【作者】 闫艳燕；

【导师】 赵波；

【作者基本信息】 上海交通大学 ， 机械工程， 2008， 博士

【摘要】 由于目前工程应用对陶瓷材料的要求日益苛刻,单相材料越来越难以满足其使用要求,故而使纳米复相陶瓷成为陶瓷材料领域研究的一大热点。但由于其对表面微观缺陷敏感、生产效率低、加工成本高等特点限制了其在高新高端技术的广泛应用,为了推动纳米复相陶瓷材料的普及和应用,探索一种高质、高精、高效的纳米复相陶瓷加工方法是现代加工面临的一项急迫的任务。本文以纳米复相陶瓷增强增韧机理、超声振动理论、断裂力学、宏微观力学等为理论基础,分别从纳米氧化锆增韧氧化铝陶瓷(ZTA纳米复相陶瓷)在二维超声振动辅助磨削(简称二维磨削)条件下的表面创成机理、材料去除机理及其表面微观质量等方面展开研究,从微观角度系统地研究了二维超声振动激励对ZTA纳米复相陶瓷加工特性的影响规律,揭示ZTA纳米复相陶瓷在二维磨削中所表现出的高效精密加工特性,为纳米复相陶瓷的二维磨削高效精密加工新方法的推广奠定理论基础。主要研究内容如下:1、以ZTA纳米复相陶瓷为加工对象,提出一种单驱动二维超声振动辅助金刚石砂轮磨削技术,通过机械阻抗综合法研究该系统的组合共振问题,分析该系统对超声激励的动态响应情况,并通过试验获取了该系统的振动特性。基于超声振动理论,从运动学角度分析新型磨削系统在二维超声振动的激励下产生的工件质点及单颗磨粒运动轨迹特征,首次建立二维磨削单颗磨粒切削轨迹方程,定义了单颗磨粒与工件的螺旋式切削轨迹,给出了单颗磨粒切入切出工件的时间、超声在切削区内的振动次数,切削弧长及超声振动临界频率条件,发现了二维磨削具有一次切削多次光磨,磨削沟槽宽化及磨削表面未切除材料痕迹尺寸变小的特点,并最终确立了二维磨削表面创成机理。2、以压痕断裂力学、塑性加工理论为基础,建立了二维磨削单颗磨粒切削模型,给出单颗磨粒临界切削厚度,并对磨削过程脆塑性去除机理进行分析,基于二维超声振动条件下单颗磨粒临界切削厚度模型,给出二维磨削陶瓷脆塑转变临界条件,建立脆塑两种情况下高效材料去除率模型,并通过试验得知相同磨削参数下,二维磨削材料去除是普通磨削的2～3倍。3、基于冲击断裂力学,振动切削理论及普通磨削磨削力模型,建立二维超声振动辅助磨削过程中的磨削力数学模型,从磨削力特性对二维超声辅助磨削技术的加工特性进行解释,并通过试验分析了二维超声振动及磨削加工参数对磨削力及其力比的影响规律。4、通过二维磨削ZTA纳米复相陶瓷表面粗糙度单因素试验讨论不同加工参数及二维超声振动对表面粗糙度的影响规律。基于自适应模糊神经推理系统(ANFIS)构建了ZTA纳米复相陶瓷磨削表面粗糙度的预测模型,通过各加工参数间复杂的非线性问题的处理,获得近似实际加工结果的输出值,预测精度可达到81.25%。根据自适应模糊推理预测模型形成的模糊规则曲面得出四个输入项对ZTA纳米复相陶瓷磨削表面粗糙度的影响程度,由大到小依次是砂轮粒度,磨削方式(二维磨削或普通磨削)、磨削深度、轴向进给量、工作台速度。5、基于扫描电镜、透射电镜、X射线衍射、白光干涉仪等测试技术探索性地讨论ZTA纳米复相陶瓷二维磨削表面/亚表面损伤特征,研究ZTA纳米复相陶瓷二维磨削过程中应力诱发氧化锆马氏体相变程度,以及由此引起的磨削表面残余应力的变化规律,从微观角度研究超声激励下磨削表面微裂纹的成核、生长和扩展规律以及变质层的分布,指出与普通磨削相比,二维磨削利于ZTA陶瓷获取较好的表面微观特征。6、提出了在超声振动条件下ZTA纳米复相陶瓷断裂的模拟试验方法。基于该方法分析具有预制裂纹的ZTA纳米复相陶瓷材料在超声振动条件下裂纹扩展方式,确立其断裂判据,通过该断裂模拟试验得出:沿晶断裂是普通磨削主要的断裂模式,而穿晶断裂是二维磨削主要的断裂模式,进一步证明二维磨削具有较好的材料去除特性。更多还原

【Abstract】 Currently single-phase ceramics does not meet the higher requirement of engineering application, so nanocomposite ceramics has attracted a lot of attention and has become one of the hot-points in the field of material research. On the other hand, it is hard to machine nanocomposite ceramics, especially surface microdefects of finished surface may lead to low reliability of ceramics parts, so its wide potential application brings great challenges to modern machining techniques. It is necessary to develop precise machining technology to raise working efficiency and improve surface quality.Based on the toughening and reinforcing mechanisms of ceramics, ultrasonic vibration theory, fracture mechanics and macro micro mechanics, it worked on surface formation mechanism, material removal mechanism and surface quality of nano zirconium toughening alumina ceramics (ZTA nanocomposite ceramics) under two-dimensional ultrasonic vibration assisted grinding (TDUVAG), and it analyzed how two-dimensional ultrasonic vibration has the effect on the processing characteristic of ZTA nanocomposite ceramics, which may reveal efficient precision finishing characteristic ZTA nanocomposite ceramics under TDUVAG and provide fundamental basis for the popularization of TDUVAG. The main research contents were listed as follow:1. New technique of two-dimensional ultrasonic assisted grinding (TDUVAG) for ZTA nanocomposite ceramics was put forward, the resonance vibration of the system was analyzed by the mechanical impedance theory, vibratory response of the system was deduced by elastic-plastic mechanics, and vibration characteristics of the system was measured by test. Based on ultrasonic vibration theory, microscopic cutting trace of abrasive particle under two dimensional ultrasonic vibrations were analyzed, and cutting trace formula of abrasive particle was built fistly, and the spiral cutting trace of single abrasice grain was defined, cutting time, ultrasonic vibration time, and cutting arc length of single abrasive grain in the cutting zone are deduced, and the critical frequency condition of ultrasonic vibration was given. Based on the series of research, surface formation mechanism of TDUVAG was established.2. Based on indentation fracture mechanics and plastic working theory, it worked on the removal mechanism of ZTA nanocomposite ceramics under TDUVAG,the critical cutting thickness of abrasive particle under TDUVAG was built, and the critical condition of brittle-ductile transition of ceramics under TDUVAG was given by plastic working theory, high efficient material removal rate model of ceramics under TDUVAG, and experiment results showed that the material removal rate under TDUAG is about twice as that under common grinding.3. Based on impulse theories and the grinding force model under common grinding, the mathematics grinding force model under TDUVAG was built, and the processing characteristic of TDUVAG was analyzed according to the characteristic of grinding force,and it analyzed how ultrasonic vibration and grinding parameters had affect grinding force and grinding force ratio by tests.4、How grinding parameters and ultrasonic vibration affect surface roughess Ra was analyzed by single-factor test of surface roughness Ra, experimental results showed that TDUVAG may obtain the less surface roughness Ra than common grinding. By means of adaptive-network-based fuzzy inference system, the prediction model of surface roughness of ZTA ceramics was built, and the model may obtain the higher precsion (81.25%) by dealing with nonlinear problem among grinding parameters, and fuzzy rule curved face formed by prediction model showed four input factors have different influence on surface roughness Ra, and they are abrasive grain size, grinding method (TDUVAG or common grinding), grinding depth, axial feed and speed of worktable from top to bottom.5、The surface/subsurface damages of ZTA ceramics under TDUVAG were observed by XRD、SEM、TEM and white light interferometer. The phase transformation, surface residual stress, microcrack and grinding badness layer in the grinding surface of ZTA nanocomposite ceramics under TDUVAG were analyzed by comparative trials,experimental results showed TDUVAG may form the higher compressive stree caused by martensitic transformation of zirconia grain, the microcracks in the grinding surface under TDUVAG differed from that under common grinding, and grinding badness layer of ZTA nanocomposite ceramics under TDUVAG is shallower than that under common grinding, as a result, TDUVAG may obain the better grinding surface integrity of ZTA ceramics.6、The fracture analog experiment was designed to study the fracture behaviour of ZTA ceramics under ultrasonic vibration. With the aid of the experiment, crack formation and its expand pattern of ZTA ceramics under ultrasonic vibration were analyzed, its fracture criterion was established and the experiment results showed that intercrystalline fracture is the main fracture pattern of ZTA ceramics under common grinding, and transcrystalline fracture is the main fracture pattern of ZTA ceramics under TDUVAG, and the finding add to evidence showing that TDUVAG has better material removal property.更多还原