【作者】 金群英；

【导师】 周志雄； 邓朝晖；

【作者基本信息】 湖南大学 ， 机械制造及自动化， 2004， 硕士

【摘要】 纳米结构陶瓷涂层材料是近年来研制出来的新型工程材料，在工业上有着广阔的应用前景。对这种材料的磨削加工是一个难题。目前在国内对纳米结构陶瓷涂层材料的精密磨削尚缺少深入系统的研究，因此在这方面所进行的研究工作就具有非常现实而重大的意义。 本文研究用金刚石砂轮磨削纳米WC／12Co涂层材料的磨削加工损伤，结合压痕断裂力学知识分析材料磨削时中位裂纹和横向裂纹的产生和扩展机理，最终建立起一个适用于纳米结构陶瓷涂层材料磨削加工情况的产生磨削损伤的临界力模型，并通过实验验证了该模型。依据该产生磨削损伤的临界力模型可以定量地判断材料的去除机理。本文的另一个重要内容是通过研究磨削参数对亚表面损伤深度的影响来揭示材料的亚表面损伤与磨削加工中的相关因素，如砂轮的切削深度、工件进给速度、砂轮粒度号、砂轮粘结剂类型等，之间的关系。 通过对比研究不同磨削条件下材料的亚表面损伤来逐步展开对本课题的研究，并取得一些有意义的结论： 1．在磨削纳米结构陶瓷涂层材料时主要产生两种形式的裂纹，即中位／径向裂纹和横向裂纹； 2．依据产生横向裂纹的临界力模型并结合实验结果，发现在所有磨削条件下，纳米WC／12Co涂层磨削表面最明显的特征是塑性流动，在大的单颗磨粒磨削力的条件下也同时伴有少量的脆性断裂。 3．随着切削深度和工件进给速度的增大，亚表面损伤深度增大。而砂轮转速对亚表面损伤深度的影响不大。 4．砂轮的磨粒尺寸越大，亚表面损伤深度越大。用金属粘结剂砂轮进行磨削产生的损伤深度比相同粒度号的树脂粘结剂砂轮和陶瓷粘结剂砂轮大。而树脂粘结剂砂轮和陶瓷粘结剂砂轮磨削产生的亚表面损伤深度差别不大。砂轮粘结剂类型对亚表面损伤深度的影响远没有砂轮切削深度和工件进给率的影响大。 本文通过对纳米WC／12Co涂层材料亚表面损伤的研究，从中得出规律可以用来对纳米结构陶瓷材料的精密磨削进行指导，并对加工过程进行预报。通过研究最终建立了纳米结构陶瓷涂层材料的亚表面损伤深度和单颗磨粒的磨削深度之间的关系模型。更多还原

【Abstract】 Nanostructured ceramic coatings, a kind of new engineering materials, are developed in recent years. This kind of materials will be extensively used in industrial applications. But machining difficulties have been associated with the uses. Under current state-of-the-art, no detailed and thorough study on the precision grinding nanostructured ceramic coating have been reported. So the research work in this respect has a very realistic and great meaning.The present paper deals with the grinding damage in n-WC/12Co coating ground with diamond wheels. The formation and propagation of median/radial and lateral cracks are analyzed using "indentation fracture mechanics" approach. Finally critical grinding condition models, which are fit for nanostructured ceramic coatings, are proposed and also verified by the experiments. Based on the critical load model the material removal mechanism can be quantitatively analyzed. The other important aspect of this paper is to announce the effects of grinding conditions on the depth of subsurface damage to reveal the inherent relation among the subsurface damage and relevant factors in grinding, such as wheel depth of cut, table federate, wheel grit size, wheel bond type and so on.Investigations had been conducted by comparing the subsurface damage of material under different grinding conditions. Some meaningful conclusions had beenmade:l.Two major crack patterns are identified, namely median/radial cracks andlateral cracks.2.Based on the critical load for lateral cracking and the experimental results, we found that grinding mark is the most significant characteristic on the ground n-WC/12Co under all grinding conditions. At the higher the normal force per grit, brittle fracture is also observed.3.The depth of subsurface damage grows with the increase of wheel depth of cutor table federate.4.Larger grit size results in deeper damage. The depths of damage are larger in the coatings ground with the mental bond wheel than in those ground with the vitrified and resin bond wheels. There is no great difference among those coatings ground with the vitrified and resin bond wheels. The effects of wheel bond type on the depth of damage are insignificant when compared with those from wheel depth of cut and table federate.The present paper investigated the subsurface damage of nanostructured WC/12Co coating. Some laws, which can guide the precision grinding nanostructured ceramic coatings and predict the grinding process, are obtained. A model between subsurface damage depth of nanostructured ceramic coatings and the cut depth per grit is established.更多还原