Effects of voids and rotation on plane waves in generalized thermoelasticity

In the present paper, we study the influence of rotation, thermal and voids parameters on the reflection phenomenon of plane waves in generalized thermoelastic solid with one relaxation time. The governing field equations for isotropic and homogeneous thermoelastic half-space with voids and rotation are formulated in the context of Lord and Shulman theory of generalized thermoelasticity. The solutions of these governing equations indicate the existence of four coupled plane waves, namely; P₁; P; P₃ and P₄ waves in the thermoelastic medium. The boundary conditions at stress-free thermally insulated surface are satisfied to obtain the system of four nonhomogenous equations in the reflection coefficients of various reflected waves for the incidence of P₁ wave. A particular material is modeled as the thermoelastic solid half-space to compute the complex absolute values of speeds and reflection coefficients. The speeds and reflection coefficients are shown graphically to observe the influences of rotation, thermal relaxation time and voids parameters.     

Synthesis of rational tooth profiles for plane gear transmissions

The line of engagement, which does not vary during operation, has been determined via solving the variation problem. It is found that the obtained line of engagement does not move off the pitch point, and it is the arc of circle. The optimal teeth profiles consisting of two segments: the convex segment at pinion tip and of concave segment at the dedendum has been obtained.     

平卷簧专用工具绕制法

提出了一种采用专用工具绕制平卷簧的方法。     

Bifurcation of a special line and plane symmetric Bricard linkage

In this paper, the attention is drawn to a special Bricard linkage with both line and plane symmetry. The closure equations of the linkage have been derived. The characteristics of bifurcation have been discussed in details. The result not only provides the solution to avoid bifurcation, but also offers the possibility in design of reconfigurable structures.     

曲轴振动抛光机的设计与研究

压缩机曲轴轴颈及曲轴销是动配合,要求表面粗糙度通常在Ra0.4以下,常用磨削的方法加工及抛光.由于其形状不规则,安装复杂,产量低,加工成本高,设备昂贵.提出采用振动抛光机配合行星传动的专用设备进行抛光,可一次装夹30根曲轴,取得了令人满意的效果.     

Behaviour of multirecess plane hydrostatic thrust bearings under conditions of tilt and rotation

A theoretical study of the behaviour of capillary-compensated fourrecess plane hydrostatic thrust bearings under conditions of tilt and rotation was made. The influence of radius ratios on the load and flow characteristics and a comparison with continuous-recess bearings are reported.     

New rational interpolation functions for finite element analysis of rotating beams

A rotating beam finite element in which the interpolating shape functions are obtained by satisfying the governing static homogenous differential equation of Euler–Bernoulli rotating beams is developed in this work. The shape functions turn out to be rational functions which also depend on rotation speed and element position along the beam and account for the centrifugal stiffening effect. These rational functions yield the Hermite cubic when rotation speed becomes zero. The new element is applied for static and dynamic analysis of rotating beams. In the static case, a cantilever beam having a tip load is considered, with a radially varying axial force. It is found that this new element gives a very good approximation of the tip deflection to the analytical series solution value, as compared to the classical finite element given by the Hermite cubic shape functions. In the dynamic analysis, the new element is applied for uniform, and tapered rotating beams with cantilever and hinged boundary conditions to determine the natural frequencies, and the results compare very well with the published results given in the literature.     

有基准要求的轮廓线(面)公差特征项目的合理确定

在GB/T 11821996《形状和位置公差 通则、定义、符号和图样表示法》中，形位公差特征项目中的线轮廓度和面轮廓度，分为形状公差（无基准要求）和位置公差（有基准要求）。也就是说，当没有基准要求时线轮廓度和面轮廓度可作为形状公差特征项目，当有基准要求时线轮廓度和面轮廓度又可作为位置公差特征项目。对于有基准要求的轮廓线和轮廓面的公差特征项目，仍称为线轮廓度和面轮廓度，这是否恰当，本文认为有必要进行深入探讨。 a） b） c） 图1 a） b） 图2 图1a）和图2a）分别为线轮廓…     

Intrinsic transmission functions of a plane kinematic chain with variable angles and lengths of the links

Formulae for determining the values of the first and second intrinsic transmission functions of a plane single-loop kinematic chain with variable lengths of the links and many degrees of freedom are derived. A method of defining the intrinsic transmission functions of a multiloop kinematic chain is proposed. Its application is illustrated by an example.     

平面高级杆组装配构形特殊位置的计算机代数解

根据平面高级杆组装配构形的位置方程以及相应的Jacobia矩阵,应用计算机代数法,经过逐次消元,导出了对应装配构形位置方程出现特殊位置时的导出方程组,由此得到了用结构参数表示的该类杆组装配构形在特殊位置上的全部位置符号解。并分析了特殊位置数目、形态及杆组中各构件在奇异点处各种可能的装配模式。     

基于平面地磁感应线圈测量高速自旋弹丸转速的方法

针对高自旋弹丸的转速测试问题,推导了在三维转动中地磁感应线圈的输出公式,并在合理的假设下对高自旋弹丸的输出信号进行了简化,给出了输出信号的半周期确定方法及基于相位信息的转速测试原理。测试结果表明,利用本文方法得到的转速曲线和遥测结果是一致的。     

转弯式堆垛机的控制原理及特殊功能

概述转弯式堆垛机的特点及其与一般巷道式堆垛机的区别，并以威娜宝立体库中使用的转弯式堆垛机为例，详述其控制原理和特殊功能。     

Synthesis of a special RPSPR spatial linkage function generator for six precision points

A closed form approach to kinematic synthesis of function generation is formulated for a special RPSPR spatial linkage for six precision points. Several illustrative examples showing the applicability of the proposed approach are discussed and presented in detail. To the best of our knowledge, this paper is the first to consider a RPSPR spatial linkage as a function generator.     

Optimising the number and position of the measuring points on a plane curve using an algorithm for comparing the angle between the normal directions

The purpose of this study is to investigate the determination of the number and location of measuring points for a plane curve using a coordinate measuring machine in order to reduce the time taken to measure the curve. The study begins by establishing the data points for a plane curve on the design blueprint, and then proposes an algorithm for comparing the angle between the two normal directions. The angle can be used in conjunction with the preset allowance distance error value to determine which positions of the measuring points are better, and to reduce the number of measuring points. A cubic spline curve is adopted as the measuring curve so that all derived points fall on the cubic spline to meet the requirement of integrating real measuring and the computer-aided drafting.     

Some measurements of fluid pressures between plane parallel thrust surfaces with special reference to radial-face seals

This paper describes some experiments carried out with plane thrust surfaces of the type used in radial-face seals, to study the pressures in the gap between the surfaces.Even without a pressure difference across the face, the fluid film was found to be capable of withstanding appreciable loads, and measurements of load and face separation for different shaft speeds and liquids were made. These generated pressures were often accompanied by a centripetal pumping action causing inward radial flow.Similar measurements were made with an applied pressure difference across the face, as in the case of a seal. In all the tests, the pressure exerted by the fluid between the faces was found to be greater than that expected on theoretical grounds. Reasons for the discrepancies are discussed.     

Analysis of rotation in the lubrication of a porous slider bearing: Small rotation

A mathematical model is developed to investigate the behaviour of a plane-inclined porous slider bearing under the effect of a uniform small rotation. The Beavers-Joseph slip condition was used for the slip velocity at the porous boundary. The expressions for dimensionless pressure distribution, load-carrying capacity and coefficient of friction are obtained. It is concluded that the load-carrying capacity and coefficient of friction depend on the direction and magnitude of rotation. For a negative rotation the load-carrying capacity increases and the coefficient of friction decreases. The load-carrying capacity also decreases with increase in the slip velocity parameter.     

Analysis and visualization of rotation searching efficiency in two-round rotation based magnetic tracking

A magnetic sensor attaching on the moving object will have a maximum intensity measurement when the rotating magnetic field is pointing at it. Before solving the position and orientation, the magnetic field could be rotated in two orthogonal planes to find the maximal pointing direction. In order to realize a real-time tracking, efficient searching strategies for this maximum-oriented magnetic field rotation must be provided. This paper sets up a novel rotation searching efficiency model to quantitatively evaluate the relationship between the rotation searching time and the rotation axis in the two-round rotation based magnetic field measurement. Based on this model, two searching strategies are proposed. Simulation results suggest that both searching strategies can realize full space tracking without any latency larger than 30 ms. Corresponding system platform is under development.     

平面连杆机构在全自动平压机中的应用

根据自动平压机的工作原理,主要从极位夹角、压力角和静力等方面对连杆机构在机器中的应用进行分析。     

On the kinematic geometry of relative screw motions

We present an exact formulation for the central problem of screw theory, namely, the determination of the principal screws of given relative screw motions. Using the Study??s dual-line coordinates, a method for the kinematic synthesis of spatial gears with skew axes is introduced. This approach allows showing that the principal screws of the system can be determined via the extreme values of the pitch. The well known equation of Plücker??s conoid associated with the three-systems has been derived, and it is shown that the principal axes of it are two screw axes located at its center and at right angles. More specifically, these two axes and the common normal to all screw axes form a reference frame that simplifies the expression of Plücker??s conoid. Finally, geometric conditions are discussed for some of the special screw systems.     

The geometry of the knee in the sagittal plane

A geometric model of the tibio-femoral joint in the sagittal plane has been developed which demonstrates the relationship between the geometry of the cruciate ligaments and the geometry of the articular surfaces. The cruciate ligaments are represented as two inextensible fibres which, with the femur and the tibia, are analysed as a crossed four-bar linkage. The directions of the ligaments at each position of flexion are calculated. The instant centre, where the flexion axis crosses the parasagittal plane through the joint, lies at the intersection of the cruciates. It moves relative to each of the bones during flexion and extension. The successive positions of the flexion axis relative to a fixed femur and to a fixed tibia are deduced. The shapes of articular surfaces which would allow the bones to flex and extend while maintaining the ligaments each at constant length are calculated and are found to agree closely with the shapes of the natural articular surfaces. The calculated movements of the contact point between the femur and the tibia during flexion also agree well with measurements made on cadaver specimens. The outcome is a geometric simulation of the tibio-femoral joint in the sagittal plane which illustrates the central role played by the cruciate ligaments in the kinematics of the knee and which can be used for the analysis of ligament and contact forces.