轴向运动简支-固支梁的横向振动和稳定性

研究一端简支一端固支轴向运动梁的横向振动和稳定性。提出在给定边界条件下确定一匀速运动梁固有频率和模态函数的方法。当轴向运动速度在其常平均值附近作简谐波动时,应用多尺度法给出轴向变速运动梁参数共振时的不稳定条件。用数值仿真说明相关参数对固有频率和不稳定边界的影响。     

基于高阶理论的层板自由振动有限元分析

本文用高阶理论对角铺设层板的自由振动进行了有限元分析,算例表明文中方法是较精确的。文中还讨论了铺层角、材料的纵横向弹性常数以及板的长宽比等对频率的影响。     

含横向导支端Euler-Bernoulli梁弯曲振动的固有特性分析

分析了起重机抗倾覆稳定性动态设计过程中,将起重机结构抽象成具有横向导支端的Euler-Bernoulli梁结构的必要性,计算并研究了此类梁在简单边界条件——两端导支(S-S)、导支-自由(S-F)、导支-简支(S-SS)和导支-固支(SC)下的弯曲振动固有频率和振型函数。用数值算法计算发现:一端导支另一端自由或导支横梁存在横向刚体模态;一端导支一端自由或导支及一端导支一端简支或固定的两种横梁的振动特性十分相似;导支端将引起振型函数凹凸性的变化。最后,对近工况复杂导支-弹性支撑与约束下的横梁模态参数进行了求解。     

温度对两端固支管道振动特性影响分析

采用三种有限元模型和实验的方法分析了两端固支管道各阶固有频率,选择其中一个较好有限元模型.利用该模型计算了管道在高温下的振动特性.提出了管道设计过程中不仅要在常温下进行振动特性分析,而且更应该注意对管道在工作温度下的振动特性分析,最终为管道系统的安全性和设计提供了理论依据.     

复合材料离心叶轮应力和振动有限元计算与分析

采用有限元方法,首先对钢制离心叶轮工作时在离心力作用下的应力进行了计算和分析。在此基础上,对复合材料离心叶轮在离心力载荷条件下的最大应力和固有频率进行了计算评估。预测纤维复合材料层压结构极限强度对叶轮安全设计和轻量化设计是至关重要的,失效判定采用Tsai-Wu失效准则,为避免因共振使叶轮设计寿命明显降低,计算了叶轮的固有频率和模态振型以分析其动态特性。结果表明,复合材料碳纤维/环氧树脂可承受叶轮线速度在605m/s运行时的应力,在风机启停工作转速范围内没有共振转速相匹配。本文研究结果为纤维增强复合材料风机叶轮的设计及应用奠定了基础。     

利用有限元数值计算方法模拟板的振动

利用有限元数值分析的方法对振动过程进行仿真研究。获得振动过程中结构的内力、位移等数据。分析过程完全在计算机中完成 ,避免了复杂的实验工作 ,也可以避免仪器的系统误差与操作不当造成的失真。数值计算方法研究振动过程具有分析过程简单 ,控制与操作方便 ,分析结果详细、形象的优点。     

RV减速器扭转振动的固有特性及灵敏度分析

以RV减速器为研究对象,综合考虑系统刚度和摆线轮偏心角度对扭转振动特性的影响,采用集中参数法,建立了该系统13个自由度的修正扭转动力学模型。通过求解自由振动方程得到系统固有频率及主振型,分析了摆线轮偏心角度对系统固有频率的影响。利用偏导数法分析了系统固有频率对转动惯量和刚度的影响。研究结果表明,轴承刚度为系统固有频率的关键影响因素。     

薄板矩形盒带拉延槛拉深的有限元分析

在薄板矩形盒拉深试验的基础上,进行压料面带拉延槛拉深的有限元模拟分析后指出,在压料面直边部设置相应的拉延槛,增大法兰直边的进料阻力并控制直边流入速度,可相应提高拉深成形极限。设置拉延槛后,使直边轴向拉深变形量增加,整体塑性变形充分,因而相对减轻法兰起皱趋势,并提高矩形盒的整体刚度和成形性。     

机匣静叶耦合振动分析的有限元建模方法研究

悬臂静子叶片连同机匣是航空发动机静子系统的典型结构.应用有限元法分析结构周向弯曲振动的模态频率和振型,分别采用实体单元建模、梁壳单元建模、质量单元取代叶片的三种建模方法建立结构的有限元模型.通过对比分析三种有限元模型的计算结果和计算规模,结构的梁壳有限元模型有较好的计算精度并减小计算规模;在分析低阶模态中用质量单元取代叶片的建模方法满足计算精度,有限元的计算规模大为减小.     

基于有限元的空调管路振动分析

空调室外机管路在工作时会产生相应的振动,管路在长期振动下容易断裂导致冷媒的泄漏。为了解管路的固有特性,本文对压缩机管路模型进行了模态分析,并研究了在改变回气管和排气管的结构下,压缩机管路系统固有频率的相应变化值。通过分析可知,排气管结构的改变对压缩机管路系统固有频率值的影响较为明显,达到了减振和避振的目的。     

矩形薄板通透开裂缝对固有频率和模态的影响分析

针对四边固支矩形板薄受到通透开裂影响,引起模态中固有频率和模态振型变化的问题,对两种开裂位置中不同开裂长度进行了研究。首先,应用ANSYS软件建立有限元模型;然后,对开裂裂缝平行于薄板短边且位于板中心(对称开裂)和不位于板中心(不对称开裂)的各25种裂缝长度进行了仿真计算,获得了薄板的固有频率和模态振型。分析结果表明,裂缝的长度和位置影响矩形薄板的固有频率和振型;开裂的缝长和开裂中心位于节线上或者附近是产生模态交叉的两个重要因素,可为板结构开裂的检测提供依据。     

Free vibration analysis of a thin rectangular plate with multiple circular and rectangular cut-outs

The present work is to investigate the variation in the natural frequency of a rectangular plate with the change in position of cut outs of different sizes along its diagonal and major axis line by considering different aspect ratios of plates. In this regard the free vibration analysis of an isotropic rectangular plate of various aspect ratios with different sizes of multiple circular and rectangular cut-outs is carried out by using an Independent coordinate coupling method (ICCM) under simply supported boundary condition. The ICCM utilizes independent coordinates separately for plate domain and hole domain, in which the reduced mass and stiffness matrices can be derived, by matching the deflection conditions for each hole imposed on the expressions. The resulting equation is useful for the calculation of the Eigen values. The position, size, and number of cutouts have been varied in all the possible ways to investigate their effects on the natural frequency of the rectangular plate.     

有限元法计算长方型橡胶空气弹簧隔振器的垂向刚度

针对传统计算橡胶空气弹簧垂向刚度的局限,提出用有限元法进行计算,解决了囊内空气变化问题。并对长方型橡胶空气弹簧隔振器进行了垂向刚度的计算,与试验值的对比结果说明,该方法是可行的。     

Interlaminar stresses of a rectangular laminated plate with simply supported edges subject to free vibration

The interlaminar stresses in a laminated rectangular orthotropic plate with four sides simply supported edges during free vibration was determined by using the integration method involving the dynamic inertia terms and displacements. The approximate stresses solutions are obtained under the effect of frequencies of vibration for four-layer symmetric cross-ply laminates with the ply configurations [0°/90°]_s and [90°/0°]_s, angle-ply laminates with the ply configuration [45°/−45°]_s. Numerical results show that the natural frequency has significant effects on the dominant interlaminar stresses in the stacking sequences [0°/90°]_s, [90°/0°]_s and [45°/−45°]_s.     

主颚板机械强度理论计算与有限元分析研究

为了确保液压动力钳的上扣质量,针对液压动力钳主颚板的结构特点以及受力情况,利用确定结构危险截面的方法,推导出了主颚板机械强度的理论计算公式,并通过实例应用,分别采用理论计算公式与有限元分析方法进行计算,二者误差仅为3.1%,验证了理论计算公式的正确性。同时针对主颚板存在的应力集中现象,利用有限元法对不同大小的过渡圆角半径进行分析比较,发现最佳过渡圆角半径为R3mm,此时主鄂板的最大应力降低了10%,应力集中现象得以改善。     

A finite thin circular beam element for in-plane vibration analysis of curved beams

In this paper, the stiffness and the mass matrices for the in-plane motion of a thin circular beam element are derived respectively from the strain energy and the kinetic energy by using the natural shape functions of the exact in-plane displacements which are obtained from an integration of the differential equations of a thin circular beam element in static equilibrium. The matrices are formulated in the local polar coordinate system and in the global Cartesian coordinate system with the effects of shear deformation and rotary inertia. Some numerical examples are performed to verify the element formulation and its analysis capability. The comparison of the FEM results with the theoretical ones shows that the element can describe quite efficiently and accurately the in-plane motion of thin circular beams. The stiffness and the mass matrices with respect to the coefficient vector of shape functions are presented in appendix to be utilized directly in applications without any numerical integration for their formulation.     

A finite thin circular beam element for out-of-plane vibration analysis of curved beams

A finite thin circular beam element for the out-of-plane vibration analysis of curved beams is presented in this paper. Its stiffness matrix and mass matrix are derived, respectively, from the strain energy and the kinetic energy by using the natural shape functions derived from an integration of the differential equations in static equilibrium. The matrices are formulated with respect to the local polar coordinate system or to the global Cartesian coordinate system in consideration of the effects of shear deformation and rotary inertias. Some numerical examples are analyzed to confirm the validity of the element. It is shown that this kind of finite element can describe quite efficiently and accurately the out-of-plane motion of thin curved beams. This paper was recommended for publication in revised form by Associate Editor Seockhyun Kim Chang-Boo Kim received his B.S. degree in Mechanical Engineering from Seoul University, Korea in 1973. He then received his D.E.A., Dr.-Ing. and Dr.-es-Science degrees from Nantes University, France in 1979, 1981 and 1984, respectively. Dr. Kim is currently a Professor at the School of Mechanical Engineering at Inha University in Incheon, Korea. His research interests are in the area of vibrations, structural dynamics, and MEMS.     

复合材料开孔薄板受力有限元分析

对复合材料开孔层合板应力集中情况进行了深入探讨,给出理论上分析计算复合材料开孔应力集中的一般方法,得出了影响应力集中问题的主要因素.并通过有限元分析软件NASTRAN对一典型开孔复合材料层合板进行有限元分析,得出开孔复合材料板应力集中较金属材料严重的结论,具有一定的工程指导意义.     

基于ANSYS的矩形截面阶梯型变幅杆有限元分析

文章推出了矩形截面阶梯型变幅杆的力学模型及频率方程．应用ANSYS软件对给定长度的变幅杆固有频率进行了模态分析及谐响应分析，井通过其后处理功能得到了小端面的相对位移．由此计算振幅放大系数及固有频率．得到的结果与传统理论结果符合的较好。