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1.
依据新的精确的锥壳屈曲分支方程 ,研究承受轴向压力的刚性圆顶夹支截锥壳的稳定性。构造的屈曲模态接近分支点变形。应用 Galerkin法计算了各种截锥比壳体在全锥度的临界特征值、屈曲荷载和临界应力。结果表明 ,轴压屈曲临界应力σcr 随几何参数ν的减小和截锥比λ的增大而减小。  相似文献   

2.
功能梯度材料剪切板屈曲后的自由振动   总被引:2,自引:0,他引:2       下载免费PDF全文
基于Reddy高阶剪切变形理论和广义Kámán型方程,对热环境中功能梯度材料剪切板屈曲后的自由振动进行了分析,分析中同时考虑材料热物参数对温度变化的依赖性及热传导.数值算例给出均匀和非均匀温度场中功能梯度材料剪切板在轴向压缩荷载作用下的振动特性,并讨论了材料组分指数、温度场等参数变化所带来的影响.  相似文献   

3.
激波风洞高低压段钢膜片破裂特性研究   总被引:1,自引:0,他引:1       下载免费PDF全文
激波风洞是用于高超声速飞行器气动外形设计和优化的常用地面试验装置,基于爆轰驱动技术,激波风洞能够在短时间(毫秒级)内产生高温、高压的驱动气体来模拟高超声速试验气流.主膜片位于激波风洞中的爆轰驱动段和激波管段之间,试验时膜片在爆轰脉冲压力下打开,膜片的打开状态和脱落情况对激波风洞气流品质有很大的影响. 同时,膜片也是形成激波的先决条件. 传统的风洞采用铝质膜片进行试验,在激波风洞中需要承压能力更强的膜片, 此时铝质膜片不再适用, 需要采用钢质膜片.因此, 对激波风洞中的钢膜片破裂特性进行研究很有必要.将数值计算结果与试验结果进行比较, 发现数值计算结果与试验结果吻合得比较理想,计算结果具有可靠性. 基于膜片的应力-应变模型, 建立了膜片打开的动力学模型,根据CJ爆轰理论, 采用有限元软件计算模拟了膜片破裂的过程,分析总结了膜片破裂的机制和力学特性规律.采用控制变量法对不同厚度和凹槽长度的膜片进行分析研究,得到了膜片破膜压力和有效破膜时间的变化规律. 在激波风洞试验中,根据膜片总破膜时间设计了适用于JF-12复现风洞的膜片参数.  相似文献   

4.
文章用三维弹性理论的非线性应变公式研究了弹性薄板的后屈曲特性,旨在探讨冯·卡门平板大挠度方程的可靠性范围。计算结果表明,当板中薄膜力较大时,用冯·卡门方程描述后屈曲问题会产生较大的误差。  相似文献   

5.
弹性直杆动态屈曲与后屈曲的实验研究   总被引:7,自引:0,他引:7       下载免费PDF全文
对传统的霍普金森压杆装置(SHPB)进行改进,用于研究弹性直杆的动态屈曲与后屈曲,并且分析了影响实验精度的因素。实验结果表明,在轴向应力波作用下弹性直杆的动态屈曲临界载荷明显高于静态的,并且在屈曲发生后,在直杆中有弯曲波产生,其波速大约为弹性剪切波的波速。  相似文献   

6.
研究了轴向力作用下受圆柱横向约束的弹性杆的屈曲和后屈曲行为。通过有限元模拟,分析了细长压杆发生正弦和螺旋屈曲的轴向临界力,提出了正弦和螺旋屈曲临界点判定方法,且与文献结果比较验证了分析的正确性。同时考察了长细比和边界条件等因素对临界力的影响。结果表明正弦屈曲临界力和螺旋屈曲临界力随杆的长细比减小而增大。杆在一定长度范围内,端部约束条件对临界屈曲载荷及模态的影响不可忽略;当杆的长度足够长时,可以忽略边界条件对临界载荷的影响。  相似文献   

7.
本文运用ABAQUS有限元软件模拟深海输油管道的后屈曲及屈曲传播现象.将深海输油管道视为内、外层为合金钢材,夹心为聚氨酯泡沫的输油管道.采用线弹性-线性硬化的本构关系,运用Riks分析法获得后屈曲平衡路径,以此模拟管道中的屈曲传播过程,并获得屈曲传播压力.通过数值算例,综合讨论了不同初始缺陷、不同径厚比、不同夹层与夹心厚度比对、不同的材料弹性模量对屈曲传播过程和压力的影响.最后将输油管退化为单层管,将传播压力的有限元结果与实验结果、Palmer理论解比较.结果表明有限元值、实验结果、理论值三者比较吻合.验证了有限元分析的正确性.  相似文献   

8.
功能梯度材料制成的微纳结构元件的力学性能截然不同于常规材料制成的宏观结构.本文基于Kirchhoff板理论以及考虑剪切变形的Mindlin板理论,研究了表面效应影响下功能梯度夹层纳米板的屈曲和后屈曲行为.通过平衡分析导出了屈曲和后屈曲的控制方程,得到了单轴和双轴压缩下临界屈曲载荷的解析解.利用Galerkin方法,给出了加载边可动和不可动两种边界条件下临界后屈曲载荷解答.数值结果表明,表面效应对功能梯度纳米层合板稳定性的影响与组成板的材料的体积分数有关,也与结构表面积与体积的比值有关.考虑剪切变形会减小功能梯度纳米层合板的屈曲和后屈曲的临界载荷;对于较薄纳米层合板可以忽略剪切变形的影响.  相似文献   

9.
基于Karman型大挠度方程,用修正迭代法分析了均布压力下夹支正交异性圆锥扁壳的几何非线性的后屈曲行为,给出二阶近似的荷载挠度特征关系式及临界荷载,给出了三种正交异性参数对应数值结果,分析了正交异性参数对壳体变形和屈曲荷载的影响。  相似文献   

10.
压电板屈曲和后屈曲的有限元分析   总被引:9,自引:0,他引:9  
采用板的一阶剪切理论,并考虑结构的几何非线性,基于Total Lagrange方法,建立了在弱非线性耦合假设下压电智能结构的有限元控制方程.分析了不同边界条件下压电板的屈曲和后屈曲.计算结果表明,在单向压力作用下,材料的压电效应和外加电压对板的屈曲载荷及后屈曲影响很小;而电场对位移加载简支板的屈曲影响较显著.该文为压电材料的工程应用提供了理论指导,同时提供了一种有效的有限元分析方法.  相似文献   

11.
The objective of this work is to analyze the elastic buckling and initial post-buckling behavior of slender beams subjected to uniform heating. The beams are assumed to be double-hinged with fixed ends, preventing thermal expansion. Consequently, destabilizing compressive forces arise that may lead to beam buckling. When the temperature is further increased, the beam experiences finite displacements, with the result that the analysis is geometrically non-linear. The modulus of elasticity and the thermal induced strain, key material properties for this problem, are temperature-dependent. Thus, the coefficients of the governing equations are not constant. This suggests the physical non-linearity of the mathematical model. Hence, the analysis is geometrically and physically non-linear. The analysis is sensitive to the beam initial temperature, as the thermal strain is a function of the initial and final temperatures. The material is considered to be linear elastic, and consequently viscoelastic and plastic effects are not taken into account. Furthermore, the beam cross-section properties are assumed to be constant, which is consistent with the small strain formulation. A perturbation method is applied to the governing non-linear differential equations so that the initial post-buckling behavior may be analytically determined when temperatures above the critical temperature are applied to the beam. To illustrate the application of the formulation we present a case study for the aluminum 7075-T6 alloy, a material commonly used in aerospace and naval industries. Nonetheless, it is expected similar behavior for other metallic materials. The curves that define the variation of the modulus of elasticity, the thermal strain and the yield stress with temperature are considered in our analysis. The change in length, reaction forces at the supports and geometric configurations are obtained as a function of temperature and the beam slenderness ratio. The critical buckling loads and temperatures and the initial post-buckling analysis are also calculated in the context of the temperature-independent physical properties. Our results emphasize the importance of modeling the material's non-linearity if accuracy is required. However, from a practical application point of view results are acceptable if temperature-independent physical properties are employed, especially for large slenderness ratios.  相似文献   

12.
  总被引:2,自引:0,他引:2  
The non-linear governing differential equations of immovably simply supported functionally graded material (FGM) rod subjected to thermal loads were derived. The thermal post-buckling behaviors of FGM rod made of ZrO2 and Ti-6Al-4Vwere analyzed by shooting method. Firstly, the thermal post-buckling equilibrium paths of the FGM rod with different gradient index in the uniform temperature field were plotted, and compared with the behaviors of the homogeneous rods made of ZrO2 and Ti-6A1-4V materials, respectively. For given value of end rotation angles, the influence of gradient index on the thermal post-buckling behaviors of FGM rod was discussed. Secondly, the thermal post-buckling characteristics of the FGM rod were analyzed when the temperature difference parameter is changed while the bottom temperature parameter remains constant, and when the bottom temperature parameter is changed while the temperature difference parameter remains constant, and compared with the characteristics of the two homogeneous material rods.  相似文献   

13.
Equilibrium paths of post-buckling are measured for large slenderness column specimensmade of the fiber reinforced composite material. The influence of the initial curvature is investigatedexperimentally and compared with the result of the initial post-buckling theory. Both the theoreticaland experimental results reveal that the column with the initial curvature has stable post-buckling be-haviors and is not sensitive to the imperfection in the form of initial curvature. The experimental re-sults show that when the lateral buckling displacement is less than 20 percent of the column length, theexperimental results agree with the results from the theory of initial post-buckling quite well, whilethey agree with the results from the large deflection theory in a quite large range.  相似文献   

14.
为分析表面效应对多孔梁在轴向压力下的屈曲和后屈曲行为的影响,使用Gurtin–Murdoch表面弹性理论,建立了轴向可伸长梁的非线性后屈曲控制微分方程。其中假设梁的孔隙分布在其厚度上具有对称和非对称的两种非均匀模式。采用打靶法数值求解,给出了不同孔隙率系数下多孔纳米梁发生屈曲的临界载荷和后屈曲平衡路径曲线,讨论了表面材料特性对后屈曲行为的影响。结果表明:纳米梁具有十分显著的表面效应,表面效应对多孔纳米梁的屈曲和后屈曲行为有重要影响。  相似文献   

15.
A new and simple method is developed to establish the pseudo orthogonal properties (POP) of the eigenfunction expansion form (EEF) of crack-tip stress complex potential functions for cracked anisotropic and piezoelectric materials, respectively. Di?erent from previous research, the complex argument separation technique is not required so that cumbersome manipulations are avoided. Moreover, it is shown, di?erent from the previous research too, that the orthogonal …  相似文献   

16.
陈履坦  何起光  陈小伟 《爆炸与冲击》2022,42(12):124201-1-124201-17

二级轻气炮是一种常见的超高速发射装置,多年来其数值研究大多采用简化一维模型,鲜有三维有限元模型。以14 mm口径高压气体驱动二级轻气炮为研究对象,采用耦合欧拉-拉格朗日(coupled Eulerian-Lagrangian, CEL)算法,根据膜片破裂与否,将二级轻气炮模型解耦为2个分级三维数值模型。为确定实验难以测得的参数(材料摩擦因数和膜片破膜压力),设计正交试验,拟合确定活塞与泵管间摩擦因数为0.82,弹丸与发射管摩擦因数为0.30和膜片破膜压力为11.73 MPa。正交结果表明,摩擦因数对计算结果影响较大,在高压气体驱动二级轻气炮的计算中不应忽略。通过上述方法建立数字化高压气体驱动二级轻气炮,完整复现气炮发射过程,计算的弹丸终速与实验结果吻合度高。选取验证工况详细分析了气炮发射过程内流场变化,并呈现关键时刻的压力云图。该气炮简化方法、分级思想和关键参数确认方法可推广应用于固体发射药驱动、爆轰驱动等其他驱动形式的二级/多级轻气炮。

  相似文献   

17.
本文利用凝聚矩阵求隔板与箱联结点赘余力,进而分析带柔性隔板的曲线连续箱梁及其隔板的内力,并对刚、柔性隔板与无隔板多跨曲箱梁以及直条法与曲条法进行分析比较,表明本文计算结果是令人满意的,从中得到有关结论。  相似文献   

18.
  总被引:2,自引:1,他引:1  
IntroductionAxiallycompressedstresseswilloccurinaconstrainedelasticbeamsubjectedtoatemperaturerising .Ifthemagnitudeofthecompressedstressesexceedacertainlimit,thermalbucklingoftheheatedbeam ,whichisoutofitsinitialconfiguration ,willtakeplace .So ,investigationsonthermalbucklingofrodsandbeamsareverynecessaryandimportantforthedesignofstructuresworkinginhightemperatureenvironmentsandofsomethermalsensitiveelasticelements.Becausethermalelasticpost_bucklingofbeamsandrodsareinducedbythethermallyaxial…  相似文献   

19.
基于层合板壳理论,考虑反对称铺设层合板的拉弯耦合效应和后屈曲过程中的非线性几何变形,推导了由应力函数和挠度表示的复合材料层合板的后屈曲控制方程。引入无量纲参数对控制方程和边界条件进行无量纲化,以消除材料参数及几何尺寸对分析结果的影响。采用摄动法将无量纲的非线性控制方程及边界条件展开成一系列非齐次线性摄动方程组,分析各阶摄动方程的通解与特解的构造,并逐次求解,建立了反对称铺设复合材料层合板受单向均布压力作用的临界屈曲荷载及后屈曲平衡路径的理论解。进而运用ABAQUS软件对复合材料层合板在面内压缩载荷作用下的屈曲和后屈曲进行有限元分析,结果表明理论解与ABAQUS结果十分接近,验证了理论解的正确性。在此基础上进一步讨论了铺设角度、铺设层数和拉弯耦合效应等对层合板后屈曲性能的影响。研究发现层合板的屈曲载荷受铺设角度与层数的影响较为显著,而拉弯耦合效应使板的屈后强度大大降低。  相似文献   

20.
建立了轴对称转动粘弹性不可移简支梁的几何非线性动力学模型.应用Laplace变换和摄动法分析了超静定粘弹性杆的平衡解,得到了转动粘弹性梁的预应力平凡平衡态.应用Galerkin和摄动法得到了粘弹性梁平凡解的失稳临界值,分析了梁轴向伸长对失稳临界值的影响;通过极限分析获得了系统的后屈曲稳态近似解,讨论了平凡解二次分岔后的近似稳定吸引域,并数值仿真了系统平凡解失稳后初始挠动向稳态解的演变.本文的大范围稳定性分析发现了粘弹性系统叉式分岔失稳后的平凡态又经二次鞍结点分岔而稳定以及单向跳跃(突变)等不同于弹性系统的现象.  相似文献   

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