Finite element simulations of crack propagation in functionally graded materials under flexural loading

Cracks in stepped and continuously graded material specimens under flexural loading were investigated via finite element analysis. Calculation of mechanical energy release rates and propagation angles with crack-opening displacement correlation and the local symmetry (K_II = 0) criterion, respectively, provided results most efficiently and accurately, as compared with compliance and J-integral approaches and other deflection criteria. A routine was developed for automatic crack extension and remeshing, enabling simulation of incremental crack propagation. Effects of gradient profile and crack geometry on crack-tip stresses and crack propagation path are examined, and implications of these for optimal design of graded components against failure by fast fracture are discussed.     

陶瓷微球增强铝基复合材料

介绍一种以铝土矿陶瓷微球增强的铝基复合材料，具有价格低、增强物与基体合金润湿性好、界面反应几乎不存在等优点。又因其增强物为微球，有利于减小应力集中，延缓裂纹萌生与扩展，同时也提高了铸造流动性和塑性成形能力。讨论了其制造工艺、有关特性和问题。     

绝缘材料水树产生及发展机理的研究现状

本文介绍了水树枝的定义、分类以及影响因素,在参考了16篇中外文献的基础上综述了常用绝缘材料中水树的生长过程和引发机理,推导出水树长度与老化时间、电场强度等因素的关系式。     

Growth and optical properties of Er,Yb:YAl3(BO3)4 crystal

Single crystal of erbium, ytterbium-codoped yttrium aluminum tetraborate Er,Yb:YAl₃(BO₃)₄(Er,Yb:YAB) has been grown by the flux method. The absorption spectrum in the visible and NIR regions of Er,Yb:YAl₃(BO₃)₄ crystal are measured at room temperature and fluorescence spectrum of Er,Yb:YAl₃(BO₃)₄ crystal are also measured at room temperature, excited by 976 nm laser. Not only the strong NIR emission peaks located at 1548 nm was observed, but also the visible up-conversion luminescence has been found. The specific heat of the Er/Yb:YAB crystal at room temperature is 0.81 J/g °C.     

自然通风冷却塔的节能改造

系统地阐述了冷却塔塑料塔芯材料的结构及特点 ,介绍了 6座自然通风冷却塔节能改造工程的应用实例 ,并对其进行了经济性比较及节能分析。改造后的冷却塔冷却能力明显提高 ,可降低机组煤耗( 2～ 4 ) g/ (kW·h)     

纳米有序结构制备技术现状

随着对纳米材料需求的不断增长，人们对如何制备纳米有序结构的技术产生了极大的兴趣。主要概述了近期来制备纳米有序结构的一些基本方法例如膜板合成法、自组织方法、欠电位沉积法、掠角沉积法等，并在此基础上简要的介绍了一些相关的概念原理和应用。     

Development of Measurement Facilities for Analyzing Petroleum Products

The question of developing measurement provisions for the parameters of petroleum products is considered. The main technical features of a KLAN-1 mobile laboratory unit for analyzing petroleum products intended for rapid analysis of fuel and lubricating materials in storage and on sale are provided.