 DEG C cooling rate, can eliminate the residual stress in the quartz glass, to stress birefringence optical path difference reduced quartz glass to the national standard stress birefringence in class 1. Proposed the use of microwave heating as a low temperature heating heating process should be to force, of high temperature microwave heating medium (SiC powder) on the quartz glass surface element pollution,. The results show that the microwave heating medium will invade the surface of quartz glass at high temperature, and the penetration depth is less than 0.3 mu m, which can be removed by subsequent grinding and polishing.

【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ171.731

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