直齿圆柱齿轮的可靠度对设计参数的灵敏性分析

由于在设计、生产、使用、维护等产品生命周期各阶段的不确定因素的影响，使机械零件的质量产生波动，可靠度降低。文中试图在机械设计初期，结合概率统计分析理论和可靠性设计理论，揭示出机械零件的可靠度与基本设计变量之间的本质联系，推导出可靠度对参数的灵敏性计算公式，用直齿圆柱齿轮的计算实例进行分析，深刻探讨齿轮设计参数的变化对齿轮可靠度的影响方向和灵敏程度。其结论对齿轮的设计人员、制造和使用人员在理论和实践中均具有重要的参考价值。     

局部照射对大鼠睾丸性激素、白细胞的影响

为了解不同剂量局部照射对大鼠睾丸重量、超微结构及性激素、白细胞的影响,对大鼠不同剂量局部照射后,睾丸组织称重,超微结构观察,测定血清睾酮、促卵泡激素水平,白细胞计数。结果表明,睾丸组织重量随照射剂量增中及时间延长。逐渐减轻,并与照射剂量及时间呈正相关;但当照剂量增加,照射时间延长至一定程度后,睾丸重量基本不变,出现相 期,超微结构观察可见生精细胞变性、坏死、随时间延长呈不可逆性变化,间质细胞形态结     

Close-coupled nozzle atomization integral simulation and powder preparation using vacuum induction gas atomization technology

We simulate the gas-atomization process of a close-coupled annular nozzle for vacuum induction gas atomization at a three-dimensional scale.Moreover,the relationship between the simulated droplet type and experimentally metallic powder is established by comparing the morphology of droplets with powders.Herein,the primary atomization process is described by the volume-of-fluid(VOF)approach,whereas the prediction of powder diameter after secondary atomization is realized by the VOF-Lagrangian method.In addition,to completely reflect the breaking and deformation process of the metallic flow,we employ the VOF model to simulate the secondary atomization process of a single ellipsoidal droplet.The results show that the primary atomization process includes the formation of surface liquid film,appearance of serrated ligaments,and shredding of ligaments.Further,gas recirculation zone plays an important role in formation of the umbrella-shaped liquid film.The secondary atomization process is divided into droplet convergence and dispersion stages,and the predicted powder diameter is basically consistent with the experiment.In general,the four main powder shapes are formed by the interaction of five different typical droplets.     

能量有限元预示复合材料结构动响应研究进展

复合材料结构高频动响应预示是飞行器等结构设计中的重要研究内容之一.为了探讨精确预示复合材料结构高频动响应方法,分析比较了目前较为通用的3种动力学响应预示方法,指出能量有限元法最适合求解具有各向异性特征的复合材料结构高频动响应问题.紧接着概述了国内外关于能量有限元方法和该方法在复合材料结构高频动响应预示方面的研究进展.在此基础上分析了能量有限元法在预示复合材料结构高频动响应问题中尚待深入研究的问题.