水基自形成CoFe2O4 磁性液体的零磁场粘滞特性

在零磁场下 ,水基自形成CoFe2 O4磁性液体粘度 η与CoFe2 O4纳米微粒体积分数Φ显示出特异的关系 ,然而 ,球形刚性粒子填料悬浮液粘度理论不能很好解释 .通过对水基自形成CoFe2 O4磁性液体中的微粒相互作用分析发现 ,此磁性液体的沉降和在磁场中的成链需有以预团聚体为核的大粒子存在 .在这一基础上 ,建立了团聚涨落模型 .于是 ,平均粒径、Einsten系数和粒径分布偏差均成为微粒体积分数的函数 ,也即对Popplewell粘度公式的修正 .最后得到与实验很好吻合的 η～Φ曲线及关系式 .     

Measurement on Effective Shear Viscosity Coefficient of Iron under Shock Compression at 100GPa

The oscillatory damping curve of a shock front propagating in iron shocked to 103 GPa is measured by use of two-stage light-gas gun and electric pin techniques. The corresponding effective shear viscosity coefficient is deduced to be about 2000 Pa.s from Miller and Ahrens＇ formula. The result is consistent with that of Mineev＇s data at 31GPa, while it is higher by five orders than the predictions based on the static measurements at about 5 GPa and 2000K and molecular dynamic simulation up to 135-375 GPa and 4300-6000 K, and the discussions are presented.     

Shear viscosity of aluminum studied by shock compression considering elasto-plastic effects

The strength always exists before the material melts. In this paper, the viscoelastic-plastic model is applied to improve the finite difference method, and the numerical solutions for the disturbance amplitude damping behavior of the sinusoidal shock front in a flyer-impact experiment are obtained. When the aluminum is shocked to 101 GPa, the effect of elastoplasticity on the zero-amplitude point of the oscillatory damping curve is the same as that of viscosity when η = 700 Pa·s,and the real shear viscosity coefficient of the shocked aluminum is determined to be about 2800±100 Pa·s. Comparing the experiment data with the numerical results of the viscoelastic-plastic model, we find that the aluminum is close to melting at 101 GPa.     

动态荷载下石英玻璃的透光性及损伤演化研究

在一级轻气炮上,利用光透射测量技术观测了石英玻璃在冲击（低于它的Hunoniot弹性极限）以及冲击后再卸载过程中的透射率随时间变化特征.发现石英玻璃在18 GPa附近的冲击条件下,15 μs内保持了良好的透明性.但处于压缩透明状态的石英玻璃在卸载波的作用下其透明状态仅维持约07 μs,透射率在随后的08 μs内下降了约30%.这一现象是由石英玻璃在卸载波的作用下发生损伤所致.透光性的时间效应与玻璃中局部损伤及演化特性密切相关,球状粒子的生长和散射模型对这一现象给出了合理解释.对Dolan等人［关键词： 石英玻璃 冲击 卸载 散射     

纳秒尺度金属熔化相变数值模拟及实验验证

本文基于非均匀成核相变动力学理论和热传导方程研究了在极快速升温(10¹²K/s)条件下金属达到过热状态后发生熔化相变时,通过金属/光学窗口界面温度的演化历史研究了金属内部温度的变化情况.分析结果表明,当金属内部无熔化发生时,界面温度将很快达到平衡,此变化满足理想接触界面模型;而当金属内部有熔化发生时,界面温度受熔化速率的影响不能立即达到平衡而是经历了一个下降的弛豫过程.计算结果与实验观测结果进行比较后发现两者符合得较好,由此可以获得金属在高压下的熔化速率,熔化温度等相关信息.本文的研 关键词： 相变动力学 热传导 金属铁 冲击波     

教书育人之我见

教书育人是每个教师的职责。教师不仅仅是备好课,讲好课的知识的传授者,更是灵魂教育的启发者和引导者。作者始终秉承学高为师,身正为范的原则,以全身心的爱投入到教学中。在讲授《大学物理》课程时,利用科学家不畏艰难、求真务实、勇于创新的科学精神引导学生树立正确的人生观和价值观;引入前沿科学帮助同学们扩展视野,确立人生目标。上课时通过观察自然现象,演示相关实验等方法激发学生的学习兴趣,提高学生自主学习的能力。这些举措丰富了课堂内容,取得了良好的教学效果。     

A fiber-array probe technique for measuring the viscosity of a substance under shock compression

A fiber-array probe is designed to measure the damping behavior of a small perturbed shock wave in an opaque substance, by which the effective viscosity of substance under the condition of high temperature and high pressure can be constrained according to the flyer-impact technique. It shows that the measurement precision of the shock arrival time by using this technique is within 2 ns. To easily compare with the results given by electrical pin technique, the newly developed method is used to investigate the effective viscosity of aluminum （Al）. The shear viscosity coefficient of A1 is determined to be 1700 Pa.s at 71 GPa with a strain rate of 3.6× 10^6 s-1, which is in good agreement with the results of other methods. The advantage of the new technique over the electrical pin one is that it is applicable for studying the non-conductive substances.     

冲击压缩下物质黏性系数与冲击波阵面扰动衰减特性研究

为解决高温高压下物质黏性的测量问题,Sakharov曾提出一种冲击波小扰动实验方法,但人们一直未从理论上给出这类特定冲击波流场中扰动振幅衰减特性与黏性系数之间的量化关联.本文首次针对Mineev等的实验条件采用数值解方法定量地研究了金属铝(Al)中复杂流场演化过程、正弦形波阵面上相对扰动幅度的演化特征和它们的黏性效应,给出了相对扰动幅度衰减曲线的零点相对距离与黏性系数之间的定量关系.与Zaidel的均匀流场模型以及Miller等的非均匀流场模型相比,本文求解的流场演变问题已经接近实验的真实情况.利用本文数     

飞片加载产生正弦冲击波及其波阵面演化模拟

飞片加载冲击波小扰动实验方法是目前测量高温高压下物质粘性的实用方法之一针对飞片碰撞小扰动实验,采用二维Navier-Stokes方程的差分方法,研究了金属铝中复杂压力流场的演化过程,给出了这类特定冲击波流场中正弦形扰动振幅振荡衰减特性与粘性系数之间的定量关系.结果表明:数值解比以往用于分析冲击波小扰动实验的解析解结果更...     

Theoretics-directed effect of copper or aluminum content on the ductility characteristics of Al-based(Al_3Ti,AlTi,AlCu,AlTiCu_2)intermetallic compounds

First-principle simulations have been applied to investigate the effect of copper(Cu) or aluminum(Al) content on the ductility of Al_3Ti,AlTi,AlCu,and AlTiCu_2 alloys.The mechanical stable and elastic properties of Al-based intermetallic compounds are researched by density functional theory with the generalized gradient approximation(DFT-GGA).The calculated lattice constants are in conformity with the previous experimental and theoretical data.The deduced elastic constants show that the investigated Al_3Ti,AlTi,AlCu,and AlTiCu_2 structures are mechanically stable.Shear modulus,Young's modulus,Poisson's ratio,and the ratio B/G have also been figured out by using reckoned elastic constants.A further analysis of Young's modulus and Poisson's ratio reveals that the third added element copper content has significant effects on the Al-Ti-based ICs ductile character.