复合固体推进剂中固体填料的安息角测试与仿真

复合固体推进剂含有固体颗粒较多，离散单元法是一种适合固体推进剂生产过程数值仿真的有效方法，颗粒物料的接触参数是保证离散单元法仿真精度的关键。本文以复合固体推进剂的主要组分铝粉和高氯酸铵固体颗粒为研究对象，通过实验测试获得了相关物料的安息角，利用专业离散元软件EDEM仿真模拟了安息角测试实验过程，建立了物料安息角与接触参数之间的联系。研究表明，滚动摩擦系数和滑动摩擦系数越大，安息角越大，物料流动性越差。对比仿真与实验结果，通过逆向反推法确定了物料的滑动摩擦系数和滚动摩擦系数两个关键接触参数。铝粉与高氯酸铵1∶2混合颗粒的滑动摩擦系数为0.2，滚动摩擦系数为0.05。为固体推进剂加工生产过程离散元数值仿真提供了关键基础数据。     

基于响应面中心复合设计的固体推进剂摩擦感度理论

为了确定固体推进剂生产过程中的各因素对摩擦感度的影响,采用响应面法(RSM)与中心复合试验设计(CCD)相结合,以摆锤角度、滑柱压力、试样温度为影响因素,以固体推进剂摩擦感度值为响应值设计试验,采用摩擦感度测试仪进行试验,并分析试验结果拟合了响应面模型。结果表明,在三个响应面评价精度指标中,相对均方根误差为0.14、决定系数R~2为0.9309、校正拟合度R_(adj)~2为0.8686,说明方程拟合精度高且误差小;由模型方差分析得方差比值F为14.96,表明模型对响应面的影响程度较高;概率值p为0.0001,表明模型有0.01%的概率对响应面无影响;响应曲面图表明了各因素之间的相互作用;优化模型得到最小摩擦感度值所对应的三因素范围为角度小于45°,压力小于2 MPa,温度小于45℃。     

Hot workability of Mg-9Y-1MM-0.6Zr alloy

The behavior evolvement of Mg-9Y-1MM-0.6Zr (WE91) alloy during hot deformation process was discussed. The flow stress behavior of magnesium alloy over the strain rate range of 0.001 to 1 s-1 and the temperature range of 653 to 773 K was studied on a Gleeble-1500D hot simulator under the maximum deformation degree of 60%. The experimental results showed that the relationship between stress and strain was obviously affected by the strain rate and deformation temperature and the flow curves observed were typical of the occurrence of dynamic recrystallization. The flow stress of WE91 magnesium alloy during high temperature deformation could be represented by the Zener-Hollomon parameter in the hyperbolic Arrhenius-type equation. The average deformation activation energy Q and strain coefficient n were 224.11 kJ/mol and 3.08 by calculation,respectively. The processing maps were calculated and analyzed according to the dynamic materials model. The map at strain of 0.916 exhibited three domains with peak efficiency of 49%,44% and 42%,respectively. It was found that the alloy could be extruded at 693 K with mechanical properties of σ0.2=240 MPa,σb=315 MPa and δ=15.5%.     

残余应力研究现状及在镁合金中的应用前景

综述了残余应力研究现状；分析了残余应力产生的原因；总结了残余应力的各种测试手段和消除方法,并比较了它们的优缺点；展望了镁合金中残余应力的研究和发展方向.     

均匀化热处理对AZ151镁合金显微组织的影响

采用热分析仪、光学显微镜和布氏硬度机等仪器,研究了不同的均匀化热处理条件下AZ151镁合金的显微组织和布氏硬度值,分析了温度对均匀化效果的影响以及硬度值随温度的变化,研究表明:温度是均匀化过程中的主要影响因素,并且扩散过程的速度随着温度的提高而增加;升高温度也不能使AZ151中的Mg17Al12完伞分解,AZ151镁合金合理的均匀化工艺为430℃/16 h.     

Effect of Gd content on microstructure and mechanical properties of Mg-Y-RE-Zr alloys

Four kinds of Mg-Y-RE-Zr alloys with different Gd contents were prepared,and the effect of Gd content on microstructure and mechanical properties of the alloys was researched.Based on the experimental investigation,the compounds at the grain boundaries are mainly Mg_(24)Y_5,Mg_(41)Nd_5,and Mg_5Gd phases.The average grain size of as-cast alloys is 50-60μm.After T4(535℃, 24 h)treatment,Mg_5Gd phases mostly decompose and dissolve into the matrix,and the disperse spotted phases are mainly Mg_(24)Y_5 and Mg_(...     

Mg-Y-Nd-Gd-Zr合金的热变形和加工图

采用GLEEBLE-1500热模拟实验机对Mg-Y-Nd-Gd-Zr合金在变形温度为523～723 K、应变速率为0.002～1.000 s-1、最大变形程度为50%的条件下,进行了高温压缩试验研究.采用指数关系式描述了合金在热变形过程中的稳态流变应力.利用动态材料模型构建了热加工图,结合组织观察结果认为,该合金在变形温度为673 K、应变速率为1.000 s-1时功率耗散效率达到峰值0.36,因此,中温高应变速率区域为最佳加工性能区域.要想获得较大范围的最佳加工性能区域,应采用多道次小变形量进行加工.     

半固态金属浆料制备新技术

半固态加工技术具有许多优良的特点，近年来得到迅速发展。广泛用于生产半固态金属的方法为触变成形，而流变成形与触变成形相比，前者更节约能源、流程更短、设备更简单，因此流变成形技术将是金属半固态加工技术的发展方向。半固态加工技术的发展趋势是，进一步简化加工工艺流程，进一步降低加工成本，扩宽半固态加工技术的应用范围。本文主要介绍最近几年在半固态浆料制备和加工中的几种新工艺和新技术的原理、特点及其应用，其中有新MIT工艺、冷却斜槽法、双螺旋流变注射成形法、剪切一冷却一轧制法、NRC工艺、不同液体混合法、近液相线铸造法等方法。     

Homogenization heat treatment of Mg-7.68Gd-4.88Y-1.32Nd-0.63Al-0.05Zr alloy

The microstructures and mechanical properties of the Mg-7.68Gd-4.88Y-1.32Nd-0.63A1-0.05Zr magnesium alloy were investigated both in the as-cast condition and after homogenization heat treatment from 535 to 555 ℃ in the time range 0-48 h by op- tical microscopy, scanning electron microscopy and hardness measurement. The as-cast alloy consisted of ct-Mg matrix, Mgs（Y0.5Gd0.5） phase which is a eutectic phase, strip of Al2（Y0.6Gd0.4） phase, little A13Zr and Mg（Y3Gd） phase. With the increasing of homogenization temperature and time, the Mgs（Y0.5Gd0.5） phase was completely dissolved into the matrix. The Al2（Y0.6Gd0.4） phase was almost not dissolved which impeded grain boundaries motion making the grain size almost not changed in the process of ho- mogenization. The optimum homogenization condition was 545 ℃/16 h. The tensile strength increased, yield strength decreased and the plasticity improved obviously after 545 ℃/16 h homogenization treatment.     

对俄服装贸易的分析和市场特点的探讨

本文在调查研究莫斯科、列宁格勒市（即圣彼得堡）的服装市场后对俄罗斯服装市场作了简要的概述，并对“中国服装如何进入俄罗斯市场”的几个重要问题作了分析。