Influence of Cavitation on Unsteady Vortical Flows in a Side Channel Pump

Double-sided lapping is an precision machining method capable of obtaining high-precision surface. However, during the lapping process of thin pure copper substrate, the workpiece will be warped due to the influence of residual stress, including the machining stress and initial residual stress, which will deteriorate the flatness of the workpiece and ultimately affect the performance of components. In this study, finite element method (FEM) was adopted to study the effect of residual stress-related on the deformation of pure copper substrate during double-sided lapping. Considering the initial residual stress of the workpiece, the stress caused by the lapping and their distribution characteristics, a prediction model was proposed for simulating workpiece machining deformation in lapping process by measuring the material removal rate of the upper and lower surfaces of the workpiece under the corresponding parameters. The results showed that the primary cause of the warping deformation of the workpiece in the double-sided lapping is the redistribution of initial residual stress caused by uneven material removal on the both surfaces. The finite element simulation results were in good agreement with the experimental results.     

Effect of interfacial friction force on material removal in full aperture continuous polishing process

Full aperture continuous polishing using pitch lap is a key process of finishing large flat optical workpiece. The friction force of the workpiece and pitch lap interface significantly affects material removal. In this work, the friction force was determined by a measurement system that uses force transducers to support the workpiece. Experimental and theoretical analyses have been carried out to investigate the evolution of friction force with polishing time and its effect on material removal. Our results show that the friction coefficient of the workpiece/lap interface decreases during polishing, which is due to surface smoothing of the viscoelastic pitch lap by loading conditioner. In addition, the spatial average and uniformity of material removal rate (removal coefficient) increases with the increase of friction coefficient, which is due to rough lap surface, provides more sharp asperities to charge the polishing particles.     

Elimination of the friction effects in unconfined compression tests of biomaterials and soft tissues

The mechanical properties of biomaterials and soft tissues are determined conventionally using unconfined compression tests. In such tests, frictionless specimen/platen contact in unconfined compression tests has to be assumed in determining the material properties of the materials. Previous theoretical analysis demonstrated, however, that the effects of the friction at the specimen/platen contact interface on the measured stress responses are non-negligible. In this study, a computational approach was proposed to eliminate the effects of friction. The friction coefficient between the specimen and the compression platens is measured first. Using a finite element model, the stress-strain relationship, without the influence of the friction effects, can be derived from the experimental data obtained in conventional unconfined compression tests. In order to validate the proposed approach, unconfined compressive tests of rubber have been performed.     

卫星动量轮轴承摩擦力矩性能可靠性动态预测

基于灰置信水平、自助-最小二乘法和最大熵原理建立动态预测模型,并应用于卫星动量轮轴承摩擦力矩性能可靠性的动态预测。首先,对摩擦力矩原始数据分组得到样本,并选定本征样本,提出了由灰置信水平求解各样本变异强度的新方法,进而求得各样本可靠度的实际值;其次,将紧邻的5个样本变异强度融入自助-最小二乘法线性拟合得到拟合系数,由最大熵原理得到下一个样本的变异强度预测值和上下区间;然后,持续更新紧邻的5个变异强度,得到各样本可靠度的预测值和上下区间,最终实现滚动轴承摩擦力矩性能可靠性的动态预测。试验结果表明,恒转速条件下可靠度预测误差均小于4.1%,变转速条件下可靠度预测误差不超过9.4%,充分验证了所提出动态预测模型的可行性和正确性。     

铌酸锂晶体的研磨亚表面损伤深度

针对光学材料研磨过程引入的亚表面损伤层(SSD)深度对工件的抛光工序效率和表面质量的影响,探索了光学材料在研磨过程中的亚表面损伤规律。采用角度抛光的方法测量了软脆材料铌酸锂(LN)晶体的损伤层深度,分析了研磨方式、磨粒粒径和研磨压力对工件亚表面损伤层的影响规律。结果表明:研磨方式对损伤缺陷的影响最为显著,相同研磨条件下游离磨料研磨后的损伤层深度约为固结磨料研磨的3~4倍,游离磨料研磨后工件亚表面存在多处圆弧形裂纹,固结磨料研磨后主要显现细小裂纹和"人"字型裂纹;当磨粒粒径从W28下降到W14后,游离研磨的亚表面损伤层深度下降至原来的45%,而固结研磨的损伤层深度下降至30%;另外,研磨压力的降低有利于减小工件的亚表面损伤。该研究对LN晶体研磨方式及研磨工艺的选择具有指导意义。     

梯度功能研抛盘力学模型与材料均匀去除试验

针对材料非均匀去除问题,提出了一种基于梯度功能研抛盘的新颖加工方法。以Preston方程为理论基础,开展了梯度功能研抛盘与工件接触应力的数值模拟和弹性力学计算,通过半逆解法推导接触应力方程,建立了一套关于梯度功能研抛盘的双层结构力学模型与工件材料去除水平的预测体系。在ZrO2陶瓷上进行了不同部位材料去除速率研磨试验,以平均材料去除速率的标准差为各区域均匀性去除的评价标准,试验结果表明,在0~30 min、30~60 min、60~90 min三个时间段,采用梯度功能研抛盘加工后的标准差分别为6.47 nm/min、3.76 nm/min、5.09 nm/min,而普通研抛盘加工后的标准差分别为55.23 nm/min、54.73 nm/min、35.92 nm/min。两种盘均维持在150~400 nm/min的材料去除速率,但梯度功能研抛盘在加工过程中能同时实现材料的均匀去除,减少工件研磨后的修整工序,使加工过程简单高效。     

A swing arm method for profile measurement of large optical concave surfaces in the lapping process

Generally, optical components are fabricated by grinding, lapping, and polishing. Usually, these processes take a long time to obtain high surface quality. Therefore, in the case of large optical components, on-machine inspection (OMI) is essential, because the workpiece is fragile and difficult to set up for fabricating and measuring. This paper describes a swing arm method for measuring the surface profile of large optical concave mirrors. The measuring accuracy and uncertainty for the method are studied. Experimental results show that this method is especially useful in the lapping process, where an accuracy of 3–5 μm is obtained. Inspection data is also provided to correct the residual figuring error in lapping or polishing processes .     

红外锗窗片的双面磨抛工艺

依据双面研磨和抛光的原理,提出了红外锗窗片双面磨抛的加工工艺,从技术特点和生产实践过程等方面对工艺进行分析和验证,多次批量加工实践证明,零件能够达到使用要求,同时有效地解决了平面零件的平行度问题,大幅度提高了生产效率,是一种有推广价值的加工红外锗窗片的新方法。     

固着磨料双面研磨压力模糊自整定PID控制方法研究

以NUMPOWER1060数控系统为主控单元,结合力-位控制和模糊推理的特点,提出了一种模糊自整定PID参数的力-位控制方法。利用高精度扭矩传感器和力传感器对Z轴电机输出扭矩与研磨压力之间的关系进行了标定,通过检测Z轴输出扭矩间接获得了研磨压力的大小。根据Z轴进给速度调节因子uv对研磨压力的影响规律,建立了模糊控制规则集,设计了模糊控制PID算法,保证了研磨压力的恒定。工件研磨试验表明该方法提高了工件的表面质量。     

Matrix-presentation linear least square error method of inverse elastic-plastic large deformation finite element model for upsetting

The main purpose of this paper is to develop the matrix presentation linear least square error method of inverse elastic-plastic large deformation finite element model for upsetting to obtain the friction coefficients during the upsetting process. This inverse model assumed the linear material and based on the modified experimental loading increments using the linear modified experimental upsetting loading standard proposed in this paper. Then the friction coefficients of contact boundary between the workpiece and the die at specific finite element analysis stages can be derived. Finally, using the cubic spline fitting, the history of friction coefficient during the upsetting process can be obtained. It is demonstrated that the workpiece profile of upsetting experiment is quite identical to the workpiece profile of simulation using the result obtained in this paper as the history of friction coefficient of contact boundary, and furthermore the distribution of stress and strain of the workpiece during upsetting process can be understood.     

基于喷射抛光实验研究结果的异形抛光实验台设计

介绍了标准的液体喷射抛光实验,提出了近壁面附近固液两相流中的颗粒作用导致的流体摩擦剪切去除材料的机制假设,然后通过实验研究了抛光时间、样品表面初始粗糙度、喷头形状、喷射距离、喷射压力和pH值对抛光结果的影响。结果表明,抛光结果随时间趋于稳定并与初始粗糙度无关,圆形喷头比扇形喷头抛光效率高,喷射距离和压力影响一致,pH值越低影响越大。最后基于理论假设和实验结果设计了一个可以用于精密光学制造中异形表面抛光的实验装置。     

Improvement of the accuracy of friction coefficient determination with Amsler-type friction machines

The error of friction coefficient determination with Amsler-type machines depends strongly on the friction losses in the machine’s spindle unit. It is shown theoretically that the error is inversely proportional to the product of the lower roller diameter times the friction coefficient to be measured and directly proportional to the friction coefficient of the rolling bearings employed; the error can reach 100% or more. A method of static and dynamic torque sensor calibration is developed to ensure friction coefficient measurement accuracy within ±2%.     

砂轮约束磨粒喷射精密光整加工材料去除机理研究

基于磨粒特征尺寸与砂轮、工件间液膜厚度比值的变化,研究了砂轮约束磨粒喷射精密光整加工材料去除机理。分析了在两体加工及三体加工模式条件下,单颗磨粒运动特点以及磨粒由两体研磨加工向三体抛光加工转变的临界条件。实验证明,砂轮约束磨粒喷射光整加工中,随着加工循环的增加,工件表面微观形貌变化规律与理论分析相同,实验结果和理论分析吻合很好。     

Polishing pad for reducing edge roll-off while maintaining good global flatness of silicon wafer

In the double-sided polishing process of silicon wafers, there is a strong demand to reduce amount of edge roll-off (ERO) while improving global flatness of a wafer. In the present study, we clarified the negative effects of uneven wear of the polishing pads on the global flatness of a wafer can be suppressed when the deformation of the polishing pads is large. As for the ERO, we found small deformation of the polishing pad near the top surface was effective in reducing the amount of ERO. In addition, we revealed small distance from the surface of the polishing pad at the area under the wafer to that at the area around the wafer was also effective in reducing the amount of ERO. On the basis of the findings, we developed a three-layered polishing pad which was expected to reduce the amount of ERO while achieving the good global flatness.     

考虑热弹流润滑作用的滚珠丝杠副摩擦力矩建模与分析

针对以往研究中滚珠丝杠副摩擦力矩计算方法中未考虑润滑作用对其影响,或未考虑接触弹性滞后效应以及滑移摩擦效应对其影响的情况。首先基于单个滚珠接触效应建立其热弹流润滑方程;然后在考虑润滑效应的基础上建立其黏性摩擦力、弹性滞后摩擦力及滑移摩擦力方程;最后提出一种基于全滚珠载荷分布与热弹流润滑耦合的滚珠丝杠副摩擦力矩计算模型,建立了预紧力、转速与摩擦力矩之间的耦合关系。试验结果表明,当预紧力从1 kN变化到6 kN,在滚珠丝杠低转速(100 r/min)时,摩擦因数变化范围为0.005 6～0.006 5。随转速的提髙摩擦因数升高且变化量逐渐增大,说明国际标准DIN ISO3408-3:2006中将滚珠丝杠副空载摩擦力矩测量速度定为100 r/min具有合理性,验证了所提出的摩擦力矩计算方法的准确性。     

基于ANSYS的单磨粒与工件接触摩擦的研究

磨粒与工件的摩擦状况是直接影响抛光过程及抛光质量的重要因素。根据单磨粒对工件表面接触压力的实验数据,利用ANSYS有限元分析软件,研究了单磨粒对工件表面的接触压力和摩擦力,结果表明,磨粒与工件间的摩擦边界条件更接近粘着摩擦。     

高载荷条件下的材料表面摩擦因数测量

针对材料表面高载荷条件的要求，提出了测量摩擦因数的方法，并进行了相应测试装置的设计，该测试装置由正向加载装置、侧向加载装置和数据处理装置3部分组成。可以用来测量高载荷条件下材料表面的静摩擦因数和滑动摩擦因数，同时得到整个滑动过程中摩擦因数变化情况。利用该装置对某国防减摩涂层进行了测试，结果表明在高载荷条件下该涂层对碳钢表面具有较好的减摩效果。     

Torque sensor calibration using virtual load for a manipulator

Accurate load sensing of a manipulator becomes increasingly important in performing various tasks involving contact with an environment. Most of the research has been focused on improving the hardware of a force/torque sensor. The torque sensors for a manipulator suffer from crosstalk, which is difficult to compensate for even with sophisticated calibration. This research proposed a novel calibration method composed of two steps. Through the primary calibration, the torque sensor output can be related to the joint torques. The secondary calibration, which is based on a virtual load, is conducted to compensate for the crosstalk of a torque sensor. The virtual load is obtained from the sensed joint torques and manipulator configuration. Using the proposed calibration method, the external load acting on the end-effector of a manipulator can be accurately measured even with relatively low-quality torque sensors. The experimental results showed that the error in the load sensing was significantly reduced by the proposed calibration method.     

蛇形机器人行波运动的研究

对蛇形机器人的行波运动机理进行了研究,基于Serpenoid曲线建立了蛇形机器人行波运动的形状控制模型、运动学模型、机构动力学模型及环境动力学模型,给出了求解过程。仿真结果表明：在行波运动中,各关节输入力矩大小呈周期变化,且随其与蛇体重心距离的增加而减小。蛇体中心关节的最大输入力矩为蛇形机器人所需最大输入力矩。对称关节输入力矩幅值变化规律相同,但相差不同;运动初始弯角保持不变,关节输入力矩随着环境摩擦因数的增加而增加。环境摩擦因数保持不变,关节输入力矩随着初始弯角的增加而减小。     

磨料流微去除力学分析与可控因素影响

研究了磨料流抛光中磨粒微去除力学建模方法以及可控因素影响抛光效果的问题。以力为纽带,提出磨粒去除工件表面微凸材料的动力来源于三个方面--介质作用力、磨粒挤压载荷和磨粒冲击载荷。利用建立的力学模型,分析了磨料流加工的内在因素,其中可控因素包括：加工温度、加工压力、活塞的移动速度、磨料黏度、磨粒物理性质（如尺寸、硬度）等;研究了各可控影响因素与工件表面抛光质量及效率的关系;量化了可控因素的大小对磨粒作用在工件表面的力的影响程度;将磨粒作用在工件表面的力合成并分解为与活塞运动方向相同的轴向力和垂直于工件壁面的切向力,指出微去除效果随轴向力与径向力的比值改变而发生变化,设计出简易的测量轴向力和径向力的方案。用试验验证了所建模型和可控因素对抛光效果影响,以及工件表面的加工纹理方向直接影响工件表面粗糙度的减小率和材料去除率的正确性。