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921.
本文首先简要介绍了经典力学中的吉布斯-阿沛耳方程以及加速度极小原理。接着使用加速度极小原理推演了平面柔性多体系统的运动方程并与采用拉氏方程建立的该系统运动方程进行比较,证明了运用加速度极小原理建立运动方程要优于利用拉氏方程建立运动方程。此外,还运用加速度极小原理建立了大应变梁的运动方程。最后,基于加速度极小原理对大应变梁弹塑性运动进行直接求解,并将所得计算结果与采用ANSYS程序计算所得的结果进行了比较。按本文所得的结果与按ANSYS程序所得的结果很好地吻合,这证明了本文方法的正确性。应该指出,运用加速度极小原理是解决力学问题的很好的途径,它不仅可以简便地建立力学的控制方程,而且还可以得到较好的近似解答。 相似文献
922.
Tianhu Hao 《Acta Mechanica Sinica》2006,21(6):601-607
This paper presents an exact solution of the crack tip field in functionally gradient material with exponential variation
of elastic constants. The dimensionless Poisson's ratios ν
0 of the engineering materials (iron, glass . . .) are far less than one; therefore, neglecting them, one can simplify the
basic equation and the exact solution is easy to obtain. Although the exact solution for the case ν
0≠0 is also obtained, it is very complicated and the main result is the same with the case ν
0=0 (it will be dealt with in Appendix VII). It has been found that the exponential term exp (ax+by) in the constitutive equations becomes exp (ax/2+by/2−kr/2) in the exact solution.
The English text was polished by Keren Wang. 相似文献
923.
This paper investigates pitch motion and in orbital plane elastic vibration of a spacecraft with a flexible beam type appendage undergoing prescribed slew maneuver. The governing equations are transformed into a standard quasi-linear form, and then solved by Butenin's variation of parameters approach. Validity of the analytical solutions is assessed over a range of system parameters and initial conditions by comparing them with the results of numerical integration. The results show that they are very good approximations and provide extensive insight into the dynamical response of the system. 相似文献
924.
925.
In this work, a general inelastic framework for the derivation of general three-dimensional thermomechanical constitutive laws for materials undergoing phase transformations is proposed. The proposed framework is based on the generalized plasticity theory and on some basic elements from the theory of continuum damage mechanics. More specifically, a new elaborate formulation of generalized plasticity theory capable of accommodating the multiple and interacting loading mechanisms, which occur during the phase transformations, is developed. Furthermore, the stiffness variations occurring during phase transformations are taken into account by the proposed framework. For this purpose, the free energy is decomposed into elastic and inelastic parts, not in a conventional way, but in one which resembles the elastic-damage cases. Also, a rate-dependent version of the theory is provided. The concepts presented are applied for the derivation of a three-dimensional thermomechanical constitutive model for Shape Memory Alloy materials. Numerical simulations to show qualitatively the ability of the model to capture the behavior of the shape memory alloys are also presented. Furthermore, the model has been fitted to actual experimental results from the literature. 相似文献
926.
N. N. Pilyugin V. S. Khlebnikov 《Journal of Applied Mechanics and Technical Physics》2003,44(2):187-192
Results of experimental investigations of trans or supersonic flow around two bodies (cone–disk or sphere–disk) connected by a cylindrical rod along the axis of symmetry are presented. The special features of the flow are analyzed. It is found that the dependence of the drag coefficient Cx of a pair of bodies on the Mach number within the range 0.6 M 1.7 is nonmonotonic. The reasons for the hysteresis in the dependences Cx(M) for two bodies at the stages of flow acceleration and deceleration and discrete variation of the Mach number are clarified. The influence of cone angles and sizes of both bodies on the drag coefficient is estimated. 相似文献
927.
A crucial point still to be established in the prediction of the film thickness distribution in horizontal annular two-phase flow is the mechanism(s) for transporting liquid from the bottom to the top part of the tube. To resolve this issue, the time-dependent behaviour of the liquid film is studied. Wave characteristics such as velocity and frequency are measured around the circumference. It is inferred from the autospectral density functions of film thickness variation that disturbance waves play an important, but as yet unclear, role in the formation of a liquid film in the top part of the tube. A new mechanism, based on the shape of disturbance waves is proposed. 相似文献
928.
胡俍 《应用数学和力学(英文版)》1993,(6)
On the basis of paper[1],assuming the logarithm of thickness at arbitrary point on a U-shaped bellows meridian is linear with the logarithm of distance between that point and axis of symmetry,perturbation solutions of the corresponding problems of large axisymmetrical deflection are given.The effects of thickness distribution variation,which result from technology factors,on stiffness of bellows are discussed. 相似文献
929.
Duan Zhuping Wang Wenbiao Zheng Qingrong Huang Guojun Chen Diwen 《Acta Mechanica Sinica》1996,12(3):200-212
Based on the principle given in nonlinear diffusion-reaction dynamics, a new dynamic model for dislocation patterning is proposed
by introducing a relaxation time to the relation between dislocation density and dislocation flux. The so-called chemical
potential like quantities, which appear in the model can be derived from variation principle for free energy functional of
dislocated media, where the free energy density function is expessed in terms of not only the dislocation density itself but
also their spatial gradients. The linear stability analysis on the governing equations of a simple dislocation density shows
that there exists an intrinsic wave number leading to bifurcation of space structure of dislocation density. At the same time,
the numerical results also demonstrate the coexistence and transition between different dislocation patterns.
The project supported by the National Natural Science Foundation of China, Grant No.19392300 相似文献
930.
含压电片层合壳的有限元分析与控制仿真 总被引:5,自引:0,他引:5
本文首先针对含压电材料的一般结构,推导了按位移和电位移求解时的混合变分原理,在此基础上,通过对面电荷取变分,直接得到了含按电压驱动压电片层合壳的有限元方程,最后给出了利用压电片进行静变形和振动控制的仿真算例,并进行了分析。结果表明,本文建立的有限元方程准确、可靠。 相似文献