多晶氟化镁超精密磨削表面残余应力仿真及工艺研究

发布时间：2018-04-08 09:26

本文选题：多晶氟化镁　切入点：超精密磨削　出处：《哈尔滨工业大学》2017年硕士论文

【摘要】：多晶氟化镁是一种典型红外光学材料,具有透光性好、机械强度高、抗热冲击性强、耐化学腐蚀、各向同性、介电常数和介电损耗较小等特点,广泛应用于红外窗口领域。该材料可进行超精密磨削,但难以获得高质量表面,其表面质量以及使用性能受残余应力制约。因此,本文对多晶氟化镁材料的残余应力以及磨削工艺进行研究。本课题以多晶氟化镁为研究对象,基于超精密磨削加工技术,研究表面成型的机理。结合有限元仿真和磨削实验,提出减小磨削后表面残余应力、提高磨削后表面质量的加工方案,并在此基础上优化工艺参数,最终实现多晶氟化镁表面的高质量超精密磨削加工。基于显微压痕实验和纳米压痕实验分析了多晶氟化镁材料的力学性能,并建立材料本构模型。通过显微压痕实验计算出了维氏硬度值;通过对压痕形貌的分析,研究了多晶氟化镁材料在机械载荷下的材料破坏机制,分析了脆塑转变过程中的裂纹衍生及延展过程;通过纳米压痕实验数据建立了应力——应变关系,为仿真模型的建立提供了依据。利用AdvantEdge有限元仿真软件分析了磨削参数对磨削质量的影响。分析了砂轮转速、磨削深度和砂轮粒度对磨削过程中磨削力和磨削功率的影响规律;明确了在各个工艺参数下,磨削后表面残余应力的演变趋势,提出了能够实现最佳磨削效果的工艺参数选择方案;结合实际工况,分析了材料表面缺陷(凹坑)和多次磨削对磨削力和残余应力的影响。最终,为后续多晶氟化镁的超精密磨削实验的工艺参数选择提供了依据。基于对磨削纹路的理论研究,分析了磨削轨迹的影响因素,并确定了最佳工件转速。搭建超精密磨削实验平台,在位精密修整了砂轮,从而将圆跳动降到最低。完成了不同磨削深度和进给速度的超精密磨削加工实验,监测了加工过程中的磨削力变化,并与仿真结果进行了对比分析,结果具有一致性;利用Taylor Hobson轮廓仪检测了工件表面粗糙度,并通过Spectrum One激光光谱仪对工件红外透光性进行了检测,使用X,Pert3 Powedr X射线衍射仪检测了工件残余应力。结果表明,在一定范围内,磨削深度和进给速度变大导致磨削表面残余应力变大,表面粗糙度变小;而材料透光性受磨削参数影响不明显。最终建立了一套适用于多晶氟化镁超精密磨削加工工艺。
[Abstract]:Polycrystalline magnesium fluoride is a typical infrared optical material with good transmittance, high mechanical strength, strong thermal impact resistance, chemical corrosion resistance, isotropy, low dielectric constant and dielectric loss, etc. It is widely used in infrared window field.The material can be ground by ultra-precision, but it is difficult to obtain high quality surface. Its surface quality and performance are restricted by residual stress.Therefore, the residual stress and grinding process of polycrystalline magnesium fluoride are studied in this paper.In this paper, the mechanism of surface forming is studied based on ultraprecision grinding technology with polycrystalline magnesium fluoride as the research object.Combined with finite element simulation and grinding experiment, the machining scheme of reducing surface residual stress after grinding and improving surface quality after grinding is put forward, and the process parameters are optimized on this basis.Finally, the high-quality ultra-precision grinding of polycrystalline magnesium fluoride surface is realized.The mechanical properties of polycrystalline magnesium fluoride were analyzed based on microindentation test and nano-indentation test, and the constitutive model of the material was established.The Vickers hardness was calculated by microindentation test, the fracture mechanism of polycrystalline magnesium fluoride under mechanical load was studied by analyzing the indentation morphology, and the crack derivation and extension process during brittle plastic transition were analyzed.The stress-strain relationship is established through the experimental data of nano-indentation, which provides the basis for the establishment of simulation model.The influence of grinding parameters on grinding quality is analyzed by AdvantEdge finite element simulation software.The influence of grinding wheel speed, grinding depth and grinding wheel granularity on grinding force and grinding power is analyzed, and the evolution trend of surface residual stress after grinding is determined under various technological parameters.According to the actual working conditions, the effects of surface defects (pits) and multiple grinding on the grinding force and residual stress are analyzed.Finally, it provides a basis for the selection of technological parameters for the subsequent ultra-precision grinding experiment of polycrystalline magnesium fluoride.Based on the theoretical study of grinding pattern, the factors affecting grinding track are analyzed, and the optimal workpiece rotation speed is determined.An experimental platform for ultra-precision grinding is set up and the grinding wheel is trimmed in position to minimize the circle runout.The experiments of ultra-precision grinding with different grinding depth and feed speed are completed, and the grinding force changes in the machining process are monitored, and the results are compared with the simulation results, and the results are consistent.The surface roughness of the workpiece was measured by Taylor Hobson profilometer, the infrared transmittance of the workpiece was measured by Spectrum One laser spectrometer, and the residual stress of the workpiece was measured by Xippert3 Powedr X-ray diffractometer.The results show that, in a certain range, the grinding depth and feed speed increase the residual stress of grinding surface and decrease the surface roughness, but the material transmittance is not affected by grinding parameters.Finally, a set of ultra-precision grinding technology for polycrystalline magnesium fluoride is established.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ132.2

【相似文献】