基于累积失效法的含损伤格栅加筋板非线性屈曲状态分析

分别采用基于Mindlin一阶剪切理论八节点层合板单元和三节点层合梁单元来模拟蒙皮和肋骨,用累积失效法研究了在压缩载荷作用下蒙皮内含分层损伤复合材料正交格栅加筋板的非线性屈曲性态,分析中考虑了加载过程中蒙皮和肋骨纤维断裂、基体损伤和纤维-基体剪切失效造成的刚度退化,并采用了非线性接触单元模型处理蒙皮分层上下子板间的接触效应。通过典型算例,讨论了蒙皮铺设方式、蒙皮分层的面积和深度、肋骨与蒙皮的刚度比,累积失效行为等因素对格栅加筋板非线性屈曲性态的影响。     

复合材料加筋板极限压缩承载能力可靠性分析

基于Abaqus软件用户子程序,利用渐进失效分析方法对复合材料加筋板极限压缩承载能力进行预测。算例分析表明,对于加筋板1和2,本文方法给出的极限压缩强度与实验结果的误差分别为2.53%和1.68%。在结构可靠性分析过程中,为提高计算效率,利用屈曲载荷与极限压缩强度之间的关系建立功能函数,只需对极限压缩承载能力进行一次分析。对于加筋板1和2,本文方法相对经典可靠性方法的计算误差分别为-1.04%和-1.01%,计算时间仅为经典可靠性方法的1.18%和1.66%。     

受面内冲击载荷下加筋板的非线性动态屈曲

分析了受面内冲击载荷下加筋板的非线性弹性动态屈曲.考虑板与筋的膜力,忽略面内位移,运用Hamilton变分原理,得出非线性控制方程,采用双级数形式的挠度假设,由Galerkin方法得到离散方程组,根据B-R准则,判断加筋板的动态屈曲.     

不同长桁截面复合材料加筋板轴压屈曲分析

基于轴向压缩载荷工况,加筋板重量相同、长桁轴线间距相等、长桁截面占比相当的前提,采用试验和数值计算方法研究“I”形加筋板和“J”形加筋板屈曲特性及其失效模式。研究结果表明：“I”形加筋板与“J”形加筋板抗屈曲承载能力相当,后屈曲承载能力较“J”形加筋板提高约19.8%;特征值屈曲法计算值较试验值误差约11%,究其主要原因是特征值理论不考虑加载过程中长桁刚度对蒙皮支持变弱的影响,故其计算值较试验值偏大;考虑就地效应及横向应力分量对基体剪切强度的影响,构建加筋板失效模型,计算值与试验值误差约8%,且预测的失效模式与试验破坏模式一致性较好。     

夹具对复合材料加筋板剪切试验屈曲载荷的影响

复合材料加筋板在剪切载荷作用下的屈曲和后屈曲性能试验是难度较高的结构试验,载荷通常需要由设计合理的夹具传递到试件上,本文采用的是对拉式的剪切试验夹具.在试验中,由于引入的夹具是弹性体,与试件结合成一体,参与了屈曲过程,所以与理想的约束情况有差异.本文采用数值方法,模拟夹具对试验结果的影响,发现不同的夹持模型,对屈曲载荷...     

复合材料加筋板壳结构的后屈曲强度及破坏分析程序系统

本文介绍适用于复合材料（含各向同性材料）层合加筋板壳结构的后屈曲强度及破坏分析的程序系统的功能特点、原理和结构、通过一个受压剪载荷作用的加筋层合矩形板的破坏分析，并与试验结果作了比较，说明该程序系统的正确、可靠性。     

黏弹性板的大挠度蠕变屈曲

研究了具有初始小挠度受轴向压载黏弹性板的蠕变屈曲问题,在建立控制方程时,利用了von Karman非线性应变-位移关系,并考虑了初始挠度,用标准线性固体模型描述材料的黏弹性特性,在求解非线性积分方程时,利用梯形公式计算记忆积分式,将非线性积分方程化为非线性代数方程进行数值求解,得到了结构的蠕变变形过程,又将问题退化到小挠度情况进行研究,得到了挠度随时间扩展的解析解,分析了瞬时失稳临界载荷、持久临界载荷的物理意义,讨论了考虑几何非线性对黏弹性板蠕变屈曲的影响。     

复合材料加筋板壳结构的后屈曲强度及破坏分析程序系统

本文介绍适用于复合材料（含各向同性材料）层合加筋板壳结构的后屈曲强度及破坏分析的程序系统（ＣＯＭＰＯＳＳ程序系统）的功能特点、原理和结构，通过一个受压剪载荷作用的加筋层合矩形板的破坏分析，并与试验结果作了比较，说明该程序系统的正确、可靠性     

正交各向异性加筋板屈曲分析方法研究

为简化正交各向异性加筋板屈曲分析,本文将筋条位移场用其所在位置的板的位移表达,建立加筋板总势能,通过离散位移场,利用最小势能原理,推导出基于里兹法的正交各向异性加筋板屈曲分析控制方程,采用Matlab进行求解.基于本文推导的方程对单筋和三筋加筋板在不同压剪比下的屈曲荷载和模态进行分析,得到与Abaqus基本一致的结果....     

轴压加筋板壳的弯扭稳定性分析

以统一的方式分析了轴压加筋板壳的弯扭稳定性.根据小挠度能量法,采用了约束剪心概念并考虑了加筋条偏心距,截面的翘曲刚度及剪心和形心间位置偏差等因素的影响,推导了屈曲方程。例题计算的结果表明了所提出方法的可行性。     

Buckling analysis of discretely stiffened composite curved panels under compression and shear

An analytical method for the buckling discretely thin-wall stiffened composite curved panels under compression and shear is presented by use of finite strip-element method.In the report a simplified scheme for complex displacement functions is developed. It enables that computation to be performed in real number algebra easily. And a simple and easy way to satisify the boundary conditions is introduced.Numerical results are given and are in good agreement with available data.     

Buckling and postbuckling of stiffened cylindrical shells under axial compression

Buckling and postbuckling behaviors of perfect and imperfect,stringer andorthotropically stiffened cylindrical shells have been studied under axial compression.Based on the boundary layer theory for the buckling of thin elastic shells suggested in ref.[1],a theoretical analysis is presented.The effects of material properties of stiffeners andskin,which are made of different materials,on the buckling load and postbuckling behaviorof stiffened cylindrical shells have also been discussed.     

Reliability assessment of post-buckling compressive strength of laminated composite plates and stiffened panels under axial compression

A method for reliability assessment of the post-buckling compressive strength of laminated composite plates and stiffened panels under axial compression is presented in the paper. The prediction of the post-buckling compressive strength is performed by a progressive failure analysis which was developed based on a progressive stiffness degradation model and a nonlinear finite element analysis with a new explicit through-thickness integration scheme. A method coupled with the finite element analysis is proposed for reliability assessment where a finite difference method combined with an improved first-order reliability algorithm that omits the non-important random variables but retains sufficient accuracy was developed for reliability estimation. Two numerical examples are described demonstrating the capabilities of the method developed.     

Study on failure process of delaminated stiffened composite plates under compression

Failure behavior of the delaminated stiffened composite plates under compression is studied by the finite element method, based on a Global-Local variational model. A virtual crack closure technique and a self-adaptive grid moving scheme are proposed to predict the delamination growth process. The contact effect along the delamination front is considered. The numerical results show that the influences of the distribution and location of the stiffeners, the configuration and size of the delamination, the boundary condition and the contact upon the failure behavior of the plates are significant. The project supported by the National Natural Science Foundation of China (59975014)     

Buckling of composite panels subjected to biaxial loading

Buckling loads and modes of flat composite laminates were measured and compared with theory. Laminates were subjected to simply supported boundary conditions and biaxial loading. Displacements were measured both mechanically using dial gages and optically using shadow moiré. Predictions were obtained numerically using the Galerkin method. Buckling loads were measured during 49 tests. Overall, measurements confirmed expected trends. Buckling loads increased with an increase in transverse tensile loading as predicted. Measured buckling modes were also well predicted, including an observed increase in mode number with an increase in transverse tensile loading. Measured buckling loads were not as well predicted, and substantial error was encountered during individual tests. Discrepancies between measurement and prediction are reported in terms of the percentage error in prediction. The average and standard deviation in percentage error for 49 measurements was 1.6 percent ±15.4 percent. These discrepancies are thought to be due to specimen imperfections, difficulties in simulating truly simply supported boundary conditions and/or nonuniform loading of the composite panels.     

Dynamic near three-to-one internal resonance in composite stiffened panels

Nonlinear dynamic of composite stiffened panels to parametric and three-to-one internal resonances is investigated. The ordinary differential equation of two mode shapes is established by using Galerkin method and the condition of three-to-one internal resonance between the first mode (1,3) and the second mode (3,1) is examined near the principal resonance 2:1 of the first mode. Then, the nonlinear behavior of the two buckling mode shapes is analyzed using a perturbation analysis. We show the existence of jump phenomena for the two modes indicating a complex dynamic of the structure near the three-to-one internal resonance for the HM Graphite/epoxy materials.     

Buckling analysis of woven fabric under uniaxial tension in arbitrary direction

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Buckling of eccentrically stiffened elastic-plastic panels on two simple supports or multiply supported

Buckling due to axial compression is investigated for elastic-plastic, stiffened wide panels either continuous in the longitudinal direction over several transverse supports or finite and supported along the two edges. An analytical treatment is given of the bifurcation behaviour and of the initial post-bifurcation behaviour of perfect panels compressed into the plastic range. The behaviour of initially imperfect panels is computed numerically using an incremental method. In each increment a linear problem is solved by a combined Rayleigh Ritz-finite element method. Computed examples show a considerable imperfection-sensitivity, both for panels that bifurcate in the plastic range, and for panels with a yield stress a little above the elastic bifurcation stress.     

Buckling test and optimum design of fiber reinforced composite plates under compression

In this paper, the conclusion that the experimental results coincide with theoretical analysis has been got through buckling test of 283 composite rectangular plates. It is confirmed that the critical loads of composite plates calculated by buckling theoretical formula of anisotropic plate are reliable. The selections of optimal content of matrix and optimal off-axis which make fiber reinforced composite plates reach biggest critical loads are also discussed in this paper. The result of analysis may be used in the design for the products.