金刚石磨粒划擦过程中的机械磨损特性研究

发布时间：2018-05-09 09:30

  本文选题：单颗金刚石磨粒 + 机械磨损　； 参考：《华侨大学》2016年博士论文

【摘要】：金刚石磨粒工具被广泛应用于多种材料的高效精密加工。金刚石磨粒的机械磨损对工具寿命及加工质量都有着重要的影响。对工具中金刚石磨粒的观察发现磨粒磨损具有较大随机性。虽然学者们试图利用磨粒排布的思路来提高金刚石磨损的均匀性,但是其效果有限,其根本原因是金刚石磨粒的磨损机理尚不明确。本文选用立方八面体金刚石磨粒,分别制备了点、线、面三种与工件不同接触形式的单颗钎焊金刚石试样;并结合晶体结构规划划擦方向,设计了九种不同的划擦方式。跟踪了不同划擦方式下金刚石磨粒划擦典型脆性材料(蓝宝石)和塑性材料(Ta12W)时的材料去除体积、划擦力、磨粒磨损体积及磨损形貌。比较分析了接触形式、工件材料及划擦方向对金刚石磨粒机械磨损的影响规律。采用光滑粒子流体动力学(SPH)方法和理论计算推导建立了金刚石磨粒划擦应力理论模型,分析不同划擦方式对金刚石磨粒划擦过程的影响及应力变化特征,最终建立起了金刚石磨粒的磨损理论模型,较好解释了金刚石磨粒的磨损规律。通过上述分析和讨论,本文的主要研究成果工作可概述如下:(1)影响金刚石磨粒机械磨损的主要原因是接触形式、工件材料类型和划擦方向。其中接触形式的影响最为显著,面接触时金刚石磨粒的耐磨性明显超过点、线接触形式下的金刚石耐磨性,其中{100}晶面接触形式的耐磨性最高。点、线接触情况下,其接触面积小而导致接触应力增大是使其耐磨性变差的主要原因。(2)金刚石磨粒机械磨损形式主要包括:裂纹,台阶状断裂,河流状解理以及片状解理。金刚石磨粒的片状解理多发生在{111}晶面,而台阶面沿{111}晶面产生断裂破碎,裂纹多沿110晶向产生。划擦蓝宝石时,这四种机械磨损形式都存在,但划擦Ta12W时,以河流状解理和片状解理为主。(3)工件材料类型对金刚石的磨损形式有着显著的影响,划擦蓝宝石(脆性材料)时金刚石磨粒主要受到挤压应力的作用而产生沿一定角度的破碎;划擦Ta12W(塑性材料)时,金刚石磨粒受到剪切力矩和挤压应力的综合作用而形成平整的剪切面。(4)建立了金刚石磨粒划擦机械磨损理论模型,分析不同接触形式下的应力特征模型,较好地解释了金刚石的磨损规律;利用PBC模型,可较好解释金刚石磨损形貌的产生原因。本文的研究成果丰富了金刚石磨粒机械磨损的理论研究,对优化金刚石磨粒工具性能、制备新型金刚石磨粒工具具有实际指导意义。
[Abstract]:Diamond abrasive tools are widely used in high-efficiency precision machining of many kinds of materials. The mechanical wear of diamond abrasive particles has an important effect on tool life and machining quality. It is found that the abrasive wear of diamond particles in the tool is random. Although scholars try to improve the uniformity of diamond wear by using the idea of abrasive particle arrangement, its effect is limited, and the basic reason is that the wear mechanism of diamond abrasive particles is not clear. In this paper, cubic octahedron diamond abrasive particles are used to prepare single brazed diamond samples with different contact forms of points, lines and surfaces with workpiece, and nine different scratching methods are designed in combination with the crystal structure planning scratching direction. The material removal volume, scratch force, abrasive wear volume and wear morphology of typical brittle material (sapphire) and plastic material (Ta12W) were tracked under different scratching methods. The effects of contact form, workpiece material and scratch direction on the wear of diamond abrasive are compared and analyzed. The theoretical model of diamond abrasive scratch stress is established by using smooth particle hydrodynamics (SPH) method and theoretical calculation. The influence of different scratching methods on diamond particle scratch process and the characteristics of stress variation are analyzed. Finally, the wear theory model of diamond abrasive particles is established, and the wear law of diamond abrasive particles is well explained. Through the above analysis and discussion, the main research results of this paper can be summarized as follows: (1) the main reasons that affect the mechanical wear of diamond abrasive particles are the contact form, the material type of the workpiece and the scratching direction. The effect of contact form is the most obvious, and the wear resistance of diamond particles is obviously higher than that of point, and the wear resistance of diamond in line contact form is the highest, among which the {100} crystal surface contact form is the highest. When the contact area is small, the increase of contact stress is the main cause of poor wear resistance.) the mechanical wear forms of diamond grain mainly include: crack, step fracture, fluvial cleavage and flake cleavage. The lamellar cleavage of diamond grains occurs in the {111} crystal plane, while the step surface breaks along the {111} crystal plane and the crack occurs along the 110 crystal direction. These four kinds of mechanical wear forms exist when scratching sapphire, but when scratching Ta12W, the material type of workpiece mainly composed of fluvial cleavage and flake cleavage has significant influence on the wear form of diamond. When scrubbing sapphire (brittle material), diamond abrasive particles are mainly crushed at a certain angle due to the effect of extrusion stress, and when scratching Ta12W (plastic material), The diamond abrasive particles formed a flat shear surface by the combined action of shearing moment and extrusion stress. (4) the theoretical model of diamond abrasive friction mechanical wear was established, and the stress characteristic model under different contact forms was analyzed. The wear law of diamond is well explained, and the cause of diamond wear morphology can be explained by using PBC model. The research results in this paper enrich the theoretical study of diamond abrasive wear, and have practical guiding significance for optimizing the performance of diamond abrasive tools and preparing new diamond abrasive tools.
【学位授予单位】：华侨大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG74

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