The design of a precision bilaminar resonating transducer assembly tool

The performance of bilaminar resonating transducers depends on the thickness and uniformity of the transducer's bond layers. Optimal resonant performance requires a bond thickness between the crystals of ≤5 μm. In addition, a later product assembly step requires precise alignment between each of the transducer components. This article describes a precision tool, designed and built for an industrial sponsor, for assembling these transducers. The tool consists of a screen printer and a press. The screen printer includes a stencil and a powered squeegee cart that rides on a bearing rail. The press contains a bellows that applies pressure, as well as two vacuum heads that hold transducer components in place while pressure is applied. Precision design techniques, such as the use of kinematic couplings and flexures, were used throughout the tool. Bond thicknesses of assembled transducers were evaluated by inspecting each transducer's cross-section with a scanning electron microscope. Preliminary results in indicate that the requirement for a bond thickness of <5 μm was easily achieved; most thicknesses were an optimal 1 μm.     

Design and stiffness analysis of a compliant spherical chain with three degrees of freedom

This paper introduces and investigates a compliant spherical 3R open chain that is obtained by the in-series connection of three identical circularly-curved beam flexures with coincident centers of curvature and mutually orthogonal axes of maximum rotational compliance. The considered open chain is intended to be used directly as a spherical mechanism in pointing devices or as a complex spherical flexure for the development of spatial parallel manipulators. The compliance matrix of the proposed chain is first determined via an analytical procedure. After finite element validation, the obtained equations are used in a parametric study to assess the influence of circularly-curved beam flexure geometric parameters on the overall stiffness performances of the considered compliant spherical 3R open chain. In addition, comparison with an equivalent compliant spherical chain employing straight beam flexures is reported to highlight the added benefits of using circularly-curved beam flexures in terms of reduced parasitic motions.     

Application of Piezoelectric Actuator and Compliant Structures to Achieve Flapping Wing Motion for a MAV

Micro Aerial Vehicles(MAVs)are the smallest artificial aircraft.Most of the flapping wings MAVs are powered by electric motors of various capacities.We report in this paper the application of piezoelectric actuators as power system for a flapping wing MAV using a compliant displacement amplification mechanism.The actuator used for this application is a pre-stressed cut piece of TH-7R type Thunder actuator.A two-bar compliant mechanism with two flexures has been developed to convert the linear displacement into angular movement and amplification.The specimens were made from carbon fiber links and nylon flexures.We also proposed to use the product of frequency(F)and tip displacement(D),F*D as a criteria for the characterization of an amplifying mechanism.The best specimen according tO this criterion is obtained for a 5mm length flexure specimen made of three layers of nylon.The F*D value obtained for this specimen was 0.58 Hz.m.ANSYS finite element analysis results for different flexural thickness and Iengths were obtained and have been compared to the experimental results.The effect of both the thickness and length of the flexure on a particular arrangement has been discussed.     

Shaking force balancing of a 2-DOF isotropic horological oscillator

Despite centuries of research and significant advances, the escapement mechanism used to count and maintain oscillations of mechanical time bases remains a complex mechanism and a major source of energy losses. We showed in previous work that, instead of the widely used rotational one degree-of-freedom (DOF) oscillators, 2-DOF flexure oscillators have the potential of revolutionizing mechanical watchmaking by eliminating the traditional escapement, replacing it by a simple crank driving a pin. Additionally, using flexures increases the quality factor of the time base, leading to further potential improvements in timekeeping accuracy and energy consumption. However, a significant challenge of these new time bases is their balancing such that the influence of external accelerations on their frequency is minimized, a necessary condition for accurate timekeeping in portable applications. This article presents a novel 2-DOF planar flexure oscillator called Wattwins and demonstrates how it can be made insensitive to linear accelerations such as gravity. For this purpose, a new approach to shaking force balancing is developed based on the decomposition of perturbations into effects corresponding to different orders of center of mass displacement. A full analytical model for frequency tuning and shaking force balancing of the 2-DOF oscillator is derived using a pseudo-rigid-body model and assuming that it can be decomposed into two independent 1-DOF oscillators. The results are validated by the finite element method and show that practical mechanical watch specifications can theoretically be reached. A physical prototype was also constructed and preliminary experimental results confirm the theory as well as the simulations.     

X-ray calibrated tunneling system utilizing a dimensionally stable nanometer positioner

To determine to what extent tunneling probes can be used for metrology or as position-sensitive transducers on the atomic scale, accurate characterization of tunneling current as a function of distance must be ascertained. This report describes a system for making such characterizations and observing their repeatability in air. Also, it is often necessary to position two objects to within nanometers in order to perform precision measurements. Included in the narrative, a dimensionally stable screw-wedge-lever system is described for manually moving a tunneling probe to within 15 nm of a conducting surface. The conducting surface is translated via a magnetically actuated single crystal flexure system previously calibrated through direct x-ray interferometry over a 20-nm range. This limited calibration range dictated dimensional positioning below 15 nm. Also, tunneling current measurements demanded dimensional stability below one nanometer. The complete system is demonstrated to hold the relative probe-surface separation to within 1 nm over a 15-minute duration. Also, the vibrational resonance of the structure is determined using the power spectrum analysis during electron tunneling. Resulting data using platinum, palladium, and silver tips in conjunction with a carbon surface show that current-displacement values vary from run to run with a positional difference of up to 1 nm for a given current. These variations suggest limitations for using tunneling probes in air to perform angstrom metrology.     

Critical Condition Expectancy of Flange Beam at the Loss of Flat Form of Stability with Riveted Flanges under the Influence of Random Forces and Initial Flexures

The functioning of multipart flange beam with riveted flanges, which are loaded with random external forces, is examined. Prior to elastic assembling the beam had random initial flexures of the flanges. We obtained relations for determination of probability of flange beam critical condition by the loss of flat form of flexure under the influence of random shear forces, which occur at the welding points between web plate and flanges of the beam. The examples for determination of probability of critical condition of flange beam under the influence of random initial flexures of the flanges are provided. __________ Translated from Problemy Prochnosti, No. 5, pp. 131 – 137, September – October, 2005.     

三自由度柔性镜框结构力学性能分析

为实现小型光学元件的柔性安装和精密调整,设计了一种三自由度柔性安装结构,并对其力学特性进行了理论研究。首先,从柔性镜框的工作原理出发,建立了柔性结构的力学模型,推导了模型的刚度表达式,并利用有限元分析方法进行了验证分析。然后,根据推导的刚度表达式分析了主要结构参数对柔性镜框力学特性的影响,并讨论了减小寄生运动的措施。最后,以通光口径为135 mm的平面反射镜为例,进行了柔性结构的设计计算和参数优化,并对其力学性能进行了仿真分析。验证结果表明:给定的参数范围内,刚度的理论计算和有限元分析结果的相对误差5.5%,表明所推导的刚度计算公式具有足够的精度,验证了理论模型与计算的正确性。同时,柔性镜框力学特性分析结果对柔性镜框的结构设计、力学性能分析和参数优化具有理论指导意义。     

Thin optic constraint

The success of using thin substrates in various fields has urged researchers to further study the possibilities of improving the technology for future applications. For example, the high surface-area-to-weight ratio and strength of sheet glass allow flat-panel display technology to result in high-definition televisions that can be hung on walls like paintings. Sheet glass is also the prime candidate for grazing-incidence foil-optic X-ray telescopes, such as the segmented mirror approach considered for the NASA C onstellation X mission, where cost limitations necessitate lightweight substrates.The effects of different parameters present during the metrology of thin optics, such as gravity, frictional and thermal forces, are identified and analyzed. These forces alter the optic’s surface topography by tens of microns depending on how the optics are manipulated and constrained. This renders metrology and thus surface shaping process results inconclusive.A metrology truss utilizing monolithic flexures to kinematically constrain thin optics during metrology is designed. This device mitigates the effects of the forces mentioned above that are induced on the thin sheet while being mechanically constrained, thus significantly improving the repeatability of the optic surface map measurements.     

干涉式大气垂直探测仪支撑面弹簧缝形的优化设计

通过对面弹簧进行有限元分析计算,得到螺旋线缝形面弹簧各参数r0、α、θ1、b在轴向拉伸不同位置时,对其轴向刚度Kx、径向刚度Ky、刚度比i(i=Ky/Kx)的影响规律,从中可以选取一组合理的参数值,使面弹簧轴向刚度Kx小、而使径向刚度Ky大、刚度比i大、环境适应性最强的面弹簧。有限元分析方法为设计满足要求的面弹簧,提供了理论基础。     

高速公路路基施工质量的测试方法和仪器选用

准确评价路基施工质量,是保证道路结构强度达到设计要求的重要措施。以太澳(太原—澳门)高速公路在建路基为工程实例,选择有代表性的试验段,以点对点的方式,分别运用动载落锤弯沉仪(FWD)(1t、3t和5t)、静载贝克曼梁(BB)、手持式落锤弯沉仪(PFWD)、路面雷达(GPR)、介电常数仪、灌砂法等仪器和手段得到了弯沉、介电常数、压实度等。论证了FWD、PFWD和GPR等测试仪器可应用于高速公路路基施工质量控制。