共查询到20条相似文献,搜索用时 46 毫秒
1.
The present study aims at implementation of a strain rate dependent, non-linear, micro-mechanics material model for laminated, unidirectional polymer matrix composites into the explicit finite element code LSDYNA. The objective is to develop an accurate and simple micro-mechanical, rate dependent material model, which is computationally efficient. Within the model a representative volume cell is assumed. The stress-strain relation including rate dependent effects for the micro-model is derived for both shell elements and solid elements. Micro-failure criterion is presented for each material constituent and failure mode. The implemented model can deal with problems such as impact, crashworthiness, and failure analysis under quasi-static loads. The developed material model has a wide range of applications such as jet engine jackets, armor plates, and structural crashworthiness simulation. The deformation response of two representative composite materials with varying fiber orientation is presented using the described technique. The predicted results compare favorably to experimental values. 相似文献
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We reported some dynamic and viscometric data on an Australia strong flour-water dough. In oscillatory shear flow experiments, we found the linear viscoelastic strain limit is extremely low, of O(10–3), consistent with other published data on doughs. The relaxation spectrum derived from the dynamic data is broad, indicating the blend nature of dough. In the start-up of a simple shear flow, we found the shear stress increases nonlinearly with time to a peak value and then decreases rapidly, with no steady-state response. The concept of steady-state viscosity is not very meaningful here, unless the strain at which the measurements are taken is also specified. The stress peaks are strain-rate dependent; but they occur at a strain of O(10), for the strong flour/water dough used, over four decades of strain rates. The experimental data were used to construct a phenomenological model for dough, consisting of an hyperelastic term (representing the elastic gluten network of permanent cross-linked long chain polymers), and a viscoelastic contribution (representing the suspension of starch globules and other long-chain components in dough that are not parts of the permanent cross-linked gluten network). The model predictions compared favourably with experimental data in oscillatory and shear flows. 相似文献
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本文讨论微重力场中带球面隔板的球腔内液体晃动问题。选择Legendre函数作为Ritz方法的基函数,计算液体的自由晃动及腔体横向振动激励的受迫振动。计算结果表明,自由晃动频率随隔板位置的下降而趋于升高。液体晃动的动力学效应可用等效的质量—弹簧系统模拟。 相似文献
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Yan-Zhu Liu 《Acta Mechanica Solida Sinica》1988,1(4):407-418
The phase-plane method of nonlinear oscillation is used to discuss the influence of the small dissipation upon the Euler-Poinsot motion of a rigid body about a fixed point. The equations of phase coordinates are applied instead of Eulerian equations, and the global characteristics of the motion of rigid body are analysed according to the distribution and the type of the singular points. A Chaplygin's sphere on a rough plane, a rigid body in viscous medium and one with a cavity filled with viscous fluid are discussed as examples. It is shown that the motions of rigid bodies dissipated by various physical factors have a common qualitative character. The rigid body tends to make a permanent rotation about the principal axis of the largest moment of inertia. The transitive process can change from oscillatory to aperiodic with the decrease in dissipation. 相似文献
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The underlying geometric structure of the standard OGY control scheme is analyzed. Some of the main mechanisms that under certain conditions lead to failure of the control algorithm are revealed. The limited controllability available in a system is investigated and it is shown that it may lead to serious problems that will significantly enlarge the state space region of failure of the standard OGY controller. A minimal distance algorithm is analyzed and shown to be, for some problems, more advantageous than the standard OGY technique. Nevertheless, for a broad category of problems, the minimal distance scheme is also shown to fail. As a solution for these problems, two new techniques are proposed: the penalized minimal distance and the multi-step OGY-type scheme. The standard OGY and minimal distance algorithms are particular cases of the new techniques proposed. Finally, we give a necessary condition that estimates the region of controllability under the multi-step OGY-type control. We demonstrate a significantly improved basin of convergence for the new multi-step OGY-type algorithm. 相似文献
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A technique is developed for determining the thermoviscoelastoplastic geometrically nonlinear axisymmetric stress–strain state of laminar shells of revolution under loads that induce meridional stress and torsion. The technique is based on the hypotheses of rectilinear element for the whole stack of layers. The relations of the theory of deformations along paths of small curvature are used as equations of state. The solution is reduced to the numerical integration of a system of ordinary differential equations. The technique is tried out by a test example and illustrated by determining the geometrically nonlinear thermoviscoelastoplastic state of a corrugated shell 相似文献
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Stability of a spinning liquid-filled spacecraft 总被引:4,自引:0,他引:4
Summary The stability of a spinning liquid-filled spacecraft has been investigated in the present paper. Using Galerkin's method,
the attitude dynamic equations have been given. The Liapunov direct method was employed to obtain a sufficient condition for
stability. Three kinds of characteristic modals were investigated: free motion of inviscid fluid, slosh motion and non-slosh
motion. All characteristic problems can be solved numerically by the Finite Element Method or the Boundary Element Method.
It has been demonstrated that the viscosity of the fluid has a dissipative effect at large Reynolds number, while the slosh
motion plays a destabilizing role. The non-slosh model of fluid does not affect the stability criterion.
Accepted for publication 19 October 1996 相似文献
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滑块碰撞与圆周率π看似不相关的两个事物却具有某种联系,本文研究了滑块碰撞动力学,利用计算工具MATLAB,发现在理想情况下,滑块的碰撞次数与π有一定的关联,并在理论上证明了计算结果。 相似文献
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A. S. Vereshchagin S. N. Vereshchagin V. M. Fomin 《Journal of Applied Mechanics and Technical Physics》2007,48(3):375-384
A mathematical model is constructed and an analytical solution is obtained for the problem of a one-dimensional steady flow
of a mixture of different gases with hollow permeable particles. The case of a one-dimensional unsteady flow of such a mixture
is analyzed numerically. The numerical solutions are compared with experimental data on the motion of the peak concentration
of helium in a fixed bed filled with cenospheres (solid hollow permeable spherical particles). The permeability of cenosphere
walls and the drag coeficient of cenospheres in the gas flow are determined.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 3, pp. 92–102, May–June, 2007. 相似文献
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The paper proposes a modification of the mixed variational principle from which stationarity conditions are derived in the
form of a mixed system of equations resolved for the first derivatives of the displacement and stress components acting in
a plane perpendicular to one of the coordinate axes. The variational principle allows decreasing the dimension of the problem
of elasticity thus reducing the system of equations to a canonical form. The modified mixed principle helps immediately obtain
a canonical system of equations for various applied theories. This possibility is demonstrated with the example of the Timoshenko
theory of plates
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Translated from Prikladnaya Mekhanika, Vol. 43, No. 5, pp. 55–62, May 2007. 相似文献
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本文从经典力学观点讨论人体在鞍马上的全旋运动,理想化的全旋运动要求人体以不变的章动角作匀速进动,同时绕纵轴朝相反方向自旋,以保证在运动过程中始终面向前方。文中规定一种带特殊完整约束条件的刚体规则进动作为这种运动的理想模式,并利用人体的多刚体模型分析鞍马上的直体全旋及托马斯全旋的运动规律,导出肩关节支撑力及肌肉控制力矩的计算公式。 相似文献
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The motion of a rigid body about fixed point with small radial mass-unbalance in homogeneous gravitational field was discussed. The dynamical equations described by state variables of the body were established, and approximate analytical solutions for a spinning body with high speed were obtained by use of the average method. The influence of the radial mass-unbalance of the rotor to the precession character of a free-rotor gyroscope was analyzed. And a physical explanation of the drift phenomenon of the gyro was given. An applicable formula of gyro‘ s constant drift in analytical form was obtained, which is perfectly coincident with the numerical calculate‘on 相似文献
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包覆电磁场激活板的圆柱尾迹的数值研究 总被引:19,自引:3,他引:19
利用电磁场作用于电介质溶液的Lorentz力可以控制溶液的流动.对置于弱电介质溶液中,包覆电磁场激活板的圆柱周围的绕流进行数值研究,讨论了电磁场激活板的安装位置,激活方式等对圆柱尾迹的影响. 相似文献
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建立了横观各向同性不可压饱和多孔弹性梁拟静态弯曲的数学模型,并给出了一般的求解方法。作为例子,研究了端部不同渗透条件对梁中点承受突加常集中载荷作用的饱和多孔悬臂梁拟静态弯曲的影响,给出了挠度和孔隙流体压力等效力偶沿梁轴线的分布以及随时间的响应曲线。结果表面:端部渗透条件对饱和多孔弹性梁的弯曲行为有显著的影响,梁的弯曲挠度既可随时间单调递增、亦可单调递减,其性态依赖于梁端部的渗透条件。同时发现不同于经典单相弹性梁,由于孔隙流体压力的作用,不承受载荷作用的梁段亦发生弯曲,并且Man-del-Cryer效应亦存在于不可压饱和多孔弹性梁的拟静态响应中,这些结果有助于揭示传热管道、植物根茎等力学行为的机理。 相似文献
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三角翼大迎角不可压粘流的数值模拟 总被引:6,自引:0,他引:6
研究了人工压缩法拟压缩性系数β的选取,采用函数形式的β有效地加速了收敛过程.采用求解不可压N-S方程,对三角翼大迎角绕流进行了数值模拟,得到了与实验吻合很好的结果.分析和讨论了大迎角旋涡流动的复杂物理现象 相似文献
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G. A. Vanin 《International Applied Mechanics》2007,43(1):54-63
A multimoment theory of elasticity of inhomogeneous media is used to develop algorithms for determining a sequence of essentially
independent fundamental parameters associated with the structure, composition, and characteristics of the medium components.
The general form of stress concentration factors is established by analyzing specific models of media. It is found that the
mean tangential stresses in a fibrous medium with a transverse stress state are asymmetric. As an example, the methods are
used to solve specific problems for plates and shells
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Translated from Prikladnaya Mekhanika, Vol. 43, No. 1, pp. 66–76, January 2007. 相似文献