共查询到20条相似文献,搜索用时 625 毫秒
1.
Timoshenko梁理论中考虑了截面剪切变形的影响,推导了一种新的计算剪切系数的方法.首先采用悬臂梁纯弯曲变形条件下截面剪应力分布的精确解,基于能量原理得到了各种梁截面剪切系数新的表达式,然后推导了弯扭耦合变形条件下截面剪应力分布的精确解,进一步获得了该条件下截面的剪切系数.结果表明,悬臂梁端面作用力偏离截面的弯曲中心将使剪切系数变小,通过与Cowper计算结果的对比发现结果偏小,其原因是Cowper没有考虑与外力垂直的剪应力的影响,因此新的计算结果更优越. 相似文献
2.
单箱双室简支箱梁剪切变形及剪力滞双重效应分析 总被引:1,自引:1,他引:0
基于各个翼板选取不同的最大剪切转角差为剪力滞广义位移,应用能量变分原理分别推导出了考虑和不考虑剪切变形时单箱双室截面控制微分方程组,结合边界条件给出了箱梁纵向应力和竖向挠度的初参数解,从力学、数学角度上证实了剪切变形和剪力滞效应是两个相对独立的力学行为,进一步阐述了二者对箱梁的影响,即剪切变形对箱梁截面纵向应力无影响,但是对竖向挠度有很大的影响.数值算例表明,利用该文解和数值解分析跨中截面剪力滞系数横向分布规律,二者吻合程度良好,其横向分布规律与单室箱梁类似,唯独不同之处是边腹板处的剪力滞效应比中腹板处的剪力滞效应略微大一些;挠度计算表明,剪切效应使得该箱梁在集中和均布荷载作用下跨中挠度分别增大4.6%和2.7%. 相似文献
3.
4.
5.
6.
不同模量横力弯曲梁的解析解 总被引:13,自引:0,他引:13
选择处于平面复杂应力状态下横力弯曲梁,对结构进行了中性层的判定,推导出中性轴、正应力、剪应力、位移的计算公式,得到如下结论:对于复杂应力状态下的不同模量弹性弯曲梁,其中性轴位置与剪应力无关,因此用正应力作为判据而得到解析解,改进了以往用主应力判定中性点的多次循环的计算方法.把解析解的结果与经典力学同模量理论,以及有限元数值解进行了比较,结果表明:解析解很好地考虑了拉压不同模量的效应.还提出了对不同模量结构的计算修正以及对结构优化的思想. 相似文献
7.
赵延军周彦斌刘官厅 《数学的实践与认识》2022,(9):194-200
采用不同高阶剪切变形理论研究一维六方准晶梁的自由振动问题,应用哈密顿原理,推导了一维六方准晶梁的自由振动控制微分方程.采用Navier法获得了一维六方准晶简支梁自由振动的精确解,并将不考虑相位子场所求解结果与已有解进行比较,验证求解结果的有效性.最后研究材料尺度对一维六方准晶梁固有频率的影响. 相似文献
8.
考虑非局部剪切效应的碳纳米管弯曲特性研究 总被引:2,自引:2,他引:0
基于Hamilton(哈密顿)变分原理和非局部连续介质弹性理论,建立了新型非局部Timoshenko(铁木辛柯)梁模型(ANT),推导了碳纳米管(CNT)的ANT弯曲平衡方程以及两端简支梁、悬臂梁和简支 固定梁的边界条件表达式,分析了剪切变形效应和非局部微观尺度效应对碳纳米管弯曲特性的影响.数值计算结果显示,碳纳米管的弯曲刚度随着小尺度效应的增强而升高.其次,这种小尺度效应对自由端受集中力的悬臂梁碳纳米管有明显作用,其刚度变化规律和其它约束条件的碳纳米管一样,这一点是ANT模型区别于普通非局部纳米梁模型的主要特点.经分子动力学模拟验证,ANT模型是合理分析碳纳米管力学特性的有效方法. 相似文献
9.
10.
中心刚体-外Timoshenko梁系统的建模与分岔特性研究 总被引:5,自引:1,他引:4
对于中心刚体固结悬臂梁系统,当不考虑梁剪应力(即Euler-Bernoulli梁)影响时,匀速转动梁的平凡解是稳定的。而对于深梁,有必要考虑剪应力(即Timoshenko梁)的影响,此时其匀速转动平凡解将出现拉伸屈曲。为此采用广义Hamilton变分原理建立了中心刚体固结Timoshenko梁这类刚-柔耦合系统的非线性动力学模型,应用数值方法研究了匀速转动Timoshenko梁非线性系统的分岔特性,以及失稳的临界转速。 相似文献
11.
I. J. Gnip S. A. Veyelis V. I. Kersulis S. I. Vaitkus 《Mechanics of Composite Materials》2007,43(1):85-94
Data obtained in investigating the ultimate strength and deformability of expanded polystyrene under short-term shear loading
according to EN 12090 are discussed. Linear regression equations are used for describing the ultimate shear strength and modulus
in relation to the density of EPS. A correlation is found to exist between the ultimate strength of EPS and its density and
specimen thickness. An empirical dependence between the shear modulus and density of EPS is established. The strains corresponding
to the conditional limit of proportionality and to the ultimate shear strength of EPS in short-term loading are determined.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 1, pp. 121–134, January–February, 2007. 相似文献
12.
Mindlin板几何非线性分析的附加内部剪应变法 总被引:1,自引:0,他引:1
本文在几何非线性分析的Mindlin板元中引入单元附加内部剪应变,有效地解决了薄板情况下的剪切自锁问题.文中导出了相应的能量相容条件,给出了有限元非线性列式的全过程及有关簿板及中厚板大挠度问题的数值结果. 相似文献
13.
A. S. Gupta J. C. Misra M. Reza 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2005,56(6):1030-1047
An analysis is made of the steady shear flow of an incompressible viscous electrically conducting fluid past an electrically
insulating porous flat plate in the presence of an applied uniform transverse magnetic field. It is shown that steady shear
flow exists for suction at the plate only when the square of the suction parameter S is less than the magnetic parameter Q. In this case the velocity at a given point increases with increase in either the magnetic field or suction velocity. The
shear stress at the plate increases with increase in either S or the free-stream shear-rate parameter σ1 or Q. The analysis further reveals that solution exists for steady shear flow past a porous flat plate subject to blowing only
when the square of the blowing parameter S1 is less than Q. It is found that the induced magnetic field at a given location decreases with increase in Q. Further the wall shear stress decreases with increase in S1. No steady shear flow is possible for blowing at the plate when S12 > Q.
Received: June 16, 2004; revised: October 24, 2004 相似文献
14.
A rigorous mathematical proof of Howard's conjecture which states that the growth rate of an arbitrary unstable wave must
approach zero, as the wave length decreases to zero, in the linear instability of nonviscous homogeneous parallel shear flows,
is presented here for the first time under the restriction of the boundedness of the second derivative of the basic velocity
field with respect to the vertical coordinate in the concerned flow domain. 相似文献
15.
The closed-form analytic expressions for the stresses at any point of an elastic plate coupling in different ways to a base
as a result of a two-dimensional shear strip-loading are obtained. The contact between the horizontal layer and the base is
either smooth-rigid or rough-rigid or welded. The variations of the shear stresses with the horizontal distance have been
studied numerically. It is found that the effect of different boundary conditions on the stress field is significant and the
stresses for an elastic layer lying over an elastic half-space differ considerably from those of an entire homogeneous elastic
half-space. 相似文献
16.
Howard’s conjecture, which states that in the linear instability problem of inviscid heterogeneous parallel shear flow growth
rate of an arbitrary unstable wave must approach zero as the wave length decreases to zero, is established in a mathematically
rigorous fashion for plane parallel heterogeneous shear flows with negligible buoyancy forcegΒ ≪ 1 (Miles J W,J. Fluid Mech.
10 (1961) 496–508), where Β is the basic heterogeneity distribution function).
An erratum to this article is available at . 相似文献
17.
Using the vector magnetograms observed at Huairou Solar Observing Station of National Astronomical Observatories, the magnetic shear angles of solar active regions at the ascending phase of cycle 23 (1996-2000) were calculated. It is found that the statistical distribution of the magnetic shear angles can be fitted well by Gaussian curves. And the dominant sign of the magnetic shear angles is negative (positive) in the northern (southern) hemisphere. It is consistent with the N-S sign asymmetry of force-free field constant α and current helicity. 相似文献
18.
Results obtained by Joseph(J. Fluid Mech.
33 (1968) 617) for the viscous parallel shear flow problem are extended to the problem of viscous parallel, shear flow problem
in the beta plane and a sufficient condition for stability has also been derived. 相似文献
19.
Yongqi Wang Tasawar Hayat Abdul Majeed Siddiqui 《Mathematical Methods in the Applied Sciences》2005,28(3):329-347
The present investigation deals with an undulating surface model for the motility of bacteria gliding on a layer of non‐Newtonian slime. The slime being the viscoelastic material is considered as a power‐law fluid. A hydrodynamical model of motility involving an undulating cell surface which transmits stresses through a layer of exuded slime to the substratum is examined. The non‐linear differential equation resulting from the balance of momentum and mass is solved numerically by a finite difference method with an iteration technique. The manner in which the various exponent values of the power‐law flow affect the structure of the boundary layer is delineated. A comparison is made of the power‐law fluid with the Newtonian fluid. For the power‐law fluid with respect to different power‐law exponent values, shear‐thinning and shear‐thickening effects can be observed, respectively. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
20.
In this two part paper, the first part deals with five different nonlinear theories applicable to the analysis of arches in the context of solving the large displacement and the large rotation problem. These theories include, classical theory, first-order shear deformation theory, third-order shear deformation theory, modified classical theory and the Donnell-type theory. All the theories are developed using the Total Lagrangian approach. Simplifications and assumptions used in each of the theory are discussed. Explicit strain displacement gradient relations and element independent equilibrium equations in terms of displacement gradients are given for all the theories. Limitations of each of theory are discussed. In the second part of this paper, application of these theories for the classification of arch geometries is considered. 相似文献