A2 弯曲振动变幅杆的设计

按照一般的变幅杆设计理论，超声弯曲振动变幅杆的设计将会非常复杂，为满足工程上的需要，我们在本文中给出一种简单的近似有效的弯曲振动变幅杆的设计方法，并以弯曲理论来分析其放大倍数，在考虑了转动及剪切形变的影响后，还阐述了更精确的设计理论，通过实验发现实测的变幅杆谐振频率很接近于理论设计值。     

A2弯曲振动变幅杆的设计

按照一般的变幅杆设计理论，超声弯曲振动变幅杆的设计将会非常复杂，为满足工程上的需要，我们在本文中给出一种简单的近似有效的弯曲振动变幅杆的设计方法，并以纯弯曲理论来分析其放大倍数，在考虑了转动惯性及剪切形变的影响后，还阐述了更精确的设计理论，通过实验发现实测的变幅杆谐振频率很接近于理论设计值     

扭转振动超声变幅杆计算及其等效电路

在平面波近似条件下,对几种常用的扭转振动半坡变幅杆(截面极惯性矩变化规律为圆锥、指数及悬链线型)进行了系统的理论分析。导出了变幅杆的等效电路,得出了变幅杆的输入机械阻抗、共振频率方程及振幅放大倍数的数学表达式。文中理论分析及所得结果可作为设计或计算扭转变幅杆的理论基础和依据。     

抗性负载超声复合变幅杆振动特性研究

在抗性负载情况下,利用纵振型变幅杆等效四端网络,对频率方程和放大系数进行了研究,并推导出圆锥过渡段和指数过渡段阶梯形复合变幅杆频率方程和放大系数的一般公式;并通过MATLAB编程,分别绘制了共振频率及放大系数随负载变化的曲线图。这将对超声复合变幅杆的设计和应用提供一定的理论依据。     

一端带有圆柱杆的复合纵振超声变幅杆的简明设计理论

对一端带有圆柱杆的各种复合型纵振超声变幅杆，用“替代法”（在变幅杆的两端面处，利用机械阻抗相等的办法），求出其谐振频率方程，使设计简单化。为便于应用，本文求出了此种类型的多种复合型变幅杆的谐振频率方程。     

计及应力螺栓的超声换能器和变幅杆及其组合的性能计算

本文提出一种可对计及应力螺栓的超声换能器和变幅杆任意组合进行计算的数学模型,组合件按其形状分割,变幅杆按其形状函数分为若干段,各段用统一的网络等效,对不同的网络连接方式进行简化,最后由简化的总等效四端网络二端电学或力学量的两两之商求得一系列性能参数。对以上方法可编制灵活的计算程序,因而能方便地计算组合件任意λ/4或λ/2振动节的谐振频率和电流或速度传递函数。通过一个实例作了验证性的计算,并与常规解析法作了比较,获得了基本一致的满意结果。     

非轴对称变幅杆的设计及阶梯形变幅杆圆滑过渡的研究

在功率超声应用中,最常用的工具头是非轴对称的斧头形变幅杆.本文通过面积等效法将这种非轴对称形状变为轴对称形状.再用通用的计算程序进行计算,用表观弹性法考虑横向振动耦合的影响.对一个实例具体作了计算,结果表明,使用面积等效法和表观弹性法处理非轴对称形状的变幅杆是可行的.本文对阶梯形变幅杆圆滑过渡的影响也作了计算和探讨.     

大尺寸矩形截面幂函数复合变幅杆的研究

利用传输矩阵法,计算得到了幂函数复合变幅杆一维纵振动的频率方程,并在此基础上运用表观弹性法分析了大尺寸矩形截面幂函数复合变幅杆,得到了考虑横向耦合振动后的谐振频率方程,最后利用有限元软件ANSYS对三组变幅杆进行了模态分析。结果表明：变幅杆谐振频率的计算值与模拟值符合得很好,与一维理论相比,考虑横向耦合振动的二维理论具有更高的精确度。     

长条形超声塑料焊接焊头的简明设计

焊头是超声塑料焊接设备中一个很重要的部件,其设计的好坏直接关系到焊接质量。将长条形焊头通过合理开槽划分为若干相等的单元．每个单元可作为复合阶梯形变幅杆来处理,用传递矩阵法得出了焊头单元的频率方程,为长条形开槽焊头的设计提供了理论依据。实验表明,利用该方程设计的长条形焊头,其实测频率与设计频率符合很好。本设计方法物理意义明显,计算简单,非常适合工程设计。此外利用该方法可方便的求出开槽数、槽宽度以及槽长度等因素对焊头尺寸的影响,也为焊头的优化设计提供了一定的理论依据。     

轻质长条形反射镜结构优化设计

为解决空间反射镜镜体质量和面形精度在轻量化设计过程中会引起相互冲突的问题,针对某型离轴三反光学系统的长条形主反射镜进行了结构优化设计研究,提出了一种基于SiC材料的中心支撑的轻量化结构,同时引入了多目标集成优化方法,以镜体质量(Mass)和面形(RMS)同时作为优化目标,得到一个反射镜最佳结构模型,其质量为2.32 kg,轻量化率达到了73.8%;然后,对反射镜支撑结构进行了结构设计和说明,并对该组件进行了仿真分析,在X、Y、Z三轴方向1 g重力工况下的RMS值分别达到2.5 nm、2.2 nm、7.3 nm,4 ℃均匀温升载荷工况下的RMS值为3.2 nm,远小于设计要求的RMS≤λ/50(λ=632.8 nm),满足设计要求。     

Optimization design of irradiance array for LED uniform rectangular illumination

Light-emitting diode (LED) large-scale uniform rectangular illumination has a wide range of applications and is usually created by an irradiance superposition scheme. Abandoning the traditional method, we propose an approach to generate this illumination mode and enhance efficiency. With this method, an independent rectangular irradiance distribution is generated by each LED lens unit, and the large-scale illumination is obtained by arraying the irradiance distribution. Two slim direct-lit LED backlightings with a distance-height ratio of 3 were designed. An optical performance with irradiance nonuniformity less than 0.0228 and efficiency greater than 96% were obtained. Compared with the traditional methods, the efficiency is significantly enhanced and the number of the LED units is dramatically reduced by this new method.     

Analysis and design of broadband U-slot cut rectangular microstrip antennas

Broadband microstrip antenna using variations of U-slot has been widely reported. However, in most of the reported work, an in-depth explanation about the mode introduced by U-slot and procedure to design U-slot cut antennas at any given frequency is not explained. In this paper, first an extensive analysis to study the broadband response in symmetrical and a new configuration of asymmetrical U-slot cut rectangular microstrip antennas is presented. The U-slot tunes higher-order orthogonal mode resonance frequency of the patch with respect to fundamental mode to realise wider bandwidth. Further formulation in resonant length at modified patch modes in symmetrical U-slot cut antenna is proposed. Frequencies calculated using these formulations show closer agreement with simulated and measured results. Using proposed formulations, a procedure to design U-slot cut antenna at different frequencies over 800–4000 MHz range which shows broadband response is explained. Thus, the proposed work gives an insight into the functioning of widely used U-slot cut antennas and the formulations will be helpful for designing at any given frequency.     

带夹套水冷矩形真空炉的有限元法分析设计

主要论述了如何利用有限元分析设计法完成真空容器结构优化设计,利用大型有限元分析软件ANSYS完成了带夹套水冷的矩形真空容器内外层壳体壁厚及炉门厚度的优化计算,并据此建立了三维实体模型,将模型导入ANSYS软件施加两种工况下的约束和载荷,划分单元,进行了整体有限元分析和二次优化,给出了分析结果.     

基于零阶算法的矩形面宽带纵振换能器设计

传统换能器的优化一般采用试算修改的方式进行,这样的方式在待优化参数较多时不仅比较繁琐而且有可能会漏掉各参数组合下较好的设计点,对此提出了利用零阶算法进行换能器多参数联合优化设计的方法。建立了一种带宽评价函数,通过该评价函数和零阶算法尝试了对矩形面纵振换能器带宽的优化设计。经有限元仿真和样机测试表明,两款换能器的性能达到了预期指标要求,实现了宽带工作。得到的两款宽带换能器性能为:1#换能器工作频带为10~21.5 kHz,带内起伏约3 dB,发射电压响应大于134 dB;2#换能器工作频带为7.5~31.5 kHz,带内起伏约6 dB,发射电压响应大于131 dB。该方法可以作为换能器设计的一种新方式。     

The refined theory of magnetoelastic rectangular beams

Summary. The problem of deducing a one-dimensional theory from a three-dimensional theory for a soft ferromagnetic elastic isotropic body is investigated. Based on the linear magnetoelasticity, the refined theory of magnetoelastic beams is presented by using the general solution for the soft ferromagnetic elastic solids and the Lure method. Based on the refined theory of magnetoelastic beams, the exact equations and solutions for the homogeneous beams are derived and the equations can be decomposed into three governing differential equations: the fourth-order equation, the transcendental equation and the magnetic equation. Moreover, the approximate equations and solutions for the beam under transverse loadings and magnetic field perturbations are derived directly from the refined beam theory. By omitting higher order terms and coupling effects, the refined beam theory can be degenerated into other well-known elastic and magnetoelastic theoretical models.     

The instability of a rectangular elastic solid

Summary The paper starts with a critical survey of recent investigations of related problems. The title problem shown in Fig. 2 is then solved whenq is constant directional and whenq is hydrostatic, using the complete formulation given byNovozhilov with the only assumption being that the elongations and shears are small compared to unity. Since the angles of rotation were retained in the formulation, and the obtained expressions did reduce for thin plates to the correspondingEuler-type expressions, it is concluded thatLegenya's suggestion, that the classic stability theory of plates and shells should be reconsidered taking into consideration the angles of rotation, is based on erroneous results. The results of the present paper confirm that whenq=p the solid can become unstable which contradicts the findings of other investigators. The paper concludes with a comparison of buckling pressure versus slenderness ratio curves which are based on results of a number of investigators. These graphs demonstrate that the classical theory of buckling of thin plates (and beams) yields accurate results up toh/L=0.15, thus verifying the validity of a usual assumption of structural mechanics.

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Zusammenfassung Die Arbeit beginnt mit einer kritischen Übersicht über die neueren Untersuchungen verwandter Probleme. Das gestellte Problem, in Fig. 2 erläutert, wird im folgenden für richtungstreue und für hydrostatische Querlastq gelöst, wobei die vonNovozhilov angegebene Formulierung benützt wird und die Dehnungen sowie die Schubverformungen klein gegen eins angenommen werden. Da die Drehwinkel in der Rechnung behalten werden und sich die erhaltenen Ausdrücke für dünne Platten auf entsprechendeEulersche zurückführen lassen, wird gefolgert, daß derLegenyasche Vorschlag, die klassische Stabilitätstheorie sollte durch Hineinnahme des Drehwinkeleinflusses ergänzt werden, auf fehlerhaften Ergebnissen beruht. Das hier gefundene Ergebnis, daß der Quader fürq=p instabil werden kann widerspricht den Ergebnissen anderer Autoren. Die Arbeit schließt mit einem Vergleich von Knicklast-Schlankheitsgrad-Kurven, die aus den Resultaten verschiedener Autoren gewonnen wurden. Die Schaubilder zeigen, daß die klassische Beul-(Knick)-Theorie dünner Platten (und Stäbe) genaue Ergebnisse bis zum Schlankheitsgradh/L=0,15 liefert und bestätigen so die Gültigkeit einer in der Baumechanik üblichen Annahme.

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The results of the present paper were obtained in the course of research conducted under NASA grant NSG-420. Parts of the presented results are also included in a dissertation submitted by the junior author (ST) to New York University.     

Static and dynamic mechanical properties of cattle horns

As the main weapon of defense and attack, the horns of bovid animals have a remarkable ability to bear static or dynamic loads. In this study, we experimentally investigated the mechanical properties of cattle horns. Firstly, the load-bearing capacity of a whole horn was measured by quasi-static compression tests. The results show that a single horn can withstand a force as high as 7.6 kN, and such a high strength can prevent the horn from failure during fighting. Secondly, quasi-static compression tests with a low strain rate were conducted on cattle horn piece samples using a universal test machine, and dynamic compression tests with a high strain rate were performed using the split Hopkinson pressure bar technique. Both static and dynamic tests showed that the compressive moduli and the yield strengths of horn pieces decrease from the distal end to the proximal end of the horn. In addition, the mechanical properties of the horn exhibit a distinct dependence on the strain rate of the applied load.