复合材料整体壁板固化变形控制方法研究

针对优化工艺参数和结构尺寸在整体壁板固化变形控制方面的局限性问题,提出了通过面板非对称铺层来控制整体壁板固化变形的方法.采用整体壁板和非对称层合板固化变形的特征,面板采用非对称铺层,并且使固化变形方向和筋条固化变形方向相反,可以有效地抵消筋条回弹和树脂收缩引起的固化翘曲变形.并根据上述方法对某复合材料机翼壁板进行固化变形控制方法设计,分别计算初始铺层顺序、优化桁条铺层顺序和蒙皮非对称铺层三种情况下机翼壁板的固化变形量.结果表明,优化桁条铺层顺序对减少机翼壁板固化变形效果不明显,而机翼壁板蒙皮采用非对称铺层能明显减小机翼壁板的固化变形,从而验证了提出方法的可行性和正确性.     

复合材料厚板结构三维有效弹性常数计算模块化程序

为实现复合材料厚板结构三维有效弹性常数的模块化计算,利用MSCPatran的二次开发语言PCL开发模块化计算程序．针对具有周期性铺层方式的复合材料厚板结构,该程序可自动生成等效后的三维正交各向异性材料．将该程序用于复合材料太阳翼连接架的静力分析,生成连接架各局部复合材料结构的三维正交各向异性材料,得到其在设计载荷下的应变分析结果．有限元分析结果与试验结果比较表明,该程序能有效计算复合材料厚板结构的三维弹性常数,提高复合材料三维建模的效率及可靠性．     

基于Python的复合材料船体梁极限强度分析

为在复合材料船体结构数值仿真分析中进行快速建模和分析,采用Python脚本语言和Abaqus前处理模块,开发出针对复合材料船体梁极限强度计算的通用模块.该模块考虑复合材料的各向异性、失效准则及铺层方式等因素.实例表明：所开发的程序界面友好、可操作性强,能有效提高复合材料船体梁极限分析的效率.     

大展弦比复合材料机翼动力学分析

针对结构非线性对大展弦比机翼动力学特性影响很大的问题,使用MSC Patran和MSC Nastran软件进行有限元建模及分析,将大展弦比机翼建成薄壁盒型梁模型．研究大变形对机翼动力学特性的影响,比较复合材料盒型梁模型和金属盒型梁模型的计算结果,并讨论复合材料铺层顺序的改变对机翼动力学特性的影响．研究表明：复合材料机翼的各阶固有频率明显高于铝合金机翼;铺层顺序会影响复合材料机翼的固有频率．     

Abaqus/CAE高级实用技巧(续1)

目前,复合材料在工程中的应用越来越广泛．对于大量使用的层合复合材料,Abaqus／CAE引入专门用于复合材料的设计模块Plyup建立复合材料层合板,使建模变得更为简单,应用该模块可方便地对复合材料进行铺层设计．对于每个铺层,可选择铺层应用的区域、使用的材料、铺层的铺设角度和厚度等．对于铺层较多的结构,Abaqus／CAE提供很方便的检查手段,可使铺层沿厚度方向将每层分离展示,效果一目了然,是数字化设计的优点之一．     

基于MSC Patran的飞机结构战伤快速修理程序

为使用模块化方法实现飞机结构战伤的快速修理,以MSC Patran为平台,利用其二次开发语言PCL和模型日志文件,通过自动加载编译函数文件、参数化建模、用户自定义菜单和图形界面、自动提交分析和读取结果等技术,开发飞机结构战伤快速修理程序. 使用此程序分析几个典型案例,结果表明该程序不仅能满足多数飞机结构战伤修理的要求,而且可以大大缩短修理时间.     

热层合结构横向应力分析的仿真

复合材料热层合结构已广泛应用于航天飞行器.横向应力对复合材料热层合结构的破坏失效具有重要影响.文中基于层合板的一阶剪切变形理论,利用后处理方法,编制设计了复合材料热层合结构横向应力分析计算软件.应用该计算软件对薄板结构厚度方向温度梯度、材料的性能、结构的厚度等参数对热结构的横向应力分布的影响进行了分析讨论.算例表明,剪切弹性参数对热结构的横向应力沿厚度方向的分布影响明显.该方法能用于相关热结构的分析设计.     

基于MSC Nastran的复合材料尾翼优化分析

以Patran为前处理软件,MSC Nastran为求解器,复合材料铺层数为设计变量,以结构质量最轻为目标函数,对复合材料尾翼进行优化设计,并总结复合材料结构优化设计中的思路、方法和步骤.     

邮船大跨距板架参数化建模和动力学分析程序开发

针对豪华邮船大跨距板架静力学和动力学分析需要进行大量繁琐建模工作的问题,研究NAPA、MSC Patran/Nastran等多个软件协同运行的方法,借助Visual Studio开发流程化设计程序,并通过Isight优化软件验证程序的适用性。该程序可实现邮船多层大跨距板架设计的参数化建模和自动分析计算,从而快速获得多方案设计结果,提高设计和分析效率。     

飞机复合材料结构修理工程分析方法研究

本文主要对复合材料结构失效分析、胶层失效分析、贴补修理分析、挖补修理分析展开分析,其中对胶层失效分析从基于材料强度的分析方法、断裂力学的分析方法、粘聚区模型、连续损伤力学模型展开论述与分析,希望给相关理论研究提供一些参考依据。     

Three-dimensional finite element analysis of interlaminar stresses in thick composite laminates

The three-dimensional finite element computer program has been developed to investigate interlaminar stresses in thick composite laminates. The finite element analysis is based on displacement formulation employing curved isoparametric 16-node elements. By using substructure technique, the program developed is capable of handling any composite laminates which consist of any number of orthotropic laminae and any orientations. In this paper, solid laminates and laminates with a circular hole were taken to study interlaminar stresses at the straight edge and the curved edge, respectively. Various solid laminates such as [45_n/0_n − 45_n/90_n]_s, [45/0/ − 45/90]_ns, and [45/0/ − 45/90]_sn (n = 1˜4) were analyzed. Also, [45/0/ − 45/90]_sn laminates with a circular hole were studied for n = 1 ˜ 20. The effect of laminate thickness and stacking sequence on the interlaminar stresses near the free edge was investigated. Interlaminar stresses were governed by stacking sequence rather than laminate thickness. The boundary layer width did not increase with laminate thickness but with the number of plies in the repeating unit.     

基于UG二次开发的参数化建模方法

对于目前有关UG二次开发中零件的常用参数化建模方法,论文提出了两种更为简单快速的建模方法.第一种方法是以内齿圈参数化设计为例,通过先建立零件的模板模型,然后在其对话框的回叫函数中,编写代码更改参数,最后更新,实现零件的参数化.第二种方法是以超声变幅杆为例,利用UG建模环境中的JA文件录制功能,将零件的建模过程进行录制,用得到的代码在对话框的回叫程序中替代原本用API或grip开发的零件建模程序,然后将对话框的输入值与代码中模型的参数进行关联,实现零件的参数化.这两种方法的应用能有效减少设计人员的重复劳动,提高设计效率.     

面向属性的参数化建模在Revit API中的应用

为改进目前构件级建模过程存在的效率低问题,提出面向属性的参数化建模过程.此方法使建模师不需要重复传统建模操作,通过设置模型属性参数就可以实现相关数据的统计和计算从而快速建模.以球面网格结构为例,将参数化建模思想融入到Revit二次开发技术中,借用VS开发工具实现三维模型的快速生成.在操作时,用户只需通过用户界面输入矢高、跨度和环数等结构参数即可以完成模型的快速建立.通过此程序,还可以实现肋环形和施威德勒型2种类型的选择,实时监测设置的参数是否满足规范要求.     

弹体结构自顶向下的参数化装配体建模方法

为提高导弹弹体建模的质量和效率,对弹体结构的建模过程进行研究。提出了弹体 结构的自顶向下的参数化装配体建模方法。以UG 为平台,开发了弹体结构快速建模系统,实现 了弹体结构快速建模、模型快速修改和对整个装配体的参数驱动和参数管理。选取典型弹体结构 为实例,验证了该方法的可行性和有效性。     

Modeling the material grading and structures of heterogeneous objects for layered manufacturing

The emphasis of this work is to discuss a scheme for modeling the material grading and structures of heterogeneous objects. To model the material grading of a heterogeneous object, a termed ‘grading source’ is defined. The grading sources are reference features, which specify the type and position of grading, and a material grading function for controlling the material variation within the geometric boundary of the objects. Within the proposed modeling scheme, a concept on representing objects, which are both heterogeneous in material and structure (e.g. composite laminates), will also be elaborated. For downstream layered manufacturing purposes, a contour sub-division algorithm on each layer arising from slicing a heterogeneous object is proposed. Within each slice, the material grading is decomposed into sub-contours according to the different grading variation. A parameter called ‘grading step-width’ is defined to control the number of sub-contours and resolution of the grading. With such discretization, it is, therefore, possible to build a heterogeneous object on layered manufacturing machines of different fabricating precision specification.     

A Neuro-Fuzzy Approach to Identify Lettuce Growth and Greenhouse Climate

A hybrid neuro-fuzzy approach called the NUFZY system, which embeds fuzzy reasoning into a triple-layered network structure, has been developed to identify nonlinear systems. A set of membership functions at the input layer is partially linked with a layer of rules, using pre-set parameters. By means of a simplified centroid of gravity defuzzification method, the output becomes linear in the weights. Therefore, very fast estimation of the weight parameters can be achieved by using the orthogonal least squares (OLS) method, which also provides a method to efficiently remove the redundant fuzzy rules from the prototype rule base of the NUFZY system. In this paper, the NUFZY system is applied to identify lettuce growth and greenhouse temperature from real experimental data.Results show that the NUFZY model with the fast OLS training can perform quite well in predicting both lettuce growth and greenhouse temperature. In contrast to the mechanistic modeling procedures, the neuro-fuzzy approach offers an easier route and a fast way to build the nonlinear mapping of inputs and outputs. In addition, the resulting internal network structure of the NUFZY system is a self-explanatory representation of fuzzy rules. Under this frame, it is a perspective that one is able to incorporate the human knowledge in this approach, and, hopefully, to deduce any interpretable rules that describe the systems' behavior.     

An integrated method for predicting damage and residual tensile strength of composite laminates under low velocity impact

An integrated approach is presented to analyze the whole process of damage initiation and development for composite laminates under impact loading as well as tensile loading after impact using the 3D progressive damage theory. The real impact damage status of composite laminates is employed to analyze the residual tensile strength instead of the artificial premises adopted by traditional methods. This integrated approach can not only improve the prediction accuracy of the ultimate strength but also avoid large numbers of experiments for obtaining the impact damage parameters. A parametric modeling program package based on the analytical method has been developed.     

基于二次参数化技术的风电机组序列化建模

针对常规建模方法在庞大复杂风电机组应用上的不足,在建立单台风电机 组全参数化模型的基础上,以风电机组序列整体为研究对象,根据同序列不同功率机组之间 各零部件设计参数变化规律,研究应用二次参数化技术和参数序列化方法实现了高效的风电 机组模型建立与管理;并结合三维模型参数驱动技术,研发了风电机组序列建模系统,可有 效减少建模和造型工作量、降低设计失误率、提高设计效率,验证了该建模方法的正确性与 合理性。     

One-sided Post-processing for the Discontinuous Galerkin Method Using ENO Type Stencil Choosing and the Local Edge Detection Method

In a previous paper by Ryan and Shu [Ryan, J. K., and Shu, C.-W. (2003). \hboxMethods Appl. Anal. 10(2), 295–307], a one-sided post-processing technique for the discontinuous Galerkin method was introduced for reconstructing solutions near computational boundaries and discontinuities in the boundaries, as well as for changes in mesh size. This technique requires prior knowledge of the discontinuity location in order to determine whether to use centered, partially one-sided, or one-sided post-processing. We now present two alternative stencil choosing schemes to automate the choice of post-processing stencil. The first is an ENO type stencil choosing procedure, which is designed to choose centered post-processing in smooth regions and one-sided or partially one-sided post-processing near a discontinuity, and the second method is based on the edge detection method designed by Archibald, Gelb, and Yoon [Archibald, R., Gelb, A., and Yoon, J. (2005). SIAM J. Numeric. Anal. 43, 259–279; Archibald, R., Gelb, A., and Yoon, J. (2006). Appl. Numeric. Math. (submitted)]. We compare these stencil choosing techniques and analyze their respective strengths and weaknesses. Finally, the automated stencil choices are applied in conjunction with the appropriate post-processing procedures and it is determine that the resulting numerical solutions are of the correct order.     

An energy conserving non-linear dynamic finite element formulation for flexible composite laminates

Finite element formulation for non-linear dynamic analysis of flexible composite laminates is presented. A first-order shear-deformation theory, capable of modelling finite deformations and finite rotations in geometrically exact manner, is developed. A model allows simulation of a general elastic material with varied mass density, degree of orthotropy and elastic material parameters and is suitable for non-linear elasto-dynamic analysis of relatively thin and flexible laminates composed of fibre-reinforced composites. Coupling of mid-surface and shell-director fields is exactly taken into account, so that the kinetic energy is not of simple quadratic form. An implicit, one-step, second-order accurate numerical time-integration scheme is applied. In particular, the energy and momentum conserving algorithm, which exactly preserves the fundamental constants of the shell-like body motion, is accomodated for composite laminates. Spatial finite element discretization is based on the four noded multilayered shell finite element with isoparametric interpolations. Fully discrete weak form of the initial boundary value problem is consistently linearized in order to achieve a quadratic rate of asymptotic convergence typical for the Newton–Raphson based solution procedures. Numerical examples are presented.