旋转超声磨削加工建模与仿真研究

旋转超声磨削加工结合超声加工和磨削加工的技术优势，在难加工零件的精密制造中具有较大应用潜力。根据旋转超声磨削加工机理，建立旋转超声磨削加工中材料去除体积和加工表面粗糙度的数值计算模型。基于MATLAB软件编写旋转超声磨削加工仿真程序，对材料去除体积、加工表面形貌和表面粗糙度进行仿真模拟，并探究不同加工参数对表面粗糙度和材料去除体积的影响规律。仿真结果表明：主轴转速与超声振动频率之比(n/f)对加工表面形貌和去除体积有决定性影响，n/f比值增大能够有效降低表面粗糙度和提升材料去除体积；详细探讨了磨粒直径、振幅等参数对旋转超声磨削加工表面形貌和去除体积的影响规律，并仿真模拟了参数优化前后的加工表面形貌。     

应用响应曲面法的机器人铣削工艺优化

为保证机器人铣削加工效率的同时减小切削力、振动加速度和表面粗糙度，从而优化铣削工艺，通过试验研究了不同铣削工艺对机器人切削性能的影响。应用响应曲面法，以切削力、振动加速度和表面粗糙度为响应值，选取主轴转速、进给量和切削深度3类数值因子，以及铣削方式与走刀方向2类类别因子进行优化参数，并建立了各个响应值的二阶预测模型。结果表明：Y方向铣削可以获得较小的切削力和表面粗糙度，逆铣的振动加速度幅值明显小于顺铣加工。同时，进给量和切削深度对切削力和振动加速度具有显著影响，主轴转速对表面粗糙度影响较为显著。优化结果表明高主轴转速、大进给量和小切深时，在保证加工效率的同时切削力、振动加速度和表面粗糙度都较小。     

光学玻璃超声振动磨削亚表面损伤的试验研究

进行光学玻璃BK7超声振动辅助磨削试验,采用截面抛光法配合HF酸腐蚀法并通过扫描电子显微镜观测获得亚表面裂纹的最大深度,研究了主轴转速、磨削深度、进给速度和超声振动振幅对亚表面损伤裂纹最大深度的影响规律,分析了亚表面裂纹的几种形态及其成因。结果表明,随着主轴转速和超声振动振幅增大,磨削深度及进给速度减小,亚表面最大裂纹深度明显减小。超声振动的引入改善了磨削时的加工条件,对提高加工表面及亚表面的质量有一定帮助。     

超精密加工中表面波纹度与主轴系统不平衡关系

针对超精密加工工件表面出现的表面波纹度问题,研究超精密机床液压主轴系统不平衡问题与表面波纹度之间的关系。加工工件的面形检测结果首先利用选出的最优小波变换进行各个尺度的分解及重构,接着利用功率谱密度分析小波分解后各个尺度上的信号谱能量得到相关频率信息,结合主轴系统部件的模态及旋转频率信息,对检测结果中主要误差特征进行提取。主轴系统频率信息由两种方法进行计算,从面形波纹度中提取出来的典型误差特征包含机床主轴固有频率和旋转频率及其高倍频,电源基频50 Hz及其整数倍频和次谐波信号,这些频率特征正好与主轴系统不平衡频率以及电动机工频噪声干扰频谱特征对应,这说明主轴系统不平衡是导致加工工件波纹度出现的主要原因,这种辨识方法为超精密机床加工精度的提高提供了辨识依据。     

车削加工中振动对表面轮廓影响的仿真分析

通过分析表面轮廓成形运动，建立了切削加工中表面轮廓的仿真模型，开发并编写了表面轮廓形貌的仿真程序，在仿真中考虑了切削参数、振动对表面轮廓形貌的影响，分析了其表面空间频率。结果表明，振动频率比是分析和描述表面轮廓特性的重要参数，利用所建立的仿真模型得到的表面轮廓形貌，能预测车削加工表面轮廓。     

陶瓷基复合材料旋转超声加工特性研究

针对陶瓷基复合材料加工方法的优势和不足,采用旋转超声加工方法对陶瓷基复合材料进行加工,完成旋转超声加工方法与传统加工方法的对比试验。试验表明,钻削力随着主轴转速的增加而减小,随进给速度的增加而增加;扭矩随着主轴钻速的增加而减小,随进给速度的增加而增加;工件表面粗糙度随着主轴转速和进给速度的增加先降低后增加。超声加工方法获得的钻削力、扭矩和表面粗糙度均优于传统加工方法。     

切削振动条件下的表面轮廓仿真分析

对在切削振动条件下得到的表面轮廓进行仿真,分析其表面空间频谱,提出根据加工参数、切削振动与表面微观形貌的关系优选主轴转速以优化加工表面质量的方法     

基于频域分析的凸轮轴波纹度磨削加工研究

针对发动机凸轮轴凸轮表面的磨削过程,建立了凸轮表面波纹度磨削的振动模型;通过计算凸轮轴的旋转频率,并与砂轮主轴的振动频谱线对比,发现凸轮表面波纹度主要受砂轮振动系统的影响,且波纹度频谱曲线异常的波成分由砂轮振动系统相应的波成分决定;其次,针对砂轮振动系统,由动力学模型预测,并结合测量数据,确定振动异常的振源;最后提出了磨削加工波纹度的相关改善措施。     

高体积分数SiCp/Al复合材料旋转超声铣磨加工的试验研究

由于大量高硬度增强相SiC颗粒的存在,高体积分数铝基碳化硅（SiCp/Al）复合材料的机械加工十分困难。旋转超声加工被认为是加工这种材料的有效方法。通过超声辅助划痕试验,分析高体积分数SiCp/Al复合材料旋转超声铣磨加工的材料去除机理。在超声振动的作用下,材料中铝基体发生塑性变形,其表面得到夯实;SiC增强相被锤击成细小的颗粒而发生脱落,形成较大的空洞。由于材料加工的缺陷大多产生于SiC颗粒的去除过程中,SiC颗粒的去除方式对加工表面的质量起着决定性的作用,选择合适的工艺参数可以有效提高加工表面质量。旋转超声加工工艺特征试验表明,超声振动可有效降低切削力;主轴转速对轴向切削力的影响最大,其次是进给速度,切削深度对轴向切削力的影响较小;另外主轴转速对表面质量的影响效果也最大,并随主轴转速的增大表面粗糙度增大。因此在加工过程中,可以适当加大切削深度,在保证加工质量的基础上,选择较大的进给速度,在保证刀具寿命的前提下,选择合适的主轴转速,以获得较优的加工表面质量和加工效率。     

工程陶瓷纵扭复合超声振动螺旋磨削 制孔表面质量研究

针对工程陶瓷传统磨削制孔存在表面质量较差等问题,对超声振动辅助加工及螺旋加工的工艺优势进行了归纳分析,提出了纵扭复合超声振动螺旋磨削制孔的加工方法。利用超声加工机床和白光干涉仪及马尔表面轮廓仪,对纵扭复合超声加工、纵向超声加工和普通磨削加工对孔表面质量的影响情况进行了研究;并进一步探究了施加纵扭复合超声振动后超声振幅、螺距、主轴转速、螺旋进给速度对加工孔表面质量的影响规律。研究结果表明:相比纵向超声加工和普通加工,纵扭复合超声加工有利于提高制孔表面质量;纵扭超声螺旋磨削加工超声振幅、螺距对孔底和孔壁表面粗糙度的影响趋势相似,主轴转速及螺旋进给速度对两者表面粗糙度的影响趋势总体上相反。     

The effects of dynamic characteristics on the surface texture in mirror grinding

In order to make clear the effects of mirror grinding conditions on the ground surfaces in the surface mirror grinding of sintered carbide adopting an in-process electrolytic dressing method, experiments are conducted to measure the vibration signals of the workpiece during grinding and the profile of the ground surface. It is found that components with low frequency vibration signals have a very close relation to the undulation of a ground surface and components with high frequencies to the surface roughness .     

Design of an offset hydrostatic thrust bearing under dynamic loading conditions

An offset hydrostatic thrust bearing is analysed to determine the effect of vibration of the rotating plate on the performance characteristics. The flow developed is asymmetric because the surface rotation axis is offset from the bearing axis. The governing Reynolds equation is solved using semianalytical methods. The average load capacity, frictional force and lubricant flow rate are strong functions of the bearing offset L, bearing number λ, film thickness profile H, film thickness variation ? and the ratio between the frequency of vibration of the rotating plate and the angular speed of rotation.     

A multi-spectrum analysis of surface roughness formation in ultra-precision machining

The formation of surface roughness in ultra-precision diamond turning is investigated using a multi-spectrum analysis method. The features on a diamond turned surface are extracted and analyzed by the spectrum analysis of its surface roughness profiles measured at a finite number of radial sections of the turned surface. It is found that the tool feed rate, the spindle rotational speed, the tool geometry, the material properties, as well as the relative tool-work vibration are not the only dominant components contributing to the generation of surface roughness. The material induced vibration caused by the variation of material crystallography is another major factor. The vibration causes a significant variation of the frequency of the surface modulation of the machined surface. With the use of the multi-spectrum analysis method, it is possible to conjecture the patterns of this vibration as well as to evaluate the properties of the workpiece materials.     

超声振动辅助混粉电火花表面强化粗糙度研究

进行超声振动辅助混粉电火花表面强化实验,分析超声振动辅助混粉电火花表面强化过程中各因素,例如脉宽、脉间、峰值电流、混粉浓度和超声振动振幅等对强化层表面粗糙度的影响规律,研究结果表明,各因素对强化层表面粗糙度影响规律明显,研究结果可以对超声振动辅助混粉电火花表面强化的工艺参数优化提供依据,对进一步的理论和实验研究具有一定的指导意义.     

干气密封滑动密封端面高频微幅摩擦振动研究

为揭示干气密封端面间摩擦振动规律,通过对密封端面在干摩擦状态下的微观形貌与受力进行分析,基于分形理论构建包含分形参数的密封端面法向位移激励,以及干气密封在干摩擦状态下的两自由度摩擦振动系统模型,并对摩擦振动系统模型的影响因素进行数值分析.研究结果表明:法向振动位移和速度随着分形维数与转速的增大先增大后减小;密封环面分形...     

Residual stress fluctuates periodically via the workpiece rotation phase during low frequency vibration cutting

The turning process is a standard machining process employed in diverse sectors. However, it produces long continuous chips that can affect the efficiency of the process, accelerate the tooling's wear, or damage the machined surface. As a solution, low frequency vibration cutting synchronizing with the spindle rotation has recently been developed as a new machining method in turning operation. It applies vibrations in the tool feed direction and can synchronously control the applied vibrations and the spindle rotation. It can also effectively divide the long continuous chips generated by the turning process and has the potential to reduce thermo-mechanical load on the tool by periodically enabling the tool to leave the workpiece due to the vibrations. Low frequency vibration cutting, the cutting characteristics of which differ from those of conventional turning, induces residual stresses in the machined surface; however, the properties of these stresses have not yet been studied. Residual stress can have both beneficial and negative effects on the fatigue life of products. While compressive residual stress increases the fatigue life of the product, tensile residual stress facilitates the growth of fine cracks on the product's surface and reduces fatigue life. Therefore, it is important to understand the characteristics of the residual stress developed on a machined surface. In this study, an annealed 0.45% C steel bar was machined via straight turning of the vibration cutting process synchronizing with the spindle rotation, and the residual stress on the finished surface was measured. Particular focus was placed on analyzing the effects of the spindle phase on the characteristics of the residual stress inside the machined surface, especially the effects of the number of vibrations per spindle rotation, D, which is a unique parameter defining the vibration condition. Our results revealed that the residual stress varied depending on the position of the finished surface owing to the change in feed with the spindle phase during the process. Furthermore, D was observed to heavily influence the distribution of the residual stress on the finished surface. By means of adjusting its value, the residual stress value could either fluctuate periodically according to the phase of the workpiece or not fluctuate.     

Numerical simulation of slider dynamics during slider–disk contact

In this paper, the dynamic behavior of pico slider in contact with the disk was calculated. The analysis model consists of a simplified suspension model, an air bearing model, and a slider–disk contact model. The contact model consists of two elements. One is surface roughness model measured by Atomic Force Microscope (AFM) and the other is micro-waviness model. The dynamic behaviors of the tri-pad slider are calculated at several rotation speeds to investigate slider vibration modes during slider–disk contact. The slider oscillation frequency depends on the rotation speed and it saturates about twice as much as eigen frequency of air bearing pitch mode.     

柔性椭圆轴承故障频率分析与CMWT-FH特征提取

柔性椭圆轴承（Elliptically shaped baring,ESB）在工作中承受循环交变应力载荷,是谐波减速器中最易损坏的核心零件。根据ESB的运动学特性,推导其滚道表面发生局部缺陷故障时的特征频率公式。由于其故障特征容易被长短轴交替产生的振动激励信号所掩盖,提出连续Morlet小波变换（Continuous Morlet wavelet transform,CMWT）与基于FFT的Hilbert频谱分析（FFT based Hilbert,FH）结合的CMWT-FH故障特征提取方法。与普通FH方法的特征提取效果对比分析,CMWT-FH方法可以更容易、更准确地识别出ESB的故障特征频率及其边频带频率：外圈故障时,外圈故障特征频率及其高次倍频两侧存在间隔为二倍转频调制频率的边频带;内圈故障时,内圈故障特征频率及其高次倍频两侧存在间隔为转频调制频率的边频带。可结合故障特征频率及调制边频带来判断故障出现在外圈还是内圈。     

准分子激光加工参数对表面形貌影响的模糊分析

采用准分子激光微细加工方法 ,选用不同的工艺参数加工Al2 O3 陶瓷材料试件。通过表面轮廓仪测量并计算表面形貌统计参数。分析了激光加工工艺参数对表面形貌的影响 ,利用模糊分析方法 ,就激光器的放大器电压、激光脉冲频率、激光扫描速度等工艺参数对表面形貌轮廓均方根值Rq 的影响进行了评价。结果表明 ,Rq 值随激光器的放大器电压和激光脉冲频率的增大而增大 ,随激光扫描速度的增大而减小。分析得出 ,激光加工工艺参数对表面形貌的影响程度不同 ,由大到小依次为激光扫描速度、激光脉冲频率、放大器电压。因此 ,可以通过合理地选择工艺参数获得所需求的表面形貌 ,为表面微观形貌修饰提供了参考依据。