国外振动新教材的内容和特点

 简要评介国外1995-2006年间出版的英语教材17种,以及习题指 导书3种. 简述这些教材的内容,分析这些教材在取材和处理方面的特点,对这些教材的分 析表明,振动课程的核心内容是确定性线性离散系统和一维连续系统的自由和受迫振动,所 采用的方法以解析为主,数值和实验为辅. 不同教材对于扩展性内容有各自的选择,包括随 机振动、非线性振动、振动控制、信号处理、实验模态分析、转子动力学等.     

Numerical simulation on micromixer based on synthetic jet

This paper studied a concept of micromixer with a synthetic jet placed at the bottom of a rectangular channel. Due to periodic ejections from and suctions into the channel, the fluids are mixed effectively. To study the effects of the inlet velocity, the jet intensity and frequency, and the jet location on the mixing efficiency, 3-D numerical simulations of the micromixer have been carried out. It has been found that when the jet intensity and the frequency are fixed, the mixing efficiency increases when Re 〈 50, and decreases when Re 〉 50 with the best mixing efficiency achieved at Re = 50. When the ratio of the jet velocity magnitude to the inlet velocity is taken as 10 and the jet frequency is 100 Hz, the mixing index reaches the highest value. It has also been found that to get better mixing efficiency, the orifice of the synthetic jet should be asymmetrically located away from the channel＇s centerline.     

实现动基座上动调陀螺仪启停锁定

本文在对动基座上ＤＴＧ启停运动进行分析的基础上，介绍了实现动基座锁定的思想与方法，并具体实现了由单片机完成的动基座上动调陀螺仪的启停锁定。     

喷管结构形式对爆震发动机性能影响分析

为了研究喷管结构形式对爆震发动机性能的影响,本文以氢气和氧气混合物为例,对不同喷管结构形式的爆震发动机工作过程进行了数值模拟。模拟结果表明:采用收敛型喷管可以增加爆震管内压力,但会造成喷管内的负推力;采用扩张型喷管会使得喷管内的压力迅速下降,但可以提供正推力;采用收扩型喷管时喷管的冲量一般较低,但爆震管的冲量会有提升,可以显著提高爆震发动机性能。     

关于“非线性Duffing方程的高精度近代解”一文的商榷

本认为「１」中的参数迭代法实际上就是一种加权殖量法,而不是一种新的方法,通过选取不同的配置点,可得到精度更高的近似解。     

积分背景网格对自适应EFG法拓扑优化的影响研究

采用应力能量范数作为误差指标,探讨了EFG法中积分背景网格对计算精度的影响,得到了合理划分背景网格的建议;建立了以节点密度为设计变量、以最小化柔度为优化日标的拓扑优化模型。采用以节点密度值为加点判据的自适应规则加点方案,开展了连续体结构的拓扑优化研究,该加点方案能有效地减少设计变量的个数,探讨了背景网格对拓扑优化结果的影响。算例结果表明,采用合适的背景网格不仅能进一步减少设计变量的个数,而且能够改善拓扑优化结果的光滑性,使计算效率和精度得到提高。     

Experimental study on wind loading on a complicated group-tower

This paper studied how wind pressures and forces affect rigid sectional models of a complicated group-tower using experimental wind tunnel tests. The group-tower was composed of five separate sub-towers with different diameters and heights. The basic characteristics of the mean and fluctuating wind pressure distributions on typical parts of the sub-towers were analyzed along the heights of each sub-tower, and their distribution trends are discussed. Also, the mean base shear and moment coefficients and their characteristics are presented. The wind pressure and wind force results showed that because the group-tower structure consisted of five separate lofty towers, the mutual aerodynamic interferences were serious; thus, the mean and fluctuating wind pressure, wind force distributions and the mean base shear and moment coefficients were quite complicated.     

Analyses on structural damage identification based on combined parameters

IntroductionServiceloads,environmentalandaccidentalactionsmaycausedamagetostructures .Whenthestructuraldamageissmalloritisintheinteriorofthestructure,itsdetectioncannotbedonevisually.Inspectionofexistingbuildingsandbridgesaftercatastrophicevents,suchasearthquakesandhurricanes,aswellasundernormaloperatingconditions ,isoftentimeconsumingandcostlybecausecriticalmembersandconnectionsareconcealedundercladdingandotherarchitecturaldecorations.Formanyimportantstructures,suchashospitals,firestations,mi…     

引入特征粗糙度参数的Stribeck曲线试验研究

为探讨表面粗糙度对Stribeck曲线的影响,对不同初始表面的不锈钢销试件与45#钢盘试件在浸油润滑条件下进行摩擦磨损试验,研究摩擦系数的变化规律.结果表明:摩擦副表面越粗糙,对应Stribeck曲线上混合润滑区域面积越大,曲线斜率越小,使得不同表面粗糙度下的摩擦系数试验模型不具有唯一性.因此,将由分形参数导出的能客观表征粗糙表面的"特征粗糙度"参数引入Stribeck动压参数,从而提出新的动压参数.在新的动压参数下,具有不同表面粗糙度摩擦副的Stribeck曲线具有较好的一致性,继而可建立与粗糙度无关的摩擦系数试验模型.     

基于双光纤光栅的冰压力传感器研究

冰压力是高纬度地区结构的重要荷载,然而传统的基于电阻应变计开发的冰压力传感装置在稳定性与耐久性上遇到难以跨越的难题。光纤光栅是目前在智能材料系统与结构健康监测研究与应用最为广泛的敏感材料之一,具有分布式绝对测量、抗腐蚀能力强等优点。本文基于双光纤光栅应变测量原理,考虑冰压力测试装置的环境条件,设计开发出冰压力传感装置,详细推导和试验验证了该装置的传感特性,并将试验与理论结果进行了对比。研究结果表明该装置具有温度自补偿、测量值与荷载作用点无关、线性度和重复性好、精度较高等优点,具有良好的应用前景。     

Insights on vortex-induced,traveling waves on long risers

This paper is based on portions of a keynote presentation, which explored the boundaries of what is understood about the vibration behavior of long cylinders excited by vortex shedding. The source of data is a recent field experiment on a long flexible cylinder, densely instrumented with fiber optic strain gauges. The paper emphasis is on previously unknown or unexplained phenomena and in some cases offers provocative insights as opposed to conclusive proofs. Three particular topics are covered: (i) the occurrence of peak strain and fatigue damage rates at unexpected locations, (ii) the dominance of traveling wave rather than standing wave response, and (iii) the appearance of stable cylinder trajectories, such as figure eights and crescents in pure traveling wave regions. Potential explanations are offered and areas for promising additional research are proposed.     

基于弹性地基梁计算的Daubechies条件小波Ritz法研究

在现有的Daubechies小波Ritz法中,为方便边界条件的引入,借助于位移转换矩阵将Daubechies小波待定系数转换为节点位移。但该方法会降低计算精度,并且计算结果是多个离散的单点位移,不利于进一步解得弯矩、剪力、荷载集度。为寻求更为高效精确的弹性地基梁计算方法,对现有的Daubechies小波Ritz法进行改进,以避免位移转换矩阵的出现,从而提高了计算精度。结合广义变分原理,采用Lagrange乘子法,将边界条件作为附加条件引入自然变分条件下的泛函表达式,构造新的修正泛函。以该修正泛函的驻值条件建立求解矩阵方程组,进而解得未知场函数。此法称为Daubechies条件小波Ritz法。该法计算结果直接是小波基函数待定系数,单元内部任意点的位移均可通过小波基函数得到,也可进一步解得弯矩、剪力、荷载集度,因此比原有方法更为有效。最后,采用受均布荷载的两端铰支弹性地基梁算例,将Daubechies条件小波Ritz法计算结果与基于弹性地基梁理论的解析解进行比较,挠度值（保留小数点后6位小数）与解析解完全一致,弯矩值的相对误差为0.03%,说明Daubechies条件小波Ritz法具有较高计算精度。     

基于微裂纹界面摩擦生热的点火模型

开展了基于微裂纹界面摩擦生热的细观点火模型研究,采用有限元方法对包含化学反应放热和摩擦生热的热传递方程进行了离散求解,计算模型中考虑了炸药颗粒熔化对升温过程的影响。着重分析了点火模型中主要参数(热点尺度、应变率和界面压力)对炸药点火的影响规律。数值研究表明,随着热点尺度的增大,热点的温度上升越快,越容易发生点火;应变率越大或者界面压力越高,热量积累越快,炸药越容易点火。     

基于反应谱值分析的爆破震动破坏评估研究

采用反应谱方法研究了爆破震动信号的振动速度和频率特征,提出了采用反应谱曲线积分值来评估爆破震动破坏效应。通过对289组爆破地震波数据的统计表明,在反应谱曲线的积分值小于5时,爆破地震动不会对所研究的普通民房结构物产生震动破坏效应。     

Experimental study on the effect of unsteadiness on boundary layer development on a linear turbine cascade

 The results from an experimental investigation of unsteady boundary layer behavior on a linear turbine cascade are presented in this paper. To perform a detailed study on unsteady cascade aerodynamics and heat transfer, a new large-scale, high-subsonic research facility for simulating the periodic unsteady flow has been developed. It is capable of sequentially generating up to four different unsteady inlet flow conditions that lead to four different passing frequencies, wake structures, and freestream turbulence intensities. For a given Reynolds number, two different unsteady wake formations are utilized. Detailed unsteady boundary layer velocity. turbulence intensity, and pressure measurements are performed along the suction and pressure surfaces of one blade. The results display the transition and development of the boundary layer, ensemble-averaged velocity, and turbulence intensity. Received: 23 September 1996/Accepted: 19 February 1997     

基于动态光弹性方法的冲击载荷作用下自由边界主应力研究

当物体在冲击载荷作用下,物体内部会产生应力波,研究应力波的传播过程及规律对研究物体受冲击载荷作用具有重大的意义.应力波在物体内传播时,在自由边界处产生的主应力状态对于理论求解和计算有着重要意义.采用动态光弹性方法,结合新型动光弹系统及相关实验设备采集物体在冲击载荷作用下的等倾线和等差线条纹图,通过分析等倾线的条纹,得出等倾线与自由边界相交所成角度不为0°或909,得出在物体自由边界处两个主应力均存在且不为零的结论.针对上述结果,采用电测方法进行验证,两试验结果相符合,方案可行且准确.     

基于FPGA的数字闭环光纤陀螺研究

着重对全数字闭环光纤陀螺的信号处理方法进行了详细的分析，指出了闭环控制系数A和K对闭环控制的影响，同时研究了基于FPGA的数字闭环控制系统实现方法以及利用VHDL语言进行FPGA软件设计的优点，并给出了基于FPGA设计的光纤陀螺的实验结果。     

叶片榫头接触应力的求解研究

接触应力分析是不易检测、难于计算，但对于设计又是非常重要的一个难题。文中将实验检测技术与数值计算方法相结合，求解飞机发动机叶片榫头上的接触应力分布。基本思路是：1)用实验检测技术求出叶片榫头接触面上若干点的应力或应变值；2)通过给叶片根部接触面施加一定的约束条件，用数值计算法计算发动机叶片在离心力载荷作用下的全场应力分布，并进一步求出接触面上的接触应力分布；3)解除接触面上的约束条件，代之以计算获得的接触载荷，计算叶片在离心力载荷以及接触载荷共同作用下的全场应力或应变分布，并比较计算结果与实验结果；4)修改约束条件或计算模型，重复上述操作，直至计算结果与实验结果比较一致。研究表明，本文提出的方法能够较准确地给出接触面的载荷分布，判断约束条件的合理性具有简单、易行的特点。由于接触应力的复杂性，本问题还有深入研究的必要。     

基于流形覆盖思想的无网格方法的研究

本语言基于流形思想,利用有限覆盖,单位分解等概念,引入建立在覆盖上的覆盖函数和具有紧支撑特性的单位分解函数,建立场逼近的近似表达,由弱形式的Galerkin变分得到数值分析模型,结合边界条件用于边值问题的求解,由此建立了一类新的无网格数值方法,论文采用这种方法分析了平面弹性问题,分析了体积闭锁现象,h、p型收敛性等,提出了一种选择覆盖大小的方案,且对狭长城采用了椭圆覆盖形式,取得了比较好的效果。     

Study on multihole pressure probe system based on LabVIEW

Experimental Techniques - The multihole pressure probes are widely used to determine flow velocity vectors and pressures in the fluid machinery fields due to their robustness, convenience, and...