受移动载荷梁的最大弯矩分析

对受移动载荷梁的最大弯矩进行了详尽的分析．并结出了确定最大弯矩的方法和程序．     

绳长对起重机载荷消摆的影响

对于继续控制的起重机载荷消摆的，在我们已提出的基于时间最优两拍消摆策略的基础上，本文进一步分析了绳长变化对一消摆 影响。     

起重机载荷摆振模型的简化条件及误差

研究了起重机载荷摆振模型在简化过程中所产生的相对误差,得到了相对误差公式。结论是：在平衡点附近线性化产生的误差为二阶无穷小量,在现行起重机设计规范规定的范围内,可忽略不计;对密度大的货物空气阻力可忽略不计。但对高速起重机或起重机在吊运疏松货物时,简化模型的误差太大,影响研究结论的正确性。因此,迄今为止关于起重机载荷摆振的研究成果仅适用于低速起重机。     

塔式起重机载荷摆振的仿真研究

依照文献1提出来的数学模型编制了塔机载荷摆振仿真软件。它可以帮助研究者在计算机上仿真塔机的起升、变幅、回转运动,动画显示载荷的摆动情况;仿真塔机的联锁保护功能,动态显示、打印实验数据和摆振的相轨迹供研究者使用。通过并行接口接上按钮、转换开关以后也可以用于对塔机司机的操作训练。     

考虑弯扭耦合旋转叶片的动力学分析

应用拉格朗日方程建立了旋转柔性叶片非线性动力学控制方程.文中考虑了由于质量偏心所造成的弯曲与扭转振动的耦合,并假设了弯曲与扭转的一价振型对方程进行了离散,通过数值仿真给出了旋转运动所产生的叶片端部弯曲位移及转角位移,揭示了在叶片扭转刚度较大时,转角位移非常小.本文所建立的动力学方程可用于考虑弯扭耦合时实际旋转叶片的动力学分析.     

倒立摆的移动控制

构造了带自由摆的倒立摆，利用现代控制论的方法，使倒立摆在保持直立的状态下能够向任意位置移动，从而为两足步行机器人的步行研究提供借鉴．     

超空泡射弹尾部冲击载荷的仿真研究

为了研究超空泡射弹尾拍冲击载荷的特性,利用Logvinovich G.V.的独立膨胀原理对流体域提出了一种简化处理模型,并采用流固耦合的方法,对初始扰动角速度、射弹质量、质心位置和刚度对尾拍力的影响进行了仿真计算.结果表明：初始角速度和弹体质量的增加都会使尾拍力增大,而弹体弹性模量的增加会使尾拍力变小;碰撞次数随初始角...     

非移动交变载荷作用桁架自应力分析

初步分析了一种常用桁架的自应力状况,这一分析方法对一般桁架的自应力分析有参考价值。     

平面柔性梁有限元动力学模型

提出一种在绝对坐标系中建立小应变有限转动平面梁动力学方程的有效方法。梁的位移用统一的绝对坐标描述 ,把位移分解成变形和刚体位移。根据哈密顿原理建立小变形小应变梁有限元动力学方程。该法用于多柔体系统动力学建模具有简洁、易于编制通用程序特点 ,数值示求解不存在严重的病态 ,算例表明方法有效可靠。     

倒摆运动稳定性的相空间动力学分析

采用拉格朗日方程导出倒摆的非线性运动微分方程,并由相空间动力学方法分析相图中平衡点的性质,得出倒摆在不同初始条件下的振动情况     

Dynamic reliability analysis of spacial flexible beam

In order to investigate the dynamic response reliability of the spacial flexible beam, the Monomial Cubature Rules (MCR) based Stochastic Response Surface Method (SRSM) is applied to derive the surrogate model of the nonlinear implicit limit state function. A small set of sample pairs for flexible beam dynamic response is generated by taking the integral points of MCR as sample points. Based on these sample pairs and SRSM, the surrogate model of the implicit limit state function is established. The results show that the proposed method has an excellent performance in terms of accuracy and efficiency compared with the Probabilistic Collection Method (PCM) based SRSM and Monte Carlo method, and that the dispersion of system parameters has a significant effect on the dynamic response reliability of the spacial flexible beam.     

Stochastic dynamic analysis of a spatial flexible beam

The uncertainty dynamic response of a spatial flexible beam with large overall motion is investigated. The stochastic differential equations of a three-dimensional beam with large overall motion are derived by using the virtual work principle. The polynomial chaos method and monomial cubature rules are applied to derive a set of completely implicit differential equations. Then the polynomial coefficients are obtained by the variable order method and regression method so as to find the numerical characteristics of the response. As an illustrating example, dynamic modeling of a spatial flexible beam by considering the probabilistic of geometric and physical parameters is presented. The accuracy and efficiency of the method are verified by comparing the results with those given by the Monte Carlo simulation method. The results show that the probabilistic parameters have a significant effect on the dynamic response of the flexible beam and that the dynamic modeling with probabilistic parameters can objectively reflect the dynamic behavior of the objective systems.     

移动荷载作用下周期支撑无限长梁动力响应

基于解析法,分析了具有周期等间距弹性支撑的无限长梁在移动荷载作用下的动力响应.当荷载进入考察梁段之前与离开后,梁不会产生振动.而且对于梁在空间距离上呈周期对的观测点,动力响应相同.无限长梁的振动方程采用Euler-Bernoulli梁微分方程,同时满足4个空间边界条件,利用Fourier变换求解微分方程.数值计算表明,当荷载移动速度较小时,梁的振动为准静态;同时,随荷载速度与激励频率增大,梁的振动变形也较大.     

Motion function reliability analysis of a rotating flexible beam with random parameters

The assumed mode method and stochastic response surface method are combined to analyze the motion function reliability of a rotating flexible beam with random parameters. Firstly, based on Lagrange's equations and the assumed mode method, the rigid-flexible coupling dynamic model which takes the coupling term of the deformation in the expression of longitudinal deformation is studied. Then considering the physical and geometrical parameters under randomness, the probability analysis is made by the stochastic response surface method. The rationality and efficiency of the modeling and the method presented are verified by an example. The results demonstrate that the third order stochastic response surface method leads to good precision with acceptable time consumption compared with the Monte Carlo (MC) method, and that the randomness of density has a greater effect on the reliability of the system.     

Dynamic modeling and simulation for the rigid flexible coupling system with a non-tip mass

The rigid flexible coupling system with a mass at non-tip position of the flexible beam is studied in this paper. Using the theory about mechanics problems in a non-inertial coordinate system, the dynamic equations of the rigid flexible coupling system with dynamic stiffening are established. It is clearly elucidated for the first time that, dynamic stiffening is produced by the coupling effect of the centrifugal inertial load distributed on the beam and the transverse vibration deformation of the beam. The modeling approach in this paper successfully solves problems of popular modeling methods nowadays: the derivation process is too complex by using only one dynamic principle; a clearly theoretical mechanism for dynamic stiffening can't be offered. First, the mass at non-tip position is incorporated into the continuous dynamic equations of the system by use of the Dirac function and the Heaviside function. Then, based on the conclusions of orthogonalization about the normal constrained modes, the finite dimensional state space equations suitable for controller design are obtained. The numerical simulation results show that: dynamic stiffening is included in the first-order model established in this paper, which indicates the dynamic responses of the rigid flexible coupling system with large overall motion accurately. The results also show that the mass has a softening effect on the dynamic behavior of the flexible beam, and the effect would be more obvious when the mass has a larger mass, or lies closer to the tip of the beam.     

新型嵌入式弹性联轴器的动力特性分析

推导出新型嵌入式弹性联轴器扭转刚度计算公式和动力学基本方程,并进行动力特性分析,与国内弹性套柱销联轴器计算比较,不仅缓冲减振、减小动载荷,而且具有尺寸小、结构简单等优点。     

非惯性系下旋转柔性叶片的动力学分析

旋转柔性叶片是汽轮机关键零部件,针对叶片振动损伤问题,考虑经历大范围运动的柔性叶片刚性运动与弹性变形运动之间的相互耦合,应用哈密顿原理建立了旋转柔性叶片非线性动力学控制方程.考虑旋转离心惯性力的影响以及轴向变形与横向变形之间的耦合,基于假设模态法对方程进行离散,研究了不同转速下梁端部位移的响应.研究结果表明,刚性旋转运动对柔性叶片端部位移的响应具有明显的影响,并且由于离心力的存在,出现了动力刚化现象,文中所用方法及数值仿真结果可用于研究旋转柔性叶片的振动失效问题.     

变速移动荷载作用下弹性地基梁的动态反应

目的为确定移动荷载的速度、加速度以及地基刚度等参数对梁动态挠度和弯矩的影响.方法利用Fourier积分变换法,推导在变速移动荷载作用下,弹性地基上无限长梁动态挠度和弯矩解析表达式.结果在给定移动荷载速度的情况下,梁的挠度随荷载移动加速度的增大而减小,当加速度为正时减小的幅度大,加速度为负时减小的幅度小;梁的弯矩与梁的挠度一样随移动的加速度增大而减小.在给定荷载移动的加速度的情况下,梁的弯矩随荷载移动的速度增大而增大.结论梁的动态挠度和弯矩随着车辆荷载移动速度和加速度的变化而变化.     

Modal analysis on transverse vibration of axially moving roller chain coupled with lumped mass

The modal characteristics of the transverse vibration of an axially moving roller chain coupled with lumped mass were analyzed. The chain system was modeled by using the multi-body dynamics theory and the governing equations were derived by means of Lagrange’s equations. The effects of the parameters, such as the axially moving velocity of the chain, the tension force, the weight of lumped mass and its time-variable assign position in chain span, on the modal characteristics of transverse vibration for roller chain were investigated. The numerical examples were given. It is found that the natural frequencies and the corresponding mode shapes of the transverse vibration for roller chain coupled with lumped mass change significantly when the variations of above parameters are considered. With the movement of the chain strand, the natural frequencies present a fluctuating phenomenon, which is different from the uniform chain. The higher the order of mode is, the greater the fluctuating magnitude and frequency are.     

梁桥在多辆车辆荷载作用下的振动分析

采用无限自由度桥梁模型对梁桥在多辆移动车辆荷载作用下的强迫振动问题进行了分析 ,给出了简支梁桥在两辆移动汽车分别以不同的车重和不同的车速作用下的跨中动位移的时程曲线 ,并与一辆汽车荷载作用下的动位移和静位移作了比较。本文对直观地了解桥梁与车辆耦合振动系统的动力特性规律和机理具有一定的参考价值。