约束层阻尼圆柱壳的自由振动

给出了被动约束层阻尼圆柱壳(PCLD)的自由振动特性．波传播法被用来求解两端简支的PCLD圆柱壳的振动,而不是用有限元法、传递矩阵法和Rayleigh-Ritz法．基于Sanders薄壳理论,导出了PCLD正交各向异性圆柱壳的控制方程．数值结果表明当前的方法要比目前其它方法有效．讨论了粘弹性层和约束层的厚度,正交各向异性约束层的弹性模量比率和粘弹性层的复剪切模量对频率参数和损失因子的影响．     

中厚度复合材料夹芯层板变分渐近精细模型

为准确预测对中厚度复合材料夹芯层板分层开裂至关重要的沿厚向应力/应变分布,利用板固有小参数将原三维板分析严格拆分为沿厚向的一维分析和二维板非线性分析,并将原三维能量渐近扩展为系列二维近似能量泛函;通过对近似能量泛函中主导变分项(含翘曲项)的渐近修正,得到与原三维模型尽可能接近的近似能量,从而构建无需任何场变量假设的精细模型,并转换为工程常用的Reissner模型形式．通过4层复合材料夹芯板柱形弯曲算例表明：基于所构建模型重构的三维场精度较一阶剪切变形理论和经典层合理论更好,与精确解基本一致;由于所构建的变分渐近模型为等效单层板模型,在保证足够精度的前提下,相比三维有限元计算可减少2~3阶计算量,在精确性和有效性间取得较好的折衷．     

Effect of Torsion and Warping on the Free Vibration of Sandwich Beams

The problem on free vibrations of wide sandwich beams is tackled in this paper. Torsional and warping effects in addition to flexure are included in the formulation of the dynamic problem. In order to show the effects of bending-torsion coupling and warping on the natural frequencies and the corresponding vibration modes, three cases are considered. First, the warping and torsion effects are neglected, second, the effect of warping on the coupling terms is neglected, and third, the effect of warping on the coupling terms is included. The viscoelastic core is modeled by elastic translational and rotational springs. The finite-difference method is used to solve the partial differential equations of motion with different boundary conditions for the top and bottom layers. Results for different materials, fiber orientations, depth-to-width ratios, and boundary conditions are found. The natural frequencies and the corresponding vibration modes obtained are in a good agreement with those cited in the literature. If the bending-torsion coupling is pronounced, the inclusion of warping affects the natural frequency considerably.__________Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 41, No. 2, pp. 163–176, April–May, 2005.     

夹层圆板的大幅度振动

本文利用哈密顿原理导出了夹层圆板轴对称大幅度自由振动的基本方程,并给出了表板很薄情况下的简化形式.作为算例,利用修正迭代法求出了具有滑动固定边界条件夹层圆板对轴称大幅度自由振动的一种解析解,并由此导出了夹层圆板振幅和振频的解析关系式.     

夹层圆板大幅度振动的进一步研究

本文给出了具有滑动固定边界条件、并计及表板抗弯刚度的夹层圆板轴对称大幅度自由振动问题的解。在求解此问题时,使用了修正迭代法,并把本文结果与文[1]结果作了比较。     

具有主动约束层阻尼板的振动杂交控制*

本文研究了局部附加主动约束阻尼层(LACL)板的主、被动杂交控制问题.基于弹性、粘弹性、压电材料的本构关系,建立了系统的控制方程.利用Galerkin方法和GHM方法将偏微分方程转换为维数不高的常微分方程组,应用LQR方法进行了数值模拟.计算结果表明,这种主动和被动结合的杂交控制方式具有良好的控制效果.     

夹层结构杆在弹性基础上的弹塑性变形

对位于弹性基底上的、具有可压缩非线性芯子的3层弹塑性杆的弯曲问题进行了研究．研究分析了由2个受力层和1个芯子层组成的3层构件的力学响应．解决了位于弹性基底上的3层杆弯曲的复杂问题．对所给出的弹性解法进行了收敛性检验,以保证该弹性解是可以接受的．计算结果表明,材料的塑性和物理非线性对位于弹性基底上的夹层结构杆的变形影响很大．     

Controllability of vibrations of a system of objects with distributed and lumped parameters

The problem of vibration damping in a system described by the set of a wave equation and a second-order ordinary differential equation is considered. The state functions of the system are related through the boundary conditions for the wave equation.     

Local Buckling around an Interfacial Crack in a Viscoelastic Sandwich Plate

Buckling around an interfacial crack in a clamped sandwich plate is studied. The layers of the plate are assumed to be linearly viscoelastic, isotropic, and homogeneous. The investigations are carried out within the framework of a piecewise homogeneous body model with the use of a three-dimensional linearized theory of stability. The corresponding boundary value problems are solved numerically by employing the FEM and the Laplace transform. The calculated critical times are presented for various problem parameters. In this case, the upper and lower layers are assumed to be viscoelastic and are described by Rabotnov operators, whereas the midlayer is regarded as purely elastic. The influence of rheological parameters on the critical time is also analyzed.     

Numerical Determination of Damping in Metal Matrix Composites

Damping in metal matrix composites is mainly caused by inelastic matrix deformation induced by the great difference in the mechanical properties of the single constituents of the materials. In this study, the finite-element method in combination with a highly accurate material model is employed to examine the effects of both the fiber volume fraction and the external loading amplitude on the energy dissipation process in an Al/SiC composite under a cyclic mechanical load.