GH4169合金的X射线荧光光谱分析

采用x射线荧光光谱仪测定GH4169合金中的锰、硅、镍、铬、钼、铝、钛、铌。研究了测量条件及基体 吸收—增强效应的校正。还时测量精度进行了研究,各元素的相对标准偏差分别为0．0466％～O．6777％。与 化学分析结果对照结果良好。     

选择溶解条件--ICP-AES法测定铝合金中10元素

在铝合金中,对常量、微量、痕量元素等的测量,传统上采用化学的方法来分析,手续繁杂,分析时间 亦长,有时不能满足大批量快速分析的要求。ICP-AES分析法,以其优异的分析性能被广泛应用于各种材料 的主要、次要,痕量、超痕量多元素的同时分析。但是,影响等离子炬状态的因素很多,只有在最佳工作状态下 操作,才能充分发挥ICP光源的优越性。     

武钢二炼钢厂炉机匹配系统算法研究

武钢集团第二炼钢厂的炉机匹配系统可简化为两道工序的车间作业排程问题。其问题的关键在于合理调配3台转炉的工作时段以满足4台铸机的不间断运转。本文提出了一种快速有效的算法——压缩-扩张算法，为整个系统的最后实现，提供了最关键的支持。     

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.     

Calibration of the Weibull stress scale parameter, σu, using the Master Curve

This work proposes that the Weibull stress scale parameter, σ_u, increases with temperature to reflect the increasing microscale toughness of ferritic steels caused by local events that include plastic shielding of microcracks, microcrack blunting, and microcrack arrest. The Weibull modulus, m, then characterizes the temperature invariant, random distribution of microcrack sizes in the material. Direct calibration of σ_u values at temperatures over the DBT region requires extensive sets of fracture toughness values. A more practical approach developed here utilizes the so-called Master Curve standardized in ASTM Test Method E1921-02 to provide the needed temperature vs. toughness dependence for a material using a minimum number of fracture tests conducted at one temperature. The calibration procedure then selects σ_u values that force the Weibull stress model to predict the Master Curve temperature dependence of K_Jc values for the material. At temperatures in mid-to-upper transition, the process becomes more complex as fracture test specimens undergo gradual constraint loss and the idealized conditions of high-constraint, small-scale yielding assumed in E1921-02 gradually degenerate. The paper develops the σ_u calibration process to incorporate these effects in addition to consideration of threshold toughness effects and the testing of fracture specimens with varying crack-front lengths. Initial illustrations of the calibration process for simpler conditions, i.e. 1T crack-front lengths, use the temperature dependent flow properties and a range of toughness levels for an A533B pressure vessel steel. Then using the extensive fracture toughness data sets for an A508 pressure vessel steel generated recently by Faleskog et al. [Engng. Fract. Mech., in press], the paper concludes with calibrations of both m and σ_u over the DBT region and assessments of the Master Curve calibration approach developed here.     

论公司有限责任制度的弊端及其对策

公司有限责任制度,是现代企业制度的重要表现形式,但有限责任制度在实现股东的有效保障时,也 暴露出不利于公司债权人的弊端,要克服这一弊端,就必须完善公司债权人保护制度。     

基于随机有限元的梁单元反应变异性分析

针对工程中由于不确定因素的影响而导致的结构反应的变异,利用随机有限元推导了在多个随机变量作用下梁单元结构反应变异的公式,以镗刀杆工作的位移变异为例,详细地介绍了其计算过程,并将其与解析法和Monte-Carlo法进行了对比,分析了各自的适用范围,为不确定性结构的可靠性分析奠定了基础。     

电容式两相流层析成象系统仿真研究

以油料在管道中输送为例进行电容层析成象仿真.利用有限元方法对电场建立数学模型,在SGI indigo 2 工作站上,使用AVS可视化软件和反投影算法,对3种典型流态模型反演及显示其流体成份分布的图象.     

确定局部结构已知的半群的一种算法

给出了确定局部结构已知的有限半群的推理法则，提出了一种新的计算机算法。