【作者】 赵博；

【导师】 郭东明；

【作者基本信息】 大连理工大学 ， 机械制造及其自动化， 2016， 硕士

【摘要】 微晶玻璃是一种同时具有玻璃相和晶相的多晶脆性材料,具有膨胀系低、硬度大,耐磨性好,机械强度高,热稳定性优良等特点,在航空、航天和国防科工等领域的光学元器件制造中的得到广泛应用。微晶玻璃作为一种典型的脆性材料,超精密磨削加工是实现其高效低成本加工重要的方法,但是在磨削过程中不可避免的会在工件的表面和亚表面产生加工损伤,加工损伤会降低元器件的强度、成像质量和稳定性等使用性能,进而降低元器件的使用寿命。因此,研究微晶玻璃超精密磨削的表面和亚表面损伤特征,对于实现微晶玻璃的高效低损伤磨削加工具有重要指导意义。本文通过微晶玻璃磨削试验分别对#500、#1500、#2000和#5000金刚石砂轮磨削后微晶玻璃的表面形貌、表面粗糙度以及表面和亚表面损伤特征进行了系统的研究,分析了不同磨粒粒度金刚石砂轮磨削微晶玻璃的材料去除机理,并进一步研究了磨削微晶玻璃材料发生脆性去除时,亚表面损伤深度(SSD)与表面粗糙度PV值(SR)之间的关系。本文的主要研究内容如下：(1)通过#500、#1500、#2000和#5000金刚石砂轮磨削微晶玻璃试验,研究了砂轮粒度对微晶玻璃表面形貌、表面粗糙度和表面损伤的影响。结果表明,随着砂轮磨粒粒度的减小,微晶玻璃表面越来越光滑,表面粗糙度值减小,表面损伤形式逐渐由脆性断裂造成的凹坑和微裂纹向塑性流动造成的微磨痕过渡。(2)采用截面显微观测法、角度截面显微观测法和透射电子显微镜法分别对不同粒度金刚石砂轮磨削微晶玻璃的亚表面损伤进行检测,并分析其材料去除机理。结果表明,随着砂轮磨粒粒度的减小,磨削后工件的亚表面损伤深度逐渐减小,#500金刚石砂轮主要以脆性断裂方式实现去除材料；#1500和#2000金刚石砂轮同时以脆性断裂和塑性流动方式去除材料；#5000金刚石砂轮主要以塑性流动方式去除材料,亚表面损伤形式由亚表面微裂纹和崩碎逐渐过渡为靠近磨削区域材料的塑性流动。(3)基于压痕断裂力学的相关理论,利用磨削过程中材料发生脆性断裂时,亚表面损伤深度与表面粗糙度PV值的关系模型,进一步建立了磨削微晶玻璃亚表面损伤深度与表面粗糙度的数值关系。使用#500金刚石砂轮在不同的进给速度下进行微晶玻璃的磨削试验,测量磨削后微晶玻璃的表面粗糙度PV值与亚表面损伤深度,验证了数值模型的有效性。更多还原

【Abstract】 Glass-ceramics is a polycrystalline brittle material consisting of glass phase and crystalline phase. Glass-ceramics with low thermal expansion coefficient is widely used in aerospace industry, defense industry and other fields, owing to its good physical properties, excellent mechanical property and favorable chemical stability, especially for its extraordinary low thermal expansion coefficient. As an important processing method for brittle materials, grinding inevitably induces the surface and subsurface damage. The surface and subsurface damage will reduce the strength of the glass-ceramics components and the long term stability, affect the image quality, and finally reduce the service life of the optical element. In consequence, that efficiently machining glass-ceramics with low surface and subsurface damage has become the focus of the glass-ceramics machining.In this study, the surface topography, surface and subsurface damage characteristics and material removal mechanism of glass-ceramics ground by diamond wheels with different abrasive sizes of #500,#1500,#2000 and #5000 are investigated. The relationship between the subsurface damage depth and surface roughness of ground glass-ceramics is also established. Main research content of this study is as following:(1) Glass-ceramics were ground by diamond wheels with different abrasive sizes of #500,#1500,#2000 and #5000, and the surface topography, surface roughness, and surface damage characteristics of ground glass-ceramics were investigated. With the decrease of abrasive sizes of the diamond wheels, the surface of the glass-ceramics became more and more smooth, the surface roughness of the glass-ceramics decreased, and the surface damage form transforms from pits and microcracks which caused by brittle fracture to micro-scratches which caused by plastic flow of glass-ceramics gradually.(2) To investigate the subsurface damage of the glass-ceramics ground by diamond wheels with different abrasive sizes, many detection methods including cross-section microscopic observation method, angle cross-section microscopic observation method and transmission electron microscopy were taken. With the decrease of abrasive sizes of the diamond wheels, the subsurface damage depth of the glass-ceramics decreased, and the subsurface damage form transforms from microcracks in the subsurface layer to plastic flow of glass-ceramics closing to the material grinding surface. With the decrease of abrasive sizes of the diamond wheels, glass-ceramics removed in brittle-mode grinding changed to removed in ductile-mode grinding.(3) Based on the related theory of indentation fracture mechanics, the relationship between the subsurface damage depth and surface roughness of ground glass-ceramics was established when the subsurface damage was microcracks. To verify the correctness of the relationship, glass-ceramics was ground by #500 diamond wheel with different feed rates and the subsurface damage depth and surface roughness of the ground glass-ceramics were measured.更多还原