尖头弹丸撞击下金属靶板弹道极限的两种工程模型

研究了圆锥形头和卵形头刚性弹垂直撞击塑性金属靶板扩孔冲塞型和延性扩孔型穿孔模式,考虑靶板背面自由边界的影响,提出两种两阶段工程分析模型,得到最小穿透能量的解析解。由球形空腔膨胀理论和两阶段总耗能最小确定第一阶段的侵彻深度,由功能原理和圆柱形空腔膨胀理论计算第一阶段侵彻扩孔耗能,延性扩孔型第二阶段耗能近似按Taylor扩孔理论计算,扩孔冲塞型第二阶段耗能考虑了加速塞块和剪断塞块所损耗的能量。与铝合金和装甲钢靶板弹道试验数据比较表明,本文两阶段模型的计算结果与试验结果吻合较好。     

弹性支承圆弧梁内力分析

以现代桥梁及房屋结构为工程背景,提出弹性支承曲线梁计算模型,按结构力学方法推导出弹性支承圆弧梁的内力计算公式,分析讨论了竖向和抗扭弹性支承对内力的影响．     

葡萄糖还原氢氧化铜制备球形氧化亚铜及其粒度控制研究

以Cu(OH)2为前躯体,用葡萄糖还原制备了不同粒径的单分散球形氧化亚铜粉末。利用扫描电镜和smileview软件对Cu2O粉末进行了表征分析,并通过上述分析考察了反应温度和反应物浓度等因素对Cu2O粉末粒径的影响。结果表明,随着反应温度与葡萄糖投加浓度的提高,颗粒粒径减小;而随着氢氧化钠投加浓度的提高,颗粒粒径增大;体系内最终颗粒密度n+∞或颗粒个数n与各影响因素的变化呈直线关系。最后根据晶体成核生长模型初步分析了反应条件对Cu2O颗粒粒径的影响机理。     

以函数为参量的间歇发酵非线性动力系统及其辨识

建立以连续分段线性函数为参量的间歇发酵非线性动力系统,证明该动力系统的主要性质及解的存在性.以实验数据拟合得到的光滑曲线为依据,提出了连续分段线性函数为优化变量的辨识模型,论述可辨识性.依状态变量与辨识函数的相关性,构造求解辨识模型的优化算法,并给出优化算法的收敛性分析及数值结果.     

Numerical model and experimental demonstration of high precision ablation of pulse CO_2 laser

To reveal the physical mechanism of laser ablation and establish the prediction model for figuring the surface of fused silica, a multi-physical transient numerical model coupled with heat transfer and fluid flow was developed under pulsed CO_2 laser irradiation. The model employed various heat transfer and hydrodynamic boundary and thermomechanical properties for assisting the understanding of the contributions of Marangoni convention,gravitational force, vaporization recoil pressure, and capillary force in the process of laser ablation and better prediction of laser processing. Simulation results indicated that the vaporization recoil pressure dominated the formation of the final ablation profile. The ablation depth increased exponentially with pulse duration and linearly with laser energy after homogenous evaporation. The model was validated by experimental data of pulse CO_2 laser ablation of fused silica. To further investigate laser beam figuring, local ablation by varying the overlap rate and laser energy was conducted, achieving down to 4 nm homogenous ablation depth.     

多层吸能元件在冲击波作用下大变形问题的模态解

通过实验研究了多层吸能元件在冲击波作用下的大变形模式,基于虚速度原理建立了问题的模态近似解。实例计算表明理论值与实验结果吻合很好,分析了硬化、动态应变率以及元件静态孙载力,层数和惯性对结果的影响。     

蜂窝钢管约束混凝土靶的准静态球形空腔膨胀模型及其应用

基于空腔膨胀理论建立工程模型是研究侵彻问题的常用方法。针对射弹侵彻蜂窝钢管钢管约束混凝土靶问题，考虑被打击单元钢管及其外围混凝土的综合约束作用，粉碎区混凝土采用Hoek-Brown (H-B) 准则，建立了蜂窝钢管约束混凝土靶的准静态球形空腔膨胀模型和刚性弹侵彻深度预测公式，并分析了综合约束刚度对侵彻过程的影响。算例表明：蜂窝钢管约束混凝土靶不同于半无限混凝土靶，侵彻过程中的扩孔压力不为常数；综合约束刚度越大，扩孔压力越大；侵彻深度预测公式计算结果与文献侵彻试验吻合较好。     

刚性尖头弹垂直撞击金属厚靶板极限速度分析

研究了刚性尖头弹垂直撞击金属厚靶板扩孔冲塞型和延性扩孔型穿孔模式,提出分析最小穿透能量的两阶段工程模型．应用功能原理和圆柱形空腔膨胀理论得到第一阶段侵彻扩孔耗能．考虑靶板背面自由边界的影响,应用Taylor扩孔理论计算延性扩孔型穿孔第二阶段耗能;考虑加速塞块和剪断塞块所损耗的能量,由动量和能量原理导出扩孔冲塞型穿孔第二阶段剪切冲塞耗能．由两阶段总的耗能最小确定第一阶段的侵彻深度,从而得到最小穿透能量的解析解．与铝合金和装甲钢靶板弹道试验数据比较表明,该文两阶段模型的计算结果与试验结果吻合较好。     

Analytical solutions for finite cylindrical dynamic cavity expansion in compressible elastic-plastic materials

Analytical solutions for the dynamic cylindrical cavity expansion in a com-pressible elastic-plastic cylinder with a finite radius are developed by taking into account of the effect of lateral free boundary, which are different from the traditional cavity expan-sion models for targets with infinite dimensions. The finite cylindrical cavity expansion process begins with an elastic-plastic stage followed by a plastic stage. The elastic-plastic stage ends and the plastic stage starts when the plastic wave front reaches the lateral free boundary. Approximate solutions of radial stress on cavity wall are derived by using the Von-Mise yield criterion and Forrestal’s similarity transformation method. The effects of the lateral free boundary and finite radius on the radial stress on the cavity wall are discussed, and comparisons are also conducted with the finite cylindrical cavity expansion in incompressible elastic-plastic materials. Numerical results show that the lateral free boundary has significant influence on the cavity expansion process and the radial stress on the cavity wall of metal cylinder with a finite radius.