基于率相关改进桥联模型的CFRP材料动态力学性能研究

桥联模型在预测CFRP材料静态力学性能上具有较高的精度,但目前鲜有基于桥联模型描述CFRP材料动态力学性能的报道。基于此,采用考虑应变率效应的本构方程与强度准则改进桥联模型。利用文献实验数据对改进后的模型进行了确认,针对侵彻弹使用环境,设计制备了CFRP层合结构并进行SHPB动态实验。理论预估模量与实验结果基本一致,理论强度值高于实验值约7%,由此校验了相关改进桥联模型在动载环境下的适用性。结合课题组已有的CFRP壳体侵彻试验结果,进一步验证了该理论模型可用于CFRP材料在冲击载荷下的性能预测。进一步的试验结果细观分析和数值模拟研究表明,X方向试样的动态破坏模式以层间分层为主,而Y方向则以纤维的压缩破坏与基体的剪切破坏为主。为CFRP材料用于抗冲击等动态载荷下的力学行为预测提供了一种可行的分析手段。     

抗肥皂草素单克隆抗体的制备和鉴定

用肥皂草素－Ｉ免疫ＢＡＬＢ／Ｃ小鼠,免疫的脾细胞同ＳＰ２／Ｏ小鼠骨髓瘤细胞融合,在５次融合中,通过酶联免疫吸收实验方法（ＥＬＩＳＡ）,筛选出分泌特异性抗体的杂交瘤细胞２５个克隆,其中５个进行鉴定。２Ｂ２,１Ａ５克隆分泌抗肥皂草素－Ｉ（肥Ｉ）的抗体;４Ｂ２克隆分泌抗肥皂草素－ＩＩ（肥ＩＩ）的抗体;１Ａ６,４Ｃ３克隆分泌的抗体,除抗肥Ｉ外,同肥ＩＩ有较强的免疫交叉反应。４Ｂ２,１Ａ５克隆杂交细胞接种到     

用DDS产生PM和FM:采样调制信号所带来的影响

直接数字合成（ＤＤＳ）可用来产生高线性度的ＰＭ和ＦＭ信号。本文就采样调制信号所产生的杂波作了分析,并给出了具体的解析表达式来预测其电平,最后用实验结果证明了理论表达式的准确性。     

GM(2,1)模型的几种变换形式

ＧＭ（２,１）模型在灰色理论中是对非纯粹的指数发展过程进行预测的一种重要灰色模型,本文给出ＧＭ（２,１）模型的几种不同形式,并得到了灰作用量ｂ的一个重要结论。     

环氧树脂对PU硬泡的增强试验研究

本文通过一系列实验,制备了密度为０．３ｇ／ｃｍ＾３的环氧树脂改性ＰＵ硬泡,并对其进行了准静态压缩力学性能测试。研究表明,ＰＵ硬泡的强度和模量均有较大幅度提高。同时,从ＰＵ硬泡泡孔结构及互穿聚合物网络入手初步分析了增强机理．     

双机械手对称式协调力控制稳定性分析

本文利用双机械手协调内力和外力控制系统的简化模型，分析了在双手紧夹持物体与环境接触时，１） 机械手等效电机的动态特性；２） 双手所夹持物体的刚度；３） 双手所操作物体的动态特性；４） 机械手的采样控制延时；５） 双手的非对称性等系统未建模因素对双手对称式协调外力和内力控制稳定性的影响，并给出仿真结果。此结果与实验结果基本相符。     

柴油机磨损寿命的灰色马尔柯夫模型预测

基于灰色系统理论,将灰色ＧＭ（１,１）预测模型和马尔柯夫预测模型的优点结合起来,形成一个灰色马尔柯夫预测模型,拓宽了灰色预测的应用范围。特别地,这种模型的预测结果比其它随机波动性较大的数据到模型的预测结果精确得多。对柴油机磨损寿命进行预测,取得了令人满意的结果。     

泛函微分方程x’（t）＝a（t）f（x（μ（x（t））））的解的性态

本文研究偏差变元依赖状态自身的泛函微分方程ｘ’（ｔ）＝ａ（ｔ）ｆ（ｘ（μ（ｘ（ｔ））））（１）的解的渐近性态。进一步推广或部分推广Ｄｕｎｋｅｌ［１］、Ｅｄｅｒ［２］、Ｗａｎｇ［３］、吴汉忠［４．５］及作者［６～８］等人的工作。文中使用了一些新方法,也得到了一些新结果。     

美陆军未来的训练方案

本文介绍“２１世纪美陆军训练方案”的构思和柜架。它由３个平行部分组成：（１）“２１世纪战士”系统,即分队施训部分;（２）“２１世纪勇士”系统,即院校培训或自我提高部分;（３）“２１世纪作战网”系统,即一揽子施训部分。此外,还重点介绍了“２１世纪战士”（自动化训练管理）系统的５个组成部分：１）陆军标准化训练系统;２）训练支援系统;３）“塔德斯”（教具、教学器材、模拟器和教学模拟）手段;４）标准化行动     

一种组合预测模型及预测值的模糊分级

基于多元线性回归模型及ＧＭ（１，ｎ）模型，给出了一种组合预测模型，进行了组合预测的精度分析及预测值的等级分类，并讨论了其在实际问题中的应用．     

The mechanical performance and a rate-dependent constitutive model for Al3Ti compound

The Al₃Ti compound has potential application in the high temperature structure materials due to its low density, high strength and stiffness. The mechanical behaviors of the material under different loading rates were studied using compression tests. The results indicate that Al₃Ti is a typical brittle material and its compressive strength is dependent on the strain rate. Therefore, a series of rate-dependent constitutive equations are needed to describe its mechanical behaviors accurately. However, it is still short of professional research on the material model for Al₃Ti. In this study, the material model was developed on the basis of JH-2 constitutive equations using the experimental data. The model was then applied in simulating the impact process of Ti/Al₃Ti metal-intermetallic laminate composites so as to validate the established model. Good agreement between simulation and experiment results shows the constitutive model predict the material responses under high rate and large deformation accurately. This work provides more support for the theoretical and numerical research on the intermetallic.     

Prediction of three-dimensional elastic behavior of filament-wound composites based on the bridging model

This work provides a method to predict the three-dimensional equivalent elastic properties of the filament-wound composites based on the multi-scale homogenization principle.In the meso-scale,a representative volume element(RVE)is defined and the bridging model is adopted to establish a theoretical predictive model for its three-dimensional equivalent elastic constants.The results obtained through this method for the previous experimental model are compared with the ones gained respec-tively by experiments and classical laminate theory to verify the reliability of this model.In addition,the effects of some winding parameters,such as winding angle,on the equivalent elastic behavior of the filament-wound composites are analyzed.The rules gained can provide a theoretical reference for the optimum design of filament-wound composites.     

微结构连续损伤理论

本文从微结构理论出发,用相对变形描述微结构之间的微空隙和微裂纹引起的材料损伤的影响,得到用损伤张量描述的各向异性损伤的微结构连续损伤力学理论。该微结构损伤模型可化简为目前公认的几种主要损伤模型:如J.P. Cordebojs和F. Sidoroff的弹性各向异性损伤模型,D. Krajcino-vic和G.U.Fonseka的脆性材料平面裂纹损伤模型,J. Lemaitre的各向同性损伤理论及Kachanov的以面积减少为变量的损伤模型等。作者运用这一理论对混凝土材料的单向拉、压基本受载情形进行了数值分析,并与D. Krajcinovic的损伤模型计算结果及实验结果作了比较,所得结果与实验值比较吻合,特别是在失稳后阶段给出了较好描述,初步表明了本理论的有效性和实用性。     

Neural network modeling to evaluate the dynamic flow stress of high strength armor steels under high strain rate compression

An artificial neural network (ANN) constitutive model is developed for high strength armor steel tempered at 500 °C, 600 °C and 650 °C based on high strain rate data generated from split Hopkinson pressure bar (SHPB) experiments. A new neural network configuration consisting of both training and validation is effectively employed to predict flow stress. Tempering temperature, strain rate and strain are considered as inputs, whereas flow stress is taken as output of the neural network. A comparative study on Johnson–Cook (J–C) model and neural network model is performed. It was observed that the developed neural network model could predict flow stress under various strain rates and tempering temperatures. The experimental stress–strain data obtained from high strain rate compression tests using SHPB, over a range of tempering temperatures (500–650 °C), strains (0.05–0.2) and strain rates (1000–5500/s) are employed to formulate J–C model to predict the high strain rate deformation behavior of high strength armor steels. The J-C model and the back-propagation ANN model were developed to predict the high strain rate deformation behavior of high strength armor steel and their predictability is evaluated in terms of correlation coefficient (R) and average absolute relative error (AARE). R and AARE for the J–C model are found to be 0.7461 and 27.624%, respectively, while R and AARE for the ANN model are 0.9995 and 2.58%, respectively. It was observed that the predictions by ANN model are in consistence with the experimental data for all tempering temperatures.     

Dielectric constant predictions for energetic materials using quantum calculations

The dielectric constant (DC) is one of the key properties for detection of threat materials such as Improvised Explosive Devices (IEDs). In the present paper, the density functional theory (DFT) as well as ab-initio approaches are used to explore effective methods to predict dielectric constants of a series of 12 energetic materials (EMs) for which experimental data needed to experimentally determine the dielectric constant (refractive indices) are available. These include military grades energetic materials, nitro and peroxide compounds, and the widely used nitroglycerin. Ab-initio and DFT calculations are conducted. In order to calculate dielectric constant values of materials, potential DFT functional combined with basis sets are considered for testing. Accuracy of the calculations are compared to experimental data listed in the scientific literature, and time required for calculations are both evaluated and discussed. The best functional/basis set combinations among those tested are CAM-B3LYP and AUG-cc-pVDZm, which provide great results, with accuracy deviations below 5% when calculated results are compared to experimental data.     

直接挤出成型用环氧树脂的流变性及其可打印性

直接挤出成型制造适用于任何含或不含添加剂的膏状或凝胶状复合材料,对复合材料制造技术具有深远意义。通过探讨热固性环氧树脂的流变学行为与挤出成型特性,得出热固性环氧树脂在直接挤出成型制造应用中的通用性流变学参数。通过向复合材料中加入增稠剂,对其流变学行为进行设计。结果表明:在高剪切速率(50 s~(-1))和低剪切速率(0.01 s~(-1))下,添加30%纳米黏土的环氧树脂的流变学行为较适合挤出式3D打印工艺。利用龙门式气动挤出式3D打印机,对复合材料的打印成型质量进行试验分析和验证。结合试验结果探讨了喷头高度对复合材料成型质量的影响,并且提出适用于喷头高度临界值的计算方法。探讨了挤出率、剪切速率等因素对成型质量的作用规律。针对多层打印问题,提出包含补偿系数的多层打印的临界喷头高度的计算方法。以上研究对促进基于复合材料的挤出式3D打印具有积极意义。     

A three-stage model for the perforation of finite metallic plates by long rods at high velocities

A three-stage theoretical model is presented herein to predict the perforation of a thick metallic plate struck normally by a long rod at high velocities. The model is suggested on the basis of the assumption that the perforation of a thick metallic plate by a long rod can be divided into three stages: (1) initial penetration; (2) plug formation and (3) plug slipping and separation. Various analytical equations are derived which can be employed to predict the ballistic limit, residual velocity and residual length of the long rod. It is demonstrated that the present model predictions are in good agreement with available experimental results for the perforation of finite steel targets struck normally by steel as well as tungsten alloy long rods at high velocities. It is also demonstrated that the dynamic maximum shear stress of a plate material has strong effect on plug formation and plug thickness which, in turn, exerts considerable influence on the residual velocities and lengths of a long rod at impact velocities just above the ballistic limit.     

固体中的高压声速

高压声速是表征凝聚介质在极端条件下性质的重要参数之一。从冲击绝热线和Gruneisen物态方程出发,导出了与冲击绝热线相容的等熵线,进而给出了沿等熵压缩线和等温压缩线以及冲击绝热线的声速的计算公式。对铝和钨的Hugoniot声速进行了计算,计算结果与实验结果符合得很好。     

基于MSOA神经网络模型的装备保障费用预测

引入基于多步骤优化方法(MSOA)神经网络模型用以预测装备保障费用。实验结果表明,与传统的ARIMA时间序列模型和常规BP神经网络模型相比,基于MSOA神经网络预测模型具有更高预测精度。因此,该模型是一种更有效的装备保障费用预测模型。     

一种金属橡胶元件建模方法研究

用理论和试验相结合的手段研究金属橡胶弹性元件的动力学建模,提出一种新的建模方法,用此方法建立了基于迟滞回线拟和分解的高次弹性复合阻尼模型。该模型用非线性刚度和非线性复合阻尼机理构造,模型中的参数由试验数据辨识。用所建模型重构恢复力-位移迟滞回线,结果表明该模型能很好描述这类非线性振动系统的特性。