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41.
高精度转台控制系统研究 总被引:1,自引:0,他引:1
—本文针对精密转台控制系统在大偏差下的不稳定问题,对其控制系统进行了分析和设计,同时对其高分辨率的指令系统进行了设计,为提高转台的精度及其动态性能提供了新的途径。 相似文献
42.
Reissner板弯曲的复变函数分析方法 总被引:1,自引:0,他引:1
本文建立了Reissner板弯曲问题的复变函数分析方法,它可以有效地用于分析含一般孔洞板弯曲的应力集中问题。作为应用,文中还给出了一些计算实例。 相似文献
43.
This paper deals with a variational formulation for the sensitivity problem of beam systems in the context of deformable solids with cracks. Natural frequencies are defined as state variables involved in the energy functional of the system, while the cracks length and position are treated as system parameters. The hierarchical equation system is formed and solved for the first and second derivatives of the natural frequency functions with respect to the cracks length and position. An analytical procedure for calculations of the second-order sensitivities of natural frequencies is proposed for the non-symmetrical equation system operator. Numerical algorithms are worked out and implemented computationally. Analytical and numerical aspects of the problem are discussed in detail through a number of illustrative results.The support of this work by the State Committee for Scientific Research (KBN) under Grant No. 4-050-0148/17-98-00 is gratefully acknowledged. 相似文献
44.
一种提高薄板稳定分析精度的方法 总被引:1,自引:0,他引:1
在薄板稳定分析中,九参数三角形薄板单元因其形状简单,使用方便,在实际工程中得到了广泛应用。本文基于参数调正的几何刚度矩阵,对九参数三角形薄板单元的一致刚度矩阵进行了修正,为提高计算精度提供了一种有效方法。 相似文献
45.
46.
Tong-Yi Zhang 《Acta Mechanica Sinica》2002,18(5):537-550
The paper gives an overview on experimental observations of the failure behavior of electrically insulating and conducting
cracks in piezoelectric ceramics. The experiments include the indentation fracture test, the bending test on smooth samples,
and the fracture test on pre-notched (or pre-cracked) compact tension samples. For electrically insulating cracks, the experimental
results show a complicated fracture behavior under electrical and mechanical loading. Fracture data are much scattered when
a static electric field is applied. A statistically based fracture criterion is required. For electrically conducting cracks,
the experimental results demonstrate that static electric fields can fracture poled and depoled lead zirconate titanate ceramics
and that the concepts of fracture mechanics can be used to measure the electrical fracture toughness. Furthermore, the electrical
fracture toughness is much higher than the mechanical fracture toughness. The highly electrical fracture toughness arises
from the greater energy dissipation around the conductive crack tip under purely electric loading, which is impossible under
mechanical loading in the brittle ceramics.
The project supported by an RGC grant from the Research Grant Council of the Hong Kong Special Administrative Region, China 相似文献
47.
Gao Yuanwen 《Acta Mechanica Solida Sinica》2007,20(2):180-188
An analysis of buckling/snapping and bending behaviors of magneto-elastic-plastic interaction and coupling for cantilever rectangular soft ferromagnetic plates is presented.Based on the expression of magnetic force from the variational principle of ferromagnetic plates,the buckling and bending theory of thin plates,the Mises yield criterion and the increment theory for plastic deformation,we establish a numerical code to quantitatively simulate the behaviors of the nonlinearly multi-fields coupling problems by the finite element method.Along with the phenom- ena of buckling/snapping and bending,or the characteristic curve of deflection versus magnitude of applied magnetic fields being numerically displayed,the critical loads of buckling/snapping, and the influences of plastic deformation and the width of plate on these critical loads,the plastic regions expanding with the magnitude of applied magnetic field,as well as the evolvement of deflection configuration of the plate are numerically obtained in a case study. 相似文献
48.
Anthony N. Kounadis 《International Journal of Non》2007,42(1):24-35
The local dynamic instability of autonomous conservative, lumped-mass (discrete) systems, is thoroughly discussed when negligibly small dissipative forces are included. It is shown that such small forces may change drastically the response of these systems. Hence, existing, widely accepted, findings based on the omission of damping could not be valid if damping, being always present in actual systems, is included. More specifically the conditions under which the above systems may experience dynamic bifurcations associated either with a degenerate or a generic Hopf bifurcation are examined in detail by studying the effect of the structure of the damping matrix on the Jacobian eigenvalues. The case whereby this phenomenon may occur before divergence is discussed in connection with the individual or coupling effect of non-uniform mass and stiffness distribution. Jump phenomena in the critical dynamic loading at a certain mass distribution are also assessed. Numerical results verified by a non-linear dynamic analysis using 2-DOF and 3-DOF models confirm the validity of the theoretical findings as well as the efficiency of the technique proposed herein. 相似文献
49.
I. Yu. Tsvelodub 《Journal of Applied Mechanics and Technical Physics》2006,47(6):899-904
An infinite elastic isotropic plate with an elliptical, physically nonlinear inclusion loaded at infinity by uniformly distributed
moments is considered. Surface loads are absent. The problem of the stress-strain state of the plate is solved in a closed
form. It is shown that, for reasonably general stress-strain relations for the inclusion, the bending-moment field (and the
corresponding curvatures) in the inclusion is homogeneous.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 6, pp. 152–157, November–December, 2006. 相似文献
50.
Benchmark solution of angle-ply piezoelectric-laminated cylindrical panels in cylindrical bending with weak interfaces 总被引:3,自引:0,他引:3
The bending problem of a simply supported, angle-ply piezoelectric-laminated cylindrical panel in cylindrical bending with weak interfaces is considered. A general spring-layer model is adopted to describe the weakness of imperfect interfaces. An exact analysis is performed via the state-space approach. A new system of physical variables is introduced and a variable substitution technique is employed to derive a state equation with constant coefficients. Numerical results are given to show the effect of weak interfaces.The work was supported by the National Natural Science Foundation of China (No. 10372088) and by the Korea Institute of Science and Technology Evaluation and Planning. 相似文献