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Search Results: 1 - 10 of 34429 matches for " Zhou Youhe "
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压电材料反平面III型裂纹电塑性区的分析
薛存,Youhe,Zhou,雍华东
固体力学学报 , 2012,
Abstract: 本文对反平面III型裂纹电塑性区进行了分析。采用条带模型得到了电塑性区大小的表达式。对于电塑性区的边界条件采用了两种处理方式,一是采用机械位移连续性边界条件,另一种是假设电塑性区的切应力保持为常数的假设。其中后一种处理方式消除了电场和应力在裂纹尖端的奇异性,与实际情况相符合。两种处理方式得到了相同的电塑性区的大小的表达式,并根据两种处理方式计算了能量释放率。类比Irwin的应力松弛模型,本文采用电位移松弛模型同样得到了电塑性区的大小。将条带模型得到的结果与电位移松弛模型得到的结果进行比较发现,在小范围塑性变形条件下,两种方法所得的结果比较接近,从而说明这两种方法的有效性,得到了比较满意的结果。
粘弹性夹芯层合旋转圆板的气动弹性动力稳定性分析
李龙飞,王省哲,Youhe,Zhou
固体力学学报 , 2013,
Abstract: 基于哈密尔顿原理,考虑作用于圆板上的空气动力载荷以及粘弹性复模量本构模型,本文建立了含有粘弹性夹芯层的旋转圆板的空气动力学模型,并给出了相应的稳定性的控制方程及边界条件。运用Galerkin方法,文中数值求解并给出了夹芯层合旋转圆板的动力学基本特征,以及结构几何参数、材料参数对于其前、后行波振动频率、阻尼和动力稳定性的影响。结果表明通过优化合理选取粘弹性夹芯层合旋转圆板的几何参数和材料参数,可提高旋转圆板的临界转速和颤振速度,从而增强其稳定性。
电活性聚合物圆柱壳静态与动态电压下的响应及稳定性
何新振,雍华东,Youhe,Zhou
固体力学学报 , 2012,
Abstract: 在电活性聚合物圆柱壳内外表面施加电压,圆柱壳会变薄并且伸长,因此相同的电压会在圆柱壳内产生更大的电场。这个正反馈可能使圆柱壳厚度不断变薄,最终导致其失稳破坏。本文研究了电活性聚合物圆柱壳在静态和周期电压作用下的响应及稳定性问题。采用neo-Hookean材料模型得到描述圆柱壳表面运动的非线性常微分方程。给出了圆柱壳在不同厚度和边界条件下外加电压随圆柱壳变形的变化曲线,结果表明存在一个临界电压,当外加电压大于这一临界值时,圆柱壳将被破坏。同时,也讨论了厚度和边界条件对临界电压的影响。圆柱壳在正弦周期电压作用下,其运动随时间的变化是周期性的或拟周期性的非线性振动。给出了圆柱壳振动固有频率的计算结果,采用打靶法得到圆柱壳振动的周期解,并且用数值法研究了周期解的稳定性。采用数值仿真得到圆柱壳振动振幅随外加动态电压激励频率的变化曲线,结果表明圆柱壳会发生多频共振,共振时圆柱壳振幅发生跳跃,导致圆柱壳失稳破坏。最后给出共振点临近点的振动曲线和相图,并对其振动特性进行讨论。
Identification of damage in rectangular plates based on neural network technique with sub-regions
矩形板结构损伤的分区域神经网络识别方法

Wang Dengming Zhou Youhe,
王等明
,周又和

力学学报 , 2005,
Abstract: This paper presents an identification approach based on neural network method with sub-regions to identify damages in a rectangular plate using the LM optimized algorithm. The numerical results of simulations for the cantilever plate with some damages show that this approach is better than that from the conventional method with single network. Since this method realizes the synchronous output of position and intensity of damages in the structure, this approach does not need many sub-networks appeared in a conventional hierarchical identification method.
EFFECT OF CHANGING TEMPERATURE ON ACTIVE CONTROL OF VIBRATING FREQUENCY OF PIEZOELECTRIC CIRCULAR PLATES 1)
变温环境对压电圆板频率主动控制的影响

Zhou Youhe,Zheng Xiaojing,
周又和
,郑晓静

力学学报 , 1998,
Abstract: This paper is to quantitatively study the characteristics of active control of vibrating frequency of a piezothermoelectric circular plate with nonlinear deformation, and the effect of changing temperature of environment and the large amplitude of vibration on the characteristics.The results show that the changing temperature of environment of the plate has influence on the controlled frequency of vibration of the plate by means of piezoelectric voltage. When the controlled voltage is high enough, the effect of vibrating amplitude on the characteristic of voltage-vibrating frequency is not notable.
A THEORETICAL MODEL OF MAGNETOELASTIC BUCKLING FOR SOFT FERROMAGNETIC THIN PLATES
软铁磁薄板磁弹性屈曲的理论模型

Zhou Youhe,Zheng Xiaojing,
周又和
,郑晓静

力学学报 , 1996,
Abstract: As an essential model of magnetoelastic interaction between magnetic field and mechanical deformation, the study on magnetoelastic buckling phenomenon of soft ferromagnetic plates in a magnetic environment has been conducted. One of the key steps for the theoretical prediction of the critical magnetic field is how to formulate magnetic force exerted on the magnetized medium. Till today, the theoretical predictions, from all theoretical models in publications, to the magnetoelastic buckling of ferromagnetic cantilevered beam plate in transverse magnetic field are higher than their experimental data.Sometimes, the discrepancy between them is as high as 100%.In this paper, the macroscopic formulation of the magnetic forces is strictly obtained from the microscopic Amperion current model. After that, a new theoretical model is established to describe the magnetoelastic buckling phenomenon of ferromagnetic thin plates with geometrically nonlinear deformation in a nonuniform transverse magnetic field. The numerical method for quantitative analysis is employed by combining the finite elemental method for magnetic fields and the finite difference method for deformation of plates. The numerical results obtained from this new theoretical model show that the theoretical predictions of critical values of the buckling magnetic field for the ferromagnetic cantilevered beam plate are in excellent agreement with their experimental data. By the way, the region of applicability to the Moon Pao's model, or the couple model, is checked by quantitative results. It is the same as the prerequisite conditions of the Moon Pao's model.
A DYNAMIC CONTROL MODEL OF PIEZOELECTRIC CANTILEVERED BEAM-PLATE BASED ON WAVELET THEORY
基于小波理论的悬臂板压电动力控制模式

Zhou Youhe,Wang Jizeng,
周又和
,王记增

力学学报 , 1998,
Abstract: Based on the scaling function transform of the Daubechies wavelet theory, an oneto-one explicit relation betWeen electric signals measured in piezoelectric sensors and denectionof the plates is established in this paper, which overcomes the deficiency of conventional methodof modal analysis which sometimes leads to failure of measuring deformation of the plate whenthe inverse matrix in the method does not exist. After that, a dynamic control model for thepiezoelectric plates with feedback of negative deflection and negative velocity signals is formulatedby the approximation of the scaling function transform of the wavelet. Due to that the reconstruction function of the scaling function transform has an ability of automatical filtering highorder frequency signals of vibration or disturbance, it is found that the phenomenon of instabilitycaused from the spilling over of measurement and controller, i.e., the controller for suppressingdisturbance of low order frequences excites some oscillations of higher order, does not occur in thiscontrol model. This merit has not been found in a conventional method. The numerical simulations exhibit that the suppression of a disturbance by the method suggested in this paper is fasterthan the conventional method of modal analysis.i) The project supported by the National Natural Science Foundation of China (No.19772014) and by the Fundationof the State Education Commission of China for Oversea Returnees.
EXISTENCE AND CHARACTERISTIC RELATION OF WAVESPEED TO SURFACE ACOUSTIC WAVES ON A ROTATING PIEZOELECTRIC HALF-BODY
转动压电陶瓷体表面声波的存在性及波速特征关系

Qing Jiang,Zhou Youhe,Qing Jiang,
周又和

力学学报 , 2000,
Abstract: This paper is to display existence and its conditions to a surface acoustic wave propogating along surface of a half-body of piezoelectric ceramics with a rotation of constant angular velocity. It is found that when the half-body rotates, whether or not a surface acoustic wave, which corresponds to either the Rayleigh wave or the Bleustein-Gulyaev wave on the surface of the half-body without rotation, exists is dependent upon those material parameters of the piezoelectric body. If a surface acoustic wave exists when the piezoelectric body rotates, the results exhibit that the surface wave is dispersive. As an example, finally, some quantitative results of the characteristic relation between the wave speed and the rotation angular velocity are given for the PZT-5H material of piezoelectric ceramics.
Analysis of chaotic motions of geometrically nonlinear ferromagnetic beam-plates exicited by transverse magnetic fields
横向磁场激励下铁磁梁式板的混沌运动分析

Gao Yuanwen Zhou Youhe Zheng Xiaojing,
高原文
,周又和,郑晓静

力学学报 , 2002,
Abstract: 在磁体力分布的磁弹性理论模型和磁场准静态假定模式基础上,对于处在周期时变磁场 中的不可移简支铁磁梁式板非线性磁弹性动力特性进行定性与定量分析.首先利用磁场的摄 动技术和结构变形的模态法,导出了关于模态坐标的非线性动力方程;然后利用Melnikov方 法,从理论上给出这一磁弹性动力系统可能出现混沌运动的必要条件及参数范围;最后采用变 步长Runge-Kutta数值积分方法对其磁弹性相互作用的混沌现象进行了定量搜索与模拟,并 利用其轨迹的Poincare截面图与Liapunov指数加以判断.结果表明磁弹性简支梁式板在横 向周期时变磁场中存在混沌吸引子,且在机械阻尼很小时其混沌吸引子表现出稠的特性.
The history of the department of mechanics in Lanzhou University
兰州大学力学专业发展的历史沿革

YU Huanran,ZHOU Youhe,WANG Shengzhe,
俞焕然
,周又和,王省哲

力学与实践 , 2007,
Abstract: 兰州大学力学专业是在原兰州大学数力系力学教研室基础上组建的,经过半个世纪的发展,已从原来单一的固体力学硕士点、博士点发展到今天的力学一级硕士点和固体力学与工程力学两个二级博士点及拥有力学一级博士后科研流动站等较为齐全的力学学科格局;以及拥有西部灾害与环境力学教育部重点实验室科研平台和理论与应用力学甘肃省科学研究与人才培养基地等.科学研究已从20世纪50~80年代的板壳非线性力学领域研究发展到今天的电磁固体力学、智能结构与动力控制、多场耦合与风沙环境力学等多学科交叉的特色研究领域与研究方向.
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