摩擦离合器的数学模型及其算例

用力学分析的方法 ,建立了摩擦离合器的数学模型 ,求出了摩擦离合器中扭力弹簧的圈数 ,其计算值与实际值基本一致 .该模型对摩擦离合器的设计有一定的参考价值 .     

高温高压下cBN单晶转变机理的密度泛函理论研究

为研究Li3N-hBN体系中cBN单晶的转变机理,本文采用基于密度泛函理论的赝势平面波方法和广义梯度近似法(GGA)系统计算了高温高压条件下hBN和cBN的低指数晶面的晶面能,分析了hBN和cBN各晶面之间的能量关系.结果表明:在1800K,5.5 GPa和2000 K,6.0 GPa下,hBN的(1010)晶面与cBN的(100)晶面的相对晶面能差分别为0.7;和1.2;,两组晶面的晶面能连续,即微观上电子密度连续.根据改进后的密度泛函理论(TFDC)可知,hBN能够向cBN直接转变.因此推断:在Li3N-hBN体系中,以Li3N为触媒,cBN单晶是由hBN直接转变而来.     

Ab initio study of dynamical properties of U-Nb alloy melt

The U-Nb alloy, as a kind of nuclear material with good corrosion resistance and mechanical properties, plays an important role in the nuclear industry. However, the experimental measurements and theoretical calculations of many parameters which are essential in describing the dynamical properties of this alloy melt, including density, diffusivity, and viscosity, have not been carried out yet. The lack of data on the dynamical properties of nuclear materials seriously hinders the high-performance nuclear materials from being developed and applied. In this work, the dynamical properties of the U-Nb alloy melt are systematically studied by means of ab initio molecular dynamics simulations and their corresponding mathematical models are established, thereby being able to rapidly calculate the densities, diffusion coefficients, viscosities, and their activation energies in the whole U-Nb liquid region. This work provides a new idea for investigating the dynamical properties of binary alloy melts, thereby promoting the development of melt research.     

cBN单晶合成效果与合成后Li基触媒组织结构的相关性研究

采用锂基触媒(Li3N)和六方氮化硼(hBN)为原料,在静态高温高压条件下加入(270/325目)籽晶批量合成出了大颗粒立方氮化硼(cBN)单晶(＞70目).通过X射线衍射仪(XRD)对触媒层内物相进行标定,采用K值法、绝热法、RIR值等理论方法,计算出样品触媒层内各物相的质量分数,比较了单晶合成效果好与差的触媒层内物相含量的差别;利用扫描电子显微镜(SEM)对样品触媒层的形貌进行观察,比较了单晶合成效果好与差的触媒层形貌的差别.结果表明:cBN单晶合成效果不同,其触媒组织结构有着明显的差异.当单晶合成效果较好时,触媒层中Li3BN2的含量为49;,cBN的含量为5;,hBN的含量为46;,触媒层内存在较均匀的熔融球状组织和管状组织,且离单晶表面越近管状组织越多;当单晶合成效果较差时,触媒层中Li3BN2的含量为10;,cBN的含量为49;,hBN的含量为41;,触媒层内只存在熔融球状组织.分析认为,触媒层中的cBN和Li3BN2的含量是影响大颗粒cBN单晶合成效果的主要因素.