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本文基于Total Lagrangian增量叠加方法,采用Kirchhoff应力增量和Green应变增量表示的动力虚功方程和Kirchhoff应力-Green应变的单积分型本构关系,导出粘弹性大变形的动力变分方程。依此采用Newmark法和八节点轴对称等参数元与二十节点三维等参数元编制了轴对称及三维问题的动力响应计算程序,典型例题的计算结果表明分析符合结构的物理性质。 相似文献
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本文应用由Simo和Rifai建议的混合假定附加应变途径,采用第二Piola-Kirchhoff应力张量和Green-Lagrange应变张量作能量共轭的应力应变度量,导出了Lagrange几何非线性下的胡海昌-Washizu三变量变分原理的Galerkin形式以及相应的混合假定应变元公式。 相似文献
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本文基于总体拉格朗日坐标描述法,采用Kirchoff应力张量和Green应变张量定义,导出了严格意义下的杆单元增量列式,计算表明本文方法可以有效用于空间桁架结构大位移问题分析。 相似文献
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提出一种任意四边形Reissner-Mindlin板元,挠度和转角均采用分片双线性函数。但剪切应变用它的线性扦值所代替,当板厚趋于零时这对应于Kirchhoff条件,因而避免了Locking现象。给出数值结果表明该单元的有效性。 相似文献
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离散Kirchhoff三角形薄板单元的改进 总被引:2,自引:0,他引:2
本文构造了一类改进的离散Kirchhoff三角形薄板单元。通过对离散Kirchhoff单元能量表达式的分解,发现存在一项不影响单元的收敛,但能控制单元精度的积分--有关绕Z轴的转动偶的积分。该项在经典薄板理论下是不存在的,但在粗网络下它会对单元的精度产生重要影响。通过合理调整该项在能量泛函中的比例,会使单元的精度得到明显改善。 相似文献
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本文用摄动的方法将Reissner板的变曲问题转化为一系列Kirchoff板弯曲问题的叠加,并用后者简单的Green函数按域外奇步法求解。数值算例表明,这种算法单且精度高。 相似文献
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Quantitative measurement of liquid mass distribution is demonstrated in an impinging-jet atomizing spray using a broadband, ∼80 keV X-ray tube source for 2-D radiography and 3-D computed tomography (CT). The accuracy, precision, and sensitivity of these data are evaluated using narrowband, ∼10 keV, synchrotron radiation from the Argonne National Laboratory Advanced Photon Source (APS) at the same flow conditions. It is found that the broadband X-ray tube source can be used for 2-D measurement of the equivalent path length (EPL) and 3-D CT imaging of liquid mass distribution with typical error of 5–10%. Data are compared for cases with and without the use of potassium iodide (KI), which at 15% concentration by mass increases the attenuation coefficient eightfold and enables 2-D and 3-D measurement of EPL with a signal-to-noise ratio (SNR) of 5:1 down to 15 μm. At this concentration, the effects of energy-dependent attenuation (i.e., spectral beam hardening) are negligible for EPL up to 5 mm. Hence, the use of broadband X-ray tube sources is feasible for many practical engineering sprays with a dynamic range in EPL of ∼330:1. The advantages and limitations of using broadband and narrowband X-ray sources are discussed, and recommendations for improving performance are presented. 相似文献
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Jian-Fei Lu Dong-Sheng Jeng Sally Williams 《International Journal of Solids and Structures》2008,45(2):378-391
Based on Biot’s theory, the dynamic 2.5-D Green’s function for a saturated porous medium is obtained using the Fourier transform and the potential decomposition methods. The 2.5-D Green’s function corresponds to the solutions for the following two problems: the point force applied to the solid skeleton, and the dilatation source applied within the pore fluid. By performing the Fourier transform on the governing equations for the 3-D Green’s function, the governing differential equations for the two parts of the 2.5-D Green’s function are established and then solved to obtain the dynamic 2.5-D Green’s function. The derived 2.5-D Green’s function for saturated porous media is verified through comparison with the existing solution for 2.5-D Green’s function for the elastodynamic case and the closed-form 3-D Green’s function for saturated porous media. It is further demonstrated that a simple form 2-D Green’s function for saturated porous media can be been obtained using the potential decomposition method. 相似文献
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风力机叶片的三维非定常气动特性估算 总被引:1,自引:0,他引:1
结合动量-叶素理论、非定常空气动力和动态失速模型来计算风力机叶片的二维非定常气动特性,并在此基础上经过适当修正后考虑三维旋转效应的非定常气动特性。分析比较二维和三维两种计算结果,给出更为合理的计算叶片非定常气动特性的方法。计算结果表明,风力机叶片的三维非定常气动特性计算结果与二维时的计算结果相比有较大改善。 相似文献
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R. Rojas-Díaz A. Sáez F. García-Sánchez Ch. Zhang 《International Journal of Solids and Structures》2008,45(1):144-158
Two-dimensional (2-D) and three-dimensional (3-D) time-harmonic Green’s functions for linear magnetoelectroelastic solids are derived in this paper by means of Radon-transform. Displacement field and electric and magnetic potentials in a fully anisotropic magnetoelectroelastic infinite solid due to a time-harmonic point force, point charge and magnetic monopole are obtained in form of line integrals over a unit circle in 2-D case and surface integrals over a unit sphere in 3-D case. This dynamic fundamental solution is then split into the sum of regular dynamic plus singular terms. The singular terms coincide with the Green’s functions for the static problem and may be further reduced to closed form expressions. The proposed Green’s functions can be used in the corresponding boundary element method (BEM) formulation. 相似文献
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对曲边柱壳受轴向非均匀内压作用下的大转动几何非线性3-D动力学行为进行了研究.基于Nayfeh and Pai[1]非线性壳体理论,给出了考虑几何非线性的3-D混合型(含内力与位移)动力学模型.为了克服该强非线性模型难以求解的问题,依据分析获得的结构静动态变形关系,采用Lagrange方程推导建立了基于结构静态解的曲边柱壳多自由度3-D动力学方程,并对其进行了线性化与降阶处理,结合差分法获得了一套高效的求解算法.与LS-DYNA有限元结果的吻合,验证了本文方法的正确性.最后分析了单元数和计算时间步分别对有限元模型和本文方法的影响,发现求解精度随着计算时间步的减小不断提高直至趋于稳定.同时对采用本文方法获得的曲边柱壳动态变形模式的分析表明:结构动态响应与其所受内压载荷沿轴向的分布形式关系紧密,可以通过改变或者设计内压轴向分布形式来影响以及控制结构的动态变形模式,从而应用于曲边柱壳结构设计及优化的工程实际中. 相似文献
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《European Journal of Mechanics - A/Solids》2005,24(3):519-531
Transient dynamic response of a rolling tire impacting with a small cleat is analyzed by an explicit finite element method. A 3-D tire model considering detailed tread blocks is used to accurately simulate the local tire-cleat impact process. The frictional dynamic contact problem is formulated by making use of total Lagrangian scheme and the penalty method. By imposing mass-proportional damping to only the tire parts showing the significant lateral deformation, the dynamic viscosity effect is artificially reflected. Time-history and frequency responses of the dynamic forces exerted on the tire axis are numerically predicted and assessed through the comparison with experimental results. As well as, the effects of the tire rolling speed and the inflation pressure on the transient dynamic response are parametrically investigated. 相似文献
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IntroductionThetransientanalysisfor 3_Delastodynamiccrackproblemsisanimportantcontentinfracturemechanics.Becauseofthedifficultiesoftheproblems,thecalculationofDSIFfor 3_Dcrackisaproblemunsolvedcompletelyuptothepresent.Chen[1]firstlyusedthefinitedifference… 相似文献
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《European Journal of Mechanics - A/Solids》2001,20(3):509-520
The primary purpose of this paper is to analyze the effects of vibrations on the comfort and road holding capability of road vehicles as observed in the variation of different parameters such as suspension coefficients, road disturbances, and the seat position. This study required the development of a mathematical model to simulate the dynamic behavior of a 3-D vehicle. With this model, various types of non-linear suspensions such as active and semi-active suspensions may be investigated. The results obtained from the simulation of the 3-D vehicle demonstrate that the use of active and semi-active suspension models on road vehicles prove to be beneficial for comfort without unduly compromising road holding capability. 相似文献
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This paper proposes a numerical method for analyzing whipping using a fully coupled hydroelastic model. The numerical analysis method utilizes a 3-D Rankine panel method, 1-D/3-D finite element methods, and a 2-D generalized Wagner model, which are strongly coupled in the time domain. The computational results were compared with those of a model test of an 18 000-TEU containership. The slamming pressures and whipping responses to regular waves for bow flare and stern slamming were compared. Furthermore, the slamming pressure was decomposed into its dynamic and static components. The numerical and experimental models produced similar results. In addition, the effects of the discretization and geometric approximation of the 2-D slamming sections were investigated. 相似文献
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J.-Y. Cho A.V. Idesman V.I. Levitas T. Park 《International Journal of Solids and Structures》2012,49(14):1973-1992
A finite element approach is suggested for the modeling of multivariant stress-induced martensitic phase transitions (PTs) in elastic materials at the nanoscale for the 2-D and 3-D cases, for quasi-static and dynamic formulations. The approach is based on the phase-field theory, which includes the Ginzburg–Landau equations with an advanced thermodynamic potential that captures the main features of macroscopic stress–strain curves. The model consists of a coupled system of the Ginzburg–Landau equations and the static or dynamic elasticity equations, and it describes evolution of distributions of austenite and different martensitic variants in terms of corresponding order parameters. The suggested explicit finite element algorithm allows decoupling of the Ginzburg–Landau and elasticity equations for small time increments. Based on the developed phase-field approach, the simulation of the microstructure evolution for cubic-tetragonal martensitic PT in a NiAl alloy is presented for quasi-statics (i.e., without inertial forces) and dynamic formulations in the 2-D and 3-D cases. The numerical results show the significant influence of inertial effects on microstructure evolution in single- and polycrystalline samples, even for the traditional problem of relaxation of initial perturbations to stationary microstructure. 相似文献