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1.
As an essential model of magnetoelastic interaction between magnetic field and mechanical deformation, the study on magnetoelastic
buckling phenomenon of soft ferromagnetic plates in a magnetic environment has been conducted. One of the key steps for the
theoretical prediction of the critical magnetic field is how to formulate magnetic force exerted on the magnetized medium.
Till today, the theoretical predictions, from theoretical models in publications, of the magnetoelastic buckling of ferromagnetic
cantilevered beam-plate in transverse magnetic field are all higher than their experimental data. Sometimes, the discrepancy
between them is as high as 100%. In this paper, the macroscope formulation of the magnetic forces is strictly obtained from
the microscope Amperion current model. After that, a new theoretical model is established to describe the magnetoelastic buckling
phenomenon of ferromagnetic thin plates with geometrically nonlinear deformation in a nonuniform transverse magnetic field.
The numerical method for quantitative analysis is employed by combining the finite elemental method for magnetic fields and
the finite difference method for deformation of plates. The numerical results obtained from this new theoretical model show
that the theoretical predictions of critical values of the buckling magnetic field for the ferromagnetic cantilevered beam-plate
are in excellent agreement with their experimental data. By the way, the region of applicability to the Moon-Pao's model,
or the couple model, is checked by quantitative results.
This project was supported in part by the National Natural Science Foundation of China and the Foundation of the SEdC of China
for Returned Chinese Scholars from Abroad. 相似文献
2.
A two-dimensional linear spring model is established to study the microbuckling of a plane monomolecular layer adhering to
a substrate. The model is for the layer subjected to a compressive load having an arbitrary angle with the chemical bond of
the layer. The effects of the load angle, the strength of adhesion and the bending stiffness and shearing stiffness (the capability
of resisting transverse bending and in-plane shearing) of the layer on the minimal buckling force and the critical buckling
mode are discussed. It is found that the minimal buckling force increases with increasing load angle and, for a given bending
stiffness, increases with increasing strength of adhesion and decreasing shearing stiffness. Furthermore, a critical condition
under which the buckling of the layer can just occur is obtained, which is helpful to avoid buckling in an engineering application.
The project supported by the National Distinguished Young Scientist Fund, Cheung Kong Scholars Programme, the National Natural
Science Foundation of China (10272082, 10172068) and Shanghai Postdoctoral Science Foundation 相似文献
3.
Dr. B. Wu 《Archive of Applied Mechanics (Ingenieur Archiv)》1995,65(3):133-141
Summary The influence of shear deformation on the buckling behavior of a beam supported laterally by a Winkler elastic foundation is studied. A full investigation of the bifurcation points at which, under axial load, the beam becomes critical with respect to one or two simultaneous buckling modes is made. The configurations and stabilities of the equilibrium paths that bifurcate from the critical points are derived. From the results of theoretical analysis, it becomes evident that shear deformation has a considerable effect upon the equilibriums and stabilities of the post-buckling of the beam. The results for the Bernoulli-Euler beam can be obtained as a limiting case for those of the present beam by letting the shear stiffness tend to infinity.Supported by the National Natural Science Foundation of China 相似文献
4.
《International Journal of Solids and Structures》1999,36(14):2127-2141
Based on the theory of curved beams and the Biot–Savart law, a new theoretical model for magnetoelastic bending and buckling of superconducting toroidal field coils is developed and corroborated numerically. In contrast to the existing models, this model incorporates in-plane deformation of the coil. A semi-analytical approach is used to obtain the solution to the coupled problem. In order to validate the model and associated solution method, the experiment of Miya et al., 1982 is modeled. The theoretical predictions of the critical current of coils with none or one pin support are shown to be in excellent agreement with the published experimental data. It is also shown that the in-plane deformation has a significant influence on the critical current. 相似文献
5.
ON THE ORIENTATION OF BUCKLING DIRECTION OF ANISOTROPIC ELASTIC PLATE UNDER UNIAXIAL COMPRESSION 总被引:1,自引:0,他引:1
Zhang Yitong 《Acta Mechanica Solida Sinica》2001,14(2):130-137
The theory of small deformation superimposed on a large deformation of an elastic solid is used to investigate the buckling
of anisotropic elastic plate under uniaxial compression. The buckling direction (the direction of buckling wave) is generally
not aligned with the compression direction. The equation for determining the buckling direction is obtained. It is found that
the out-of-plane buckling of anisotropic elastic plate is possible and both buckling conditions for flexural and extensional
modes are presented.
As a specific case of buckling of anisotropic elastic plate, the buckling of an orthotropic elastic plate subjected to a compression
in a direction that forms an arbitrary angle with an elastic principal axis of the materials is analyzed. It is found that
the buckling direction depends on the angle between the compression direction and the principal axis of the materials, the
critical compressive force and plate-thickness parameters. In the case that the compression direction is aligned with the
principal axis of the materials, the buckling direction will be aligned with the compression one irrespective of critical
compressive force and plate-thickness.
Project supported by the National Natural Science Foundation of China (No. 19772032). 相似文献
6.
With the aid of the micro-mechanical model of knitted fabric proposed in Part 1 we analyze the buckling of a knitted fabric sheet when it is subjected to a tension along the wale direction. The large deformation of the fabric sheet in the critical configuration is considered and, to avoid possible deviation due to the approximation of the theory of thin plate, the three-dimensional theory of instability is used. The fabric sheet is considered as a three-dimensional body and all boundary conditions are satisfied. It is shown that the buckling of the fabric sheet is possible, two buckling modes and the corresponding buckling conditions are obtained, but only the flexural mode is physically possible as observed in experiments.The project supported by the National Natural Science Foundation of China (10272079) 相似文献
7.
The catastrophe theory is used to study the impact buckling of elastic structures. A criterion for impact buckling is established based on the proposed catastrophe system, in whose bifurcation set the critical step load is located. By the present theory, the impact torsional buckling for a clamped cylindrical shell is studied and the critical step torques for different imperfections are given. Also, the static critical torque is given, and it is shown that the critical step torque is smaller than the critical static torque.The project is supported by National Natural Science Foundation of China 相似文献
8.
In this paper, the dynamic buckling of an elastic-plastic column is studied. Let its dynamic buckling under step load be reduced
to a bifurcation problem caused by the propagation of axial elastic-plastic stress wave. The critical buckling condition is
given and the reflection of the elastic-plastic stress wave is taken into consideration. In the end, numerical computation
and conclusions are presented and obtained.
Foundation item: the National Natural Science Foundation of China (19672038) 相似文献
9.
Experimental studies on dynamic plastic buckling of circular cylindrical shells under axial impact 总被引:1,自引:0,他引:1
In the present paper, experimental studies on dynamic plasticbuckling of circular cylindrical shells under axial impact are
carried out. Hopkinson bar and drop hammer apparatus are used for dynamic loading. Three groups of circular cylindrical shells
made of copper are tested under axial impact. From the experiments, the first critical velocity corresponding to the axi-symmetric
buckling mode and the second critical velocity corresponding to the non-axisymmetric buckling mode are determined. The present
results come close to those of second critical velocity given by Wang Ren[4–6]. Two different kinds of non-axisymmetric buckling modes oval-shaped and triangle shaped are founded. The buckling modes under
two loading cases, viz. with small mass but high velocity and with large mass and low velocity using Hopkinson bar and drop
hammer, are different. Their critical energies are also discussed.
The project is supported by the National Natural Science Foundation of China (19672039) and the Foundation for Returned Scholar
from Abroad of Shanxi Province 相似文献
10.
On the basis of the first-order shear deformation plate theory and the zig-zag deformation assumption, an incremental finite
element formulation for nonlinear buckling analysis of the composite sandwich plate is deduced and the temperature-dependent
thermal and mechanical properties of composite is considered. A finite element method for thermal or thermo-mechanical coupling
nonlinear buckling analysis of the composite sandwich plate with an interfacial crack damage between face and core is also
developed. Numerical results and discussions concerning some typical examples show that the effects of the variation of the
thermal and mechanical properties with temperature, external compressive loading, size of the damage zone and ply angle of
the faces on the thermal buckling behavior are significant.
Project supported by the National Natural Science Foundation of China (No. 59975013). 相似文献
11.
An experimental investigation on the dynamic axial buckling of cylindrical shells using a Kolsky Bar
Several experiments were performed with a Kolsky Bar (Split Hopkinson Pressure Bar) device to investigate the dynamic axial
buckling of cylindrical shells. The Kolsky Bar is a loading as well as a measuring device which can subject the shells to
a fairly good square pulse. An attempt is made to understand the interaction between the stress wave and the dynamic buckling
of cylindrical shells. It is suggested that the dynamic axial buckling of the shells, elastic or elasto-plastic, is mainly
due to the compressive wave rather than the flexural or bending wave. The experimental results seem to support the two critical
velocity theory for plastic buckling, withV
c1
corresponding to an axisymmetric buckling mode andV
c2
corresponding to a non-symmetric buckling mode.
The project supported by National Natural Science Foundation of China 相似文献
12.
软铁磁薄板磁弹性屈曲的理论模型 总被引:5,自引:0,他引:5
铁磁弹性薄板的磁弹性屈曲问题一直作为电磁——弹性力学相互作用的一个基本模型进行研究,而作用在其磁介质上的磁力计算则是定量理论预测准确与否的关键.到目前为止,文献上已有的理论模型对悬臂铁磁梁式悬臂板在横向磁场中磁弹性屈曲的理论预测值始终高于实验值,有的甚至相差100%左右.本文基于电磁力计算的微观安培电流模型,严格给出了软铁磁薄板等效横向磁力的宏观计算表达式.在此基础上,建立了电磁——力学相互耦合作用的非线性理论模型.该模型能描述铁磁薄板结构在非均匀横向磁场环境中的磁弹性失稳(或屈曲).其定量分析采用了有限元法和有限差分法相结合.数值结果显示:本模型给出的磁弹性屈曲的临界磁场值与实验值符合良好.与此同时,文中还对文献中认为较成功的Moon-Pao模型的基本假设进行了分析.定量结果发现:Moon-Pao理论模型的基本假设仅在梁式板的长厚比L/h比较大时(约在200左右),是可以接受的,而当L/h较小时,该假设将导致理论值与实验值的较大误差.L/h比值越小,理论值与实验值的误差越大 相似文献
13.
Zhang Yitong 《Acta Mechanica Solida Sinica》2002,15(3):236-243
Out-of-plane buckling of anisotropic elastic plate subjected to a simple shear is investigated. From exact 3-D equilibrium
conditions of anisotropic elastic body with a plane of elastic symmetry at critical configuration, the eqution for buckling
direction (buckling wave direction) parameter is derived and the shape functions of possible buckling modes are obtained.
The traction free boundary conditions which must hold on the upper and lower surfaces of plate lead to a linear eigenvalue
problem whose nontrivial solutions are just the possible buckling modes for the plate. The buckling conditions for both flexural
and barreling modes are presented.
As a particular example of buckling of anisotropic elastic plate, the buckling of an orthotropic elastic plate, which is subjected
to simple shear along a direction making an arbitrary angle of θ with respect to an elastic principal axis of materials, is
analyzed. The buckling direction varies with θ and the critical amount of shear. The numerical results show that only the
flexural mode can indeed exist.
Project supported by the National Natural Science Foundation of China (No. 19772032). 相似文献
14.
BUCKLING ANALYSIS UNDER COMBINED LOADING OF THIN-WALLED PLATE ASSEMBLIES USING BUBBLE FUNCTIONS 总被引:2,自引:0,他引:2
Bubble functions are finite element modes that are zero on the boundary of the element but nonzero at the other point. The
present paper adds bubble functions to the ordinary Complex Finite Strip Method(CFSM) to calculate the elastic local buckling
stress of plates and plate assemblies. The results indicate that the use of bubble functions greatly improves the convergence
of the Finite Strip Method(FSM) in terms of strip subdivision, and leads to much smaller storage required for the structure
stiffness and stability matrices. Numerical examples are given, including plates and plate structures subjected to a combination
of longitudinal and transverse compression, bending and shear. This study illustrates the power of bubble functions in solving
stability problems of plates and plate structures.
The work was partly supported by the Natural Science Foundation of Jiangxi Province of China and by the Basic Theory Research
Foundation of Nanchang University. 相似文献
15.
The paper analyzes the nonlinear deformation of a current-carrying thin shell in coupled electromagnetic and mechanical fields.
The nonlinear magnetoelastic kinetic equations, physical equations, geometric equations, electrodynamic equations, expressions
for the Lorentz force of a current-carrying thin shell in a coupled field are given. The normal Cauchy form nonlinear differential
equations that include ten basic unknown functions are obtained by the variable replacement method. The difference and quasi-linearization
methods are used to reduce the nonlinear magnetoelastic equations to a sequence of quasilinear differential equations that
can be solved by discrete orthogonalization. Numerical solutions for the stresses and strains in a current-carrying thin strip
shell with two edges simply supported are obtained as an example. The dependence of the stresses and strains in the current-carrying
thin strip shell on the electromagnetic parameters is discussed. In a special case, it is shown that the deformation of the
shell can be controlled by changing the electromagnetic parameters 相似文献
16.
Experimental and theoretical study of the nonlinear response of agiant magnetostrictive rod 总被引:1,自引:0,他引:1
In this paper, a magnetomechanical coupling constitutive relation of the giant magnetostrictive material was investigated
experimentally and theoretically. A grain-oriented magnetostrictive rod of iron and rare earth was tested under a combined
magnetomechanical loading. Two types of experimental curves were obtained, i.e., the magnetostrictive curve of the extensional
strain vs the magnetic field, and the curve of the magnetic polarization intensity vs the pre-stress. A new theoretical constitutive
model, based on the density of domain switching, is developed. Comparison of the theoretical predictions with the experimental
results indicates that this model can capture the main characteristics of the magnetoelastic coupling deformation of a giant
magnetostrictive rod.
The project supported by the National Natural Science Foundation of China (10025209, 10132010, 10102007) 相似文献
17.
In this paper, the dynamics of a generalized two-neuron model with self-connections and distributed delays are investigated, together with the stability of the equilibrium. In particular, the conditions under which the Hopf bifurcation occurs at the equilibrium are obtained for the weak kernel. This means that a family of periodic solutions bifurcates from the equilibrium when the bifurcation parameter exceeds a critical value. Explicit algorithms for determining the stability of the bifurcating periodic solutions and the direction of the Hopf bifurcation are derived by using the theory of normal form and center manifold [20]. Some numerical simulations are given to illustrate the effectiveness of the results found. The obtained results are new and they complement previously known results.This work was supported by the National Natural Science Foundation of China under Grants 60574043 and 60373067, the Natural Science Foundation of Jiangsu Province, China under Grants BK2003053. 相似文献
18.
M. O. Peach N. S. Christopherson J. M. Dalrymple G. L. Viegelahn 《Experimental Mechanics》1988,28(1):65-69
This paper does not stand alone; it is directly related to N.S. Christopherson's experimental study1,2 of the magnetoelastic bending of thin steel plates, presented at a recent SEM meeting. It is, in fact, an extension of that study and relies upon some of Christopherson's data.In 1968, Moon and Pao presented a theory of the magnetoelastic buckling of a beam plate in a uniform magnetic field which differed from experimental results by a factor of two. Attempts to explain the discrepancy still leave approximately 25-percent error in the theoretical results as compared with experiment.We show that the assumption made by Moon and Pao—that a plate element experiences a force system consisting only of a couple, whose magnitude is proportional to the rotation of the element—is invalid for finite plates. An experiment is suggested for determining whether the assumption is valid for infinite plates. The present state of knowledge concerning magnetoelastic buckling is briefly summarized. Several types of magnetoelastic buckling are identified and briefly contrasted. Attention is directed to the importance of field discontinuities in problems involving magnetic deformation. Two paradoxical aspects of the Moon-Pao formula for the magnetoelastic buckling of beam plates are pointed out and briefly discussed. 相似文献
19.
Instead of the biharmonic type equation, a set of new governing equations and solving method for circular sector plate bending
is presented based on the analogy between plate bending and plane elasticity problems. So the Hamiltonian system can also
be applied to plate bending problems by introducing bending moment functions. The new method presents the analytical solutions
for the circular sector plate. The results show that the new method is effective.
Project supported by National Natural Science Foundation (No. 19732020) and the Doctoral Research Foundation of China. 相似文献
20.
The springback phenomenon of strong anisotropic sheet metals with U-channel bending as well as deep-drawing is numerically
studied in detail by using Updating Lagrange FEM based on virtual work-rate principle, Kirchhoff shell element models and
the Barlat-Lian planar anisotropic yield function. Simulation results are compared with a benchamark test. Very good agreement
is obtained between numerical and test results. The focus of the present study is on the numerical simulation of the springback
characteristics of the strong anisotropic sheet metals after unloading. The effects of the planar anisotropy coefficients
and yield function exponent in the B-L yield function on the springback characteristics are discussed in detail. Some conclusions
are given.
The project supported by the National Natural Science Foundation of China (No. 19832020) and Provincial Natural Science Foundation
of Jilin China (No.20000519) 相似文献