Nonlinear Finite Element Analysis of Rubber Composite Shells

A finite-element solution for rubber composite shells is presented. Sandwich laminates with a rubber core have also been studied. Incompressibility of a rubber matrix and complexity of composite shells bring forth the need for a sound numerical model to describe the behavior of such engineering materials. The developed model was applied to a degenerate shell element within the limits of the first- and third-order shear deformation theories. The model allows to predict with a sufficient accuracy the nonlinear behavior of sandwich shells with composite skins and rubber cores and composite shells with a rubber matrix.     

瓦楞纸箱的有限元建模及屈曲分析

建立了瓦楞纸箱的有限元模型并进行了屈曲分析,计算了该瓦楞纸箱的临界载荷和屈曲模态.将临界载荷与利用凯利卡特公式计算的抗压强度进行了对比.分析结果表明,利用有限元的方法计算的瓦楞纸箱临界屈曲载荷与凯利卡特公式计算抗压强度非常接近.因此利用屈曲分析计算瓦楞纸箱的抗压强度是一种可行的方法.     

径向载荷作用下复合材料圆柱壳的非线性动力屈曲

采用半解析法求解径向阶跃载荷作用下复合材料圆柱壳的非线性动力屈曲。基于一阶剪切变形理论，由Hamilton原理推导出包含横向剪切变形以及几何初缺陷的圆柱壳的非线性动力方程，位移及载荷沿周向采用级数展开，由Galerkin方法得到微分方程组，通过有限差分法求解；根据响应情况，由B—R准则判定屈曲，确定屈曲临界载荷。     

The Secondary Buckling and Design Criterion of Composite Laminated Cylindrical Shells

Even a weak disturbance caused by an asymmetric mesh is enough to break structural symmetry, which triggers the bifurcation buckling and post-buckling behavior of composite laminated cylindrical shells under compression loading by ABAQUS. The mesh perturbation is more objective and authentic; it will not destroy the original model structure in Finite Element Analysis, comparing with the traditional perturbation method by introducing the initial imperfections into the model. A series of numerical experiments are performed to investigate the influence of different types of asymmetric mesh on the predicted secondary buckling load. The predicted secondary buckling load agrees better with analytical solution than predicted primary buckling load and the results from the traditional perturbation method respectively. Therefore, secondary buckling load provides the key design criterion for composite laminated cylindrical shells. Primary and secondary post-buckling patterns of different complexity are explored, which agrees well with experimental buckling modes. Our major conclusions can be summarized briefly: different types of asymmetric mesh have little influence on the predicted secondary buckling load; Care must be exercised regarding the mesh density in order to produce the secondary buckling mode as well as the reliable secondary buckling load.     

Buckling of Cracked Laminated Composite Cylindrical Shells Subjected to Combined Loading

A series of finite element analysis on the cracked composite cylindrical shells under combined loading is carried out to study the effect of loading condition, crack size and orientation on the buckling behavior of laminated composite cylindrical shells. The interaction buckling curves of cracked laminated composite cylinders subject to different combinations of axial compression, bending, internal pressure and external pressure are obtained, using the finite element method. Results show that the internal pressure increases the critical buckling load of the CFRP cylindrical shells and bending and external pressure decrease it. Numerical analysis show that axial crack has the most detrimental effect on the buckling load of a cylindrical shell and results show that for lower values of the axial compressive load and higher values of the external pressure, the buckling is usually in the global mode and for higher values of axial compressive load and lower levels of external pressure the buckling mode is mostly in the local mode.     

受轴向冲击圆柱壳非对称屈曲分析

轴向冲击荷载作用下薄壁圆柱壳屈曲变形研究一直受人们关注,探讨其动态响应的特征和机理,不仅可以丰富冲击屈曲研究内容,而且为提高结构的抗冲击能力提供理论基础。众多实验现象表明,圆柱壳在轴向冲击荷载作用下非对称屈曲时截面为规则几何形状,且不只三角形一种模式,也不是随机现象,而具有一定规律性。文章对环向截面屈曲耗能计算进行理论推导,通过分析对比屈曲耗能与折叠边数、圆柱壳半径的关系,根据最小耗能原理,证实变形规律存在,并分析得到,随半径增加圆柱壳非对称屈曲由三角形模式向多边形模式发展,最终有转变为轴对称变形模式的可能。     

Finite Element Model of Laminated Shells of Composite Materials

Strength of Materials - Finite element models of fiber-reinforced polymer composite elements as a characteristic part of layered structures are considered in order to adapt them to the developed...     

环向加筋圆柱壳轴向弹塑性动力屈曲

基于“离散加筋”模型,考虑了大挠度和材料硬化应变率敏感特性的影响,借助增量数值解法研究了环向加筋圆柱壳在轴向流－固冲击载荷作用下的弹塑性动力屈曲。分别采用类似B－R准则和Southwell方法来确定结构动力屈曲临界载荷。讨论了加强筋、材料硬化应变率敏感特性等因素对结构动力屈曲性态和临界载荷的影响。     

复合材料层压板单面贴补修理建模分析研究

胶接修理技术是一种优质、高效、低成本的结构修理技术.针对复合材料层板的胶接贴补修理进行计算模拟分析,并与实验结果相对比.采用ABAQUS有限元软件对层压板的损伤板和单面贴补修理板进行有限元建模,分析修补前后的应力分布情况,计算出失效强度与完好板进行对比,得出修补后的强度恢复率.     

复合材料纵横加筋圆柱壳自由振动分析

使用能力法分析了两端简支复合材料纵横加筋圆柱壳的自由振动特性,从Love’s理论出发,分别计算壳体面板和纵横加筋结构的应变能和动能,在计算加筋结构应变能和动能时,将加筋结构的作用影响平均在整个壳体区域。然后代入Lagrange方程得到频率方程。通过比较,计算方法所得到的结果与文献比较吻合。采用平均法计算的结果比采用离散方法计算的结果偏小。还研究了壳体和加筋结构参数的变化对圆柱壳自由振动频率的影响。     

用波传播方法分析复合材料层合圆柱壳的振动

用一阶剪切变形理论获得复合材料层合圆柱壳的运动微分方程，再应用波传播方法分析其自由振动的频率。通过比较，本文的计算方法所得的结果与文献^[5]比较吻合。本文还研究了几种壳体参数对圆柱壳自由振动频率的影响。h／R的比值对频率影响当周向模态n=3时较大，n=2时次之，n=1时较小。E1／E2的比值越大，频率越大。辅层的角度在n较小时对频率的影响不大，在n比较大时，角度越小影响越大。     

大型变压器绕组有限元建模与分析

研究了变压器绕组预紧力与变压器箱壁振动之间的关系。通过结合有限元模型和振动实验识别不同预紧力下绕组的特性参数；进而通过测量变压器箱壁振动，根据建立的变压器整体模型以及前面识别的绕组特性参数来计算和预测内部绕组的预紧力状况。     

受约束的圆柱壳的振动分析

本文提出的解析法可对具有任意经典边界条件和在两端间具有若干约束的圆柱壳的自振特性进行计算。文中将亮体轴向模态位移用完备正交级数表示,然后将壳体振型函数分解为一个一致收敛级数迭加上另一线性多项式,从而解决了振型级数的收敛性和可微性。这样处理比stokes变换方法更具有一般性,不但可以得到受约束的圆柱壳固有频率的精确值,而且可以求得相应的振型。     

Dynamic Analysis of Sandwich Cylindrical Shells

We present a dynamic analysis of cylindrical shells and study new mechanical effects in the distribution of stresses, strains, and displacements. Cylindrical shells are studied within the framework of the Kirchhoffndash;Love hypothesis and the refined Timoshenko model.     

胶印机整机有限元建模与综合分析

为了从整体上获取胶印机的性能数据,以某型单张纸四色胶印机的印刷单元为研究对象,综合运用多种有限元建模技术,建立了胶印机单色组整机有限元模型。在整体建模的基础上,对胶印机有限元模型进行了静力分析、模态分析和谐响应分析,获得了胶印机的静态、动态综合性能数据。分析结果表明,该型胶印机整体动态性能欠佳,有必要进行胶印机结构的动态优化。     

Experimental Investigations of Compressed Sandwich Composite/Honeycomb Cylindrical Shells

This article explains in some details the behaviour of thick, deep cylindrical sandwich panels subjected to compressive loads. In general, experimental results indicated that two different forms of failure have been observed – the first corresponds to the overall buckling and the second to the facesheet wrinkling. The obtained experimentally damages of shells are verified and validated with the use of the FE analysis, 2-D and 3-D both in the linear and non-linear approach. The unidirectional strain gauges were applied to detect the initiation of the overall buckling mode.     

Transient Dynamic Response of Clamped-Free Hybrid Composite Circular Cylindrical Shells

Dynamic response of multilayer circular cylindrical shells composed of hybrid composite materials subjected to lateral impulse load is studied in this paper. The boundary conditions (B.C.s) are considered to be clamped-free. Both isotropic (metal) and orthotropic (composite) layers are used simultaneously in the hybrid lamination. There is no limitation for fibre orientation. First order shear deformation theory (FSDT) and Love’s first approximation theory are utilized in the shell’s equilibrium equations. Equilibrium equations for free and forced vibration problems of the shell are solved using Galerkin method. Finally, time response of displacement components of Fibre-Metal Laminate (FML) cylindrical shells is derived using mode superposition method. The effect of lay up, material properties, fibre orientation and volume fraction of metal layers on the dynamic response of the shell are investigated. New interesting results are obtained and discussed providing a helpful insight for aircraft structure’s designers.     

Finite Element Analysis of the Stability (Buckling and Post-Buckling) of Composite Laminated Structures: Well Established Procedures and Challenges

Finite element procedures for the analysis of composite structures under compressive loads (buckling and post-buckling) generally are not deployed in books because they are still considered object of research whereas they are deemed as assessed by researchers that focus their papers on restricted audience topics. Therefore, regarding these procedures, a gap exists in literature between what researchers consider as well established and what has been already published. The aim of this paper is to contribute to close this gap by providing an insight in linear and non-linear buckling analyses and in their use with composite structures. Both modelling and analysis considerations are presented and discussed, focusing on what can be considered as best practice when dealing with this kind of problems. Applications (to a stiffened panel and to a wing box) are provided for demonstrating the effectiveness of the procedures presented.     

楔环连接结构有限元建模与模态分析

建立楔环连接结构的三维摩擦接触有限元模型,基于实验模态和计算模态对结构参数的敏度分析修正结构有限元模型,利用ANSYS有限元模态分析程序求解自由与固支状态下楔环连接结构的频率与振型,考察了楔环连接结构模态频率之间的内共振.