A self-running standing wave-type bidirectional slider for the ultrasonically levitated thin linear stage

A slider for a self-running standing wave-type, ultrasonically levitated, thin linear stage is discussed. The slider can be levitated and moved using acoustic radiation force and acoustic streaming. The slider has a simple configuration and consists of an aluminum vibrating plate and a piezoelectric zirconate titanate (PZT) element. The large asymmetric vibration distribution for the high thrust and levitation performance was obtained by adjusting the configuration determined by finite elemental analysis (FEA). As a preliminary step, the computed results of the sound pressure distribution in the 1-mm air gap by FEA was com pared with experimental results obtained using a fiber optic probe. The direction of the total driving force for the acoustic streaming in the small air gap was estimated by the sound pressure distribution calculated by FEA, and it was found that the direction of the acoustic streaming could be altered by controlling the vibration mode of the slider. The flexural standing wave could be generated along the vibrating plate near the frequencies predicted based on the FEA results. The slider could be levitated by the acoustic radiation force radiated from its own vibrating plate at several frequencies. The slider could be moved in the negative and positive directions at 68 kHz and 69 kHz, which correspond to the results computed by FEA, with the asymmetric vibration distribution of the slider's vibrating plate. Larger thrust could be obtained with the smaller levitation distance, and the maximum thrust was 19 mN.     

An ultrasonic linear motor using ridge-mode traveling waves

A new type of ultrasonic linear motor is presented using traveling waves excited along a ridge atop a substrate. The ridge cross section was designed to permit only the fundamental mode to be excited during operation of the motor, with a Langevin transducer used as the source of vibration in this study. The ridge waveguide was first made of lossy media to avoid reflecting vibration energy back toward the vibration source, forming a traveling wave. A 5-mm-wide, 15-mm-tall rectangular acrylic ridge was used to move a slider placed upon it toward the vibration source, in opposition to the direction of the traveling wave transmitted along the waveguide ridge. Using a low-loss 3 x 6-mm aluminum rectangular ridge combined with a damper clamped onto the far end of the waveguide, similar results were obtained. To obtain bidirectional operation, the damper was replaced with a second Langevin transducer, giving a pair of transducers located perpendicularly to the ends of the ridge and driven with an appropriate phase difference. The moving direction of the slider was reversed by shifting this phase difference by about 180 degrees. With this simple configuration, it may soon be possible to fabricate a linear micromotor system on a silicon substrate or other semiconductor wafer adjacent to other electronic and optoelectronic devices.     

An experimental investigation on flash butt welded rails

In this paper, experimental studies performed for flash butt welded rails used in Turkish railways network having 49E1 and 60E1 rail sections are presented. These studies comprise of full-scale laboratory tests such as four point bending fatigue and three-point slow bending tests, as well as related instrumentation of test specimens and data measurement. Fatigue and bending tests are prepared and carried out in accordance with EN 14587-2 standard. The fracture surfaces of the welded samples are examined to identify the associated failure modes. The fatigue test results are superimposed on a S–N diagram derived from earlier results reported as a part of the European Commission steel rails research project. A best fit curve following an exponential function is derived to describe the load deflection behavior of the weld under the slow bend testing conditions. It is shown that a single component of the equation defining the best fit curve is the factor controlling the scattering in the non-linear part of the load deflection curve, and hence control of this parameter can also be used to impart consistency to the welding process.     

Nanohot embossing using curved stage to replicate antireflection nanostructures onto light guide

A nanohot embossing using a curved stage is proposed to improve the replication ratio of nanostructures at near the edge of a thick (sub-mm-order thickness) polymer substrate. The lower replication ratio at near the edge resulting from a conventional hot embossing is due to lower compressive stress, which is simulated by the finite-element method (FEM). The height of the proposed curved stage is gradually increased from the center to the edge to bring the levels of compressive stress at the center and at the edge closer. Here, we demonstrate replications of antireflection nanostructures, which have both pitch and height of 200 nm, onto the 0.75-mm-thick light guide for the light emitting diode (LED) frontlight systems used in mobile phones. It was found that a cutting depth of 14 μm on the curved stage is necessary to achieve a high uniformity of the replication ratio at near the edge. The replication ratio at near the edge is improved from 65% to 94%. The reflectance of the antireflection structures is 0.6%, which is a high enough quality for use in LED frontlight systems.     

An ultrasonic motor using bending vibrations of a short cylinder

An ultrasonic motor using bending vibrations of a short cylinder with free-free ends is proposed, and its performance and efficiency are discussed. The motor is small in size and realizes a high mechanical output of more than 1 W. The general principle of the motor, which uses traveling waves, is as follows. When a traveling wave propagates along an elastic object, particles at the surface move elliptically. A movable object (a slider or a rotor) pressed to the elastic object may be caused to move due to the frictional forces between it and the surface. A motor based on this principal has been constructed and studied. The vibration mode used is found to have an undesirable radial component, which restricts the efficiency of the motor to about 10% at best. A large amount of the energy supplied is lost by the slippage owing to the existence of the undesirable component. It is concluded that to derive larger output power, the frictional material needs to be carefully chosen.     

Two-dimensional analysis using one-dimensional FEM forstraight-crested waves in arbitrary anisotropic crystal plates andaxisymmetric piezoelectric vibrations in ceramic disks

We have developed a hybrid method applicable to straight-crested waves in arbitrary anisotropic crystal plates and to axisymmetric piezoelectric vibrations in ceramic disks. The solutions to two-dimensional (2-D) equations of motion are described with a linear combination of eigenmodes guided by a pair of parallel edges. The guided eigenmodes and their amplitudes are determined by using one-dimensional (1-D) finite element method (FEM). The method developed here provides rapid convergence with small matrix size compared with 2-D FEM. Computer programs have been developed for three examples, SC- and AT-cut quartz plates and barium titanate (BaTiO₃) disks, for which the frequency spectra and the corresponding mode shapes were calculated. The frequency spectra of AT-cut quartz plates are compared with those obtained from Mindlin's plate equations, with the aim of examining the accuracy of the straight-crested wave solutions for Mindlin's plate equations. A convergence study is also presented for BaTiO₃ disks     

Position precision compensation method of a micro-manipulation stage based on fuzzy control

The hysteresis nonlinearity of piezoelectric micro-manipulation stage leads to the decrease of its position accuracy and dynamic performance, and it is hard to establish the accurate hysteresis model. A position accuracy compensation method was adopted based on the fuzzy control strategy to get rid of the dependence on hysteretic model. As for a one-dimensional micro-manipulation stage, the position deviation and deviation variation rate of the stage was used as fuzzy input, and the input voltage change of piezoelectric actuator was used as fuzzy output. A method of developing fuzzy rules was presented based on experiment data of PID control to acquire experience. The fuzzy relationship between the stage input and output by fuzzy reasoning and de-fuzzy process was established, and the adaptive compensation of hysteresis could be realized. In order to illustrate the feasibility of the proposed method, the experimental comparative analysis with PID control was carried out. The position errors were compared when the stage was tracking the sine signals with different frequencies. The experimental results show that the proposed fuzzy control method can make the stage have higher position tracking accuracy and faster tracking speed, and has better adaptability.     

基于模糊控制的微操作平台位置精度补偿方法

由于压电式微操作平台的迟滞非线性会导致其位置精度和动态性能下降,且难以建立精确的迟滞非线性模型,采用一种基于模糊控制策略的位置精度补偿方法,以摆脱对迟滞模型的依赖。以一种一维压电式微操作平台为对象,以平台的位置偏差与偏差变化率为模糊输入,压电驱动器输入电压变化量为模糊输出,提出采用基于PID控制的实验数据获取经验来制定模糊规则的方法。通过模糊推理和解模糊过程,建立平台输入量与输出量之间的模糊关系,实现了可消除迟滞现象的自适应补偿。为了说明所提出的位置精度补偿方法的可行性,通过实验与PID控制进行比较,分析平台跟踪不同频率正弦信号的位置误差。实验结果表明,所提出的模糊控制方法能使平台具有更高的位置跟踪精度和更快的跟踪速度,并具有较好的自适应性。     

Studies on indentation fracture toughness on ceramic and ceramic composite using acoustic emission technique

This paper is aimed at investigating the acoustic emission activities during indentation toughness tests on an alumina based wear resistant ceramic and 25 wt% silicon carbide whisker (SiC_w) reinforced alumina composite. It has been shown that the emitted acoustic emission signals characterize the crack growth during loading and unloading cycles in an indentation test. The acoustic emission results indicate that in the case of the composite the amount of crack growth during unloading is higher than that of loading, while the reverse is true in case of the wear resistant ceramics. Acoustic emission activity observed in wear resistant ceramic is less than that in the case of composite. An attempt has been made to correlate the acoustic emission signals with crack growth during indentation test.     

An analysis of nonlinear thickness-shear vibrations of quartz crystal plates using the two-dimensional finite element method

A nonlinear analysis of high-frequency thickness-shear vibrations of AT-cut quartz crystal plates is presented with the two-dimensional finite element method. The Mindlin plate equations are truncated to the first-order ones as an approximation, and then they are used for the formulation of nonlinear finite element analysis with all zero- and first-order displacements. The matrix equation of motion is established with the first-order harmonic approximation, and the generalized nonlinear eigensystem is solved by a direct iterative procedure. A displacement amplitude versus frequency curve and corresponding mode shapes are obtained and examined. The nonlinear finite element program is developed based on the earlier linear edition and can be utilized to predict nonlinear characteristics of miniaturized quartz crystal resonators in the design process.     

Effects on concrete durability of using recycled ceramic aggregates

Ceramic waste from ceramic and construction industries is one of the most important parts in the global volume of construction and demolition waste (CDW). Ceramic waste may have several uses, one of which as coarse aggregate for concrete artefacts. Within a research campaign in course at Instituto Superior Técnico (IST), concerning the reuse and recycling of CDW, the viability of replacing primary limestone aggregates with ceramic waste on the production of concrete pavement slabs has been studied. Compression and bending tests previously performed have shown the mechanical suitability of replacing, at least partially, limestone aggregates with ceramic recycled ones. In this paper, the results of the water absorption tests, either by capillarity or by immersion, and the results of the abrasion resistance tests are presented, all related to long-term concrete durability.     

Novel oxygen sensor using hot spot on ceramic rod

A novel oxygen sensor using hot spot on ceramic rod of high-T _c superconductor RBa₂Cu₃O_7−δ (R: rare earth element) has been developed. The hot spot appears by the self-heating of the local part on the RBa₂Cu₃O_7−δ ceramic rod when a voltage above threshold is applied at room temperature. This sensor operates without any separate heater by taking advantage of the high temperature of the hot spot wherein oxide ions can diffuse easily. The oxygen concentration is determined from the value of the current flowing through the rod by utilizing the change in the resistivity of the hot spot depending on oxygen partial pressure in atmosphere. Oxygen concentration of 0∼100% can be detected with high sensitivity and the response time is several seconds. The response performance of this oxygen sensor is almost the same as that of limiting-current-type zirconia sensor operating at 500°C.     

多级冲击采样器各级切割器的加工精度对截止直径的影响

多级冲击采样器各级切割器的加工精度对采样器每一级截止直径的影响不同,其中最后一级切割器加工精度的影响最大.本文以新型多级冲击采样器为例,通过理论计算解释了这一现象,给出衡量各级切割器尺寸变化对整体影响的相对值,据此提出了多级冲击器设计时应注意的一些问题.     

工装辅助加工隔膜泵导板

导板在隔膜泵的各部零件中,属于易磨损件,备件需求量大,因此我公司经常生产此产品。并且其加工周期长,工序多,在加工中占用大镗大量时间,我公司大镗属于重点设备,其承担着加工公司大量大型产品的任务,本文通过研究设计工装,实现在其他设备（龙门铣）上加工导板,以缓解大镗的生产压力,进而提高导板的生产效率及降低生产成本。     

Condensation and evaporation behaviors of micro-water droplets on SUS304 steel observed using the ac noncontact mode of AFM

The condensation and evaporation behaviors of micro-water droplets on SUS304 steel were ex-situ and in-situ observed in ambient air with the ac noncontact mode of atomic force microscope. The change of water volumes and surface areas were introduced to characterize the condensation and evaporation processes.