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141.
A mixed finite element formulation for viscoelastic flows is derived in this paper, in which the FIC (finite incremental calculus) pressure stabilization process and the DEVSS (discrete elastic viscous stress splitting) method using the Crank-Nicolson-based split are introduced within a general framework of the iterative version of the fractional step algorithm. The SU (streamline-upwind) method is particularly chosen to tackle the convective terms in constitutive equations of viscoelastic flows. Thanks to the proposed scheme the finite elements with equal low-order interpolation approximations for stress-velocity-pressure variables can be successfully used even for viscoelastic flows with high Weissenberg numbers. The XPP (extended Pom-Pom) constitutive model for describing viscoelastic behaviors is particularly integrated into the proposed scheme. The numerical results for the 4:1 sudden contraction flow problem demonstrate prominent stability, accuracy and convergence rate of the proposed scheme in both pressure and stress distributions over the flow domain within a wide range of the Weissenberg number, particularly the capability in reproducing the results, which can be used to explain the "die swell" phenomenon observed in the polymer injection molding process. 相似文献
142.
几何缺陷浅拱的动力稳定性分析 总被引:3,自引:1,他引:2
研究了几何缺陷对粘弹性铰支浅拱动力稳定性能的影响。从达朗贝尔原理和欧拉-贝努利假定出发推导了粘弹性铰支浅拱在正弦分布突加荷载作用下的动力学控制方程,并采用Galerkin截断法得到了可用龙格-库塔法求解的无量纲化非线性微分方程组。同时引入能有效追踪结构动力后屈曲路径的广义位移控制法,对含几何缺陷浅拱的响应曲线进行几何、材料双重非线性有限元分析。用这两种方法分析了前三阶谐波缺陷对浅拱动力稳定性能的影响,其中动力临界荷载由B-R准则判定。主要结论有:材料粘弹性使浅拱动力临界荷载增大且结构响应曲线与弹性情况差别很大;二阶谐波缺陷影响显著,它使动力临界荷载明显下降且使得浅拱粘弹性动力临界荷载可能低于弹性动力临界荷载。 相似文献
143.
各向异性粘弹性力学的本征化理论 总被引:1,自引:1,他引:0
在物体的异性子空间中研究了各向异性粘弹性力学,证明了对粘弹性介质,也存在运动方程及变形协调方程的本征特性,并由此得到相应的模态形式。再利用模态Maxwell本构方程,从而提出了一个各向异性粘弹性力学理论。它的优点是:(1)方程是标量型的,并且各阶之间彼此无关,方程的个数与物体的异性子空间个数相同;(2)无论物体的各向异性程度如何,其定解方程及应边界条件形式是统一、显式的;(3)对静力学问题,没有力法和位移法的区别,即在力学空间下,平衡方程和变形协调方程没有区别;(4)第一阶方程都有明确的物理意义,例如在各向同性下,1阶和2阶方程分别代表体积变形过程和剪切变形过程;(5)在力学空间下,粘弹性力学也存在类似弹性力学的应力势函数,并且它们是非人为确定的;(6)最终解是由各阶解模态叠加构成,适于工程上的近似计算。 相似文献
144.
谷粒的热——湿应力分析 总被引:2,自引:0,他引:2
针对谷物烘干问题,本文研究弹性及粘弹性圆球和椭球的热,湿应力。对圆球分析表明,热应力峰值远比湿应力峰值出现时间早,在假定材料为热,湿流变简单的Maxwell粘弹性体条件下,本文导出了圆球的热,湿应力分布公式,并应用有限元法研究了椭球的热,湿应力,文中以无量纲形成给出了圆球中心和表面应力随时间的 变化情况,以及椭球中心轴向应力峰值随椭球长,短半轴之比的变化情况。 相似文献
145.
146.
147.
根据Eshelby等效夹杂理论研究含残币形裂纹的粘弹体中裂纹张开位移随时间的缓慢增大以及含裂纹粘弹性体的等效模量随时间的变化。对于Maxwell粘弹性材料给出了模量随时间变化的显式表达式,结果表明裂纹的缓慢张开使材料模量减小更快。 相似文献
148.
Complex-mode Galerkin approach in transverse vibration of an axially accelerating viscoelastic string 总被引:1,自引:0,他引:1
Under the consideration of harmonic fluctuations of initial tension and axially velocity, a nonlinear governing equation for transverse vibration of an axially accelerating string is set up by using the equation of motion for a 3-dimensional deformable body with initial stresses. The Kelvin model is used to describe viscoelastic behaviors of the material. The basis function of the complex-mode Galerkin method for axially accelerating nonlinear strings is constructed by using the modal function of linear moving strings with constant axially transport velocity. By the constructed basis functions, the application of the complex-mode Galerkin method in nonlinear vibration analysis of an axially accelerating viscoelastic string is investigated. Numerical results show that the convergence velocity of the complex-mode Galerkin method is higher than that of the real-mode Galerkin method for a variable coefficient gyroscopic system. 相似文献
149.
Bakhtiyor Eshmatov 《应用数学和力学(英文版)》2007,28(10):1319-1330
The present work discusses the problem of dynamic stability of a viscoelas- tic circular cylindrical shell,according to revised Timoshenko theory,with an account of shear deformation and rotatory inertia in the geometrically nonlinear statement.Pro- ceeding by Bubnov-Galerkin method in combination with a numerical method based on the quadrature formula the problem is reduced to a solution of a system of nonlinear integro-differential equations with singular kernel of relaxation.For a wide range of vari- ation of physical mechanical and geometrical parameters,the dynamic behavior of the shell is studied.The influence of viscoelastic properties of the material on the dynamical stability of the circular cylindrical shell is shown.Results obtained using different theories are compared. 相似文献
150.
Stability analysis of viscoelastic curved pipes conveying fluid 总被引:1,自引:0,他引:1
Based on the Hamilton' s principle for elastic systems of changing mass, a differential equation of motion for viscoelastic curved pipes conveying fluid was derived using variational method, and the complex characteristic equation for the viscoelastic circular pipe conveying fluid was obtained by normalized power series method. The effects of dimensionless delay time on the variation relationship between dimensionless complex frequency of the clamped-clamped viscoelastic circular pipe conveying fluid with the Kelvin-Voigt model and dimensionless flow velocity were analyzed. For greater dimensionless delay time, the behavior of the viscoelastic pipe is that the first, second and third mode does not couple, while the pipe behaves divergent instability in the first and second order mode, then single-mode flutter takes place in the first order mode. 相似文献