Dynamic characteristic analysis of a 3-D semi-submerged body as a fluid-structure interaction system

An Arnoldi‘s method with new iteration pattern, which was designed for solving a large unsymmetric eigenvalue problem introduced by displacement-pressure FE (Finite Element) pattern of a fluid-structure interaction system, was adopted here to get the dynamic characteristics of the semi-submerged body. The new iteration pattern could be used efficiently to obtain the Arnoldi‘s vectors in the shift-frequency technique, which was used for the zero-frequency problem. Numerical example showed that the fluid-structure interaction is one of the important factors to the dynamic characteristics of large semi-submerged thin-walled structures.     

ANALYSIS ON ACOUSTICAL SCATTERING BY A CRACKED ELASTIC STRUCTURE

The acoustical scattering by a cracked elastic structure is studied. The mixed method of boundary element and fractal finite element is adopted to solve the cracked structure-acoustic coupling problem. The fractal two-level finite element method is employed for the cracked structure, which can reduce the degree of freedoms (DOFs) greatly, and the boundary element method is used for the exterior acoustic field which can automatically satisfy Sommerfeld‘s radiation condition. Numerical examples show that the resonance frequency is lower with the crack‘s depth increase, and that the effect on the acoustical field by the crack is particularly pronounced in the vicinity of the crack tip. This mixed method of boundary element and finite element is effective in solving the scattering problem by a cracked structure.     

飞机－道面－土基动力耦合系统有限元分析

本文将飞机－道面－土基作为一个相互作用的动力系统，对飞机滑行情况下，弹性半空间地基上刚性道面板的动响应，采用有限元法进行了计算分析。结果表明，本文计算结果与现场实测值吻合很好。由于考虑了飞机和道面之间的耦合作用，避免了实测飞机对道面作用荷载的繁琐工作，因此本文方法具有明显的实用意义。     

The movement and thermal history of an aluminium particle in a RF plasma generator

In previous studies on plasma-particle interaction, as far as we know, the rf plasma flow and temperature fields are all simulated by the non-self-consistent one-dimensional electromagnetic (1-D EM) field model. In the present paper, the complete self-consistent two-dimensional electromagnetic (2-D EM) field model incorporating the axial Lorentz force component, which is neglected in the 1-D model, is firstly adopted to calculate the aluminium particle trajectory and thermal history in atmospheric rf Ar plasma with the particle evaporation effect included. The crucial effect of reverse flow within the coil region on the particle trajectory is discovered and the results show that the 2-D EM field model must be adopted instead of the 1-D model when the plasma-particle interaction is studied. The effect of carrier gas flux on the particle movement and heating are also studied, resulting in some useful conclusions for both plasma theory and application. recommended by Prof. Wu Chengkang The project supported by the National Natural Science Foundation of China     

水库地区的水岩作用及其地质环境影响

本文综述了水库地区水环境系统的变化及水岩作用类型和机制, 在此基础上讨论了水库区地质环境的变化和环境灾害的发生, 提出以水环境变化和水岩作用为中心的水库地质环境评价和灾害预测的研究方向。     

Nonlinear Dynamics of Two-Degrees-of-Freedom Fluid Conveying Elasto-Visco-Plastic Model System

The local and global nonlinear dynamics of a two-degrees-of-freedom model system conveying fluid is studied. The undeflected model consistsof an inverted T formed by three rigid rods, with the tips of the twohorizontal rods resting on the viscous foundation. The foundationexhibits a visco-elasto-plastic response, including the Bauschingereffect. The vertical rigid rod of an annular cross-section is subjectedto a conservative (dead) force. Also, it conveys fluid having bothstatic and pulsation components. First, the method of multiple scales isused for the analysis of the local dynamics of the system withvisco-elastic response. Attention is focused on modal interactionphenomena in weak excitation at primary resonance and on hardsub-harmonic excitation. Two different asymptotic expansions areutilised to get a structural response for typical ranges of excitationparameters. Numerical integration of the governing equations is thenperformed to validate the results of asymptotic analysis in each case. Afull global nonlinear dynamics analysis of the visco-elasto-plasticsystem is performed. The role of plastic deformations in thedestabilisation of the system is discussed. Large-amplitude nonlinearoscillations of the visco-elasto-plastic system are studied, includingthe influence of material hardening and of static and periodiccomponents of pulsating fluid. Chaotic regimes of motion with andwithout plastic effects are considered. The results of the analysis maybe used in devices composed of a rather short tube connected to a notcompletely fixed foundation resting on the soil exhibitingelasto-plastic behaviour.     

Elastic-plastic contact model for rough surfaces based on plastic asperity concept

A mathematical formulation for the contact of rough surfaces is presented. The derivation of the contact model is facilitated through the definition of plastic asperities that are assumed to be embedded at a critical depth within the actual surface asperities. The surface asperities are assumed to deform elastically whereas the plastic asperities experience only plastic deformation. The deformation of plastic asperities is made to obey the law of conservation of volume. It is believed that the proposed model is advantageous since (a) it provides a more accurate account of elastic-plastic behavior of surfaces in contact and (b) it is applicable to model formulations that involve asperity shoulder-to-shoulder contact. Comparison of numerical results for estimating true contact area and contact force using the proposed model and the earlier methods suggest that the proposed approach provides a more realistic prediction of elastic-plastic contact behavior.     

软铁磁薄板磁弹性屈曲的理论模型

铁磁弹性薄板的磁弹性屈曲问题一直作为电磁——弹性力学相互作用的一个基本模型进行研究，而作用在其磁介质上的磁力计算则是定量理论预测准确与否的关键．到目前为止，文献上已有的理论模型对悬臂铁磁梁式悬臂板在横向磁场中磁弹性屈曲的理论预测值始终高于实验值，有的甚至相差１００％左右．本文基于电磁力计算的微观安培电流模型，严格给出了软铁磁薄板等效横向磁力的宏观计算表达式．在此基础上，建立了电磁——力学相互耦合作用的非线性理论模型．该模型能描述铁磁薄板结构在非均匀横向磁场环境中的磁弹性失稳（或屈曲）．其定量分析采用了有限元法和有限差分法相结合．数值结果显示：本模型给出的磁弹性屈曲的临界磁场值与实验值符合良好．与此同时，文中还对文献中认为较成功的Ｍｏｏｎ－Ｐａｏ模型的基本假设进行了分析．定量结果发现：Ｍｏｏｎ－Ｐａｏ理论模型的基本假设仅在梁式板的长厚比Ｌ／ｈ比较大时（约在２００左右），是可以接受的，而当Ｌ／ｈ较小时，该假设将导致理论值与实验值的较大误差．Ｌ／ｈ比值越小，理论值与实验值的误差越大     

心脏与血管的相互影响

心脏与血管的相互影响早就引起生理学家们的兴趣，但其在临床医学上的广泛应用则是近几年的事．这主要归功于两大生物力学成就，一是应甩泵功能曲线和时变弹性元描述心脏功能，另一是应用输入阻抗来描述血管功能．本文系统地总结和评述了２０多年来国际上关于心脏与血管相互影响的研究发展概况．