A study on an object transport system using ultrasonic wave excitation

The development of information and telecommunication industries leads to the development of semiconductor and optical industries. In recent years, the demand of optical components is growing due to the demand of faster network. On the other hand, conventional transport systems are not adequate for transporting precision optical components and semiconductors. Because the conveyor belt can damage precision optical components with contact force and a magnetic system would destroy the inner structure of semiconductor with magnetic field, a new system for transporting optical components and semiconductors is required. One of the alternatives to the existing systems is a transport system using ultrasonic wave excitation since it can transport precision components such as semiconductors and optical components without damage. In this paper, a transport system using 2-mode ultrasonic wave excitation was developed for transporting optical components and semiconductor, and its performance was evaluated. The relationship between transporting characteristics and flexural beam shapes were evaluated.     

用于超声散斑跟踪血流测速的多角度平面波局部运动补偿

血流速度剖面用于计算壁面剪切率等血流动力学指标,与动脉粥样硬化病程发展密切相关。 超快超声散斑跟踪广泛用 于血流速度剖面估计,然而多角度平面波复合成像存在血流散射体的运动伪影,不利于流速估计。 提出了一种多角度平面波复 合成像的局部运动补偿法,对射频信号时间序列的相邻帧进行局部运动补偿来消除不同径向位置的运动伪影,从而提高流速测 量准确性。 相比直接相干复合,B-MoCo 法将仿真、仿体实验中流速测量结果的归一化均方根误差平均减小了 10. 37% 、 37. 82% ,说明了 B-MoCo 法的有效性。 基于兔骼动脉的实测实验进一步证明了 B-MoCo 法的临床可行性。 综上,B-MoCo 法能够 有效提高血流速度剖面的测量精度,有助于相关心血管疾病的早期诊断与病程监测。     

Characteristics of chip generation by ultrasonic vibration cutting with extremely low cutting velocity

Recently, mirror-surface machining of brittle materials such as ferrite, glass, and optical plastics has become more important, as these materials are used in optical communications and precision devices. Non-ferrous metals such as aluminium and copper were readily turned with diamond tools, but as the need for both infra-red and reflective optics escalated, the need to machine brittle materials arose. In this paper, ultrasonic vibration cutting at 20 kHz at extremely low cutting velocity for the precision machining of brittle plastics used for optical lenses is suggested and tested. The mechanism of chip generation, and characteristics of surfaces in the ductile mode, machined by ultrasonic vibration cutting are investigated. As a result, when micro cutting by ultrasonic vibration, it was confirmed that the chips generated by ductile mode cutting are obtained at 1/40 of the critical cutting velocity of the ultrasonic vibration cutting system, which is an extremely low cutting velocity.     

磁场分布不均匀性对磁流变液剪切传力的影响

通过对磁流变液剪切传力机理的研究 ,充分考虑磁场饱和情况以及磁场各要素间的非线性关系 ,分析磁场分布不均匀性导致磁流变液中剪切力分布的变化 ,并对最具代表性的两平板间磁流变液传递剪切力的情况进行有限元分析 ,得出比较符合实际的结果。     

基于同步压缩变换的临界折射纵波波速精确测量

基于声弹性效应,采用临界折射纵波检测金属材料的残余应力有较为广泛的应用前景。然而临界折射纵波速对应力的声弹性效应较弱,这很大程度上影响了材料应力检测的分辨率。为了提高临界折射纵波波速检测精度,提出一种非线性分解技术(同步压缩变换)对临界折射纵波进行波形变换与重构,精确计算超声到达时刻。以1 060铝板为研究对象,基于有限元仿真软件分析了铝板中临界折射纵波的波形特性,以此为依据调节实验中的超声波信号从而提高实验中临界折射纵波的波形准确性。实验精确测量临界折射纵波在1 060铝板中的传播时间,并计算了铝板中的波速,误差不超过0. 05%。实验结果验证了提出的临界折射纵波波速精确计算方法的有效性。     

Dynamic shear stress of tough-pitch copper at high strain and high strain-rate

Dynamic shear tests for the tough-pitch copper at high strain and high strain rate was performed. The Split Hopkinson Pressure Bar (SHPB) compression test system was modified to yield a shear deformation in the specimen. Hat-shaped specimens for the tough-pitch copper were adopted to generate high strain of γ=3–4 and high strain-rate of γ=10⁴/s. The dynamic analysis by ABAQUS 5.5/EXPLICIT code verified that shear zone can be localized in hat-shaped specimens. A proper impact velocity and the axial length of the shear localization region were determined through the elastic wave analysis. The displacement in a hat-shaped specimen is limited by a spacer ring which was installed between the specimen and the incident bar. The shear bands were obtained by measuring the direction of shear deformation and the width of deformed grain in the shear zone. The decrease of specimen length has been measured on the optical displacement transducer. Dynamic shear stress-strain relations in the tough-pitch copper were obtained at two strain-rates.     

长环形驻波直线超声电机振子有限元分析

提出了一种长环形直线驻波超声电机振子,并对该超声电机振子进行了研究。利用有限元分析软件对振子的工作模态进行了分析,阐述了振子的工作原理。对支撑结构、影响振子振动模态固有频率的主要结构参数,进行了数值分析,确定了振子的结构形式。振子与支撑结构采用柔性铰链连接,利用第18阶正交的两个面内弯曲模态工作,实现了电机振子双接触面驱动、正反两个方向运动。证明了该类振子利用面内弯曲振动模态可以实现双面驱动、正反双向直线运动。为环型驻波直线超声电机的设计提供了理论参考。     

The influence of the waveguide on the quality of measurements with ultrasonic Doppler velocimetry

The article is devoted to the study of the influence of geometric parameters of sound-conducting walls on the quality of measurement of liquid metal flow velocities by ultrasonic Doppler velocimetry. It was shown that the thickness and radius of a sound-conducting wall (waveguide) have a notable effect on the resulting velocity profiles. The flow in a round pipe, the length of which is much larger than its diameter, is considered as a reference flow. The positive effect of a stepwise waveguides with a diameter smaller than the diameter of the piezoelectric element of an ultrasonic transducer on the quality of velocity measurements was verified experimentally. It was found that the accuracy of the resulting velocity profiles largely depends on the length and the material of the waveguides, as well as the velocity of the incoming flow of liquid metal.     

旋转行波超声电机性能提升技术进展

为推动旋转行波超声电机的发展及其在精密驱动领域的应用,综述了其性能提升技术研究进展并分析了现阶段尚且存在的技术问题。首先,从定子行波的合成、质点椭圆运动轨迹、接触界面的摩擦驱动等方面论述了传统旋转行波超声电机的运行机理。然后,从结构优化和新材料应用角度综述了旋转行波超声电机的发展及其局限性;从温升控制角度阐释了温度变化对超声电机性能的影响并介绍了现有解决方案;论述了变预压力对谐振频率漂移的耦合影响,并指出了目前研究存在的不足;从双行波驱动角度分析了超声电机发展过程中的重大突破,概况了其研究历程及可行的发展方向。最后,归纳了旋转行波超声电机亟待解决的技术难题,并建议了解决方案。     

基于超声探测的自动报警装置的设计

我们所设计的超声波安全防控自动报警装置分为3个部分．第一部分是超声波探测系统．它负责对超声波探头前方的障碍物进行探测．根据障碍物的距离发出不同的警报声音;第二部分是单片机控制系统．负责对接收到的超声波信号进行处理，并输出自动报警控制信号;第三部分是自动拨号报警系统．负责接受单片机输出的自动报警控制信号．并自动拨号报警。本装置原理简单，效果显著．能够实现大范围的监控．并且能通过调整来适应不同的环境．抗干扰和隐蔽性都不错。