【作者】 赵玲玲；

【导师】 赵清亮；

【作者基本信息】 哈尔滨工业大学 ， 机械制造及其自动化， 2013， 博士

【摘要】 光学玻璃的高精度、高效率磨削加工已经成为国家光学工业以及国家重大工程项目比如“神光Ⅲ”的重要发展方向。目前，光学玻璃的精密超精密磨削主要采用细磨粒金刚石砂轮(树脂基和金属基)进行，但是频繁的修整过程大大降低了加工效率。而大磨粒金刚石砂轮的耐磨损能力强，加工工件的面形精度高，磨削比值较大，但其高效精密的修整是实现精密磨削的关键技术。本课题采用大磨粒电镀金刚石砂轮，以BK7、熔凝石英、熔融石英光学玻璃为加工对象，为实现高精度、高效率加工，主要进行了以下研究工作：通过单颗粒金刚石刻划BK7光学玻璃实验，对尖锐金刚石与钝化金刚石的磨损状态以及工件表面塑性流动的情况进行分析，并且根据测得的法向磨削力对平面磨削后玻璃的机械残余应力进行仿真分析。结果表明，与尖锐磨粒相比，钝化磨粒具有更强的耐磨损能力，加工玻璃表面产生塑性流动的区域面积更大；在塑性域去除条件下，大磨粒砂轮磨削加工后工件表层的机械残余应力值更低。该研究为大磨粒金刚石砂轮在光学玻璃精密加工领域的应用奠定了理论基础。提出了适用于大磨粒金刚石砂轮的高效精密修整方法，并利用金刚石表面微观磨损形貌及拉曼光谱分析揭示了修整的机理。首先，通过仿真分析选用Cr12钢对电镀金刚石砂轮进行干磨粗修整，修整区域聚集的热量加快了金刚石磨损速度，使砂轮圆跳动误差快速收敛至10μm以内。粗修整之后金刚石表面有石墨和C60生成，其磨损形式主要表现为钝化磨损、氧化及扩散磨损，并伴有少量的微破碎。其次，采用杯形金刚石滚轮对砂轮进行精修整，注入的冷却液减小了砂轮的热变形量，磨粒磨损形式主要表现为热应力磨耗磨损及少量的微小断裂。最终，砂轮的圆跳动误差及轴向梯度误差分别降低至5μm和3μm以内。运用修整后的电镀金刚石砂轮对光学玻璃进行平面磨削实验，结果表明，加工后工件表面粗糙度Ra值低于25nm，亚表层损伤深度约为2μm。然后分别采用电镀金刚石砂轮、细磨粒树脂基及金属基金刚石砂轮，对大尺寸BK7光学玻璃进行磨削。根据加工表面检测结果得知，电镀金刚石砂轮磨削工件的表面粗糙度值高于细磨粒砂轮，但是沿着平行及垂直于磨削轨迹的两个方向，电镀砂轮加工工件表面的PV值分别为2.28μm、4.17μm，都明显低于其他两种细磨粒砂轮。基于最新提出的砂轮磨损量测量方法，对大磨粒及细磨粒金刚石砂轮磨削光学玻璃时的磨削比进行比较。结果表明，当平面磨削大尺寸BK7光学玻璃时，它的磨削比高达350左右，为细磨粒砂轮的50-70倍。可见大磨粒金刚石砂轮具有极高的磨削比值，这将降低砂轮磨损率，并大大提高加工效率。运用多传感器（力传感器、声发射传感器）监测技术，分析工艺参数及工件表面质量对于作用力及声发射信号的映射关系。结果表明，材料硬度值、单颗磨粒未变形切屑厚度以及砂轮-工件接触面积越大，法向磨削力就越高；材料塑性去除能力及砂轮相对于工件的加载速度越大，声发射信号就越强。另外，采用小波包变换技术，提取对应于砂轮磨损的频段信号，得出修整及磨削过程中声发射信号特征的阈值判据，为实现砂轮修整及磨削加工的监测提供了技术支撑。更多还原

【Abstract】 High-precision and high-efficiency grinding of optical glasses has become animportant development orientation for the national optical industry and major projects,such as "Shenguang Ⅲ". Generally, fine-grained diamond wheels (resin/metal bonded)have been used for precision/ultra-precision grinding of optical glasses. But the frequentwheel truing process greatly reduces the machining efficiency. Coarse-grained diamondwheels can implement a better surface accuracy machining with the greater abrasionresistance and the larger grinding ratio. However, efficient precision truing is verycritical to achieve precision grinding. In this paper, the coarse-grained electroplateddiamond wheel is used to grind BK7, fused quartz, fused silica glasses. In order torealize the high-precision and high-efficiency machining, the research works are mainlycarried out as following:By single diamond grit scratching test for BK7optical glasses, wear state of thesharp and passivated diamond grits and plastic flow on the workpiece surface wereanalyzed. According to the measured normal grinding forces, the mechanical residualstress of the ground BK7glasses was simulated. The results showed that compared withthe sharp grain, the passivated grain had a greater abrasion resistance, producing alarger area of plastic flow region. And under the premise of plastic removal mode, withthe coarse-grained diamond wheels, the mechanical residual stress of the ground opticalglasses surface was lower. These results lay a theoretical foundation for the applicationof the coarse-grained diamond wheels in the field of precision grinding optical glasses.The efficient precision truing method for coarse-grained diamond wheels wasproposed, and the abrasive wear morphology and Raman spectra analysis revealed thetruing mechanism. Firstly, according to the simulation results, Cr12steel was chosen forrough truing of the electroplated diamond wheel, with no coolant. The gathering heatspeeded up the diamond wear rate, making the wheel run-out error quickly reduced tobelow10μm. Graphite and C60generated on the wheel surface, as well as the diamondabrasives were worn in the form of passivation, oxidation and diffusion wear, with lightmicro-broken. Secondly, the cup-shaped diamond wheel was applied to precision truingof the electroplated diamond wheel. The injecting cooling liquid reduced the wheelthermal deformation. The abrasives were worn mainly in the form of abrasion wear dueto thermal stress, incidentally with a little micro fracture. Eventually, the wheel run-outerror and the axial gradient error could respectively drop to within5μm and3μm.Optical glasses were surface ground by the trued electroplated diamond wheel. Itwas found that the ground surface roughness Ra value was less than25nm, and sub- surface crack depth was about2μm. Then, the electroplated diamond wheel, thefine-grained resin bonded and metal bonded diamond wheels were respectively used togrind large-sized BK7glasses. The workpiece quality inspection results showed that forthe electroplated diamond wheel, the ground surface roughness was the highest.However the ground PV values were respectively2.28μm,4.17μm parallel andperpendicular to the direction of grinding traces, significantly less than the other twofine-grained wheels.Based on the newly proposed measurement method for wheel wear volume, thegrinding ratio of coarse-grained and fine-grained diamond wheels was compared. Theresults showed that during grinding large-sized BK7glasses using the coarse-graineddiamond wheel, the grinding ratio was up to about350, being50-70times higher thanfine-grained diamond wheels. Evidently the coarse-grained diamond wheel wasprovided with extremely high grinding ratio, which helped to reduce the wheel wear rate,and greatly improve the processing efficiency.With the multi-sensors (force sensor and acoustic emission sensor) integratedmonitoring technology, the impact of the machining parameters and ground quality onthe force and acoustic emission (AE) signals were investigated. Results showed that, thehigher material hardness, single grit un-deformed chip thickness and the wheel-workpiece contact area were, the greater normal grinding force was. And when theductile removal capacity and the wheel loading velocity relative to workpiece weregreater, AE signal was stronger. In addition, wavelet packet transform method was toextraction frequency band signal corresponding to the wheel wear. Consequently, duringthe truing and grinding process, the solved AE signal characteristics threshold couldprovide technical support for achieving the purpose of monitoring wheel dressing andgrinding.更多还原