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1.
考虑剪切效应有限变形粘弹性板的动力稳定性 总被引：4，自引：0，他引：4
Based on Reddy‘s theory of plates with higher-order shear deformations and the Boltzmann superposition principles,the governing equations were established for dynamic stability of viscoelastic plates with finite deformations taking account of shear effects,The Galerkin method was applied to simplify the set of equations.The numerical methods in nonlinear dynamics were used to solve the simplified system.It could e seen that there are plenty of dynamic properties for this kind of viscoelastic plates under transverse harmonic loads.The influences of the transverse shear deformations and material parameter on the dynamic behavior of nonlinear viscoelatic plates were investigated. 相似文献
2.
Knitted fabric is very different from woven fabric due to its more complicated knitting structures. The buckling of knitted fabric sheets subjected to simple shear in the wale direction is investigated analytically in consideration of the large deformation of fabric sheet in critical configuration. The theory on instability of finite deformation is applied to the analysis. All the stress boundary conditions of knitted fabric sheet are satisfied. An equation to determine the buckling direction angle is derived. It is shown that there are two possible buckling modes, flexural mode and barreling mode. The buckling condition equations for the flexural mode and barreling mode are also obtained respectively. Numerical illustrations reveal that only the flexural mode can actually occur and the barreling mode cannot, which agrees with the experimental observations. For a permitted buckling mode on margin boundaries, the critical value of shear amount and the buckling direction angle can be determined. 相似文献
3.
The paraboloidal membrane shell with free boundary condition is actively controlled using photostrictive actuators which can provide contactless actuation under the illumination of ultraviolet light. The governing equations of the paraboloidal shell laminated with paired photostrictive actuators are established based on membrane approximation. The modal control actions of meridional/circumferential actuators are respectively formulated and evaluated by case studies. Constant light intensity related to the velocity of the shell is adopted, and then the governing equations are written in a closed-loop form which can be solved with Newmark-β method. Considering the multi-field coupling behavior of photostrictive actuators, time histories of transverse displacement and control light intensity are simulated and evaluated. The results show that photostrictive actuators can effectively control the vibration of the paraboloidal membrane shell, and the photostrictive actuators oriented along circumferential direction can give better control effect than photostrictive actuators placed along the meridional direction. 相似文献
4.
A closed-form out-of-plane dynamic displacement response of a curved track subjected to moving loads was pro- posed. The track structure was modeled as a planar curved Timoshenko beam periodically supported by the double-layer spring-damping elements. The general dynamic displacement response induced by the moving loads along the curve on the elastic semi-infinite space was firstly obtained in the frequency domain, according to the Duhamel integral and the dynamic reciprocity theorem. In the case of the periodic curved track structure subjected to moving loads, the dynamic displacement equation was simplified into a form of summation within the basic track cell instead of the integral. The transfer function for the curved track was expressed in the form of a transfer matrix. Single and series moving loads were involved in the calculation program. For the verification of the analytical model, the mid-span vertical deflection of a simply support curved beam subjected to moving load was recalculated and compared with the same case in the reference. The research results indicate that： under the same moving loads, the displacement response of the curved track decreases slightly with the increasing track radius, and the displacement response of the curved track with the radius greater than or equal to 600 m is almost equivalent to the displacement response of the straight track; the frequency spectrum of the curved track is more abundant than that of the straight track, which may result in more wheel-rail resonance and rail corrugation in the curved lines. 相似文献
5.
Strain growth is a phenomenon observed in containment vessels subjected to internal blast loading. The elastic response of the vessel may become larger in a later stage compared to its response during the initial stage. The dynamic responses of infinitely long cylindrical containment vessels subjected to uniformly-distributed internal blast loading are studied using LS-DYNA. The development of bending modes and the interaction between the breathing mode and bending modes are observed. The methodology developed for dynamic elastic buckling analysis is employed to study the strain growth phenomenon in explosion containment vessels. It is shown that the dynamic instable vibration of a containment vessel is the basic mechanism of strain growth. 相似文献
6.
The analyses of finite deformation and stress for a hyperelastic rectangular plate with some voids under an uniaxial extension were conducted. The governing differential equations were given from the incompressibility condition of the material. The solution was approximately obtained from the minimum potential energy principle. The growth of voids was discussed. One can see that an initial central circular-cylinder void becomes an elliptic-cylinder void, but an initial non-centeral circular-cylinder void becomes an elliptic-like cylinder void and the center of void has a shift. The stress distributions along the edges of voids were given and the phenomenon of stress concentration was observed. The influences of the distribution manner and size of voids, as well as the distance between them on the growth of voids were analyzed. 相似文献
7.
Rotor systems supported by angular contact ball bearings are complicated due to nonlinear Hertzian contact force. In this paper, nonlinear bearing forces of ball bearing under five-dimensional loads are given, and 5-DOF dynamic equations of a rigid rotor ball bearing system are established. Continuation-shooting algorithm for periodic solutions of the nonlinear non-autonomous dynamic system and Floquet multipliers of the system are used. Furthermore, the bifurcation and stability of the periodic motion of the system in different parametric domains are also studied. Results show that the bifurcation and stability of period-1 motion vary with structural parameters and operating parameters of the rigid rotor ball bearing system. Avoidance of unbalanced force and bending moment, appropriate initial contact angle, axial load and damping factor help enhance the unstable rotating speed of period-1 motion. 相似文献
8.
Current guidelines recommend using single-degree-of-freedom(SDOF) method for dynamic analysis of reinforced concretec (RC) structures against blast loads, which is not suitable for retrofitted members. Thus, a finite difference procedure developed in another study was used to accurately and efficiently analyze the dynamic response of fibre reinforced polymer (FRP) plated members under blast loads. It can accommodate changes in the mechanical properties of a member's cross section along its length and through its depth in each time step, making it possible to directly incorporate both strain rate effects (which will vary along the length and depth of a member) and non-uniform member loading to solve the partial differential equation of motion. The accuracy of the proposed method was validated in part using data from field blast testing. The finite difference procedure is implemented easily and enables accurate predictions of FRP-plated-member response. 相似文献
9.
The dynamic response of an infinite beam placed on a Pasternak foundation when the system was subjected to a moving load was investigated. We used the double Fourier transform and its inversion to solve the formulations of the problem. A closed form analytic solution of the beam was obtained by the theorem of residues. We selected a numerical example to illustrate the dynamic response of the beam on Pasternak and Winkler foundations, respectively. We discuss the effect of the moving load velocity on the dynamic displacement response of the beam. The maximum deflection of the beam increases slightly with increased load velocity but increases significantly with reduced shear modulus of subgrade at a given velocity. The maximum deflection of a beam resting on a Pasternak foundation is much smaller than that of a beam on a Winkler foundation. 相似文献
10.
The response of dynamic wave pressures on structures would be more complicated and bring about new phenomena under the dynamic interaction between soil asnd structure.In order to better understand the response characteristics on deeply embedded large cylindrical structures under random waves,and accordingly to offer valuable findings for engineering ,the authors designed wave flume experiments to investigate comparatively dynamic wave pressures on a single and on continuous cylinders with two different cembedment depths in response to two wave spectra ,The time histories of the water surface elevation and the corresponding dynamic wave pressures exerted on the cylinder were analyzed in the frequency domain,By calculating the transfer function and spectral density for dynamic wave pressures along the height and around the circumference of the cylinder,experimental results of the single cylinder were compared with the theoretical results based on the linear diffraction theory ,and detailed comparisons were also carried out between the single and continuous cylinders ,Some new findings and the corresponding analysis are reported in present paoer,The investigation on continuous cylinders will be used in particular for reference in engineering applications becaus information is scarce on studying such kind of problem both analytically and experimentally. 相似文献
11.
Zhou Chengti Wang Liedong 《大连大学学报》1993,(1)
本文用汉密尔顿原理导出了复合材料叠层圆柱壳的非线性动力稳定性的控制微分方程。在基本方程中包括了非线性大挠度、圆柱壳的初始几何缺陷,以及动力载荷的惯性力等因素的影响。本文的目的是分析复合材料圆柱壳的参数共振和确定壳体结构动力屈曲时的稳定性区域和不稳定性区域,作为求解的例题,本文对三种复合材料圆柱壳进行了数例计算:即 T300—5208石墨-环氧壳体,ARALL 叠层铝合金壳体,和 E-玻璃-环氧壳体,结果表明它们具有相当不同的动力稳定性能.由本文所得出的计算结果和分析结论对于考虑和设计复合材料圆柱壳的动力稳定性具有重要的实用意义. 相似文献
12.
Zhou Cheng-ti 《大连大学学报》1991,(1)
本文论述了复合材料的强度和稳定性理论中的三个近代问题:复合材料迭层板的强度准则,多层复合材料圆柱壳的非线性稳定性理论,以及复合材料板的动力稳定性理论。关于迭层板的强度准则,论述了目前以张量多项式形式所表述的唯象性破坏准则,着重讨论和比较了各种近代理论在确定耦合系数方面的特点和差别。提出了近代理论中所存在的困难和发展趋势。在多层复合材料圆柱壳的非线性稳定性理论分析中,主要的问题在于如何研究和考虑那些非线性因素,诸如由材料的剪切模量所引起的物理非线性,横向剪切变形的影响,壳体结构的初始缺陷和几何非线性,以及前屈曲变形和边界支承条件的影响等。本文指出了考虑这些因素的方法以及它们的影响程度。复合材料板的动力屈曲性能研究是一个重要的近代研究方向。本文提出了关于复合材料本身的阻尼系数,纵向和转动惯性力影响,横向剪切效应,迭层板的初始几何缺陷,以及增强纤维的铺设方向等因素对于动力屈曲性能的影响。同时提出了计算这些影响的方法,指出这些因素在复合材料板的动力稳定性分析中有着重要作用。 相似文献
13.
Zhou Chengti 《大连大学学报》1992,(1)
本文运用柯依脱理论(Koiter'sTheory)对于复合材料圆柱壳屈曲性能的初始缺陷影响进行了一般性分析,为复合材料壳体的初始缺陷敏感度分析建立了基本控制方程;壳体的初始缺陷被设定为具有某些固定形式的或者是随机形式的,为了讨论和比较各种复合材料叠层壳体的缺陷敏感度的影响,用数值算例计算了由玻璃/环氧,硼/环氧,和炭/环氧等复合材料所组成的圆柱壳体的届曲性能。 相似文献
14.
复合材料叠层板非线性动力稳定性理论的几个基本问题 总被引：1，自引：0，他引：1
本文研究了复合材料叠层板在周期性动力谐载荷作用下的非线性动力稳定性理论中的几个基本问题。其内容包括：用Hamilton原理建立一般性基本方程,考虑了大挠度非线性;惯性力的影响;耦合效应影响,横向剪切效应的影响,以及几何初始缺陷困数等。 相似文献
15.
讨论弹性有限长度杆端部受冲击载荷作用，在轴向应为波传播和反射过程中的动态屈曲问题．利用扰动方程的解、端部支承条件和应力波反射前后波阵面相容条件得到了动态屈曲的分叉条件，临界载荷和屈曲模态．数值结果表明：临界载荷有多个分支且随时间增加而降低；由于应力波在端部的反射，使临界载荷进一步下降．这个结果就解释了实验中的一些现象． 相似文献
16.
In this paper, a nonlinear mathematical model for analyzing dynamical response to the large deformation of piles with initial displacements is firstly established with the arc-coordinate, and it is a set of nonlinear integral-differential equations, in which, the Winkeler model is used to simulate the resistance of the soil to the pile. Secondly, a set of new auxiliary functions are introduced. The differential-integral equations are transformed into a set of nonlinear differential equations,and the differential quadrature method (DQM) and the finite difference method (FDM) are applied to discretize the set of nonlinear equations in the spatial and time domains, respectively. Then, the Newton-Raphson method is used to solve the set of discretization algebraic equations at each time step. Finally, numerical examples are presented, and the dynamical responses to the deformation of piles, including configuration, bending moment and shear force, are graphically illuminated. In calculation, two types of initial displacements and dynamical loads are applied, and the effects of parameters on the dynamical responses of piles are analyzed in detail. 相似文献
17.
The effect of weld reinforcement on axial plastic buckling of welded steel cylindrical shells is investigated through experimental
and numerical buckling analysis using six welded steel cylindrical shell specimens. The relationship between the amplitude
of weld reinforcement and the axial plastic buckling critical load is explored. The effect of the material yield strength
and the number of circumferential welds on the axial plastic buckling is studied. Results show that circumferential weld reinforcement
represents a severe imperfect form of axially compressed welded steel cylindrical shells and the axial plastic buckling critical
load decreases with the increment of the mean amplitude of circumferential weld reinforcement. The material yield strength
and the number of circumferential welds are found to have no significant effect on buckling waveforms; however, the axial
plastic buckling critical load can be decreased to some extent with the increase of the number of circumferential welds. 相似文献
18.
根据薄壳非线性动力学理论和拟壳法的思想,给出了扁球面网壳在动、静荷载协同作用下的非线性动力学控制方程.然后利用扁球面网壳的非线性动力学变分方程和协调方程,在夹紧固定的边界条件下,通过Galerkin作用得到一个含二次和三次的非线性动力学微分方程.用Floquet指数方法研究了系统的分岔问题,讨论了平衡点（奇点）邻域的稳定性问题.指出了系统在纯动态作用和在动静荷载协同作用下其平衡位置的变化情况. 相似文献