密集模态挠性结构传感器/作动器的优化配置

在适当的假设条件下,推导出了压电作动器产生的弯矩与输入电压的关系式及压电传感器输出电压与输入弯矩的关系,进而得到H型密集模态挠性板模型的状态空间表达式,并由此模型出发,采用一种基于能量的传感器/作动器的优化配置策略,该准则可以很自然地研究整个动态模型的可控性和可观性,进而确定传感器/作动器的位置。针对H型密集模态挠性板振动主动控制的数值仿真表明了该准则的有效性。     

新型高倍显微镜云纹测量技术及其应用

本文介绍了两种新型的高倍显微镜云纹测量技术，即激光扫描共聚焦显微镜（LSCM）云纹法和扫描电子显微镜（SEM）云纹法。阐述了LSCM云纹和SEM云纹的形成及测量原理，同时对此两种云纹法加以对比，比较其各自的特点。此外，还对两种云纹法的应用进行探讨，针对测量物体表面变形和表征物体表面周期性结构特征这两类应用领域，分别以测量多晶铝合金板的残余变形和识别日本纹白蝶翅膀表面结构为例介绍LSCM云纹法的应用，以识别绿带翠凤蝶翅膀表面结构为例介绍了SEM云纹法的应用。实验结果证明了LSCM云纹法和SEM云纹法的可行性、灵活性及高灵敏度特性，均为高效、无损的全场测量技术，在微纳米尺度力学特性测量和表征方面有广泛的应用前景。     

ANLYTICAL SOLUTION OF THERMOELASTIC DAMPING IN RECTANGULAR MINDLIN MICRO PLATES 1)

首次给出了四边简支的 Mindlin 矩形微板热弹性阻尼的解析解. 基于考虑一阶剪切变形的 Mindlin 板理论和单向耦合热传导理论建立了微板热弹性耦合自由振动控制微分方程. 忽略温度梯度在面内的变化,在上下表面绝热边界条件下求得了用变形几何量表示的温度场的解析解. 进一步将包含热弯曲内力的结构振动方程转化为只包含挠度振幅的四阶偏微分方程. 利用特征值问题之间在数学上的相似性,在四边简支条件下给出了用无阻尼 Kirchhoff 微板的固有频率表示的 Mindlin 矩形微板的复频率解析解,从而利用复频率法求得了反映热弹性阻尼水平的逆品质因子. 最后,通过数值结果定量地分析了剪切变形、材料以及几何参数对热弹性阻尼的影响 规律. 结果表明,Mindlin 板理论预测的热弹性阻尼小于 Kirchhoff 板理论预测的热弹性阻尼. 两种理论预测的热弹性阻尼之间的差值在临界厚度附近十分显著. 另外,随着微板的边/厚比增大,Mindlin 微板的热弹性阻尼最大值单调增大,而 Kirchhoff 微板的热弹性阻尼最大值却保持不变.     

功能梯度压电圆板轴对称自由振动问题精确解

将功能梯度压电圆板的位移变量和电势变量写为分离变量的形式，由压电动力学平衡方程导出以位移、电势及其一阶导数为状态变量的状态方程，考虑周边固支接地的边界条件，导出了求解功能梯度压电圆板自振频率精确解的方程。将方程退化至一般的非梯度纯弹性圆板的形式，求解其自振频率，得到的结果与相应的理论解完全吻合，从而验证了本文方法的正确性。更进一步地对梯度函数沿板厚以指数形式变化的功能梯度压电圆板的自振频率进行了计算，并得到了梯度化对板自振频率的影响规律。     

含装甲钢和陶瓷板的钢纤维砼复合靶的抗侵彻实验研究

为考察装甲钢板和陶瓷板的抗侵彻特性,在钢纤维混凝土靶中分别加入两种不同厚度的装甲钢板和陶瓷板振动成型。在57mm轻气炮上进行了小尺寸射弹侵彻钢纤维砼复合靶试验,测量了不同速度的射弹在不同靶中的侵彻深度。研究表明,当装甲钢板的厚度在5mm范围内,射弹速度超过400m/s时,装甲钢板的厚度对侵彻深度的影响不明显。对含陶瓷板的钢纤维砼,当射弹超过一定速度时,射弹弯曲断裂。通过分析给出了射弹残余弹长与射弹的密度、射弹的动态屈服强度和垂直撞击陶瓷板的速度的函数关系,理论结果与实验数据基本一致。     

TORSIONAL VIBRATIONS OF RIGID CIRCULAR PLATE ON TRANSVERSELY ISOTROPIC SATURATED SOIL

An analytical method was presented for the torsional vibrations of a rigid disk resting on transversely isotropic saturated soil. By Hankel transform, the dynamic governing differential equations for transversely isotropic saturated poroelastic medium were solved. Considering the mixed boundary-value conditions, the dual integral equations of torsional vibrations of a rigid circular plate resting on transversely isotropic saturated soil were established. By appropriate transform, the dual integral equations were converted into a Fredholm integral equation of the second kind. Subsequently, the dynamic compliance coefficient, the torsional angular amplitude of the foundation and the contact shear stress were expressed explicitly. Selected examples were presented to analyse the influence of saturated soil's anisotropy on the foundation's vibrations.     

Design optimization of truss-cored sandwiches with homogenization

Lightweight metallic sandwich plates comprising periodic truss cores and solid facesheets are optimally designed against minimum weights. Constitutive models of the truss core are developed using homogenization techniques which, together with effective single-layer sandwich approaches, form the basis of a two-dimensional (2D) single-layer sandwich model. The 2D model is employed to simulate the mechanical behaviors of truss-cored sandwich panels having a variety of core topologies. The types of loading considered include bending, transverse shear and in-plane compression. The validities of the 2D model predictions are checked against direct FE simulations on three-dimensional (3D) truss core sandwich structures. Optimizations using the 2D sandwich model are subsequently performed to determine the minimum weights of truss-cored sandwiches subjected to various failure constraints: overall and local buckling, yielding and facesheet wrinkling. The performances of the optimized truss core sandwiches with 4-rod unit cell and solid truss members and pyramidal unit cell with hollow truss members are compared with benchmark lightweight structures such as honeycomb-cored sandwiches, tetrahedral core sandwiches and hat-stiffened single layer plates.     

Resonant Electromechanical Vibrations of Piezoelectric Plates

The scientific results on the resonant electromechanical vibrations of piezoceramic plates in the form of disks, rings, and polygons obtained over the last 30 years are analyzed, systematized, and generalized. Emphasis is on experimental methods. It is shown that all piezoceramic plates have vibration modes at which deformations are in-phase over the entire volume of the body __________ Translated from Prikladnaya Mekhanika, Vol. 41, No. 7, pp. 3–46, July 2005.     

Stress Concentration in an Orthotropic Plate with a Circular Hole under Dynamic Loading

The paper sets forth a photoelastic method for the determination of the dynamic stress concentration factor near a hole in an orthotropic plate. The stress distribution at the periphery of a circular hole is analyzed. The stress concentration factors for orthotropic and isotropic plates under dynamic and statical loading are compared     

Dynamic deformation of rigid-plastic curvilinear plates of variable thickness

A general solution is obtained for the problem of dynamic bending of an ideal rigid-plastic plate of variable thickness with a simply supported or clamped curvilinear contour under the action of a short-time high-intensity explosive-type load uniformly distributed over the surface. Several mechanisms of plate deformation are demonstrated to exist. For each mechanism, equations of dynamic deformation are derived and conditions of mechanism implementation are analyzed. Examples of numerical solutions are given. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 5, pp. 108–120, September–October, 2007.