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。     

功能梯度复合材料圆柱壳基本理论及长壳固有振动解

本文首先在功能梯度复合材料圆柱壳基本理论上将原始三维变系数控制方程转化为特殊类型各向异性及薄膜-弯曲耦联的二维常系数方程;对相当长圆柱壳提出轴向、周向分离变量振型函数,求取满足基本微分方程的固有振动解析解,得到功能梯度圆柱壳固有频率与振型分析的一般性方法,适用于任意功能梯度分布复合材料长圆柱壳。     

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。     

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。     

面板厚度对复合材料夹层梁整体及局部弯曲力学性能影响

考虑芯材局部压陷效应,对泡沫夹芯复合材料夹层梁整体及局部弯曲力学性能进行研究。分析了上面板厚度对夹层梁整体及局部弯曲力学性能影响规律。首先,对三种不同厚度上面板夹层梁进行三点弯曲试验,结果表明,夹层梁破坏模式为芯材压陷破坏和芯材剪切破坏;上面板厚度越大,夹层梁极限承载力越大;增大上面板厚度能有效减弱加载点位置芯材局部压陷效应。其次,基于考虑芯材竖向压缩变形的高阶剪切变形理论,对试验梁整体及局部弯曲受力机理进行分析,得到夹层梁上、下面板不同位置挠度及应变的分布规律。最后,对不同试验梁极限承载力进行理论分析,并与试验结果对比。     

圆柱壳开孔接管外压失稳临界压力参数化分析

外压圆柱壳开孔接管是工程中常用结构之一,研究失稳临界压力可为其结构设计提供依据。本文针对4个无量纲参数:筒体外径与有效壁厚的比值、筒体长径比、开孔率及接管与壳体有效厚度比,探究外压圆柱壳开孔接管结构失稳临界压力。运用正交试验设计方法,组合出49组不同参数的模型,采用特征值分析、几何和材料双非线性分析方法得到各分析模型的临界压力,并分析各因素对临界压力的影响。研究结果可为外压圆柱壳开孔接管结构设计提供借鉴。     

板锥网壳结构复合材料层合板的强度分析

板锥网壳结构是一种受力性能合理、技术经济效益良好的新型空间结构形式.本文结合复合材料力学理论和复合材料结构力学(板壳理论),采用组合结构有限元对复合材料层合板自身的强度和主要影响因素进行全面和深入的研究,研究复合材料板锥网壳结构的受力性能,为复合材料板锥网壳结构设计和层合板铺层设计提供理论上的依据,得出了可应用于工程实践的重要结论.     

板锥网壳结构复合材料层合板的屈曲分析

板锥网壳结构是一种受力性能合理,技术经济效益良好的新型空间结构形式.本文结合复合材料力学理论和复合材料结构力学(板壳理论),采用组合结构有限元对复合材料层合板自身的局部稳定性和主要影响因素进行全面和深入的研究,研究复合材料板锥网壳结构的受力性能,为复合材料板锥网壳结构设计和层合板铺层设计提供理论上的依据,得出了可应用于工程实践的重要结论.     

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。     

添加石墨粉对酚醛树脂基复合材料性能影响研究

本文对Novolak酚醛树脂中添加石墨粉制备碳布增强酚醛树脂复合材料进行了探索性研究.考察了250℃后固化处理前后复合材料的微结构、厚度变化以及弯曲行为,并与未添加石墨粉制备的复合材料进行了对比.结果表明:添加石墨粉后制备出的复合材料界面结合紧密、性能良好,没有分层情况,后固化处理前后的厚度、微结构及弯曲行为与未添加石墨粉的复合材料没有明显的差异.     

Modelling of porous core–shell adsorbent particles with various morphologies suspended in batch adsorber from analytical solutions of diffusion equations

Considering both intra-particle diffusion and film resistance for mass transfer, analytical solutions of transient concentration of adsorbate inside adsorbents with spherical, cylindrical, or slab-type particles were derived for batch adsorbers by solving governing equations using the Laplace transform. Assuming Henry's or rectangular isotherm, the average concentration inside adsorbents as well as transient bulk concentration were also obtained for the particles with or without the inert core. Computations were performed to compare the results according to the shape of adsorbents by adjusting adsorbent loading, Biot number (Bi), and inert core thickness. Regardless of particle morphologies, steady-state bulk concentration was only affected by adsorbent loading and inert core thickness, whereas the effect of Bi was confirmed from the decreasing reduction rate of adsorbate concentration with decreasing Bi. When diffusivity was dependent on time, time-decaying diffusivity caused the increase in steady-state concentration that was predicted by eigenfunction expansion. Experimental results using porous fibres by electrospinning were compared with the mathematical solution of a cylindrical adsorbent for the estimation of intra-particle diffusivity. Using the solutions of the diffusion equation model, novel core–shell cylindrical adsorbents can be designed and synthesized as core–shell fibres by electrospinning with a coaxial nozzle to save the cost of the active shell layer. Such core–shell structured fibres can be adopted as adsorbents for novel batch adsorption processes and the present modelling results can be extended to other processes like fixed bed adsorbers.     

压力容器稳定性分析

对于受外压的容器,除了圆筒、球壳、锥壳和有限定的开孔外,其他的很多形状以及不均匀的载荷等都无法按照现有的标准规范进行稳定性校核。通过分析结果的对比,确定了基于有限元屈曲分析为基础的压力容器稳定性分析方法和评判准则。     

薄壁筒体卧置状态圆度的探索

简述了筒节圆度对壳体制造质量的影响、产生圆度的原因、测量筒节圆度的方法和确保筒节圆度的措施。提出了薄壁筒体卧置状态自重变形量的计算公式,可以较准确地知道筒节自重对筒节圆度影响的程度。     

Druckstandfestigkeit und Betriebseigenschaften von Doppelwellendichtungen

The strength and operating properties of wave‐ring gaskets are analyzed. A cylindrical shell of constant mean thickness is introduced to simulate the gasket. It is assumed that the shell is simply supported at the inner surface of the seat. The influence of certain geometric, material and assembly parameters on the strength and leak‐tightness of the closure is investigated. The results are illustrated by a numerical example. For the assumed material of the gasket and several fixed data the other parameters of the closure are examined. The region of admissible solutions for the gasket parameters such as dimensions, applied assembly clearance and pressure is determined.     

Mid-Explosion Recovery of an Intermediate Phase of a Cylindrical Metal Shell

To understand the complex dynamic response of cylindrical metal shells under highstrain-rate loading, a mid-explosion recovery device is designed to recover cylindrical shells at an intermediary phase, chosen in this study to be the phase wherein cracks penetrate through the entire casing wall thickness. The surface dynamic processes of the expansion, fracture propagation, and rupture of a 40CrMnSiB steel cylindrical shell are measured with a high-speed framing camera for determining the appropriate inner diameter of the mid-explosion recovery device. The numerical simulation software Autodyn-3D is used to predict the influence of the device wall thickness and the maximum radial deformation of the device inner wall upon the outer fracture diameter of the casing. The casing at the desired phase is recovered by the device, and the outer diameter of the shell is found to increase by 1.77 times, while the radial deformation of the device is 5 mm. The crack distributions, the distance between the adjacent penetrating shear cracks, and the number of circumferential divisions are found to vary along the axis of the cylindrical casing.     

Biaxially oriented poly(ethylene terephthalate) bottles: Effects of resin molecular weight on parison stretching behavior

Uni- and biaxial stretching of poly(ethylene terephthalate) (PET) specimens of appropriate geometry at temperatures near the glass-rubber transition may lead to non-uniform deformation unless the draw ratio exceeds a critical value, the natural draw ratio, characteristic of the onset of strain hardening due to stress-induced crystallization. Experimental results obtained in the present investigation show that natural draw ratios in uni- and biaxial stretching decrease with increasing resin molecular weight and with decreasing temperature. Undesirable uneven wall thickness distribution in biaxially stretched cylindrical parisons can only be prevented if draw ratios in both orthogonal principal stretching directions exceed the corresponding natural values. The minimum thickness reduction required for uniform biaxial stretching of a cylindrical parison at 95°C may vary between 12 and 5 depending on the resin's molecular weight or viscosity and this will affect the optimum design of parison geometry. The degree of unbalanced biaxial molecular orientation in the wall of cylindrical parisons stretched up to or beyond the natural draw ratios also depends on the resin molecular weight. Unbalanced biaxial orientation has been investigated by means of wide angle X-ray diffraction and birefringence measurements as well as its effect on various properties: rigidity, yield stress, creep compliance, and dimensional stability.