压电陶瓷执行器迟滞与非线性成因分析

从微观上系统分析了电致伸缩效应、逆压电效应和铁电效应的位移机理,表明:三种效应的位移机理是根本不同的;压电陶瓷执行器的位移主要是由逆压电效应、铁电效应所引起的,电致伸缩效应对位移的贡献极其微弱,可以忽略不计;单纯的逆压电效应是线性的,而铁电效应则是迟滞非线性的.指出了非180°电畴转向与转向的不完全可逆,分别是造成压电陶瓷执行器非线性和迟滞的根本原因.通过实验研究了驱动电压幅值、驱动电压频率、驱动循环次数及晶片厚度对压电陶瓷执行器迟滞和非线性的影响.     

Piezoelectric ceramic actuators: A review of machinery applications

Piezoelectric ceramic actuators can be manufactured with a wide range of movements, outputs forces and operating voltages. The pros and cons of these devices are considered and typical applications described.     

Development of a model for precision contour grinding of brittle materials

A graphical computer model of the chip geometry resulting from a three-dimensional grinding operation was developed for use in relating the critical depth data obtained from the one-dimensional plunge-grinding technique. This model predicts the resulting surface finish and calculates the theoretical roughness and the final chip geometry for a precision grinding operation. The model is based on euclidean geometry at the intersection of the surfaces of two solid objects. This model was programmed to calculate the remaining surface height as the wheel progresses across the part. The output of the surface profile for successive cuts can be subtracted to illustrate the shape of the chip removed for each revolution of the grinding wheel. Chip geometry as influenced by depth of cut, feed rate, and tool shape was shown to be an important parameter in diamond turning of brittle materials. Similar relationships are developed for the additional geometric complexities of a precision grinding operation. The theoretical surface features are then compared with the actual features generated by grinding brittle materials.     

汽车轴承止动槽位置加工误差分析及减少措施

对加工过程进行详细分析,指出止动槽位置超差因素并制定了控制止动槽超差措施。     

Development and application prospects of piezoelectric precision driving technology

With the rapid development of science and technology, microelectronics manufacturing, photonics technology, space technology, ultra-precision machining, micro-robotics, biomedical engineering and other fields urgently need the support of modern precision driving theory and technology. Modern precision driving technology can be generally divided into two parts: electromagnetic and non-electromagnetic driving technology. Electromagnetic driving technology is based on traditional technology, has a low thrust-weight ratio, and needs deceleration devices with a cumbrous system or a complex structure. Moreover, it is difficult to improve positioning accuracy with this technology type. Thus, electromagnetic driving technology is still unable to meet the requirements for the above applications. Non-electromagnetic driving technology is a new choice. As a category of non-electromagnetic driving technology, piezoelectric driving technology becomes an important branch of modern precision driving technology. High holding torque and acute response make it suitable as an accurate positioning actuator. This paper presents the development of piezoelectric precision driving technology at home and abroad and gives an in-depth analysis. Future perspectives on the technology’s applications in the following fields are described: 1) integrated circuit manufacturing technology; 2) fiber optic component manufacturing technology; 3) micro parts manipulation and assembly technology; 4) biomedical engineering; 5) aerospace technology; and 6) ultra-precision processing technology.     

无油沟圆柱滚子轴承滚道及挡边磨加工方法

在介绍圆柱滚子轴承滚道无油沟套圈的磨削加工方法的过程中,重点阐述了在3M1420沟道磨床中采用成形切入磨削方法及砂轮修整时的改进方案。实践证明,采用成形切入磨削的加工方法,能够实现无油沟滚道的加工。     

基于Lamb波的压电陶瓷/环氧树脂复合材料传感器制备及应用

风力机叶片、飞机机翼等结构均为大面积曲面板类结构,基于Lamb波的结构健康检测技术对细微损伤比较敏感,是目前最具应用前景的技术之一。传统的Lamb波传感器大都采用PZT陶瓷制成,质地脆且硬度大,不能适应于曲面结构检测。将PZT陶瓷粉末与环氧树脂复合制备了一种新型柔性0-3型压电复合材料,研究了质量比、极化电场、极化温度和极化时间等因素对压电复合材料性能参数的影响,开展了多因素正交实验来确定材料制备的最优极化工艺参数。实验研究了该压电复合材料制成的传感器对Lamb波的传感响应特性,与现有的MFC、PVDF和传统压电片等传感元件的响应特性进行了对比分析。将制备的传感器应用于翼型曲面板,利用椭圆定位方法进行损伤检测。研究结果表明,PZT陶瓷/环氧树脂压电复合材料传感器具有良好的传感响应特性,能够很好地贴合于曲面板表面,与只能部分耦合于曲面板的传统压电片相比,采集的Lamb波信号更加准确,从而为曲面板类结构健康监测提供一种新型的柔性压电传感技术。     

Influence of wheel speed on surface finish and chip geometry in precision contour grinding

A geometric computer model of a precision grinding operation was developed to calculate the surface features generated during contour grinding with a radiused wheel. This simulation includes the influence of the wheel (rotational speed, diameter, and nose radius), the workpiece (radius at cutting point, rotational speed), and the feedrate of the grinding wheel over the part. The model indicates that small changes in the wheel speed relative to the workpiece can have a dramatic effect on the surface finish over a specific area. Analysis of ground surfaces reveals uniform surface profiles and easily distinguished features that could only be produced by a constant wheel speed. This occurs for an air-bearing, air-turbude grinding spindle that has limited torque and is driven under open-loop control. The effects of the relative speeds are analyzed and an energy-based “phase locking” mechanism is proposed that can provide feedback to the grinding spindle from the material removal operation. By monitoring the spindle speeds during the grinding process and evaluating the resulting surface features, the phase effect has been experimentally verified.     

超声电机宽温域低损耗压电与摩擦功能材料

为了提高超声电机的环境适应性与能量转换效率,本文分析并制造了宽温域低损耗的新型压电材料与摩擦功能材料,提出了通过相结构调控、增加第三组元、引入偶极子缺陷钉扎畴壁等手段制备宽温域低损耗压电陶瓷材料的设计与制造方法;为了提高超声电机摩擦界面能量传递效率及环境适应性,设计了具有高摩擦系数、低磨损率且耐高温的聚酰亚胺复合材料。结果表明,与传统材料相比,新型压电陶瓷材料具有低介电损耗、高机械品质因数及高温度稳定性的优势,使超声电机的能量转换效率提高3.3%,而新型聚酰亚胺基摩擦材料在摩擦系数、耐磨性以及温度范围等指标上均有明显提高,使电机的最大效率提高了6.19%。综合两种新型材料后,超声电机的最大效率提升了13.6%,可靠工作温度从-40~70℃提升至-60~120℃。本文提出的压电与摩擦功能材料既增强了超声电机的环境适应性,也改善了电机输出性能,对超声电机在航空航天等高端装备中的应用具有重要的意义。     

砂轮平衡及其在磨削工程中的应用

在机械制造领域,磨削加工以其不可替代的优势,通常作为机械零件的最后加工工序.但是,磨削加工过程中却时常出现振动,致使磨削振纹成为提高零件表面质量的主要障碍.为此,全面梳理了回转体不平衡、砂轮不平衡、磨削振动和砂轮平衡精度等相关内容;分析了砂轮平衡主要表征参数、砂轮不平衡影响因素和砂轮平衡测试技术等;最后,基于磨削工程应...     

氮化硅陶瓷磨削温度与表面变质层的仿真与实验

为了揭示氮化硅陶瓷磨削温度分布规律以及其对表面成形的影响,首先,建立氮化硅陶瓷纳米级切削的分子动力学模型;其次,研究切削过程中切削参数对切削温度的影响,以及加工过程中切削表面变质层的形成过程;最后,对 K 型热电偶测温和表面能谱分析的仿真与实验结果进行对比分析.结果表明:随着金刚石磨粒切削深度和切削速度的增加,原子晶格发生变形和非晶相变过程中时释放的能量增多,从而使切削温度升高;切削高温会引起氮化硅陶瓷发生非晶相变现象,非晶态原子重新与已加工表面断裂的原子键结合形成表面变质层;分子动力学仿真模型可以用来预测氮化硅陶瓷材料实际磨削加工中磨削温度变化情况,对生产加工具有参考价值.     

Influence of glass particle size of resin cements on bonding to glass ceramic: SEM and bond strength evaluation

This study investigated the effect of the filler particle size (micron or submicron) of experimental resin cements on the microtensile bond strength to a glass‐ceramic pretreated with hydrofluoric acid (HFA) etching or alumina airborne‐particle abrasion (AA). Cements were obtained from a Bis‐GMA/TEGDMA mixture filled with 60 mass% micron‐sized (1 ± 0.2 µm) or submicron‐sized (180 ± 30 µm) Ba‐Si‐Al glass particles. Ceramic blocks (PM9; VITA) were treated with 10% HFA for 60 s or AA for 15 s. Silane and adhesive were applied. Ceramic blocks were bonded to resin composite blocks (Z250; 3M ESPE) using one of the cements. Bonded specimens were sectioned into beams (n = 20/group) and subjected to microtensile bond strength tests. Data were analyzed using ANOVA and Student‐Newman‐Keuls' tests (5%). Failure modes were classified under magnification. Morphologies of the treated ceramic surfaces and bonded interfaces were evaluated by scanning electron microscopy. The HFA‐submicron group had lower bond strengths than the other groups. All AA‐submicron specimens debonded prematurely. Mixed failures were predominant for HFA groups, whereas interfacial failures predominated for AA groups. SEM revealed a honeycomb‐like aspect in the HFA‐treated ceramic, whereas the AA‐treated groups showed an irregular retentive pattern. Continuity of cement infiltration along the bonded interface was more uniform for HFA‐treated compared to AA‐treated specimens. Cracks toward the bulk of the ceramic were observed in AA‐treated specimens. Particle size significantly influenced the ceramic bond strength, whereas surface treatment had a minor effect. Microsc. Res. Tech. 77:363–367, 2014. © 2014 Wiley Periodicals, Inc.     

Design and performance of a small—scale diamond turning machine

Machining with single-point diamond tools is an area of increasing interest in the manufacture of optics, lens moulds, hard discs and other products Although many materials have been machined with impressive results, questions remain regarding the science of diamond turning. These questions concern the suitability of certain materials for turning, the properties of the tool and machine structure which limit the quality of the final product, and the modelling of the cutting process. To study these phenomena, a laboratory-scale diamond turning machine has been designed and built at the Precision Engineering Center. This machine, PAUL, although simple and compact, has produced excellent results on a variety of static and dynamic cutting experiments. The key points of its design, as well as an evaluation of PAUL's performance, are given in this paper.     

硅片低损伤磨削砂轮及其磨削性能

针对传统金刚石砂轮磨削硅片存在的表面/亚表面损伤问题,研制了一种用于硅片化学机械磨削加工的新型常温固化结合剂软磨料砂轮。根据化学机械磨削加工原理和单晶硅的材料特性,设计的软磨料砂轮以氧化铈为磨料,二氧化硅为添加剂,氯氧镁为结合剂。研究了软磨料砂轮的制备工艺,分析了软磨料砂轮的微观组织结构和成分。通过测量加工硅片的表面粗糙度、表面微观形貌和表面/亚表面损伤,进一步研究了软磨料砂轮的磨削性能。最后,与同粒度金刚石砂轮磨削和化学机械抛光(CMP)加工的硅片进行了对比分析。结果表明,采用软磨料砂轮磨削的硅片其表面粗糙度Ra1nm,亚表面损伤仅为深度30nm的非晶层,远好于金刚石砂轮磨削硅片,接近于CMP的加工水平,实现了硅片的低损伤磨削加工。     

A new high-aperture glycerol immersion objective lens and its application to 3D-fluorescence microscopy

High‐resolution light microscopy of glycerol‐mounted biological specimens is performed almost exclusively with oil immersion lenses. The reason is that the index of refraction of the oil and the cover slip of ~1.51 is close to that of ~1.45 of the glycerol mountant, so that refractive index mismatch‐induced spherical aberrations are tolerable to some extent. Here we report the application of novel cover glass‐corrected glycerol immersion lenses of high numerical aperture (NA) and the avoidance of these aberrations. The new lenses feature a semi‐aperture angle of 68.5°, which is slightly larger than that of the diffraction‐limited 1.4 NA oil immersion lenses. The glycerol lenses are corrected for a quartz cover glass of 220 µm thickness and for a 80% glycerol‐water immersion solution. Featuring an aberration correction collar, the lens can adapt to glycerol concentrations ranging between 72% and 88%, to slight variations of the temperature, and to the cover glass thickness. As the refractive index mismatch‐induced aberrations are particularly important to quantitative confocal fluorescence microscopy, we investigated the axial sectioning ability and the axial chromatic aberrations in such a microscope as well as the image brightness as a function of the penetration depth. Whereas there is a significant decrease in image brightness associated with oil immersion, this decrease is absent with the glycerol immersion system. In addition, we show directly the compression of the optic axis in the case of oil immersion and its absence in the glycerol system. The unique advantages of these new lenses in high‐resolution microscopy with two coherently used opposing lenses, such as 4 Pi‐microscopy, are discussed.     

Nano-abrasion machining of brittle materials and its application to corrective figuring

A method of ultraprecision abrasion machining named “Nano-abrasion machining” is proposed for optical finishing of brittle materials. The fundamental characteristics and its applicability for corrective figuring to improve form accuracy of optics of brittle materials are investigated. It is experimentally ascertained that the material removal rate and surface roughness are suitable for optical finishing. However, the cross-sectional profile of the machined spot that is dependent on the collision angle is a combination of V- and W-shape, which is unsuitable for the corrective figuring. Therefore, circular motion machining is introduced and a preferable profile with an axis-symmetric V-shape is realized. The machining method is applied to corrective figuring of optical glass of BK7. The NC program is generated with a computer program developed by modifying the scanning motion and the form accuracy is predicted. According to the simulation results, corrective figuring is performed. The flatness is improved from PV = 151 to 29 nm. From the experimental results, it is clarified that the nano-abrasion machining is applicable to corrective figuring of brittle materials.     

利用中低频振动改善熔丝制造产品表面加工质量研究

熔丝制造技术(Fused filament fabrication,FFF)因其操作简单、适用性强和成本低廉等特点,已经成为当今使用最为广泛的增材制造技术之一.然而,由于逐层累加的工艺特点,与传统加工方式相比FFF产品的表面质量存在着明显的缺陷.利用中低频振动在改善FFF产品表面质量方面有着很大的潜力,为此,将压电陶瓷...     

超声振动螺线磨削表面微观形貌建模与仿真研究

为了实现高效率、高质量、低损伤的硬脆材料加工,对工件或砂轮同时施加砂轮轴向和径向的超声振动,该方法的显著特点是磨粒切削轨迹呈三维空间螺旋线型,将其定义为超声振动螺线磨削方法。在磨削工艺和二维超声振动的多参数共同作用下,材料去除机理产生复杂变化,表面微观形貌创出过程变得极其复杂。为此,提出一种超声振动螺线磨削加工表面数值仿真方法。基于超声振动螺线磨削几何映射关系,建立磨粒相对工件的空间螺旋线切削运动模型,进而给出超声振动螺线磨削加工表面生成模型,模拟出普通磨削和超声振动磨削的三维表面微观形貌,对比分析了超声振动对表面形成过程的影响规律。最后将仿真表面与磨削试验表面对比,发现两者微观形貌特征规律基本一致,验证了仿真方法的正确性和有效性。     

Development of velocity sensor with high frequency band and its application to a vibration isolate table

The vibration sensors are widely used in the field of vibration control and measurement. In applying the modern control theory to anti-vibration controlled objects, the state variables both the velocity and displacement become useful signals. Then, the velocity sensor in comparison with the acceleration sensor, which is in generally used, is very useful. However, its frequency band is limited by high frequency resonance due to the electrical stiffness. If the velocity sensor having flat frequency band is developed, this sensor becomes easy to handle not only in the control field but also in the measurement filed. Then, this paper shows that the inverse notch filter, which is inserted in the closed loop, flattens out the frequency response originally having high frequency resonance. Firstly, the block diagram of the velocity sensor as a closed system is shown. Its sensitivity, the low break point frequency, and the high frequency resonance are formulated. Secondly, the gain and phase margins are calculated and we try to improve the frequency response based on these indices. Finally, the application of improved velocity sensor to an anti-vibration apparatus is shown.     

一种新的机器学习方法--PSVM应用于数控磨床智能诊断的研究

针对经典SVM对于样本噪声敏感的局限性问题，在经典SVM基础上，引入主成分分析(PCA)方法，提出一种改进SVM新方法-PSVM。这种新的机器学习方法，既利用了PCA降噪的特性，又具有经典SVM泛化能力强、分类快的特性。改善了经典SVM的鲁棒性。应用小波包分析对信号进行预处理，直接得到特征矢量，并作为PSVM的输入，提出满足实时性要求的分类模型WPSVM。通过实例分析，证明这种方法在分类正确率、分类速度以及适用的样本规模等方面都表现出了一定的优越性。