Nonlinear finite element analysis of a laminated cylindrical shell with transverse matrix cracks

A clamped laminated cylindrical shell is presented to investigate nonlinear structural behavior involving geometrically nonlinear deformation. In the investigation, transverse matrix cracks are considered in the stiffness of the laminated cylindrical shell. Stiffness degradation is examined for several laminated angles and transverse crack density. Micro-mechanics theory on the composite material was used to derive the degraded stiffness of the laminated cylindrical shell due to the crack density. Iterative numerical scheme was developed to calculate the degraded composite stiffness which is a complicated relation with the crack density. A nonlinear finite element program was developed using 3-D degenerated shell element and the fist order shear deformation theory to consider the large deformation of the clamped laminated cylindrical shell. The updated Lagrangian method is used for nonlinear finite element analysis. Nonlinear structural responses of the laminated cylindrical shell were examined for various stacking sequences and crack density under transversely loaded pressure. Also, the effect of crack opening/closed was considered in the examination. Through this study, it is realized that the transverse matrix crack causes moderate stiffness reduction and affects the responses of the composite shell.     

Layer-wise finite element analysis of functionally graded cylindrical shell under dynamic load

In this paper, a layer-wise finite element formulation is developed for the analysis of a functionally graded material (FGM) cylindrical shell with finite length under dynamic load. For this purpose, FGM cylinder is divided into many sub-layers and then the general layerwise laminate theory is formulated by introducing piecewise continuous approximations through the thickness for each state In this model the radial displacement is approximated linearly through each “mathematical” layer. The properties are controlled by volume fraction that is an exponential function of radius. The governing equations are derived from virtual work statement and solved by finite element method. The main contribution of the present study is to develop a discrete layerwise finite element for a 2-dimensional thick FGM cylindrical shell. Results are obtained for the time history of the displacement and stress components with different exponent “n” of functionally graded material. In addition, natural frequency and mean velocity of the radial wave propagation for different exponent “n” of functionally graded material (FGM) are studied and compared with similar ones currently obtained for FGM cylindrical shell of infinite length.     

Dynamic response and damage of composite shell under impact

The dynamic response and damage of laminated composite cylindrical shell subjected to impact load is numerically investigated using the finite element method. A nine-node isoparametric quadrilateral element based on Sander's shell theory is developed, in which the transverse shear deformation is considered. A semi-empirical contact law that accounts for the permanent indentation is incorporated into the finite element program to evaluate the contact force. The Newmark time ingegration algorithm is used for solving the time dependent equations of the shell and the impactor. The Tsai-Wu failure criterion is used to estimate the failure of the laminated shell. Numerical results, including the contact force history, interlaminate damage zone, and failure indices in the shell are presented. Effects of curvature, impact velocity and mass of impactor on the composite shell behaviors are discussed.     

催化剂颗粒撞击壁面的有限元分析

针对催化裂化过程中催化剂颗粒大量跑损的问题,采用有限元的方法建立了单颗催化剂颗粒撞击壁面的有限元模型,并运用Abaqus作为前处理器。催化剂颗粒是一种典型的脆性材料,在有限元模型中选取了相应的材料本构模型,模拟了不同参数(撞击形态、入射速度、入射角度)的催化剂颗粒撞击壁面的过程,建立了催化剂颗粒的质量损失与催化剂颗粒参数间的关系,并对模拟结果进行了分析。最后,根据数值模拟的结果,优化了催化剂颗粒的参数,提出了减少催化剂跑损的措施。研究结果表明,撞击过程中的不同催化剂颗粒参数对催化剂的磨损量会产生较大的影响,催化剂颗粒的磨损量随着入射速度和入射角度的增大而增大,当催化剂颗粒以45°的形态撞击壁面时,磨损量最小。     

用于有限元分析的板壳模型的特征造型

为满足板壳结构有限元分析的需要，将板壳结构特征化，以平面特征和曲面特征表示几何特性，以网格特征表示离散特性，厚度、载荷和约束特征表示计算特性，从而形成了造型和有限元网格划分一体化的板壳模型特征造型方案。     

液压缸承受径向载荷的非线性有限元分析

针对工程实际应用,运用ANSYS软件建立了承受径向载荷的液压缸的有限元模型,通过有限元分析得到了液压杆、活塞、导向套和缸筒的应力及变形后的间隙,保证了液压缸在承受径向载荷时的安全性.     

履带起重机履带架的非线性有限元分析

利用有限元软件ANSYS对履带起重机履带架2种简化模型进行分析对比,得到了不同地面刚度对履带架计算结果的影响关系,突破以前支重轮受力分布呈线性分布的假设,得到了更真实的支重轮受力分布规律及更准确的履带架的强度,为履带架设计提供更精确的依据,并对履带起重机履带架单独计算提出改进意见.     

橡胶-钢球支座非线性有限元分析

针对橡胶的大变形及接近不可压缩的特点,笔者对工程中常用的橡胶-刚球支座进行非线性有限元分析,得出支座受轴向拉伸时的刚度与轴向变形关系.此外,分析了泊松比对支座刚度和橡胶层中应力的影响,同时得出支座受轴向拉伸时最易失效的位置.     

有限元中体壳单元的耦合问题研究

由于转动自由度的不连续,使得体单元与壳单元之间的耦合成为有限元计算中比较难以解决的问题.通常在工程实践中采用MPC(Multipoint Constraint)法.文中提出了约束体壳单元连接处共用节点的某一旋转自由度的方法.通过与MPC法的计算对比,证明了该方法在便于实现的同时,同样有着很高的精确度.这为有限元分析中体壳单元的耦合处理提供了一种很好的借鉴方法.     

电子对撞机支架结构的非线性有限元分析

应用接触非线性有限元理论,对复杂的支架结构进行了虚拟设计。探讨了接触非线性有限元理论在实际问题中的应用,对复杂结构有限元模型的建立进行了研究,分析并得到了不同的结构形式和工作状态下,位移和应力的分布规律,以及影响各方向位移和支架强度的主要因素,为接触非线性有限元理论的实际应用及对撞区支架结构进一步改进,提供了理论依据。     

有限元分析在管壳式换热器定期检验中的应用

换热器常处于高温高压的工作环境下,并且受力复杂。在定期检验工作中比较难以掌握它的受力情况。应用有限元分析对管壳式换热器在机械场和耦合场两种不同工况下进行应力分析,分别确定应力集中位置,得出应力集中位置应力最大理论值。通过对两种工况的比较,分析得出热载荷是换热器应力值增大的主要影响因数,并且把应力集中位置作为定期检验工作的重点,从而提高缺陷的检出率,消除检验死角,为检验师制定全面检验方案提供理论基础。     

Comparative analysis of the results of finite element calculations based on an ellipsoidal shell

In the curvilinear coordinate system, we describe an algorithm for generating the stiffness matrix of the quadrilateral element of the middle surface of a thin shell based on Kirchhoff’s hypothesis with nodal unknowns in the form of displacements and their derivatives using a vector approximation of the displacement fields. The developed finite element is verified by calculating the shell with the middle surface in the form of a triaxial ellipsoid in the two-dimensional formulation. The results are compared with the calculation results obtained using ANSYS software. The efficiency of the vector approximation of the displacement fields for the calculation of arbitrary thin shells in the moment stress state is shown.     

有限元分析在谐振筒式密度传感器结构设计中的应用

在谐振筒式密度传感器的结构设计中,近似解析法和有限元矩阵法只能分析固有频率,并且分析精度不高.本文提?了采用ANSYS10.0软件分析的方法,并通过大量的分析计算,总结出谐振子同有频率受结构参数、材料特性和约束条件影响?规律,分析了静压力对谐振子固有频率的影响,以及谐振子的频域响应特性、时域响应特性、谱响应特性等动力学性能.设计?谐振筒式密度传感器,在20℃时的恒温环境下标定了传感器系数,实验表明传感器的测量偏差为0.1%.     

An applied finite element displacement analysis of a simple integral construction vehicle body shell

A finite element idealization of a full-size vehicle body shell was created and used to predict underfloor displacement patterns due to beam loadings, which were compared with experimentally measured values. Modified representations of roof and floor construction details were used to highlight their influence on the structural behaviour of the vehicle. Also comparative studies were made using “assumed stress” and “assumed displacement” element formulations.     

Passat B5密封条大变形非线性有限元分析

利用非线性有限元分析软件MARC对Passat B5的车门密封条进行仿真分析,并借助测试装置对实际产品材料参数进行准确测定,解决了该复杂结构的几何非线性、材料非线性和压缩过程边界非线性的有限元分析难点,获得良好的定量分析结果。     

3-D finite element analysis for thermo-mechanical behavior of laminated carbon-phenolic composite ring

In this paper, the thermal insulator structure of a real rocket which is fabricated in a way that laminated composite rings are connected in series is analyzed using 3-dimensional axisymmetric finite element models. Simulation of cowl zone using real operating conditions provides that the stress distribution in the laminated composite ring is largely influenced by ply-angles, axial dimensions, and boundary conditions. It is hypothesized that notably the ply-lift that is the precursor to the wedge-out occurs in the ring-to-ring bonding region to a limited ply angle. Moreover, it is suggested that the wedge-out is dropped out due to the maximum shear stress in a fixed ply-angle direction and the axial compressive stress.     

Vibration analysis of delaminated composite beams and plates using a higher-order finite element

In order to analyze the vibration response of delaminated composite plates of moderate thickness, a FEM model based on a simple higher-order plate theory, which can satisfy the zero transverse shear strain condition on the top and bottom surfaces of plates, has been proposed in this paper. To set up a C⁰-type FEM model, two artificial variables have been introduced in the displacement field to avoid the higher-order derivatives in the higher-order plate theory. The corresponding constraint conditions from the two artificial variables have been enforced effectively through the penalty function method using the reduced integration scheme within the element area. Furthermore, the implementation of displacement continuity conditions at the delamination front has been described using the present FEM theory. Various examples studied in many previous researches have been employed to verify the justification, accuracy and efficiency of the present FEM model. The influences of delamination on the vibration characteristic of composite laminates have been investigated. Especially the variation of ‘curvature of vibration mode’ (i.e., the second-order differential of deflections in vibration mode) caused by delamination has been studied in detail to provide valuable information for the possible identification of delamination. Furthermore, two approaches have been investigated to detect a delamination in laminates by employing this information.     

基于ANSYS的内啮合齿轮泵壳体有限元分析及优化

该文利用ANSYS有限元软件对内啮合齿轮泵壳体进行了强度和刚度分析,首先找出了壳体的应力主要集中区和变形量较大的位置,为壳体的设计提供了参考;其次,对壳体进行了优化,在保证壳体的强度达到设计要求的情况下,增强了泵壳的刚度,改善了泵的整体性能,减少了材料的使用,降低了泵的重量,达到节约材料资源的目的.     

Vibration analysis of composite pipes using the finite element method with B-spline wavelets

A finite element formulation using the B-spline wavelets on the interval is developed for modeling the free vibrations of composite pipes. The composite FRP pipe element is treated as a beam element. The finite pipe element is constructed in the wavelet space and then transformed to the physical space. Detailed expressions of the mass and stiffness matrices are derived for the composite pipe using the B-spline scaling and wavelet functions. Both Euler-Bernoulli and Timoshenko beam theories are considered. The generalized eigenvalue problem is formulated and solved to obtain the modal characteristics of the composite pipe. The developed wavelet-based finite element discretization scheme utilizes significantly less elements compared to the conventional finite element method for modeling composite pipes. Numerical solutions are obtained to demonstrate the accuracy of the developed element, which is verified by comparisons with some available results in the literature.     

Collapse simulation of tubular structures using a finite element limit analysis approach and shell elements

This paper describes the collapse simulation of thin-walled tubular structures using a finite element limit analysis approach and degenerated four-node shell elements. The simulation traces the path of sequential deformation of the structure modelled by considering the strain-hardening effect, which is important for the analysis of collapse behaviour and energy absorption efficiency. The collapse analysis of some square tubes was used to verify the simulation method proposed. Numerical results are compared with experimental observations for sequential collapse loads and deformation modes, showing fairly good coincidence. The collapse analysis of an S-rail was then carried out for sequential collapse loads as well as deformation modes and its results are compared with elasto-plastic analysis results obtained from the explicit dynamic code PAM-CRASH. The energy absorption capacity was studied for a variety of rectangular cross-section aspect ratios. The results show that the energy absorption capacity increases as the height-to-width aspect ratio becomes larger. Results also demonstrate that the finite element limit analysis can predict the plastic collapse load and collapse mode of thin-walled structures efficiently and systematically. The present algorithm with a simple formulation has the advantage of stable convergence, computational efficiency and easy access to strain-hardening materials compared to the incremental rigid–plastic finite element analysis.