【作者】 姜胜强；

【导师】 谭援强；

【作者基本信息】 湘潭大学 ， 一般力学与力学基础， 2012， 博士

【摘要】 工业陶瓷由于本身具有诸多优良的结构力学性能而被广泛应用于机械、电子、航空航天、仿生器械、机器人等领域。科学技术的发展促进了陶瓷材料的压制、成型以及烧结工艺不断的得到改进和提高，使得陶瓷材料的力学性能也得以提升。随着机械产品朝“高、精、尖”的方向发展，人们对陶瓷器件也提出越来越苛刻的要求，如高质量、高精度、高可靠性等。同时，陶瓷材料本身的硬脆性使得其在加工的过程中不可避免的产生加工损伤和裂纹，降低了其可靠性。如何有效的降低陶瓷材料加工过程中的损伤以及控制裂纹的扩展一直是学者们研究的重要课题。本文提出了一种陶瓷材料的预压应力加工方法，并分别从理论分析、试验研究以及模拟三个角度来阐述预压应力下陶瓷材料的断裂力学行为及其加工损伤机理。本文的研究成果可以为陶瓷材料加工的实际应用提供一定的技术指导，对发展陶瓷材料的高效、低损伤新加工工艺具有重要的科学意义和工程应用价值。本文共分为七章，各章节的主要研究内容如下：第一章阐述了本文的研究背景，回顾了陶瓷材料断裂力学行为近几十年来的研究成果；从陶瓷材料的加工机理、去除机理以及研究方法与手段出发，综述了陶瓷材料加工的研究现状；提出了陶瓷材料的预压应力加工方法，概括了全文的研究内容及研究意义；第二章以陶瓷材料的压痕断裂力学为基础，建立了陶瓷材料在预压应力作用下的划痕力学模型，分析了模型内部应力场随角度变量的分布；研究了预压应力、载荷比等对模型内部主应力及最大剪切应力的影响，并得到了不同裂纹形态下的应力场强度因子；第三章以工业中常见的碳化硅、氧化铝陶瓷为研究对象，通过施加不同大小的预压应力进行划痕试验；观察了材料表面/亚表面裂纹的扩展结果、材料的损伤情况、划痕沟槽的几何形状变化，以及记录了划痕过程中的声发射信号等；综合以上研究结果，分析了预压应力对材料内部裂纹扩展以及材料去除机理的影响；第四章对预压应力下碳化硅陶瓷的磨削过程进行了实验研究，采用Kistler测力仪测量了不同预压应力下磨削力信号的变化情况；结合磨削后材料表面/亚表面的损伤情况、表面粗糙度以及残余应力的变化趋势等，分析了预压应力对陶瓷材料磨削过程中裂纹扩展以及加工质量的影响；第五章采用Cluster方法建立了在微观上能近似材料微结构，且在宏观上能表征其力学性能的陶瓷材料离散元力学模型；建立了陶瓷材料磨削加工的方法，分析了陶瓷材料磨削过程中裂纹的动态扩展过程以及磨削力的变化情况；采用正交试验方法研究了不同磨削加工工艺下的磨削力，材料损伤等；基于离散元法提出了陶瓷材料加工后表面/亚表面残余应力分析的新方法，分析了残余应力分布情况，综合以上研究结果，优化了其加工工艺参数；第六章基于离散元法建立了预压应力下碳化硅陶瓷单点金刚石精密切削加工的离散元模型，分析了预压应力对材料内部裂纹扩展的影响，并以此与预压应力划痕试验进行对照分析；基于正交试验方法，对陶瓷材料的精密切削加工工艺参数进行了优化；分别了切削工艺参数对残余应力分布的影响，并得到了残余应力云图；第七章对本文的研究内容进行了简要总结，并对今后的研究工作进行了展望。从本文理论分析、试验研究以及模拟三个角度的研究结果来看，在陶瓷材料施加预压应力加工过程中，预压应力的存在将一定程度上阻止中位裂纹的扩展及降低材料的损伤。若施加合适大小的预压应力，将有助于改善材料的去除，从而达到主动控制材料损伤的目的；但预压应力并不是越大越好，过大的预压应力又将给材料带来新的损伤。更多还原

【Abstract】 Industrial ceramics have been widely used in machinery, electronics, aerospace, bionicdevices, robotics and other fields due to their excellent mechanical properties. Thedevelopment of science and technology promoted and improved the processes of thecompressing, forming as well as sintering process of ceramic materials, which has enhancedthe mechanical properties of ceramic materials. With the development of machinery productsheading to the direction of ‘high, fine, sharp’, ceramic components have to meet a higherstandard, such as high-quality, high precision and high reliability. Because of the intrinsichard and brittle properties of ceramics, damage and cracks are almost inevitable during thetraditional machining processes, and once the damage is remained the reliability of the finalproducts would be reduced. How to effectively reduce, or even eliminate if possible, theremaining damage induced during the machining processes and control the propagation ofcracks has becoming an important research subject. In this thesis, a method of pre-stressingmachining of ceramic materials was presented and the fracture behavior of ceramic materialsunder pre-stressing were illustrated from the viewpoints of theoretical analysis, experimentalinvestigation as well as numerical simulation. The results of this research can provide atechnical guidance for the practical application of ceramic materials and can have animportant impact on both scientific researches and engineering applications for thedevelopment of high efficiency, low-damage of machining method of ceramic materials.This thesis was written in seven chapters, and main research objectives and outcomes ofeach chapter are briefly described as following:In chapter one, an introduction of the background of this research was given, anda literature review of fracture of ceramics was delivered. From the viewpoints ofmachining method, machining mechanism of ceramic materials and research method,the machining status of ceramics was described. The pre-stressing machining methodwas elaborated and the research contents and the significance of this thesis wereoutlined.In chapter two, a mechanical model of pre-stressing scratching of ceramicmaterials was developed. The stress distribution changed with the angle variablewithin the material under pre-stressing was analyzed. The effects of pre-stress andload ratio on the principal stress and maximum shear stress were studied, and thestress field intensity factor under different crack form was proposed.In chapter three, a series of scratching tests were carried out under different pre-stresses of silicon carbide and aluminum ceramics. The surface/sub-surface crack,material damage and the shape of scratch groove were observed, and the AE signalswere also recorded in the scratching test. Combining these results, the effects ofpre-stress on the crack propagation and material removal mechanism were analyzed.In chapter four, the grinding process of SiC ceramic under pre-stressing wasinvestigated in experiment. The signal of grinding force in the grinding process wascollected by the Kistler dynamometer. Combining the grinding surface, cross-sectiondamage, surface roughness and the residual stress of SiC ceramic, the effects ofpre-stress on the crack’s propagation and machining quality of SiC ceramic ingrinding process were also analyzed.In chapter five, based on discrete element method (DEM), the discrete elementmodel of SiC ceramic was established and calibrated using PFC2D numerical code.The cluster method was introduced so that the DEM model of SiC ceramic was closedto the reality material in the viewpoint of microscopic. The grinding process ofceramic materials was established base on the DEM simulation. The dynamics ofcracks propagation process and the changing of grinding force were analyzed. Basedon the orthogonal test, the grinding parameters under different pre-stress wereinvestigated, and the material damages were also studied. And based on the DEMmethod, the measurement of surface/sub-surface residual stress of ceramic afterprocessing was proposed, and the distribution of residual stresses were investigated.The grinding parameters of grinding process were optimized.In chapter six, the DEM model of pre-stressing cutting process of ceramicmaterial was established, and the effect of pre-stress on the crack propagation wasalso analyzed. The simulation results were compared with the results of scratchingtests. Based on the orthogonal test, the cutting parameters of ceramic materials wereoptimized. The distribution of residual stresses were investigated, and the residualstress nephogram was also accomplished.In chapter seven, the contents of this thesis were briefly summarized, andpotential future work was also discussed.From the research results of theoretical analysis, experimental investigation as well asnumerical simulation of this thesis, it can be seen that the existence of pre-stress shouldshorten the depth of median cracks and reduce the sub-surface damage. Moreover, if thepre-stress was kept in a proper range, the depth of median crack was decreased and thepropagation length of lateral crack was limited. And the existence of pre-stress can bepropitious to change the material removal mechanism, and than to achieve the aim of initiative control the material damages. But it is not that a higher pre-stress would get a bettermachining quality. If the pre-stress exceeded the proper range, it would be lead to producesome additional damages.更多还原