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1.
脉冲热能沉积薄板中热弹性弯曲运动的分析   总被引:2,自引:0,他引:2  
研究脉冲热能沉积薄板中,由于板厚方向的温度梯度和空间径向温度Gauss分布状态,所产生的辐射热能引起的弯曲运动效应。文章从非耦合的经典的Bernoulli—Euler理论出发,得到热弯曲动力学方程,求解初值问题,利用Laplace变换和Hankel变换,针对短脉冲和连续热辐射进行了分析,并给出热弹性弯曲波的数值计算结果。与文献[8]的实验结果比较,二者是相符的。  相似文献   

2.
 基于空间轴对称热弹性理论和最大剪应力强度理论,建立了脉冲激光辐照下薄片发生反冲塞破坏的一个理论模型,导出了薄片反冲塞的激光功率密度阈值条件。以空间均匀分布的ms级脉冲激光辐照铜薄片为例进行了理论计算和数值模拟,给出了激光功率密度阈值随薄片厚度线性增加的关系,得到了与文献中相应实验结果基本一致的薄片反冲塞破坏的激光功率密度阈值数据。  相似文献   

3.
薄壁结构广泛应用于实际工程中,局部材料性能的变化、局部热应力等因素均影响结构的屈曲承载力。为考察局部升温对薄壁结构屈曲承载力的影响,通过激光辐照实现薄壁结构的局部快速升温。采用温度-位移耦合法进行非线性热屈曲分析,获得了激光功率密度、辐照光斑半径和薄板厚度对薄板热屈曲的影响;在此基础上采用弧长法分析轴向受压薄板结构在局部激光辐照下的整体屈曲承载力。数值结果表明:薄板结构的整体屈曲承载力随激光辐照时间的增加及辐照光斑半径的增大呈线性下降趋势,随薄板厚度的增加近似呈指数增大。  相似文献   

4.
 利用有限Hankel变换法,导出了周界等温-弹性支撑圆薄板在激光束辐照下的轴对称耦合热弹性弯曲振动近似解;针对具有不同弹性模量和热膨胀系数的薄板进行了热力耦合和非耦合弯曲振动的解析和有限元计算与分析。结果表明:热力耦合效应使薄板振动的振幅和周期都有所减小,其程度与材料的性能参数(如弹性模量和热膨胀系数等)密切相关,材料弹性模量和热膨胀系数越大,板振动中的热力耦合效应就越明显。  相似文献   

5.
强激光辐照下预载柱壳热屈曲失效的数值分析   总被引:3,自引:0,他引:3       下载免费PDF全文
 采用有限元方法(ANSYS7.0)和简易的热力耦合本构关系,较系统地数值研究了预载柱壳受激光辐照时的热力响应和热屈曲失效行为,分析了几种壳体在不同预载条件下(轴压或内压)的屈曲模态和屈曲特征值,给出了屈曲模态和热屈曲失效与激光强度、辐照时间、预载条件和壳体几何尺度及形状间的定量或定性关系。计算结果表明:(1)屈曲失效行为主要集中在激光辐照区内且以径向屈曲为主。(2)在一定范围内,屈曲特征值与光斑中心点温度近似有线性关系。(3)激光辐照区内高温引起的材料软化和预载径向变形的耦合作用是柱壳发生热屈曲失效的根本原因,有效提高结构刚度,可使屈曲特征值提高。(4)壳体形状的改变对内压柱壳有更为明显的影响,其中圆柱形壳体屈曲特征值最大,因此具有较高的安全性。  相似文献   

6.
张国亭  黄俊杰  阿拉坦仓 《物理学报》2012,61(14):140205-140205
研究弹性理论中一类非自伴算子矩阵的本征向量展开定理. 证明了其本征向量组具有辛正交性, 给出了本征向量组完备的充分必要条件, 并将所得结果应用于板弯曲问题和矩形薄板均匀变压屈曲挠度方程中.  相似文献   

7.
本文根据弹性理论最小势能原理和变分技术,确定不同弹性材料层胶合的复合板弯曲运动时的中和面位置,并引人复合板的等效弹性常数和等效质量,从而导出复合薄板弯曲振动方程和边界条件的简洁形式;跟据粘弹性理论还得出:粘弹性层和弹性层复合板的振动方程;采用模态分析和傅里叶变换法给出矩形复合薄板自由振动和强迫振动的一般分析解;以钢板作为基板,进行数值计算得出不同厚度、不同材料覆盖层的复合板的等效刚度、泊松比和面密度,以及简支条件下简正模式的阻尼常数、阻力系数和固有频率。  相似文献   

8.
假设弹性势能正比于曲率平方,由变分原理,得到了在外力作用下处于平衡状态的弹性物体的形状方程.通过实验验证了弹性势能的假设.对于特定边界条件,弯曲薄板给出了水滴和心形形状.  相似文献   

9.
利用蒙特卡罗软件GEANT4模拟太阳宇宙射线中能量为1 MeV~10 GeV质子对航天飞行器的影响,透射质子对半导体材料的损伤效应,计算外壳铝层对质子能谱的屏蔽效应.模拟结果表明,质子在介质中的线性能量转移、射程等和参考数据吻合较好;沿质子轨迹纵向能量沉积出现Bragg峰,且非弹性作用是影响能量沉积Bragg曲线的重要因素;对于半导体Si材料,反冲原子主要分布在质子轨迹线周围,并沿轨迹线横向‘扩散',浓度降低;Al层屏蔽使入射质子能谱硬化,当Al层厚度超过10 mm时,厚度增加对屏蔽效果的改善不明显,反而次级粒子辐射增强效应变大.  相似文献   

10.
刘培生 《物理学报》2010,59(12):8801-8806
压缩是工程材料最基本的承载方式之一,多孔材料中的孔棱受到压缩载荷时可能产生屈曲行为.建立了各向同性三维网状高孔率多孔材料的简化结构失效模型,分析了这种材料在不同压缩载荷作用下由于孔棱发生屈曲而引起的失效模式,系统地得出了单向压缩、双向压缩和三向压缩等三种承载形式下这种多孔体受压而导致孔棱屈曲时名义主应力与孔率的数理关系.在此基础上,进一步得出了此类材料在压缩载荷作用下发生孔棱屈曲的载荷条件.  相似文献   

11.
Based on the first order shear deformation theory and classic buckling theory, the paper investigates the creep buckling behavior of viscoelastic laminated plates and laminated circular cylindrical shells. The analysis and elaboration of both instantaneous elastic critic load and durable critic load are emphasized. The buckling load in phase domain is obtained from governing equations by applying Laplace transform, and the instantaneous elastic critic load and durable critic load are determined according to the extreme value theorem for inverse Laplace transform. It is shown that viscoelastic approach and quasi-elastic approach yield identical solutions for these two types of critic load respectively. A transverse disturbance model is developed to give the same mechanics significance of durable critic load as that of elastic critic load. Two types of critic loads of boron/epoxy composite laminated plates and circular cylindrical shells are discussed in detail individually, and the influencing factors to induce creep buckling are revealed by examining the viscoelasticity incorporated in transverse shear deformation and in-plane flexibility.  相似文献   

12.
用有限元方法研究了三维弹性细杆在扭矩作用下的屈曲.利用自然坐标形式的细长空间曲杆的能量方程和2节点12个自由度的自然坐标形式的三维曲梁单元,采用特征值分析方法,研究分析了同时受有轴力和扭矩作用时的空间弹性细杆的屈曲问题.数值结果与存在的理论解极为吻合.具有一定曲率和挠率的空间细长曲杆,其临界扭矩值与扭矩的指向有着极其明显的关系.  相似文献   

13.
三合板的一般弹性理论   总被引:2,自引:0,他引:2       下载免费PDF全文
杜庆华 《物理学报》1954,10(4):395-412
一.引言 本文所指之三合板是一种轻质板材,在航空工业上近年来有广泛的应用。板由三层材料构成:外层为二硬薄钣(金属薄钣),夹心为较轻软之材料(如泡状醋酸赛璐珞、软木、或蜂巢状金属材料)。前者称为表钣,后者称为夹心,表钣与夹心胶合成一综合板。三合板之形变与应力之计算在十多年来曾引起力学家与工  相似文献   

14.
A general model of dynamic bending of isotropic micropolar elastic thin plates with independent fields of displacements and rotations is presented. The model has been justified asymptotically based on the solutions for special cases subject to simplifying assumptions. The model incorporates transverse shear deformations. Neglecting transverse shear, a model of the dynamics of micropolar elastic thin plates is also constructed. Then, we study free and forced oscillations and derive the natural frequencies, the amplitudes of the forced oscillations and the resonance conditions for micropolar elastic hinge-supported rectangular and circular plates. Finally, the basic characteristic features of micropolar plates are numerically analysed for different values of various elastic and inertial constants of the micropolar material.  相似文献   

15.
In this article, the buckling behavior of nanoscale circular plates under uniform radial compression is studied. Small-scale effect is taken into consideration. Using nonlocal elasticity theory the governing equations are derived for the circular single-layered graphene sheets (SLGS). Explicit expressions for the buckling loads are obtained for clamped and simply supported boundary conditions. It is shown that nonlocal effects play an important role in the buckling of circular nanoplates. The effects of the small scale on the buckling loads considering various parameters such as the radius of the plate and mode numbers are investigated.  相似文献   

16.
This paper is concerned with the determination of exact buckling loads and vibration frequencies of multi-stepped rectangular plates based on the classical thin (Kirchhoff) plate theory. The plate is assumed to have two opposite edges simply supported while the other two edges can take any combination of free, simply supported and clamped conditions. The proposed analytical method for solution involves the Levy method and the state-space technique. By using this analytical method, exact buckling and vibration solutions are obtained for rectangular plates having one- and two-step thickness variations. These exact solutions are extremely useful as benchmark values for researchers developing numerical techniques and software for analyzing non-uniform thickness plates.  相似文献   

17.
Atomic force microscopy observations of the free surface of gold thin films deposited on silicon substrates have evidenced the buckling of the films and the formation of blister patterns undergoing plastic folding. The classical elastic buckling and plastic deformation of the films are analyzed in the framework of the F?ppl-Von Kármán theory of thin plates introducing the notion of low-angle tilt boundaries and dislocation distributions to describe this folding effect. It is demonstrated that, in agreement with elementary plasticity of bent crystals, the presence of such tilt-boundaries results in the formation of buckling patterns of lower energy than "classical" elastic blisters.  相似文献   

18.
The steady state response of a damped circular plate transversely or rotationally driven at a diameter is determined by the series-type method. With the reaction force or moment acting along a diameter of a circular plate regarded as an unknown harmonic load, the response of the plate to the load is expressed by the Green function. The force or moment distribution along the diameter is expanded into Fourier series with unknown coefficients, and the simultaneous linear equations for the coefficients are derived by the restraint condition on the diameter. The dynamic response of the plate is determined by solving the equations. The method is applied to circular plates driven by a sinusoidally varying transverse deflection or angular rotation at a diameter, and the steady state response of the plates is studied.  相似文献   

19.
In this paper, the axisymmetric dynamic behavior and snap-through buckling of thin elastic shallow spherical shells under harmonic excitation is investigated. Based on Marguerre kinematical assumptions, the governing partial differential equations of motion for a pre-loaded cap are presented in the form of a compatibility equation and a transverse motion equation. The continuous model is reduced to a finite degree of freedom system using the Galerkin method and a Fourier-Bessel approach. Results show that pre-loaded shells may exhibit co-existing stable equilibrium states and that with the application of sufficiently large dynamic loads the structure escapes from the well corresponding to pre-buckling configurations to another. This escape load may be much lower than the corresponding quasi-static buckling load. Indeed, complex resonances can occur until the system snaps-through, often signalling the loss of stability. As parameters are slowly varied, steady state instabilities may occur; these can include jumps to resonance, subharmonic period-doubling bifurcations, cascades to chaos, etc. Moreover a sudden pulse of excitation may lead to a transient failure of the system. In this paper, we examine how spherical caps under harmonic loading may be assessed in an engineering context, with a view to design against steady state instabilities as well as the various modes of transient failure. Steady state and transient stability boundaries are presented in which special attention is devoted to the determination of the critical load conditions. From this theoretical analysis, dynamic buckling criteria can be properly established which may constitute a consistent and rational basis for design of these shell structures under harmonic loading.  相似文献   

20.
In this paper, an analytical solution is provided for the nonlinear free vibration behavior of plates made of functionally graded materials. The material properties of the functionally graded plates are assumed to vary continuously through the thickness, according to a power-law distribution of the volume fraction of the constituents. The fundamental equations for thin rectangular plates of functionally graded materials are obtained using the von Karman theory for large transverse deflection, and the solution is obtained in terms of mixed Fourier series. The effect of material properties, boundary conditions and thermal loading on the dynamic behavior of the plates is determined and discussed. The results reveal that nonlinear coupling effects play a major role in dictating the fundamental frequency of functionally graded plates.  相似文献   

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