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B. Saravanos 《International Journal of Mechanical Sciences》1974,16(8):573-584
Previous work on the buckling of thin elastic cantilever beams when subjected to tip forces applied by means of an articulated rod is here extended to cases when the axis of the rod is directed at any angle to the beam axis. The system is typical of engineering situations in which mechanical control circuits involve a bellcrank lever connected to an articulated rod, the remote end of which is loaded by a tube directionally guided in rollers. The function of the articulated rod is to permit geometric changes to take place in the mechanical system.A numerical solution is provided to the differential equation system by finite-difference approximations. The resulting equations are of a sufficiently simple form as to permit evaluation of buckling forces by desk calculation; alternatively a computer adaptation can be made.The results of the analysis are verified by an experimental investigation. 相似文献
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Buckling of rotating beams 总被引:1,自引:0,他引:1
William F. White Jr. Raymond G. Kvaternik Krishna R.V. Kaza 《International Journal of Mechanical Sciences》1979,21(12):739-745
The stability of a beam subjected to compressive centrifugal forces arising from steady rotation about an axis which does not pass through the clamped end of the beam is analyzed to determine the critical rotational speeds for buckling in the inplane and out-of-plane directions. The differential equations of motion are solved numerically using an integrating matrix method in combination with an eigenanalysis to determine the eigenvalues from which stability is assessed. The results clarify several differences which have been identified in the literature relating to the proper behavior of the critical rotational speed for buckling as the radius of rotation of the clamped end of the beam is reduced. 相似文献
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A.Y.T. Leung 《International Journal of Mechanical Sciences》2009,51(11-12):807-815
Axial deformation is not involved in the formulation of linear buckling caused by axial force. Likewise, twisting is not present in linear buckling caused by axial torque. The dynamic axial–torsional buckling of structural frames in the presence of follower axial force will be solved by means of dynamic stiffness using power series. Variationally consistent natural boundary conditions are given so that the resulting dynamic stiffness is symmetrical for conservative loading. Some parts of the boundary forces disappeared for follower axial forces due to consistent tangency to the neutral axis. The deficiency of the power series method to deal with non-uniform sections is highlighted. New instability phenomena for a simple column are studied in detail. It is shown that columns can buckle under direct follower tension. Follower tension decreases the natural frequency initially and then increases it rapidly after a turning point. The first pair of modes about the major axis and that about the minor axis of a rectangular section column meet at one crossing point. A very small axial torque will change the crossing into flutter-like tongues. These tongues are common in compressive follower force. These tongues caused by axial torque are reported here for the first time. 相似文献
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针对对边简支、另一对边固定载流矩形薄板,利用Mathieu方程解的稳定性,研究在电磁场与机械荷载共同作用下的磁弹性稳定性问题。在导出载流薄板在电磁场与机械荷载共同作用下的磁弹性动力稳定方程的基础上,应用Galerkin原理将稳定方程整理为Mathieu方程的标准形式,并将其归结为对Mathieu方程的求解问题。利用Mathieu方程系数、 的本征值关系,得出载流薄板磁弹性动力稳定临界状态的判别方程,并给出当 为小激励时的稳定区域图,以及Mathieu方程稳定解区域和非稳定解区域的分界。最后通过具体数值算例,给出该矩形薄板的磁弹性动力失稳临界状态与相关参量之间的关系曲线。研究结果表明,变化电磁场和通电电流的参数,可以改变电磁力的状态,从而达到控制载流薄板的变形,应力、应变状态及其稳定性的目的。 相似文献
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A method for vibration isolation of a vertical axis automatic washing machine with a hydraulic balancer 总被引:2,自引:0,他引:2
Hai-Wei Chen Wei-Xi Ji Qiu-Ju Zhang Yi Cao Sheng-Yao Fan 《Journal of Mechanical Science and Technology》2012,26(2):335-343
This paper discusses a method for vibration isolation of a vertical axis automatic washing machine with a hydraulic balancer.
First, a way to isolate vibration through a small amplitude of the suspension rod’s axial force is proposed, and a base circle
of a cone along which the lower joint of a suspension rod moves is discussed. Based on the circle, a geometric constraint
involving the slant angle of the suspension rod, the deflection angle of the washing/spinning assembly, the suspension radius
of the tub and the eccentricity of the system at the steady state is derived. Considering that the trace along which the suspension
rod moves is also affected by the dynamics of the system, a governing equation satisfying the equilibrium conditions of the
centrifugal forces and torques is obtained. Combing the geometric constraint and governing equation together achieves a general
governing equation for vibration isolation of the system. Finally, the general governing equation is proven by simulations,
and the relations between the optimal installing height and several parameters are discussed. 相似文献
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应用Pro/Engineer建立了某四缸内燃机活塞一连杆一曲轴系统的三维实体模型,然后把模型调入ADAMS多体动力学分析软件,建立了活塞一连杆一曲轴系统的虚拟样机模型.在此基础上,对四缸内燃机曲轴进行了多体动力学分析.得到了作用在内燃机机体上的主轴承力及活塞侧压力的准确解.研究结果表明,曲轴系统运动件的惯性力对主轴承力和活塞侧压力的影响显著,因此在计算时需要对运动件惯性力进行准确、合理地考虑. 相似文献
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A solution for the buckling load of an elastically supported cantilever with continuous lateral restraint under uniform distributed axial load is developed. The restraining media are distributed along the centroidal axis and the shear forces are assumed to be proportional to the respective derivative. Boundary conditions are developed for three cases: (a) fixed supports, (b) the cantilever on an elastic support while the restraining media is fixed and (c) both cantilevers and restraining media on an elastic support. 相似文献
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基于多体动力学理论,建立了往复泵曲柄连杆机构参数化动力学模型.通过算例仿真,对往复泵曲柄连杆机构运动及受力特性进行了研究,获得了连杆随曲轴转角变化的运动规律,以及连杆两端的铰链反力变化规律. 相似文献
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Stresses and deformations resulting from centrifugal forces in rotating specially orthotropic circular plates are determined. The classical laminated plate theory is employed in the analysis, and the results are presented in a manner which illustrates the effect of anisotropy. The plate is assumed to be rigidly fixed to a concentric rod allowing no deformation in its central region. The outer boundary is either free of any constraints or the plate is placed in a stiff casing which prevents radial deformation. A stiffness ratio, which is defined as the ratio of circumferential stiffness to radial stiffness, is used as the parameter to indicate the degree of anisotropy. Having a stiffness ratio greater than one eliminated the stress build-up on the boundaries. Higher stiffness ratios reduced the compressive stresses which began to occur near the outer boundary when the boundary was restrained from radial expansion, thus contributing to stability against local buckling. The results of Tsai-Wu failure analysis also showed that the choice of a stiffness ratio higher than one gives higher resistance against ply failure in tension. 相似文献
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针对刚性质量块撞击情况,对弹性直杆在线性缓冲材料防护下的动态屈曲进行分析,得到撞击条件下杆体屈曲发生的临界弹簧刚度。以杆体整个长度发生轴向应变的最小弹性屈曲载荷为判据,分析了临界弹簧刚度与载荷作用时间、载荷幅值、缓冲材料及杆体长度的关系,以及缓冲材料位置对于杆体屈曲防护的影响等。结果表明:撞击初速和刚性块质量是引起临界弹簧刚度改变的两个因素,缓冲材料的安放位置在一定条件下影响着弹性杆屈曲防护。所得结论对于在刚性质量块作用下弹性直杆的动态屈曲防护问题提供了一定的理论依据。 相似文献
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机场跑道异物(Foreign Object Debris, FOD)探测系统易折杆设计是保证探测系统有效工作的关键,对防范FOD引起的机场安全风险具有至关重要的作用。文中以FOD探测系统支架易折杆为研究对象,提出在圆管上开半圆形缺口的设计方案以实现易折杆易断和耐疲劳的综合力学性能。通过有限元模拟方法,分析了不同圆角半径、圆管壁厚和缺口形状的易折杆在不同工作载荷下的应力应变状态。结果表明,随着缺口半径增大或壁厚减小,缺口根部应力水平提高,能够使易折杆在受到飞机撞击时快速断开,具备易折特性,但会降低疲劳寿命;反之会增加疲劳寿命,但不容易实现易折特性。合理调节壁厚和圆角半径,可以使易折杆具有易断性和耐疲劳的综合力学性能。 相似文献
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Metallic tendons are frequently used in arches and vaults to absorb the lateral thrusting forces due to gravity loads or inertial forces caused by an earthquake. Traditional tendons, however, have some limitations (e.g. sensitivity to temperature variations, buckling under compression, etc.). Shape memory alloys (SMAs) can be used to enhance the performances of metallic tendons both in service and seismic conditions. This is achieved with the tensioning control block (TCB) system. The basic components of TCB are pre-strained superelastic SMA wires, in series with the metallic tendon. The number and diameter of the SMA wires is selected based on the force levels to reach. The length is optimised with respect to the thermal behavior of the system. A number of theoretical and experimental studies have been conducted to fully understand the thermal and mechanical behavior of TCB. In the paper, the main outcomes of these studies are described. 相似文献
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WANG Zhiren WANG Ping BAI Xiangzhong 《机械工程学报(英文版)》2008,21(5):75-79
The magnetic-elasticity buckling problem of a current plate under the action of a mechanical load in a magnetic field was studied by using the Mathieu function. According to the magnetic-elasticity non-linear kinetic equation, physical equations, geometric equations, the expression for Lorenz force and the electrical dynamic equation, the magnetic-elasticity dynamic buckling equation is derived. The equation is changed into a standard form of the Mathieu equation using Galerkin's method. Thus, the buckling problem can be solved with a Mathieu equation. The criterion equation of the buckling problem also has been obtained by discussing the eigenvalue relation of the coefficients 2 and r/ in the Mathieu equation. As an example, a thin plate simply supported at three edges is solved here. Its magnetic-elasticity dynamic buckling equation and the relation curves of the instability state with variations in some parameters are also shown in this paper. The conclusions show that the electrical magnetic forces may be controlled by changing the parameters of the current or the magnetic field so that the aim of controlling the deformation, stress, strain and stability of the current carrying plate is achieved. 相似文献
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铰接式车辆因其机动性好、适应性强且生产效率高而被广泛采用,而其不足之处在于转向时横向稳定性较差,翻车事故时有发生,为解决此问题,应用虚拟样机技术对此类车辆的转向过程进行分析。基于液压系统与多体动力学系统的联合仿真,在ADAMS中建立六轮电驱动铰接车的多体动力学模型,在AMESim中搭建其全液压转向系统模型,以实现铰接车的转向过程。 通过PID控制转向油缸的油量使其铰接角维持一个定值,对铰接车的行驶转向进行分析,并考虑车速对铰接车稳态转向的影响。获得铰接车行驶转向下各个轮胎的运动轨迹,各个轮胎所受侧向力、纵向力及垂直力随时间的变化曲线和转向油缸中活塞杆的受力。结果表明:随着行驶速度的增大,铰接车的外侧各个轮胎的受力均明显的增大;且铰接车的转向半径也随着增大;全液压转向系统具有明显的不足转向特性。 相似文献
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为了发展新的并联机构形式,提出一种以圆弧弯曲截面钢带作为运动支链的6自由度钢带并联机器人机构形式。简要阐述钢带并联机器人结构组成与工作原理。采用基于变分原理的有限元静力学理论和线性屈曲分析理论建立求解钢带失稳临界力的屈曲方程。利用有限元软件ANSYS对不同结构参数的截面由圆弧弯曲形状过渡到平直形状的钢带进行失稳分析,得到钢带能承受的失稳力与结构参数的关系,并进行试验验证。对钢带并联机器人在平移运动位姿下的整机失稳机理进行系统研究,得到不同位姿参数与钢带并联机器人失稳临界力的关系。研究结果表明:弯曲截面结构的钢带能承受一定的压力,钢带失稳力随钢带圆弧截面中心角、钢带厚度增大而增大,随钢带长度增大而减小。对于机器人动平台作上升运动,在500 mm的高度,失稳临界力最大。而对于沿Y轴平动或沿=60平动且100 mm200 mm的范围,对于沿极径=500 mm平动且1020的范围,失稳临界力均比较大。研究成果能用于优化钢带并联机器人的结构设计及确定刚度工作空间。 相似文献