共查询到20条相似文献,搜索用时 15 毫秒
1.
Ibrahim A. Abbas 《Archive of Applied Mechanics (Ingenieur Archiv)》2009,79(1):41-50
In this paper, we constructed the equations of generalized magneto-thermoelasticity in a perfectly conducting medium. The
formulation is applied to generalizations, the Lord–Shulman theory with one relaxation time, and the Green–Lindsay theory
with two relaxation times, as well as to the coupled theory. The material of the cylinder is supposed to be nonhomogeneous
isotropic both mechanically and thermally. The problem has been solved numerically using a finite element method. Numerical
results for the temperature distribution, displacement, radial stress, and hoop stress are represented graphically. The results
indicate that the effects of nonhomogeneity, magnetic field, and thermal relaxation times are very pronounced. In the absence
of the magnetic field or relaxation times, our results reduce to those of generalized thermoelasticity and/or classical dynamical
thermoelasticity, respectively. Results carried out in this paper can be used to design various nonhomogeneous magneto-thermoelastic
elements under magnetothermal load to meet special engineering requirements.
An erratum to this article can be found at 相似文献
2.
本文根据Reissner-Mindlin型的全局位移场(一阶和三阶),应用有限元预测一修正法,数值计算和分析了机械载荷作用下复合材料层合圆柱壳的挠度和横向剪应力。首先按照一般的有限元分析过程(没有引入剪切修正系数)计算出层合圆柱壳的挠度预测值;然后利用Lagrange插值构造横向剪应力的一般形式,使得满足层间连续和表面上为零的条件,通过最小二乘法拟合三维应力平衡方程获得横向剪应力;最后在单元上计算和引入剪切修正系数,再经过有限元分析计算出层合圆柱壳的挠度修正值。数值计算结果与三维线弹性解的比较表明,挠度修正值和横向剪应力的精度是十分满意的。 相似文献
3.
Ibrahim A. Abbas Hamdy M. Youssef 《Archive of Applied Mechanics (Ingenieur Archiv)》2009,79(10):917-925
A general finite element model is proposed to analyze transient phenomena in thermoelastic solids. Youssef model of two-temperature
generalized magneto-thermoelasticity is selected for an homogenous, isotropic, conducting and elastic medium, which is subjected
to thermal shock, and a magnetic field with constant intensity acts tangent to the bounding plane. The numerical solution
of the nondimensional governing partial differential equations of the problem has been shown graphically. 相似文献
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5.
In this paper the problem of impulsively started aerofoil or suden change of incidence of an aerofoil in incompressible potential flow is investigated. The essence of solution lies in the representation of a timely and spatially varying wake in a largely irrotational potential flow field. This is achieved by representing the wake through velocity potential difference, which seems to be the only way of imposing a velocity difference condition in the finite element context with velocity potentials as the basic unknowns. Superposition is employed to meet various boundary conditions, which is justified by the linearity of the problem. The finite element solutions are compared with those from singularity method. 相似文献
6.
有限元边坡稳定分析方法及其应用 总被引:28,自引:0,他引:28
本文介绍了一种基于有限元应力分析的边坡稳定评价方法,讨论了边坡稳定安全系数定义的物理意义,介绍了搜索最危险滑动面的广义数学规划命题和模式搜索方法,同时给出了该方法的计算结果与其它方法计算结果的对比算例以及该方法的应用实例。 相似文献
7.
Mustapha El Hamdaoui José Merodio Ray W. Ogden Javier Rodríguez 《International Journal of Solids and Structures》2014
We consider the finite radially symmetric deformation of a circular cylindrical tube of a homogeneous transversely isotropic elastic material subject to axial stretch, radial deformation and torsion, supported by axial load, internal pressure and end moment. Two different directions of transverse isotropy are considered: the radial direction and an arbitrary direction in planes normal locally to the radial direction, the only directions for which the considered deformation is admissible in general. In the absence of body forces, formulas are obtained for the internal pressure, and the resultant axial load and torsional moment on the ends of the tube in respect of a general strain-energy function. For a specific material model of transversely isotropic elasticity, and material and geometrical parameters, numerical results are used to illustrate the dependence of the pressure, (reduced) axial load and moment on the radial stretch and a measure of the torsional deformation for a fixed value of the axial stretch. 相似文献
8.
A method to deal with an open boundary condition in the analysis of water surface waves, the tide, etc. by means of the finite element method is proposed in this paper. The present method has two important features relating to the treatment of the open boundary condition. The first feature is to consider the non-reflective virtual boundary condition which has been developed in the numerical wave analysis method. The incident wave conditions without spurious reflected waves can be imposed at the open boundary. The second feature is to identify the amplitude of the components of incident waves in terms of observed water elevations in the field of standing waves. This can be done as a parameter identification based on an optimization problem by applying the conjugate gradient method. The applicability of this method to wave propagation problems is verified by several numerical computations. 相似文献
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10.
E.L. Starostin 《Journal of the mechanics and physics of solids》2009,57(6):959-969
We study the force vs. extension behaviour of a helical spring made of a thin torsionally stiff anisotropic elastic rod. Our focus is on springs of very low helical pitch. For certain parameters of the problem such a spring is found not to unwind when pulled but rather to form hockles that pop out one by one and lead to a highly non-monotonic force-extension curve. Between abrupt loop pop-outs this curve is well described by the planar elastica whose relevant solutions are classified. Our results may be relevant for tightly coiled nanosprings in future micro- and nano(electro)mechanical devices. 相似文献
11.
George Mejak 《国际流体数值方法杂志》1991,13(4):491-505
A numerical algorithm to determine the impingement of an axisymmetric free jet upon a curved deflector is presented. The problem is considered within the potential flow theory with the allowance of gravity and surface tension effects. The primary dependent variable is the Stokes streamfunction, which is approximated through finite elements using the isoparametric Hermite Zienkiewicz element. To find the correct position of the free boundaries, a trial-and-error method is employed which amounts to solving a boundary value problem (BVP) for the Stokes streamfunction at each iteration step. An efficient method is proposed to solve this BVP. The algorithm to find the correct position of the free boundaries is tested by computing the impingement upon an infinite disc and a hemispherical deflector. To confirm the correctness of the solution, each problem has been solved using several different mesh gradings. A comparison between the Zienkiewicz and the other standard C0 finite elements is also given. 相似文献
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有限元表面应力计算 总被引:1,自引:3,他引:1
用有限元[1]通用程序进行结构计算时,最常用的是位移法,因而计算得到的位移有较高的精度。由位移计算应力时,有限元法应用的是应力-应变关系和应变-位移关系,其中应变-位移是微商关系。在数值计算中,微商只能转化为差商等用插值近似处理。这样,虽然位移精度高,但应力的计算精度就被大打折扣。本文应用弹性力学辛体系理论[2],解析求解了位移和应力的影响函数。利用有限元程序计算得到的位移,由功互等定理,不需要微分插值,就可以得到指定点的应力,应力精度大大提高。工程实际中有许多问题的最大应力往往发生在构件表面。针对表面应力问题,本文给出了半平面表面应力的影响函数,进行了数值算例计算。计算结果表明,用本文提出的影响函数法求解一点的应力,其精度明显提高,并且计算结果有很好的稳定性。用本文的影响函数法编制成子程序,可作为有限元软件应力计算的一个模块,可以更好地发挥有限元程序的功效。 相似文献
14.
《International Journal of Solids and Structures》2014,51(21-22):3798-3806
A finite element discretized symplectic method is introduced to find the thermal stress intensity factors (TSIFs) under steady-state thermal loading by symplectic expansion. The cracked body is modeled by the conventional finite elements and divided into two regions: near and far fields. In the near field, Hamiltonian systems are established for the heat conduction and thermoelasticity problems respectively. Closed form temperature and displacement functions are expressed by symplectic eigen-solutions in polar coordinates. Combined with the analytic symplectic series and the classical finite elements for arbitrary boundary conditions, the main unknowns are no longer the nodal temperature and displacements but are the coefficients of the symplectic series after matrix transformation. The TSIFs, temperatures, displacements and stresses at the singular region are obtained simultaneously without any post-processing. A number of numerical examples as well as convergence studies are given and are found to be in good agreement with the existing solutions. 相似文献
15.
In this paper we address the problem of the implementation of boundary conditions for the derived pressure Poisson equation of incompressible flow. It is shown that the direct Galerkin finite element formulation of the pressure Poisson equation automatically satisfies the inhomogeneous Neumann boundary conditions, thus avoiding the difficulty in specifying boundary conditions for pressure. This ensures that only physically meaningful pressure boundary conditions consistent with the Navier-Stokes equations are imposed. Since second derivatives appear in this formulation, the conforming finite element method requires C1 continuity. However, for many problems of practical interest (i.e. high Reynolds numbers) the second derivatives need not be included, thus allowing the use of more conventional C0 elements. Numerical results using this approach for a wall-driven contained flow within a square cavity verify the validity of the approach. Although the results were obtained for a two-dimensional problem using the p-version of the finite element method, the approach presented here is general and remains valid for the conventional h-version as well as three-dimensional problems. 相似文献
16.
In this article,a direct stress approach based on finite element analysis to determine the stress intensity fac-tor is improved.Firstly,by comparing the rigorous solution against the asymptotic solution for a problem of an infinite plate embedded a central crack,we found that the stresses in a restrictive interval near the crack tip given by the rigorous solution can be used to determine the stress intensity fac-tor,which is nearly equal to the stress intensity factor given by the asymptotic solution.Secondly,the crack problem is solved numerically by the finite element method.Depending on the modeling capability of the software,we designed an adaptive mesh model to simulate the stress singularity.Thus, the stress result in an appropriate interval near the crack tip is fairly approximated to the rigorous solution of the corre-sponding crack problem.Therefore,the stress intensity factor may be calculated from the stress distribution in the appro-priate interval,with a high accuracy. 相似文献
17.
When rewriting the governing equations in Hamiltonian form, analytical solutions in the form of symplectic series can be obtained by the method of separation of variable satisfying the crack face conditions. In theory, there exists sufficient number of coefficients of the symplectic series to satisfy any outer boundary conditions. In practice, the matrix relating the coefficients to the outer boundary conditions is ill-conditioned unless the boundary is very simple, e.g., circular. In this paper, a new two-level finite element method using the symplectic series as global functions while using the conventional finite element shape functions as local functions is developed. With the available classical finite elements and symplectic series, the main unknowns are no longer the nodal displacements but are the coefficients of the symplectic series. Since the first few coefficients are the stress intensity factors, post-processing is not required. A number of numerical examples as well as convergence studies are given. 相似文献
18.
The penalty function formulation of the finite element method is described for the analysis of transient incompressible creeping flows. Marker particles are utilized to represent moving free surfaces and to visualize the flow patterns. For determining the movement of markers from element to element, the area coordinate system of the linear triangular element is introduced. With the method presented, a punch indentation problem and an injection problem for an L-shaped cavity are solved for Newtonian and power-law fluids. 相似文献
19.
The finite element method is used to find the elastic strain (and thus the stress) for given velocity fields of the Leonov model fluid. With a simple linearization technique and the Galerkin formulation, the quasi-linear coupled first-order hyperbolic differential equations together with a non-linear equality constraint are solved over the entire domain based on a weighted residual scheme. The proposed numerical scheme has yielded efficient and accurate convective integrations for both the planar channel and the diverging radial flows for the Leonov model fluid. Only the strain in the inflow plane is required to be prescribed as the boundary conditions. In application, it can be conveniently incorporated in an existing finite element algorithm to simulate the Leonov viscoelastic fluid flow with more complex geometry in which the velocity field is not known a priori and an iterative procedure is needed. 相似文献