共查询到20条相似文献，搜索用时 93 毫秒
1.
In this paper we propose a degradation model to describe the damage-dependent behavior of saturated soft clay under cyclic loading, which is then applied to the analysis of a caisson breakwater. The degree of damage and remolding of soft clay is quantified by a damage parameter related to the accumulated plastic deviatoric strain. Through the correlation between the maximum pore pressure and the undrained strength of soft clay, we obtain a damage-dependent degradation model that employs the post-cyclic undrained strength degradation coefficient in terms of the cyclic stress ratio and the number of cycles. Based on the Tresca yield criterion, the degradation model of undrained strength of soft clay is numerically implemented in the user interface USDFLD of ABAQUS. The performance of this model is verified by a comparison between numerical results (finite element method) and experimental data (cyclic triaxial test). The model is applied to the numerical simulation of a caisson breakwater resting on a partially sand-filled soft clay seabed under cyclic wave loading. The cyclic stress distribution, pore pressure development, and strength degradation of the seabed soil are presented to illustrate the applicability and efficiency of the model in the analysis of the interaction between offshore structures and soft ground. 相似文献
2.
This paper is aimed to propose an approach to predict the dynamic characteristics of ring-plate planetary indexing cam mechanism,
which is a novel type of indexing mechanism that employs internal planetary transmission structure. Firstly, the geometry
and structure of the mechanism are discussed and the kinematic practicability is simulated with virtual prototype design.
Then a 3D finite element model of the ring-plate planetary indexing cam mechanism is developed with the commercial software
of MATLAB and ANSYS. Through the finite element analysis, the natural frequencies and the corresponding mode shapes are predicted
in one motion cycle. On the basis of the virtual prototype design and finite element analysis, an experimental prototype is
made and tested to validate the prediction of the dynamic characteristics. The agreement between experimental results and
the finite element analysis testifies that the finite element model developed is applicable to the prediction of the dynamic
characteristics of this type of mechanism. 相似文献
3.
Long-period ground motion has become an important consideration because of the increasing number of large and long-period structures. Therefore, a thorough investigation on the formation and characteristics of longperiod ground motion is desirable for engineering applications. In this work, an analytical study is performed to examine the effect of several parameters and the combining mode for equivalent harmonic components on the dynamic response of systems. The results of the work show that the harmonic components in equivalent ground motion are evidently influenced by the intensity rise time, duration, phase and combining mode. Moreover, the long-period ground motions are simplified and simulated by separate harmonic components through proper combination. The findings of the work are believed to be useful in the selection of input ground motion in structural seismic analysis. 相似文献
4.
邱承媛 《阿坝师范高等专科学校学报》2003,(2):98-100
圆周运动按运动物体所受力的种类,可分为:1.在万有引力作用下的匀速圆周运动,2.在电场中的匀速圆周运动,3.在磁场中的匀速圆周运动,4.在复合场中的圆周运动。文章以近年高考题为例对此进行讨论。 相似文献
5.
远破波作用下防波堤前海床冲刷及其相似律 总被引：1，自引：0，他引：1
波浪作用下防波堤前海床将发生冲刷 ,进而危及防波堤的安全 .通过试验和理论分析研究了远破波作用下防波堤前沙质海床冲刷 ,包括堤前冲刷深度和范围、基床尺度对堤前冲刷和淤积的影响 .为将研究成果应用于实际工程 ,研究了冲刷相似律 ,提出了模型沙比尺和冲淤比尺 相似文献
6.
研究目的：四轮独立驱动汽车四个车轮的电机转矩可以正、反向输出,有必要对其底盘集成控制系统进行针对性设计以保证各车轮间的协调运作。集成控制系统一般可以分为上层运动控制器和下层力分配器。对于运动控制器的设计,同类研究一般采用滑模控制方法来处理汽车运动的非线性特征,其中终端滑模控制因具有高的稳态精度和有限时间收敛的特点而成为研究热点。对于力分配器的设计,通常方法不能在保证运算效率的同时考虑到执行器的约束,从而很难应用于实际。本文采用终端滑模控制方法来设计运动控制器,通过分析驾驶员操作行为从而更好地追踪理想的车辆运动目标;并提出一种简单有效的转矩分配控制策略,通过考虑轮胎附着极限从而将运动总力分配至四个车轮上。创新要点：本文创新性地将终端滑模控制应用到底盘集成控制系统以实现车辆纵向、侧向及横摆运动的联合控制;本文提出了一种新颖的转矩分配控制策略,将复杂的有约束控制分配问题分解至若干个简单的无约束分配子问题。研究方法：本文采用分层式协调控制方案（图1）,应用非奇异和全局快速终端滑模控制方法设计运动控制器,提出一种基于伪逆矩阵的有约束转矩分配策略,应用驾驶员最优预瞄加速度模型来描述和分析人-车闭环系统的运动响应,通过MATLAB/Simulink和CarSim的联合仿真对所设计的四轮独立驱动汽车转矩分配方法进行对比验证。所设定的三个仿真工况包括：开环方向盘角阶跃输入（图6、7及表2）、闭环双移线工况（图8–10）和闭环对开路面制动（图11–15）,分别用以测试车辆横摆、侧向及纵向方向上的动力学响应。重要结论：本文提出的基于终端滑模控制的四轮独立驱动汽车转矩分配方法将车辆的稳态转向特性由不足转向转变为中性转向,驾驶员从而? 相似文献
7.
圆锥摆模型 总被引：1，自引：0，他引：1
何熙起 《内江师范学院学报》2004,19(4):96-98
由圆锥摆模型,引入同频率、同振幅、振动方向互相垂直的简谐振动的合成和简谐振动的旋转矢量表示法,化抽象的理论为形象的内容,这是学生易于接受、符合教学规律的教学方法。 相似文献
8.
This paper investigates the wave attenuation properties of the double trapezoidal submerged breakwaters on the flat-bed by conducting physical experiments subjected to linear and cnoidal incident waves.The method of Goda’s two points is used to separate the heights of incident,reflected and transmitted waves based on the experimental data.The possible factors affecting the wave attenuation properties of the double trapezoidal submerged breakwaters(i.e.,the relative submerged water depth,relative breakwater spacing,wave steepness and relative wave height) are investigated with respect to the reflection and transmission coefficients.The results show that there is a range,within which the breakwater spacing has little impact on the reflection coefficient,and the transmission coefficient tends to be a constant.The influence of the wave steepness is reduced while the breakwater spacing is too large or too small.Within the range of the relative wave height tested in this study,the reflection and transmission coefficients increase and decrease with the relative wave height,respectively.The double trapezoidal submerged breakwaters model indicates a good attenuation effect for larger wave steepness,big relative wave height and within the range of the relative breakwater spacing between 12.5 and 14 according to linear and cnoidal waves.The changes of wave energy spectra between the double submerged breakwaters on the flat-bed are investigated by the fast Fourier transform(FFT) method,showing that wave energy dissipation can be reached more effectively when the relative breakwater spacing is 12.5. 相似文献
9.
《天津大学学报(英文版)》2017,(6)
A modified suction caisson(MSC), which was reported by the authors of this paper previously, comprises an external short-skirted structure that is added to a regular suction caisson(RSC). It has been proved that MSCs can improve the lateral bearing capacity and limit the deflection of the caisson compared with RSCs. A series of model tests were conducted to investigate responses of MSCs subject to uplift loading in saturated sand. The effects of external skirt dimensions on the uplift bearing capacity of MSCs were considered. In addition, the influences of the sealed top lid of the skirted structure on the uplift bearing capacity and the resulting passive suction of MSCs were also studied. It was found that the uplift bearing capacities of MSCs are 1.4-1.7 times that of RSCs. Moreover, test results in serviceable conditions show that the sealed external skirted structure of perspex-made suction caissons significantly contributed to the uplift bearing capacity as a result of passive suction. 相似文献
10.
11.
ZHUHuai－liang 《上海大学学报(英文版)》2001,5(1):35-39
In this paper ,a hybrid approach was developed to investigate the transient responses of a multi-span non-uniform flexble spinning shaft with nonlinear and asymmetric supports.The non-uniform spinning shaft with variable parmeters was modeled as a Bernoulli-Euler beam column with sectional constant cross-section properties by the finite element method.The supporting stiffness behavior of the nonlinear supports was described as a piecewise-linear and asymmetric model.The equations of motion in the matrix form of a multi-span non-uniform spinning shaft with nonlinear and asymmetric supports were formulated using Hamilton‘s principle and the assumed mode method.As an example,a spinning rocket with many variable stiffness supports was numerically simulated by the direct integration method.The transient response and dynamic behavior of this rotate-dynamic system are analyzed. 相似文献
12.
In autonomous underwater vehicles(AUVs) the onboard power used to complete missions is limited.To solve this problem,a landing AUV has been designed,which conserves energy by sitting on the seafloor while monitoring the ocean.In order to study the dynamic behaviors for better control of the AUV,the dynamic analysis of the landing AUV is presented in this paper.Based on the momentum theorem and the angular momentum theorem,the dynamic model of the landing AUV is derived.The simulations of rectilinear motion,rotary motion and helix motion indicate the dynamic behaviors of the AUV.The ocean experiments validate the dynamic model presented in this paper.The experiments also verify that the landing AUV can work for a longer time than common AUVs. 相似文献
13.
ＩＮＴＲＯＤＵＣＴＩＯＮＭｏｔｉｏｎｃａｐｔｕｒｅｐｌａｙｓａｎｉｍｐｏｒｔａｎｔｒｏｌｅｉｎｔｈｅｃｒｅａｔｉｏｎｏｆｓｐｅｃｉａｌｅｆｆｅｃｔｓｉｎｍａｎｙｆｉｅｌｄｓ.Ａｓｉｄｅｆｒｏｍｕｓｅｉｎｆｉｌｍｓａｎｄａｎｉｍａｔｉｏｎｓ,ｍｏｔｉｏｎｃａｐｔｕｒｅｈａｓｃｏｍｐｒｅｈｅｎｓｉｖｅａｐｐｌｉｃａｔｉｏｎｓｉｎｔｈｅａｎａｌｙｓｉｓｏｆａｔｈｌｅｔｅｐｅｒｆｏｒｍａｎｃｅ ,ｍｅｄｉｃａｌｄｉａｇｎｏｓｔｉｃｓ,ｓｕｒｖｅｉｌｌａｎｃｅ ,ｖｉｄｅｏｒｅｔｒｉｅｖａｌ,ｅｔｃ.Ｃｏｎｖｅｎ… 相似文献
14.
Computer vision has very wide application in human motion capture research. This paper proposes a new approach to do motion
capture in video. It is composed of image sequence based tracking of human feature points and the reconstruction of the three-dimension(3D)
motion skeleton. First, every part of the human body from top to bottom is tracked on the basis of a human model. The image
difference and a morph-block similarity algorithm based on subpixels are used. Then camera calibration is done using the line
correspondences between the 3D model and the image. Finally the 3D motion skeleton is established by use of the model knowledge.
This approach does not aim at a given mode of human motion. Rather, it analyzes large scale motion from frame to frame in
complex, variational background, and sets up a 3D motion skeleton in the perspective projection. The experiment results are
presented at the end of the paper.
Project (69803009) supported by Natural Science Foundation of China (NSFC) and Key Project of National Development Planning
Committee. 相似文献
15.
16.
Mathematical modelling of translational motion of rail-guided cart with suspended payload 总被引：1，自引：0，他引：1
MITREV Rosen 《浙江大学学报(A卷英文版)》2007,8(9):1395-1400
In this paper modelling of the translational motion of transportation rail-guided cart with rope suspended payload is considered. The linearly moving cart,driven by a travel mechanism,is modelled as a discrete six degrees of freedom (DOF) dynamic system. The hoisting mechanism for lowering and lifting the payload is considered and is included in the dynamic model as one DOF system. Differential equations of motion of the cart elements are derived using Lagrangian dynamics and are solved for a set of real-life constant parameters of the cart. A two-sided interaction was observed between the swinging payload and the travel mechanism. Results for kinematical and force parameters of the system are obtained. A verification of the proposed model was conducted. 相似文献
17.
按照循环农业运行模式内涵及机理,循环农业可以有四种运行模式可供选择：土地重叠复合产出模式、农业生物共生互利高效产出模式、水资源综合利用高效产出模式、利用废弃物延伸产业链模式。这四种模式下,在农业生产领域的实际应用中呈现出多种具体的模式,诸如稻田种养结合模式、生态农业园模式、废弃物能源化模式和功能产品化模式等,具有明显的资源、生态环境和经济效益。 相似文献
18.
A giant magnetostrictive material (GMM) model is developed based on the hysteretic nonlinear theory. The Gram-Schmidt regression method is introduced to determine the parameters of the model as well as the relation- ship between the material strain and the strength and frequency of magnetic field in the model. Through comparison, it is shown that this regression method has good performance in significance test. Then the model is applied to study the motion law of a circular plate in classical GMM transducer, which helps control the transducer rapidly and accurately. 相似文献
19.
The structural circumferential periodicity of inertial excitation produced by concentrated mass was utilized to establish the mathematical model of thin circular plate carrying eccentric concentrated mass and to analyze its transverse vibration. The fundamental frequency coefficient, natural frequency and mode shape function are determined by this method. A clamped thin circular plate was taken as an example to study the mass effect on the vibrating system.Comparison between the present results and published ones exhibits excellent agreement, which shows that the analytical method in this paper can be used to predict the transverse vibration parameters accurately. 相似文献
20.
Translational torsional coupled model based nonlinear dynamic analysis of an NGW planetary gear train 总被引：1，自引：0，他引：1
This paper aims to investigate the nonlinear dynamic behaviors of an NGW planetary gear train with multi-clearances and manufacturing/assembling errors. For this purpose, an analytical translational ? torsional coupled dynamic model is developed considering the effects of time-varying stiffness, gear backlashes and component errors. Based on the proposed model, the nonlinear differential equations of motion are derived and solved iteratively by the Runge-Kutta method. An NGW planetary gear reducer with three planets is taken as an example to analyze the effects of nonlinear factors. The results indicate that the backlashes induce complicated nonlinear dynamic behaviors in the gear train. With the increment of the backlashes, the gear system has experienced periodic responses, quasi-periodic response and chaos responses in sequence. When the planetary gear system is in a chaotic motion state, the vibration amplitude increases sharply, causing severe vibration and noise. The present study provides a fundamental basis for design and parameter optimization of NGW planetary gear trains. 相似文献