变厚度圆柱壳基本方程及其应用

采用变厚度壳单元理论推导出变厚度圆柱壳弯曲问题的控制微分方程。该控制方程可退化为惯用的基于等厚度壳单元导出的变厚度圆柱壳基本微分方程。结果表明，导出的基本公式在壳体厚度变化梯度不大时与惯用的理论公式数值结果差别不大，但这种差别随着壳体厚度变化梯度增大而增大。     

拉压不同弹性模量变厚度圆柱壳基本方程及其应用

本文以变厚度圆柱壳微分单元为分析模型,导出了拉压不同弹性模量复合材料变厚度圆柱壳弯曲问题的平衡微分方程及其关系式.该方程的COLSYS数值解与ANSYS有限元结果比较表明,本文理论公式正确,基本假定合理,可作为复合材料变厚度圆柱壳较为精确的弯曲理论.     

复合材料加筋壳稳定性研究

本文根据复合材料加筋壳的材料特性,获得了环肋、纵筋、斜筋和三角形网格加筋壳的广义刚度系数,从而将圆柱壳与加筋壳恶性循环 问题统一起来,并利用Donell壳体理论,推导了在外压作用下,复合材料加筋圆柱壳总体失稳的临界压力公式,可供有关工程设计师参考。     

材料属性对功能梯度圆柱壳模态频率的影响

准确预估功能梯度(FGM)有效材料属性是建立FGM圆柱壳动力学模型的重要举措,对于正确分析FGM圆柱壳的振动特性具有重要作用。引入三种材料模型以及四种组分梯度变化形式,基于一阶剪切变形理论和Hamilton原理推导了FGM圆柱壳的模态频率方程,探讨了材料属性和温度梯度对圆柱壳模态频率的影响。结果表明:Voigt和Mori-Tanaka模型预测FGM的有效材料属性较为接近,而Reuss模型预测值偏高,且FGM的有效材料模型受组分材料的影响;广义化指数梯度有利于提高结构在热环境下的模态频率。     

圆柱壳开孔应力集中问题的边界元解法

本文将边界元法应用于圆柱壳。在建立积分方程时,作者建议用板的基本解叠加三角级数解作为圆柱壳的基本解,并导出了圆柱壳的边界元解法的基本公式。计算表明,使用该基本解,提高了计算精度。文中还提出了区域积分的处理方法。数值计算显示,用边界元法分析圆柱壳的开孔问题是十分有效的。     

轴压作用下缠绕复合材料夹芯圆柱壳力学性能研究

为研究缠绕复合材料夹芯圆柱壳的力学特性,首先开展了缠绕复合材料夹芯圆柱壳模型的轴向压缩试验,得到载荷-位移曲线与应变分布规律;进而,依据复合材料经典层合板理论,将缠绕圆柱壳模型的内外蒙皮均匀化,等效为单向纤维增强复合材料,采用ABAQUS有限元软件对结构模型进行分析,得到不同载荷下的应变规律;最后,将有限元计算结果与试验结果进行对比,轴向刚度误差为10.69%,测点应变值最大误差为12.88%,表明该方法可用于缠绕复合材料夹芯圆柱壳计算,为复合材料夹芯圆柱壳的设计应用提供指导。     

嵌入式阻尼环筋开口圆柱壳的振动性能分析

本文在应用一阶剪切变形壳理论的基础上,采用共固化工艺的嵌入式阻尼复合材料环筋开口圆柱壳作为研究对象,加强筋作离散元素处理,对此结构的动态特性进行了研究。应用Rayleigh-Ritz能量法和Navier双级数法,推导嵌入式共固化阻尼复合材料环筋开口圆柱壳的应变能和动能表达式,建立其自由振动的控制方程;另外,利用ANSYS建模获得此结构的模拟结果,对两者结果进行了比较,验证了本文方法的有效性。探讨了不同筋条高度及阻尼夹芯层厚度对本文所述环筋开口圆柱壳性能的影响。研究结论对轻质高刚度大阻尼的复合材料结构件的设计及应用有一定的参考价值。     

复合材料加筋圆柱壳的低频声散射特性研究

采用有限元/无限元相结合的方法对复合材料加筋圆柱壳以及金属加筋圆柱壳低频声散射特性进行了仿真分析。计算了不同波数情况下加筋圆柱壳和非加筋圆柱壳的散射情况,其中加筋情况分别采用了两种处理方法,包括梁单元建模与壳单元建模,结果表明加强筋的建模方法对于计算结果产生了一定影响,在一些频率点甚至十分显著。     

基于应力波的复合材料圆柱壳结构损伤概率成像研究

本文对复合材料圆柱壳结构健康监测进行了研究,采用应力波技术结合融合损伤概率成像算法,对损伤进行了监测和识别。首先通过在圆柱壳内壁设置压电传感器阵列,使用多通道阵列扫查系统依次在结构中激励和接收应力波信号;然后分别通过相关系数分析和盒维数分形分析方法处理信号,计算出不同传感器路径上的损伤指标;最后利用经过坐标变换以及图像融合方法改进的损伤概率成像算法,实现对复合材料圆柱壳结构中损伤的可视化识别。数值仿真和实验研究结果表明,应力波能够有效地监测和识别出复合材料圆柱壳结构中的损伤,所改进的融合概率成像算法能够提高损伤位置识别的精度。     

复合载荷圆柱壳径向接管极限载荷参数化分析

采用正交试验设计方法,设计了48组不同几何参数的带径向接管圆柱壳模型,利用有限元分析软件ANSYS对模型进行模拟计算,求得模型在内压与接管纵向弯矩联合作用下的极限载荷,由回归分析法得到复合载荷作用下圆柱壳接管结构极限载荷关系的经验方程。采用有限元计算结果对经验方程进行验证和应用,证明了回归方程和研究方法是可靠的,可用于求解内压与接管纵向弯矩联合作用下圆柱壳接管结构的极限承载能力,为快速求解载荷联合作用下圆柱壳接管结构的极限承载能力提供了研究方向。     

功能梯度壳体力学的一般理论

本文针对任意形状功能梯度材料壳体结构,从一般性壳体曲面理论出发,给出相应几何方程、平衡方程,在物理方程中引入沿壳体厚度的材料性能梯度分布,建立起膜弯耦联的功能梯度壳体的一般性基本方程与边界条件、初始条件,可作为各种功能梯度壳体力学分析的理论基础。     

有限长圆柱壳外压蠕变屈曲解

本文通过构造m波力学模型,以材料发生稳态蠕变为分析基础,求得有限长与无限长圆柱壳外压蠕变屈曲的统一解。并得到实验结果较好的验证。本文还分析了圆柱壳外压蠕变屈曲的特性和影响因素,指出圓柱壳截面初始偏差的大小和形状均对屈曲寿命有较大影响。     

立式埋地玻璃钢圆柱壳的稳定性分析

基于工程实际,采用承压不承拉的杆单元模型解决埋地结构与周围土体的相互作用问题,推导出杆单元与土体之间材料参数表达式,建立有限元计算模型,实现立式埋地玻璃钢圆柱壳结构稳定性有限元分析。通过与传统公式计算结果比较,得出传统稳定性计算公式不能用于计算立式埋地结构。参数对结构稳定性的影响结果表明:增加结构的厚度、弹性模量以及周围土弹性模量可提高稳定性,其中厚度的影响更为显著;结构稳定性随壳体长度的增加而降低。在工程应用中可采用加筋结构减小计算长度以及选择合适的回填材料和回填方式来提高土的弹性模量的方法,有效提高稳定安全性,对经济性影响较小。     

Free Vibration Analysis of an Adhesively Bonded Functionally Graded Tubular Single Lap Joint

In this study, the three-dimensional free vibration analysis of an adhesively bonded functionally graded tubular single lap joint was carried out using the finite element method. The functionally graded tubes of the adhesive joint are composed of ceramic (Al₂O₃) and metal (Ni) phases varying through the tube thickness. The adhesive material properties, such as modulus of elasticity, Poisson's ratio, and density were found to have negligible effect on the first ten natural frequencies and mode shapes of the adhesive joint. The optimal design parameters of the adhesive joint, such as overlap length, inner radius of the inner tube, outer and inner tube thicknesses, and the through-the-thickness material composition variation were searched using both the artificial neural networks (ANNs) and the genetic algorithms (GAs). For this purpose, the natural frequencies and modal strain energy values were calculated for an adhesive joint with random geometrical properties and material compositions through the tube thicknesses, and were used for training the proposed artificial neural network models. The outer tube thickness, the inner tube-inner radius, and the compositional gradient exponent had considerable effect on the natural frequencies, mode shapes, and modal strain energies of the functionally graded tubular single lap joint, whereas the overlap length and the inner tube thickness had a minor effect. The GAs integrated with ANNs was employed to determine optimal design parameters satisfying both maximum natural frequency and minimum modal strain energy conditions for each natural mode of the tubular adhesive joint.     

功能梯度材料单参数反演分析(英文)

功能梯度材料的材料参数随位置变化,以目前的实验手段来看,逐一测定各个材料参数的分布曲线工作量很大,有些材料常数的测定十分困难(特别是沿厚度材料常数梯度分布).本文利用细观元法探讨功能梯度材料参数的反演识别问题,即在获知实测位移或固有频率的情况下,对功能梯度材料的内部参数及其分布进行反演识别.显然,这可大大简化功能梯度材料的基本力学性能测试工作,为功能梯度材料的进一步研究奠定基础.     

Nonlinear vibration and modal analysis of FG nanocomposite sandwich beams reinforced by aggregated CNTs

In the present work, by considering the aggregation effect of single‐walled carbon nanotubes (SWCNT), the nonlinear vibration of functionally graded (FG) nanocomposite sandwich Timoshenko beams resting on Pasternak foundation are presented. The material properties of the FG nanocomposite sandwich beam are estimated using the Eshelby–Mori–Tanaka approach and differential quadrature method (DQM) is used to obtain natural frequency. The nonlinear governing equations and boundary conditions are derived using the Hamilton principle and von Kármán geometric nonlinearity. The higher order nonlinear governing equations and boundary conditions are calculated using the Hamilton principle. A direct iterative method is employed to determine the nonlinear frequencies and mode shapes of the beams. It is shown that the mechanical properties and therefore vibration of functionally graded carbon nanotube reinforced (FG‐CNTR) sandwich beams are severely affected by CNTs aggregation. A detailed parametric study is carried out to investigate the influences of Winkler foundation modulus, shear elastic foundation modulus, length to span ratio, thicknesses of face sheets on the nonlinear vibration of the structure. POLYM. ENG. SCI., 59:1362–1370 2019. © 2019 Society of Plastics Engineers     

Local aggregation effect of CNT on the vibrational behavior of four‐parameter continuous grading nanotube‐reinforced cylindrical panels

Free vibrations analysis of four‐parameter continuously graded nanocomposite cylindrical panels reinforced by randomly oriented straight and local aggregation single‐walled carbon nanotubes (CNTs) are presented based on three‐dimensional theory of elasticity. The material properties of continuously graded carbon nanotube‐reinforced composites (CG‐CNTRCs) are estimated through the Eshelby–Mori–Tanaka approach based on an equivalent fiber. The generalized differential quadrature method as an efficient and accurate numerical tool is used to discretize the governing equations and impediment the boundary conditions. One of the contributions of this work is to illustrate the influence of the four parameters of power‐law distributions on the vibration behavior of functionally graded orthotropic cylindrical panels reinforced by nanotube. The properties of CG‐CNTRC are affected by its microstructure, especially the degree of CNT aggregation that is described by an aggregation coefficient. It is shown the degree of aggregation canseriously reduce the effective stiffness and frequency parameter. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers