Update of corrected stiffness and mass matrices based on measured dynamic modal data

The physical parameters obtained from modal tests do not satisfy the dynamic constraints of eigenvalue function and orthogonality requirements due to modeling and measurement errors. The purpose of this study is to present the analytical equations on the updated stiffness and mass matrices in the satisfaction of such dynamic constraints. Minimizing the cost functions of the difference between analytical and desired physical parameter matrices, the corrected parameter matrices are straightforwardly derived by utilizing the Moore–Penrose inverse without using any multipliers. The cost functions given by a few researchers are utilized. From the comparison of the existing analytical results and the proposed equations, the validity of the proposed methods is evaluated in an application.     

受限一维无自旋费米子系统的性质研究

本文借助于一维自旋1/2-XXZ模型的Bethe-ansatz精确解, 利用局域密度近似(LDA), 讨论了谐振势中一维无自旋费米子的密度分布, 得出了ρ-u相图(这里的ρ为无量纲的粒子数密度 变量u为相互作用强度)对相图的分析表明, 随着原子密度和近邻相互作用的变化, 系统出现五个不同的混合量子相通过对热力学硬度S_ρ的计算, 发现其可作为体系的序参量, 其奇异点可用以度量受限体系中量子相变的发生     

Reorientation dynamics in liquid alcohols from Raman spectroscopy

Polarized Raman spectroscopy has been employed to study the reorientational, or more specifically the translational relaxation dynamics, of alcohol molecules in pure liquids and aqueous solutions. It is found from the spectral width measurements that alcohol molecules in pure liquids have typically translational relaxation times on the order of picoseconds, following the order methanol < ethanol < i‐propanol < n‐propanol. Temperature‐dependent measurements show that hydrogen‐bonding (HB) and hydrophobic interactions control the translational motion. The hydrophobic interaction reduces the relaxation time more apparently in view of the  CH₃ group than the skeleton motion. For alcohol–water mixtures, the increase of water concentration generally slows down the relaxation process in a non‐monotonic behavior. However, the trend stops at a certain point and the motion of alcohol molecules becomes faster when the alcohol concentration further drops. Different mechanisms have been proposed to interpret these observations, which might be helpful to gain deeper insight into the HB networks of alcohols with water. Our study strongly illustrates that Raman spectroscopy can be applied to the study of fast translational motion of molecules in HB systems. Copyright © 2011 John Wiley & Sons, Ltd.     

Harmonic generation of an obliquely incident ultrasonic wave in solid-solid contact interfaces

The conventional acoustic nonlinear technique to evaluate the contact acoustic nonlinearity (CAN) at solid-solid contact interfaces (e.g., closed cracks), which uses the through-transmission of normally incident bulk waves, is limited in that access to both the inner and outer surfaces of structures for attaching pulsing and receiving transducers is difficult. The angle beam incidence and reflection technique, where both the pulsing and receiving transducers are located on the same side of the target, may allow the above problem to be overcome. However, in the angle incidence technique, mode-conversion at the contact interfaces as well as the normal and tangential interface stiffness should be taken into account. Based on the linear and nonlinear contact stiffness, we propose a theoretical model for the reflection of an ultrasonic wave angularly incident on contact interfaces. In addition, the magnitude of the CAN-induced second harmonic wave in the reflected ultrasonic wave is predicted. Experimental results obtained for the contact interfaces of A16061-T6 alloy specimens at various loading pressures showed good agreement with theoretical predictions. Such agreement proves the validity of the suggested oblique incidence model.     

纤维增强树脂基复合材料的疲劳剩余刚度研究进展

回顾了过去二十年来公开发表的复合材料刚度退化的主要模型,对这些模型做了分类和讨论.按照模型的理论基础及研究方法将它们分为了理论模型、半经验模型和经验模型三类.理论模型是指那些完全依赖于力学分析而得到的模型,这类模型建立了材料的微观损伤机理与宏观刚度退化之间的关系.经验模型通常不需要过多的力学分析,仅对大量实验数据进行经验性拟合,一般具有简单易用的形式.半经验模型是理论与经验模型的结合------在力学分析基础上的经验处理.      

带竖缝钢筋混凝土剪力墙的抗侧刚度分析

为降低大震下结构的刚度，以减轻结构物的地层灾害，设计了一种带竖缝的钢筋混凝土剪力墙构件．根据它在水平力作用下的受力特点，建立了相应的刚度计算模型和计算公式，并与试验结果进行了对比，二吻合较好．     

饱和土中端承桩纵向振动特性研究

基于饱和多孔介质理论研究了三维轴对称条件下端承桩在饱和土中的纵向耦合振动. 首先通 过引入势函数对Biot动力固结方程解耦，采用算子分解方法及分离变量法求得饱和土层振动 解，进而利用桩土完全耦合条件得到桩土系统定解. 然后对桩顶的频率和时域响应进行参数 研究，结果表明，桩的长径比和桩土模量比对桩顶动力响应有较大影响，而渗透力对其影响 较小. 最后将幅频及时域反射波理论拟合结果与桩基实测结果加以对比，结果表明理论曲线 与实测曲线规律一致.     

三维编织复合材料弯曲性能分析

根据三维四向编织复合材料的结构特点,提出了用刚度合成法来预测复合材料的弯曲模量,并对三维编织T300／QY9512复合材料的弯曲模量进行了预测,分析结果表明,由于试件的表面单胞和内部单胞的结构不同,得到试件的弯曲模量略高于拉伸模量,该结果与试验值相符,另外,当试件尺寸较大、内部单胞数较多时,可以不考虑表面单胞和内部单胞性能差异的影响,而认为三维编织复合材料的弯曲模量只与内部单胞的性能有关,这对工程分析和试件制作具有指导意义。     

基于梁连续抗弯刚度与小波变换的结构损伤识别方法研究

为了解决基于小波变换系数难以识别结构边缘损伤的问题,以及试验中损伤对周边的影响导致小波系数难以精确定位损伤位置的问题,提出了基于梁连续抗弯刚度与小波变换的结构损伤位置识别方法。该方法结合梁结构连续抗弯刚度与小波系数边缘的特点,在未知无损梁结构振动参数的情况下,能有效识别出梁结构边缘损伤且能准确定位试验中梁结构的损伤,通过损伤梁的数值模拟与试验证明了该方法的正确性。