碳纤维增强镁基复合材料(Cf/AZ91D)层压板杨氏模量的多尺度模拟及预测

根据碳纤维增强镁基复合材料层压板的真实微观结构特点建立了其多尺度微观力学模型,包括微观尺度下的横向及纵向单胞模型以及介观尺度的结构单胞模型。杨氏模量由中尺度模型计算。宏观力学性能弹性模量根据介观模型进行计算。介观模型中用到的性能参数通过微观模型计算获得。采用多尺度建模方法预测了不同铺层模式的碳纤维增强镁基复合材料层压板弹性模量,并采用对应的实验方法进行了验证。结果表明,采用多尺度建模方法可以成功用于不同铺层方式层压复合材料弹性模量的预测,与实验结果具有相同的变化趋势,但较实验结果偏大。主要是由于模拟过程中忽略了实验中真实存在的合金及纤维性能退化而造成的。本文所提出的多尺度建模方法对于复合材料层压板设计具有重要意义。     

自组织竞争神经网络板材拉深材料参数识别

阐述了自组织竞争人工神经网络模型优化算法的特点，建立了自组织竞争人工神经网络识别模型，给出板材拉深材料性能参数输入输出层设计和样本数据的采集与处理的方法。研究了自组织竞争人工神经网络模型仿真实例，得到了较满意的识别结果，开辟了应用自组织竞争人工神经网络模型优化板材材料性能参数识别诊断研究的新领域。     

基于序列二次规划法的结构可靠度计算方法

针对传统的可靠度计算方法在求解多目标函数的约束优化及高非线性结构功能函数的可靠度求解时计算效率低、收敛性不高等问题,提出了一种基于序列二次规划法的结构可靠度计算方法。该方法引入序列二次规划法的约束优化模型并结合可靠度指标计算模型,在每一迭代步通过求解一个二次规划子问题来确定目标函数的下降方向,构造价值函数确定搜索步长,使其全局收敛以获得可靠度最优解及验算点。通过三个算例验证了该方法的有效性。     

石墨烯增强铝基复合材料的制备方法

石墨烯因其独特的二维结构和优异的性能，成为目前铝基复合材料中最具潜力的增强体材料之一。然而石墨烯增强铝基复合材料的制备在工业生产中仍存在许多问题。本文综述了国内外各种制备方法的研究现状，重点介绍了低成本、适用于大规模工业生产的搅拌铸造法，列举了近几年的最新成果，提出了目前存在的问题及改进方法，并展望了铝基复合材料在工业生产中的应用前景。     

喷淋悬挂式前处理设备的设计计算

概括介绍了该设备的设计计算,给出了结构设计的常用参数以及喷嘴的性能参数和热力计算表,是一种行之有效的方法.     

纳米-相变陶瓷复合材料的有效刚度

含纳米纤维和相变粒子的陶瓷复合材料具有较大的断裂韧性和较高的塑性形变行为，其组织结构以含纳米纤维的棒状复合体为基体，并在棒状复合体周围分布有少量的可产生相变的二相粒子。本文在Mori-Tanaka方法和有效自洽法的基础上提出复合材料刚度预报的随机二相胞元法。首先应用Mori-Tanaka方法计算出棒状复合体的刚度，考虑棒状复合体方位的随机性，根据复相陶瓷基体的应变均值，计算出复合材料基体的有效弹性模量和泊松比，复相陶瓷材料基体为各向同性体。最后将相变粒子看作夹杂在基体中的颗粒，计算出陶瓷复合材料的等效刚度。复相陶瓷的弹性模量随二相组元体积分数的增加而下降且略低于用混合律求解的结果，说明纳米纤维和相变粒子之间的相互作用降低了弹性模量；复相陶瓷的泊松比随二相组元体积分数的增加而下降且略高于用混合律求解的结果，说明纳米纤维和相变粒子之间的相互作用提高了泊松比。     

复合材料电磁传播特性及应用分析

分析了复合材料微波检测中电磁参量、电磁波频率和介质薄片厚度的计算方法。基于复合材料媒质间的电磁传播特性，提出了微波无损检测技术应用于复合材料检测时的局限性和不足。给出了由于脱粘空气层引入后，透射波振幅减小和相位延迟的解决方法。推导了层间脱粘将会改变总的传输系数的结果，对今后复合材料微波检测工作的方向进行了探讨。     

复合材料结构弹脆塑性力学行为数值研究

复合材料的脆性软化是影响其结构变形稳定性的重要因素之一。考虑软化后的残余强度对工程设计有重要意义，将弹脆塑性本构模型引入到复合材料结构的力学分析中来，给出了完整的弹脆塑性本构积分数值格式及有限元算法。通过对正交各向异性带孔板的单向拉伸的数值计算，显示出该文的理论和算法能够恰当地反映复合材料结构的脆性行为特性     

6-DOF并联坐标测量机结构参数的识别与修正

首先对6-DOF并联机构坐标测量机的组成结构及工作原理进行了介绍,然后针对该坐标测量机的运动特点,提出了一种基于逐次逼近算法的结构参数识别与修正方法.该方法以最小二乘逐次逼近算法为基础,以寻找6自由度并联机构坐标测量机的43个主要结构参数为目的.文中对所提算法的求解过程进行了详细的论述,并通过计算机仿真计算,对结构参数的识别与修正结果进行了验证.仿真结果表明,所提出的逐次逼近算法能够充分利用目标函数值的信息,优化搜索过程具有较强的方向性和目标性,且收敛速度较快.采用该方法对6自由度并联机构坐标测量机的结构参数进行识别与修正以后,可使该坐标测量机的测量精度得到明显改善.     

基于改进曲率模态的叶盘结构损伤识别研究

针对曲率模态不能识别结构端部单元损伤的问题,提出了改进的曲率模态识别模型。叶盘是航空发动机结构非常重要的部件之一,若其发生故障将对发动机安全运转造成严重的威胁。而曲率模态对结构故障具有很强的敏感性,运用曲率模态方法,从不同的损伤位置以及不同的损伤程度这两方面比较了叶盘模态振型变化情况,并且用改进的曲率模态方法对结构端部进行计算。数值计算结果表明:当发动机叶盘受到损伤,位移模态和结构频率难以有效反映出结构的损伤位置,各阶固有频率会下降;曲率模态方法能有效反映出结构损伤状况,曲率在损伤处发生突变现象,并能对损伤程度给出定性的描述;而改进的曲率模态识别模型能够识别出结构端部的损伤故障。这为航空发动机叶盘结构的损伤检测提供了理论依据。     

IDENTIFICATION OF STIFFNESS COEFFICIENTS OF LAMINATED COMPOSITE PLATES

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面向压力钢管维护作业的爬壁机器人焊接运动轨迹研究

介绍一款面向压力钢管维护作业的爬壁机器人,对其运动学特性进行分析。介绍机器人的机械结构和控制系统,然后采用D-H参数法建立机器人运动学模型,构造运动学正解方程,并采用Robotic Toolboox对机器人正逆运动学方程进行求解,在线显示机器人三维仿真图像,分析各关节的位移、速度及加速度曲线,并对机器人末端轨迹进行规划,从而验证了机器人结构的合理性。     

Inverse problem-coupled heat transfer model for steel continuous casting

An integrated approach was proposed for determining the heat transfer coefficient, which combined inverse heat transfer calculation model with temperature measurement and pin-shooting experiment. Based on the roller-layout and spray nozzle distribution, the IHTP (inverse heat transfer problem) model was developed to calculate the secondary cooling heat transfer by means of non-linear estimate method. The method transformed the inverse problem of parameter identification into solution of optimization problem using evolutionary algorithm. With the help of temperature measurement and pin-shooting experiment, the whole procedure of the model solution for identification and application in continuous casting process was given. Simulation and experiment results in plant trial confirmed the efficiency of the method used.     

颗粒增强金属基复合材料的屈服行为

运用空间轴对称弹塑性有限元方法和混合律模型，给出了应力应变分配系数与复合材料的弹性模量，屈服强度以及切线模量之间的定量关系式，并由此提出了一种新的定义颗粒增强金属基复合材料比例极限和屈服行为的方法，进而研究了颗粒形状（球体，正圆柱体以及椭球体）和材料结构参数（颗粒体积分数和颗粒根间距）对颗粒增强金属基复合材料拉伸变形行为的影响。研究表明，通过研究应力应变分析系数及其二阶导数来确定复合材料屈服行为的方法不仅适用于短纤维增强金属基复合材料，而且也适用于颗粒增强金属基复合材料。该方法可以较好地反映出颗粒形状和材料结构参数对复合材料屈服行为的影响，预测的比例极限与已发表的实验结果吻合较好。     

基于双激励信号的双惯量进给系统机械参数辨识

为了提高进给系统机械参数辨识的效率与精度,提出一种基于双激励信号的双惯量进给系统机械参数辨识方法,先采用伪随机二进制信号对机械传动环节进行频域辨识,根据系统的频响特性设计扫频信号频带,采用增广最小二乘法对双惯量动力学模型离散结构和扰动进行无偏估计,使用零极点匹配法将离散传递函数转化为连续时间传递函数,求解系统的机械参数。为了减小非线性摩擦的影响,整个实验过程均在加速中进行。最终模型的输出与实际输出拟合度达到98.61%,残差分析满足理论性能验证指标,提高了双惯量进给系统机械参数辨识精度与效率。     

Identification of material parameters from punch stretch test

To accurately describe the mechanical properties of aluminium alloy sheet during deformation, an inverse identification was presented to deal with material parameters from the popular punch stretch test. In the identification procedure, the optimization strategy combines finite element method (FEM), Latin hypercube sampling (LHS), Kriging model and multi-island genetic algorithm (MIGA). The proposed approach is used on material parameter identification of aluminium alloy sheet 2D12. The anisotropic yield criterion Hill'90 is discussed. The results show that the Hill'90 anisotropic yield criterion with identified anisotropic material parameters has a good potential in describing the anisotropic behaviours. It provides a way to obtain the material parameters for FE simulations of sheet metal forming.     

Stiffness influential factors-based dynamic modeling and its parameter identification method of fixed joints in machine tools

A universal dynamic model of fixed joints is built through considering the relative motion between the sub-structures of the fixed joints and the coupling among various degrees of freedom. The dynamic model may accurately reflect the dynamic characteristics of the joints. Based on the inverse relationship between the frequency response function matrix and the dynamic stiffness matrix of a Multi-Degree-Of-Freedom system, a high-accuracy parameter identification method is proposed to recognize the dynamic model parameters of the joints using the dynamic test data of the whole structure including the joints. The error between the theoretical and experimental results of the model is less than 10%, while the error of the Yoshimura model is three times bigger than that of the model. The effectiveness and accuracy of the dynamic model and its parameter identification have been validated. The establishment of the model will provide a theoretical foundation for the precisely dynamic modeling of the CNC Machine Tool.     

Identification of Dynamic Flow Stress Curves Using the Virtual Fields Methods: Theoretical Feasibility Analysis

An inverse approach based on the virtual fields method (VFM) is presented to identify the material hardening parameters under dynamic deformation. This dynamic-VFM (D-VFM) method does not require load information for the parameter identification. Instead, it utilizes acceleration fields in a specimen’s gage region. To investigate the feasibility of the proposed inverse approach for dynamic deformation, the virtual experiments using dynamic finite element simulations were conducted. The simulation could provide all the necessary data for the identification such as displacement, strain, and acceleration fields. The accuracy of the identification results was evaluated by changing several parameters such as specimen geometry, velocity, and traction boundary conditions. The analysis clearly shows that the D-VFM which utilizes acceleration fields can be a good alternative to the conventional identification procedure that uses load information. Also, it was found that proper deformation conditions are required for generating sufficient acceleration fields during dynamic deformation to enhance the identification accuracy with the D-VFM.     

A novel procedure for selection of materials in concept design

This work is concerned with the selection of materials for conceptual product design prior to precise definition of part geometries. The proposed selection method is based on normalized scales of 0 to 100 for all fundamental material properties. The proposed scales are independent of the units which are used for the material property values. Three important transformations of the scales are demonstrated. First, the inverse material property is simply represented by 100 minus the original scale value. For example, if a material scores 83 for weight, then its scale value for lightness is 17. Second, a procedure is given for transformation the “100-scales” of individual properties to the “100-scale” of any derived parameter. Finally, a general procedure is established for the selection of multiple parameters with weighting values if desired. A spreadsheet sample database is presented suitable for teaching or demonstration purposes.