复合材料蜂窝夹层结构T型接头拉伸性能研究

通过试验测量了复合材料蜂窝夹层结构T型整体接头的拉伸性能,得到其拉伸强度与破坏模式。建立了接头结构有限元模型,利用分类损伤判据、失效准则与刚度退化准则对结构的损伤情况进行模拟,研究了接头的拉伸破坏行为。有限元分析结果与试验结果吻合良好。研究结果表明,结构的薄弱点位于腹板内靠近蒙皮的位置。蜂窝在此处发生面外拉伸破坏,从而导致结构的最终破坏。腹板上的拉伸载荷主要通过过渡区填料传递给蒙皮,腹板与蒙皮间的搭接段对载荷传递的贡献较小。参数研究表明,对于复合材料蜂窝夹层结构T型接头,搭接段长度对结构的强度几乎没有影响,而增大蒙皮蜂窝的高度或采用低模量蜂窝可以提高结构强度。     

小议T型梁桥结构工程施工及质量控制

文章结合了现浇式T型梁桥工程施工、现浇混凝土配合比、质量控制等进行了分析。通过合理的结构设计和优质的现浇混凝土施工,辅以科学、有效的现场施工管理,高标准地完成了该公路桥梁的建设任务,具有较大的经济效益和社会效应。     

采用格型卡尔曼滤波的航空浮标定位算法研究

根据航空搜潜声呐浮标与飞机的相对方位信息,采用格型扩展卡尔曼滤波技术,对航空浮标定位方法进行了研究,建立了状态简化的2-状态定位系统的数学模型;利用蒙特卡洛仿真法,从位置估计的相对误差和均方误差两个方面,仿真分析了系统的误差性能,并获得了较好的效果。     

弯曲载荷下机织复合材料T型接头渐进失效分析

根据树脂传递模塑(RTM)成型的缎纹机织复合材料T型接头的结构特征和纤维布局特点, 基于ANSYS有限元数值分析平台, 建立符合其真实结构的几何模型和有限元分析模型。基于渐进失效强度预测方法的基本思想, 使用有限元计算软件ANSYS的参数化设计语言(APDL)开发相应的程序, 实现改进形式的Hashin失效准则。采用合适的最终失效评价方法, 建立二维机织结构复合材料T型接头受弯曲载荷时的渐进失效预测方法, 能够有效地模拟从初始加载到最终失效过程中机织复合材料T型接头结构的力学响应及损伤的萌生与发展, 并预测结构的静强度。      

T型口模气辅挤出段长度对挤出物截面形状和挤出胀大的影响

采用数值模拟的方法对T型截面口模气辅挤出成型过程中滑移段长度、挤出流量和松弛时间对挤出物的变形和挤出胀大的影响进行了研究。结果表明,气辅挤出段长度的增加可以减小挤出物的变形和挤出胀大,减小挤出流量和松弛时间对变形和挤出胀大的影响,并且当气辅挤出段的长度增加到一定值后,挤出胀大比为1且不受松弛时间和挤出流量的影响,这个值随挤出流量的增加和松弛时间的延长而增加。     

FRC/钢T型燕尾槽连接结构抗弯损伤机理及强度特性研究

针对FRC/钢水密坚固连接结构设计要求,提出纤维增强复合材料(FRC)与钢结构T型燕尾槽连接结构形式及其真空辅助成型制备方法.开展6 mm层合板与钢质槽体的T型连接接头试件制作及其拉/压弯强度试验,结果表明,当嵌入层厚度为1 mm时,20 mm宽连接试件,其拉/压抗弯极限载荷分别约为1.6~1.8 KN(拉弯)和2.6 KN(压弯);主要破坏模式表现为:钢质槽体与层合板接触端部出现初始损伤,而连接强度的失效则集中体现为嵌入层与平铺层连接界面分层以及填充芯材拉/剪断裂.通过分析,本文认为增加嵌入层厚度能有效提高连接节点的抗弯刚度,降低层间界面的应力集中水平,同时提高填充芯材的抗拉/剪强度特性也是提高T型结构连接强度的有效途径,进一步增加嵌入层厚度比例,连接结构的拉/压弯曲强度得到了显著提高.     

北衙斑岩型金矿床快速定位预测——影像线环结构-构造地球化学集成成矿预测方法

北衙碱性斑岩型金矿床为“三江”地区金沙江-哀牢山喜山期富碱斑岩带中的金多金属矿床。碱性斑岩、复式穹隆构造与金矿床呈现构造-岩浆-矿化三位一体,金矿化集中于成矿晚期热液活动阶段。矿床遥感地质方法与构造地球化学方法获取了丰富的成岩成矿影像———构造地球化学(地质信息组成的矿床定位预测网络结构“隐信息”。据此构建了影像线环结构-构造地球化学集成成矿预测方法。     

Arrow型蜂窝结构抛物柱面成型蚁狮算法优化

本研究将Arrow型零泊松比蜂窝结构用于空间抛物柱面天线.首先分析零泊松比蜂窝结构柱面成型所需加载方式,通过几何计算初步得到柱面成型所需载荷;再将ABAQUS分析、曲面拟合和型面精度计算整合为优化目标函数;然后采用蚁狮优化(ALO)算法求解使得型面精度最高的优化载荷,使用有效集法(Active Set)作为对照组,验证...     

QR分解的最小二乘格型自适应滤波算法在噪声主动控制中应用

在噪声主动控制系统中?,滤波-x递归最小二乘(FxRLS)算法收敛速度快但计算量大。本文提出了格型联合估计滤波器结构与基于QR分解的最小二乘格型(QRD-LSL)自适应滤波算法相结合的噪声控制方法,该方法对联合估计过程进行了改进并得到了基于各阶估计误差的联合过程估计权系数更新关系,格型联合估计器结构简单,QRD-LSL自适应滤波算法数值稳定性好。仿真结果表明本文提出的噪声控制方法有良好的噪声控制效果,收敛速度快,计算量小,稳态误差小,跟踪性能好。     

链篦机主要部件的结构优化分析

本文简单介绍了链篦机的工作原理,并就其中上托轮,链篦床等关键部件的结构及材质做了优化分析,从而起到提高工作效率,降低生产成本,减少能量消耗的作用。     

一种声发射源的新型平面定位方法研究

声发射现象中产生的弹性波在传播时声压遵从指数衰减规律,文中提出一种利用声衰减特性对声发射源进行平面定位的能量定位新方法。从理论上导出了该方法的定位计算公式,并用AE21C型声发射仪在高分子合成纤维平板上以铅笔芯折断产生信号为模拟源进行了实验测量,证明这种新的源定位方法可行,并具有无须测量传声媒质的声衰减和声速等优点。     

大空间内着火位置对火灾增长的影响

以大空间展厅为例,利用火源辐射模型和烟气辐射模型并结合CFAST6．0区域模拟软件的计算结果,对比分析了大空间内不同着火位置下火灾增长的情况。研究结果表明仅考虑火源热辐射的情况下,展厅内着火位置越处于左右中间对称处,其火灾增长越快,热释放速率峰值也越大,达到热释放速率峰值的时间和火灾的持续时间越短,处于展厅中心位置时所有值达峰值。对火源热辐射和烟气辐射综合考虑时,到达热释放速率峰值时间与火灾持续时间的规律同仅考虑火源辐射模型时一致,但热释放速率峰值均有不同程度的提高。     

Comparison of two methods of location of a target in devices with multi-element radiation detectors

Expressions for the statistical characteristics of devices with multi-element radiation detectors that make use of methods of target location through a determination of the centroids of the target and through scanning of the target are derived. A comparison of the precision of these methods is presented. __________ Translated from Izmeritel’naya Tekhnika, No. 12, pp. 31–33, December, 2005.     

A reliability allocation method of mechanism considering system performance reliability

It is generally believed that the reliability of a mechanical system is determined by its composition. The system operates properly when all of its components do not fail. Based on this assumption, the reliability of the system can be represented by the reliability of its components. A problem arises when applying this hypothesis to a system containing motion mechanisms. There is a phenomenon in motion mechanism that the components do not happen structural failure (we call it “Type I failure”) and joint failure (we call it “Type II failure”), but the function of the mechanism cannot meet the requirements (we call it “Type III failure”). A reliability allocation method, which synthetically considers the composition and Type III failure modes of the motion mechanism, is proposed to solve this problem. A relative dispersion factor is introduced to describe the failure dependence of components and is proposed to calculate the complexity and criticality. A series system reliability allocation model considering three types of failure modes is established. Finally, using an airplane gear door lock mechanism as an example, a comparative analysis of the system reliability allocation results with and without considering Type III failure modes is made. The allocation results show the component reliability value without considering Type III failure modes is less than that when considering them, which will increase the system hazards. The result considering Type III failure modes is more reasonable than that from the traditional method.     

定量包装商品净含量计量检验方法的探讨

为保证定量包装商品净含量计量检验结果的统一性、有效性和准确性,依据JJF 1070-2005《定量包装商品净含量计量检验规则》,对影响定量包装商品净含量检验结果的不确定度的主要来源和检验的关键点进行分析,找出每种检验方法中影响净含量检验结果的测量不确定度,为今后科学地计量检验定量包装商品净含量奠定基础。     

用边界元法计算声辐射时高次奇异积分的处理方法

边界元法应用于计算辐射声场时，由于奇积分的存在，会影响以计算结果的精度，本文描述了处理带有１／ｒ奇异积分和１／ｒ＾２二次奇异积分处理方法，包括数学证明和数值积分方法，计算结果表明这种方法能提高精度。     

计及运动副间隙的双曲柄六杆压力机机构动力学仿真向量键合图法

针对计及运动副间隙的双曲柄六杆压力机机构动力学仿真问题,提出了相应的向量键合图法.基于修正非线性连续接触碰撞力的混合模型,推导出间隙运动副的相对碰撞速度向量方程.在此基础上,建立了可以更精确描述间隙运动副的向量键合图模型,具有通用性强、模块化的特点,便于嵌入到系统的向量键合图模型中.由机构运动副的约束关系,将各构件的向...     

Integrated method of compromise-based ant colony algorithm and rough set theory and its application in toxicity mechanism classification

Attribute discretization and reduction are two key issues in rough set theory. However, almost all previous studies consider them as two separate steps, which can not capture an inherent relationship between them. In this paper, a bi-objective optimization problem is constructed for simultaneous attribute discretization and reduction. A novel compromise-based ant colony algorithm (CACA) for simultaneously solving attribute discretization and reduction is proposed, which adopts a distance metric to stepwise approach the ideal solution. To improve efficiency of the proposed method, both the cut information and attribute information are adopted to dynamically calculate heuristic information, and a local search strategy is also embedded. The grade of nature spearmint essence (NSE), wine and glass classification problems are used as three test datasets to demonstrate the validity of the proposed CACA. Furthermore, the proposed method is applied to two toxicity mechanism classification problems: the classification of three narcosis mechanisms of aquatic toxicity for 194 organic compounds and the classification of four action modes of 221 phenols. The obtained results illustrate that the proposed method has better prediction performance than linear discriminant analysis, radial basis function neural network and support vector machine.     

A topological optimization approach for structural design of a high‐speed low‐load mechanism using the equivalent static loads method

In high‐speed low‐load mechanisms, the principal loads are the inertial forces caused by the high accelerations and velocities. Hence, mechanical design should consider lightweight structures to minimize such loads. In this paper, a topological optimization method is presented on the basis of the equivalent static loads method. Finite element (FE) models of the mechanism in different positions are constructed, and the equivalent loads are obtained using flexible multibody dynamics simulation. Kinetic DOFs are used to simulate the motion joints, and a quasi‐static analysis is performed to obtain the structural responses. The element sensitivity is calculated according to the static‐load‐equivalent equilibrium, in such a way that the influence on the inertial force is considered. A dimensionless component sensitivity factor (strain energy caused by unit load divided by kinetic energy from unit velocity) is used, which quantifies the significance of each element. Finally, the topological optimization approach is presented on the basis of the evolutionary structural optimization method, where the objective is to find the maximum ratio of strain energy to kinetic energy. In order to show the efficiency of the presented method, we presented two numerical cases. The results of these analyses show that the presented method is more efficient and can be easily implemented in commercial FE analysis software. Copyright © 2011 John Wiley & Sons, Ltd.     

Al-TiO2-B2O3-C系XD合成铝基复合材料的反应机理及力学性能

研究了Al-TiO2-B2O3-C反应系XD合成铝基复合材料的反应机理.结果表明在Al-TiO2-B2O3-C系中,当B2O3/TiO2摩尔比=0.5,C/TiO2摩尔比=0时,TiO2和B2O3分别与Al结合生成热力学稳定的Al2O3和活性Ti原子、B原子,B原子和Ti原子分别穿过各自反应层结合生成热力学稳定的TiB2,过剩的Ti原子则与Al结合生成棒状物Al3Ti;加入碳粉后,Ti原子将优先与C和C与Al的化合物Al4C3反应生成TiC,Al3Ti逐渐减少,在C/TiO2摩尔比为0.5时,Al3Ti相基本消失,力学性能得到改善,其拉伸强度和延伸率分别从266MPa和3%增加到315MPa和7%.