非同轴质量偏心结构平扭耦合风振响应的研究

为了详细地对比分析结构各质量中心不在同一轴线上的偏心对结构风致平移一扭转耦合响应的影响,提出了分析非同轴质量偏心结构风振响应的基本框架.首先,建立了两层六自由度非同轴质量偏心结构的动力方程,并将其推广至N层3N自由度的非同轴质量偏心结构动力方程;然后,基于高频力平衡(HFFB)技术和多点同步扫描(MPSS)技术获得的顺风向、横风向以及扭转风荷载功率谱,考虑横风向和扭转风荷载之间的相关性以及模态之间的耦合,在频域内进行非同轴质量偏心结构的风致平移一扭转耦合响应分析.一栋120 m高的矩形钢结构建筑,被简化为15个自由度的三维分析模型作为数值研究案例.通过设置不同位置的结构质量偏心,分析研究了单轴质量偏心、非同轴质量偏心对矩形建筑结构平移一扭转风振的影响.     

Vibrations of stretched damped beams under non-ideal boundary conditions

A simply supported damped Euler-Bernoulli beam with immovable end conditions are considered. The concept of non-ideal boundary conditions is applied to the beam problem. In accordance, the boundaries are assumed to allow small deflections and moments. Approximate analytical solution of the problem is found using the method of multiple scales, a perturbation technique.     

Characterising heave,pitch, and roll motion of road vehicles with principal component and frequency analysis

For the great majority of transport vehicles, the magnitude of the heave vibration is generally more severe than pitch and roll. Consequently, the measurement, analysis, and simulation of the vehicle vibrations have been focused on vertical vibration. Despite this, it is now being increasingly recognised that the combination of heave, pitch, and roll vibratory motion can induce more severe damage to shipments than vertical vibration alone. Although the pitch and roll motion of road vehicles can now be readily measured, there is little information on how to analyse the data to produce meaningful statistical relationships between the three variables. This paper builds upon previous work that showed that there is some correlation between pitch, roll, and heave motion and that these relationships are dependent on vehicle geometry, including payload mass, centre of mass, vehicle roll centre, and moments of inertia as well as vehicle speed and the road surface. In this paper, data from a range of quasi‐controlled experiments, which involved driving vehicles at constant‐speed on selected roads, were analysed using principal component analysis as well as frequency domain analysis to reveal the relationship between heave, pitch, and roll motion. This was undertaken for a variety of vehicle speeds and routes in order to establish if they influence pitch and roll response. Results are presented in the form of distribution functions, statistical coefficients, and frequency response functions, all of which are useful for helping to define parameters for the simulation of complete, three‐axis vibrations using multi‐axis vibration test systems.     

曲线轨道空间振动响应特性研究

曲线轨道空间振动存在平面内振动、平面外弯扭耦合振动,通过建立曲线轨道空间振动频域解析模型,对曲线轨道动力响应特性进行研究。将曲线轨道视为圆形结构的一部分,利用圆形结构周期性的特性,在一个基本元之内求解曲线轨道的动力响应。通过引入移动谐振荷载作用下轨梁动力响应的频域数学模态,得出曲线轨道轨梁频域响应的级数表达。在频域内采用数学模态叠加法表示曲线轨梁的纵向、横向、垂向及扭转振动,进而求解得到基本元内轨梁的频域动力响应。经计算表明,文中提出的频域解析模型能够得到精确的曲线轨道频域响应。通过分析速度、半径、超高等因素,得到以下结论：准静态激励下单个移动轴荷载对曲线轨梁的垂向、横向及扭转振动的影响范围在作用点两侧±5m左右;轴荷载移动速度对曲线轨梁横向位移、扭转变形具有显著的影响,随着速度的增加,曲线轨道由过超高状态逐渐过渡到理想超高状态,最终进入欠超高状态,轨梁横向位移、扭转变形方向发生改变,响应幅值先减小后增加;半径、超高和速度对曲线轨梁垂向位移、横向位移及扭转变形影响较大;随着半径的增加,速度对位移响应的影响程度降低;准静态移动轴荷载列作用下曲线轨梁垂向、横向及扭转频域响应主要集中在40Hz以内的频段;横向振动、扭转振动频谱分布范围较宽。     

ON THE SPATIAL AND TEMPORAL BEHAVIOR IN LINEAR THERMOELASTICITY OF MATERIALS WITH VOIDS

The present article studies the spatial and temporal behavior of the solutions to the initial boundary value problems associated with the linear theory of thermoelastic materials with voids. The spatial behavior is described by spatial estimates of Saint-Venant type (for bounded bodies) and Phragmén-Lindelöf type (for unbounded bodies) with time-dependent and time-independent rates. Some appropriate time-weighted integral measures are used. The temporal behavior is studied using the Cesaro means of various parts of the total energy. The relations describing the asymptotic behavior of the Cesaro means are established.     

Geometrically Non-Linear Rapid Heating of Temperature-Dependent Circular FGM Plates

Based on the uncoupled thermoelasticity assumptions, axisymmetric thermally induced vibrations of a circular plate made of functionally graded materials (FGMs) are analyzed. Each thermomechanical property of the circular plate is assumed to be functions of temperature and thickness coordinate. Solution of the transient one-dimensional heat conduction equation with the arbitrary type of time-dependent boundary conditions is carried out employing the central finite difference method combined with the Crank–Nicolson time marching scheme. Afterwards, with the establishment of the associated Hamilton's principle and the accountancy of the von Kármán type of geometrical non-linearity, the motion equations are obtained with the aid of the conventional multi-term Ritz method. The solution of highly coupled non-linear motion equations is obtained utilizing a hybrid iterative Newton–Raphson–Newmark scheme. After validating the developed computer code, some parametric studies are accomplished to show the influences of various involved parameters. It is shown that temperature dependency, geometrical non-linearity, plate thickness, power law index, and the type of thermal in-plane and out-of-plane mechanical boundary conditions, all affect the temporal evolution of plate characteristics.     

Vibration of axisymmetric composite piezoelectric shells coupled with internal fluid

This paper presents the theoretical and finite element formulations of piezoelectric composite shells of revolution filled with compressible fluid. The originality of this work lies (i) in the development of a variational formulation for the fully coupled fluid/piezoelectric structure system, and (ii) in the finite element implementation of an inexpensive and accurate axisymmetric adaptive laminated conical shell element. Various modal results are presented in order to validate and illustrate the efficiency of the proposed fluid–structure finite element formulation. Copyright © 2007 John Wiley & Sons, Ltd.     

贵金属复合材料复合轧制中轧机震动的分析

针对固相复合轧制以贱金属为基的贵金属复合材料时，轧机产生的机械震动及复合材料的产品质量问题，从引起轧制压力产生波动等因素，分析了轧机产生震动的原因及产品质量问题，提出了解决此问题的一些设想。     

Average function and variance function for diagnostic purposes

According to our experience, the variance function as the standard deviation of the average function is well suited as a diagnostic tool to monitor mechanical movements. Nonlinear effects during the movement can be detected using touch-induced or rub-induced vibrations to obtain direct information about loads to be expected. An application on a gearbox demonstrates the efficiency.     

Non-visual interaction with graphs assisted with directional-predictive sounds and vibrations: a comparative study

Blind and visually impaired students need special educational and developmental tools to allow them to interact with graphic entities on PDA and desktop platforms. In previous research, stylus movements regarding the hidden graph were sonified with three directional-predictive sound (DPS) signals, taking into account an exploration behavior and the concept of the capture radius. The results indicated that the scanpaths were by 24–40% shorter in length and task completion times decreased by 20–25%. The goal of the study presented in this paper was to measure and compare the subjective performance recorded with directional-predictive vibrations (DPV) regarding the subjective performance achieved when the hidden graphic images were explored with DPS. The study also aimed to find out which kind of feedback cues would require less cognitive efforts in interpreting their meaning. The prototype of vibro-tactile pen with embedded vibration motor was used to produce DPV instead of sounds. The performance of eight blindfolded subjects was investigated in terms of the number of both feedbacks used and the time spent to complete non-visual inspection of the hidden graphs. There was a statistically significant difference between the average number of DPS and vibrations and task completion time taken by the players to discover the features of hidden graphs being explored with different capture radius. The experimental findings confirmed the beneficial use of DPS signals in the task when cross-modal coordination should benefit the user in the absence of visual information when compared with DPV patterns.