单向纤维复合材料的低频阻尼性能

为了进一步探索纤维增强复合材料的阻尼性能,本文通过拉挤工艺制作了聚乙烯基纤维增强复合材料和环氧基纤维增强复合材料,通过动态力学分析仪研究了纤维增强复合的频率和温度阻尼性能。结果表明:增强纤维的直径对阻尼性能很重要。2种纤维复合材料阻尼损耗因子随着温度的升高而下降(-20℃~60℃);随着频率的增加而增加(0.1 Hz~2 Hz)。碳纤维复合材料的阻尼性能优于玻璃纤维复合材料;聚乙烯基复合材料的阻尼性能优于环氧基复合材料的阻尼性能。     

湿热环境下CFRP复合材料吸湿过程的仿真分析

针对碳纤维增强树脂基复合材料(CFRP)在湿热环境下的吸湿老化问题,运用Abaqus软件从细观尺度上对复合材料周期单胞结构的吸湿过程进行了有限元仿真分析,获得了不同纤维分布下两类模型吸湿后内部的水分浓度场.结果 表明,CFRP复合材料的吸湿是绕过碳纤维而仅在树脂基体内部扩散的,吸湿前期速率较快但吸湿则后期要经过相对较长的时间才能达到平衡吸湿状态,基体中不同形式的纤维分布对CFRP复合材料吸湿过程会产生一定程度的影响.吸湿瞬态过程的有限元仿真分析为后续计算水分扩散进材料内部后的吸湿应力奠定了基础.     

含孔隙复合材料的力学性能分析

为研究孔隙率对复合材料力学性能的影响,基于细观力学方法,建立包含纤维、基体和孔隙三相的代表性体积单元（Representative Volume Element,RVE）.通过数值模拟得到不同孔隙率下复合材料的基本力学参数,并通过实验对比验证参数的有效性.将这些参数运用在复合材料层板的低速冲击模拟和压缩模拟中,研究孔隙率对复合材料层合板抗冲击性能和压缩强度的影响.     

超声声速测算在连续增韧陶瓷基复合材料检测中的可行性研究

陶瓷基复合材料是一种重要的超高温材料,具有耐高温、低密度、高比强、高比模、抗氧化和抗烧蚀等优异性能,其中,性能最好的一种是连续纤维增韧陶瓷基复合材料。采用声速测算的方法对材料的质量进行评估,实现对材料不均匀性的质量评价。     

矿用变频器性能测试系统设计

针对现有矿用变频器测试系统存在测试项目不全面、测试效率低、安全性差、转矩加载精度不高等问题,采用交流回馈加载技术,设计了一种由供电系统、加载试验台、测控系统组成的矿用变频器性能测试系统。供电系统为测控系统和加载试验台提供控制和动力电源;加载试验台采用共母线的变频加载方式,为被试变频器提供负载环境;测控系统实时监测系统的运行状态,通过测控主机对供电系统和加载试验台进行状态监测与集中控制。基于WinCC组态软件开发了包括监测监控模块、测试管理模块和安全管理模块的测试系统软件。监测监控模块用于实现项目信息管理,数据采集、处理、存储,并通过测控主机对设备进行控制;测试管理模块主要用于对测试项目、测试流程、测试方法等进行管理,可对变频器的漏电闭锁、瞬时断电保护、输出端短路保护、过载保护、断相保护、过欠压保护、轻载、牵引特性、温升等性能进行测试;安全管理模块从操作安全保护、设备安全保护、系统运行安全等方面保证了测试过程安全可控。提出了恒转矩加载控制算法,提高了转矩加载精度。测试结果表明,该系统测试精度高,在额定转矩范围内,转矩加载误差均小于1%;采用交流回馈加载方式,系统耗电率不超过30%;系统电磁兼容性能符合标准要求。     

FBG应变传感器的疲劳性能研究

将光纤布拉格光栅(FBG)应变传感器埋入树脂基复合材料内部,采用试验的方法研究了传感器的疲劳性能.FBG应变监测曲线变化规律符合复合材料层合板疲劳理论,经历106次循环载荷作用过程后,最大应变测量相对误差为1.11％,保持了良好的应变测试能力和较高的测量精度.实验证明:FBG能够实现对交变应变、应力的监测,具有良好的抗疲劳能力,为重要结构服役过程中的在线损伤监测、剩余寿命预报以及材料破坏失效的预警奠定了重要基础.     

基于微波暗室GNSS抗干扰接收机的测试方法

GNSS抗干扰接收机的性能测试方法研究,对提高卫星导航系统在实际应用环境下的安全性与可靠性具有重要意义。本文提出了一种基于微波暗室改进的GNSS抗干扰接收机的测试方法,该方法通过扩大模拟信号的视场角范围,实现了卫星信号的多路输出、干扰信号的动态模拟。和传统的卫星信号单路输出、干扰信号静态模拟的测试方法相比,本文提出的测试方法能够逼近室外真实的测试环境,提高了抗干扰接收机性能测试的准确性。最后通过数字仿真,分析了干扰源与信号源的夹角关系及信号模拟误差对抗干扰接收机测试带来的影响。     

舵机综合性能测试平台的系统实现

舵机是导弹控制系统的重要执行机构,为实现对空空导弹用各种舵机空载和加载性能的测试.建立了一个通用化的舵机综合性能测试平台;系统借助通用化测试仪器,通过局域网和GPIB总线,结合VMIC内存反射网,进行多个测试单元的同步测试,采用根据预先设定的任意载荷谱,进行舵机非线性旋转加载和直线横向力加载的电动加载方式,准确快速完成各种舵机综合性能测试;具有测试精度高、覆盖性广、通用性强、易扩展升级和全程自动化测试的特点,为舵机的性能研究和设计改进提供了一个良好和完整的测试环境.     

ESA Comp复合材料结构设计的专用软件

一、前言 复合材料层合板的设计过程存在着同传统金属结构设计不同的阶段。例如,复合材料的结构设计有许多种材料组合可能,而且,材料的各向异性力学行为在设计阶段可通过选择特定的纤维方向和叠     

Pro/ENGINEER复合材料的建模流程

复合材料(Composite Material)是以一种材料为基体,另一种材料为增强体组合而成的材料.各种材料在性能上互相取长补短,产生协同效应,使新材料的综合性能优于原组成材料而满足各种不同的要求.复合材料的基体包括金属和非金属两大类.复合材料按其组成分为金属与金属复合、非金属与金属复合、非金属与非金属复合三种形式.按其结构特点又分为:纤维复合材料、夹层复合材料(包括实心夹层和蜂窝夹层两种)、细粒复合材料以及混杂复合材料.     

复合材料磁悬浮列车车体结构数值模拟(Ⅰ)——适应车体设计的参数化有限元模型

为适应高性能复合材料磁悬浮列车车体结构设计和轻量化要求,对由高性能碳纤维材料、铝合金和高性能玻璃材料组合而成的复合材料磁悬浮列车进行参数化设计,使用Siemens NX建立参数化磁悬浮列车几何模型和有限元模型,实现车体结构和连接结构的精确数值模拟,为基于数值模拟技术的磁悬浮列车车体设计打好基础。     

金属缠绕垫片结构参数对压缩-回弹性能的影响

为分析金属缠绕垫片结构参数对螺栓法兰连接系统密封失效的影响规律,以柔性石墨-不锈钢金属缠绕垫片为研究对象,采用试验与数值模拟相结合的方法研究垫片的压缩-回弹性能,并以垫片外缘最小压应力为指标分析螺栓法兰连接系统的密封性能,考核垫片结构参数对垫片外缘最小压应力和密封性能的影响.结果 表明:试验与有限元数值模拟得到的柔性石墨-不锈钢金属缠绕垫片的非线性压缩-回弹曲线吻合很好;与工程常用的柔性石墨-不锈钢金属缠绕垫片结构参数相比,适当减小金属带宽度、石墨带宽度、缠绕层数及金属带角度可以在不同程度上提高螺栓法兰连接系统的密封性能.     

The Design of Image Compression Algorithms Testing and Analyzing Tool

This paper studies the evaluation methods for image compression algorithms and proposes test methods for compression algo- rithms including horizontal comparison test and vertical decomposition test. On the base of this, we design and realize a testing and analyzing tool for performance of image compression algorithms. This tool can test and analyze compression algorithms and generate kinds of analysis chart automatically, provides a lot of convenience for users and has very important practical value. In order to im- prove efficiency, veracity and perfectibility of the tool, this paper presents selection method for test images and analysis method for test results which have certain theoretical meaning.     

图像压缩算法性能的测试与分析工具

本文研究了图像压缩算法性能的评价方法,提出了图像压缩算法性能的测试算法,包括横向比较测试和纵向分解测试,并在此基础上设计并实现了压缩算法性能的测试与分析工具。该工具能够测试和分析压缩算法的性能,并自动生成各种分析图表,为用户提供了方便,具有较大的实用价值。为了提高评价的效率、准确性和全面性,文中提出了测试图像的选择方法和测试结果的分析方法,具有一定的理论意义。     

A feature-based fixture design methodology for the manufacturing of aircraft structural parts

In fixture design for the manufacturing of aircraft structural parts, there are various challenges and serious problems in industry, such as difficulty in design knowledge capture and reuse, and the arbitrary or non-standard nature of design, which influence the efficiency and quality of fixture design. This paper proposes a feature-based fixture design methodology in which previous fixture design cases and design rules are described in association with features and thus the design knowledge is integrated with geometric information of aircraft structural parts, which are the main concern of this project. In this methodology, machining features of the structural parts and their associated attributes are identified by feature recognition technique from the 3 dimensional (3D) part models defined based on model-based definition (MBD) technique. The feature-based part information models are then established and are used to retrieve previous fixture design cases and design rules stored in the knowledge base. Fixture designers will choose the appropriate retrieved design cases as the starting point for new fixture design or use previous designs to assess his/her current design. In this way the process of new fixture design can be improved. In the current stage of the research, a prototype feature-based fixture design system based on CATIA for the manufacturing of aircraft structural parts has been developed and used by a large airplane manufacturer.     

Multiphase material optimization for fiber reinforced composites with strain softening

The present paper addresses an optimization strategy of textile fiber reinforced concrete (FRC) with emphasis on its special failure behavior. Since both concrete and fiber are brittle materials a prominent objective for FRC structures is concerned with the improvement of ductility. Despite above unfavorable characteristics the interface between fiber and matrix plays a substantial role in the structural response. This favorable ‘composite effect’ is related to material parameters involved in the interface and the material layout on the small scale level. Therefore the purpose of the present paper is to improve the structural ductility of FRC at the macroscopic level applying an optimization method with respect to significant material parameters at the small scale level. The method discussed is based on multiphase material optimization. This methodology is extended to a damage formulation. The performance of the proposed method is demonstrated in a series of numerical examples; it is verified that the ductility can considerably be improved.     

大型浮吊滑动摩擦材料回转支撑力学行为

针对浮吊的轻量化设计,采用非金属滑动摩擦材料Nylatron 703XL取代以往的滚动式回转支撑.对Nylatron 703XL材料试样进行压缩试验,获得材料的压缩性能曲线,发现这种材料的压缩性能曲线呈现明显的非线性特征,对结构分析的影响显著.针对2×8 000 t大型浮吊,用Abaqus计算得到不同工况对Nylatron 703XL垫圈的力学响应和规律.计算分析摩擦因数对垫圈力学行为的影响.结果认为:Nylatron 703XL具有取代金属结构的能力,可以作为滑动摩擦材料;其在工程机械承载结构上应用的潜力巨大.     

Efficient strategies for reliability-based design optimization of variable stiffness composite structures

This study investigates efficient design optimization frameworks for composite structures with uncertainties related to material properties and loading. The integration of two decoupled reliability-based design optimization methodologies with a decoupled discrete material optimization is proposed to determine material and fiber orientation for three-dimensional composite structures. First, a deterministic and decoupled discrete material optimization is used for baseline comparison. The objective is to minimize the cost of composite structures with the design variables comprising of the piecewise patch orientations and material properties of the fiber reinforced composites. The reliability-based design optimization includes a hybrid method, and also the sequential optimization and reliability assessment method. In the sequential optimization and reliability assessment method, the inverse reliability analysis is evaluated using a stochastic response surface method and a first order reliability approach. Comparing the methods based on the optimal material and fiber orientations, the uncertainties in loads and material properties lead to different optimal layouts compared to the deterministic solutions. The numerical results also reveal that the hybrid method applied in reliability based designs results in negligible additional computational cost.     

基于MSC Patran参数化建模的飞艇蒙皮织物面内刚度预测

为研究飞艇蒙皮PBO织物的编织单胞并优化编织方案,假设单胞为宏观均匀的复合材料,基于MSC Patran,借助PCL建立参数化2D平纹织物模型,并分析编织纤维间隙、编织纤维截面夹角和树脂层厚度等参数与面内刚度的关系.结果表明,降低编织纤维间隙、减小编织纤维截面夹角、减薄树脂层厚度,可以提高织物面内刚度. 该模型及其模块可以拓展MSC Patran的功能,所开发的程序可为该类材料的编织设计提供便捷的开发工具.     

Integrated optimization of the material and structure of composites based on the Heaviside penalization of discrete material model

Based on discrete material optimization and topology optimization technologies, this paper discusses the problem of integrated optimization design of the material and structure of fiber-reinforced composites by considering the characteristics of the discrete variable of fiber ply angle because of the manufacture requirements. An optimization model based on the minimum structural compliance with a specified composite volume constraint is established. The ply angle and the distribution of the composite material are introduced as independent variables in two geometric scales (material and structural scales). The void material is added into the optional discrete material set to realize the topology change of the structure. This paper proposes an improved HPDMO (Heaviside Penalization of Discrete Material Optimization) model to obtain a better convergent result, and an explicit sensitivity analysis is performed. The effects of the HPDMO model on the convergence rate of the optimization results, the objective function value and the iteration history are studied and compared with those from the classical Discrete Material Optimization model and the Continuous Discrete Material Optimization model in this paper. Numerical examples in this paper show that the HPDMO model can effectively achieve the integrated optimization of the fiber ply angle and its distribution in the structural domain, and can also considerably improve the convergence rate of the optimal results compared with other DMO models. This model will help to reduce the manufacture cost of the optimal design.