焊接专家系统设计及开发技术

论述了焊接专家系统的基本原理和结构,着重介绍了开发焊接专家系统的技术,包括传统的开发工具和新的先进技术在焊接专家系统中的应用.     

定向凝固水平连铸多晶铜的动态本构方程

以带有同步组装技术的分离式Hopkinson压杆装置作为热模拟装置，采用基于MTS（Mechanical Threshold Stress）模型建立的FCC晶体结构的动态本构方程，确定了定向凝固水平连铸多晶铜动态本构方程参数，研究了其动态冲击特性，获得高温段（685K-1085K）的理论应力-应变曲线与实验曲线相当吻合，而在低温段（低于685K）的理论曲线与实验曲线出入较大。结果也表明定向凝固水平连铸多晶铜在485K和685K之间有一温度能使其回复能达到阀值。     

高纯钛的反复弯曲疲劳

通过对不同应力幅度下高纯钛的反复弯曲疲劳的研究，发现在较低应力幅度下（～±１００ＭＰａ），材料表现出循环软化，伴随表面滑移带数量的增加、发达的滑移带挤出片的出现。疲劳裂纹萌生主要与滑移带相关，在挤出物内存在两类疲劳损伤形式：沿滑移带的孔洞和与滑移带垂直的微裂纹。在较高应力幅度下（～±２００ＭＰａ），则表现为硬化，次滑移及晶界附近多个滑移系同时起动，有大的形变孪晶出现。裂纹于滑移带、李晶界和晶界结点萌生。断口特征复杂，但与表面变形特征有对应关系。ＴＥＭ亚结构分析表明，随应力幅度的提高，位错组态分别为散乱分布于滑移面的偶极子、位错束带和位错胞。李晶内存在复杂的精细结构，而且有堆垛层错出现。     

Nanostructured component fabrication by electron beam-physical vapor deposition

Fabrication of cost-effective, nano-grained net-shaped components has brought considerable interest to Department of Defense, National Aeronautics and Space Administration, and Department of Energy. The objective of this paper is to demonstrate the versatility of electron beam-physical vapor deposition (EB-PVD) technology in engineering new nanostructured materials with controlled microstructure and microchemistry in the form of coatings and net-shaped components for many applications including the space, turbine, optical, biomedical, and auto industries. Coatings are often applied on components to extent their performance and life under severe environmental conditions including thermal, corrosion, wear, and oxidation. Performance and properties of the coatings depend upon their composition, microstructure, and deposition condition. Simultaneous co-evaporation of multiple ingots of different compositions in the high energy EB-PVD chamber has brought considerable interest in the architecture of functional graded coatings, nano-laminated coatings, and design of new structural materials that could not be produced economically by conventional methods. In addition, high evaporation and condensate rates allowed fabricating precision net-shaped components with nanograined microstructure for various applications. Using EB-PVD, nano-grained rhenium (Re) coatings and net-shaped components with tailored microstructure and properties were fabricated in the form of tubes, plates, and Re-coated spherical graphite cores. This paper will also present the results of various metallic and ceramic coatings including chromium, titanium carbide (TiC), titanium diboride (TiB₂), hafnium nitride (HfN), titanium-boron-carbonitride (TiBCN), and partially yttria stabilized zirconia (YSZ) TBC coatings deposited by EB-PVD for various applications. This paper was presented at the International Symposium on Manufacturing, Properties, and Applications of Nanocrystalline Materials sponsored by the ASM International Nanotechnology Task Force and TMS Powder Materials Committee, October 18–20, 2004, Columbus, OH.     

用径迹显微照相技术测定Mo对硼在Ni中扩散的影响

本文建立了通过脱硼处理用径迹显微照相技术测量硼在合金中扩散系数的新方法。该法灵敏度高,简捷可靠。实验发现,Ni中加入0.5％Mo对硼的扩散影响不大;而加入3％Mo则有使硼的矿散激活能降低,频率因子减小,在900—1250℃的温度范围内有加快硼扩散的作用。     

基于人工智能的钛合金热变形工艺参数优化

在深入分析热变形工艺参数对Ti-15-3合金显微组织及成形载荷的影响的基础上,以变形温度、变形程度和变形速率等热变形工艺参数作为设计变量,以显微组织和成形力的最佳综合为目标,建立了该合金热塑性成形工艺参数的多目标优化数学模型。以显微组织参数和成形力的人工神经网络预测模型作为优化算法的知识源,将人工神经网络与修正的遗传算法相结合,对Ti-15-3合金的热塑性成形工艺参数进行优化。结果表明,提出的修正的遗传算法是有效的,采用将其与人工神经网络相结合的方法对钛合金的热塑性成形工艺参数进行优化是可行的。     

The distribution of grain boundary planes in polycrystals

During the last ten years, techniques have been developed to measure the distribution of grain boundaries in polycrystals as a function of both lattice misorientation and grain boundary plane orientation. This paper presents a brief overview of the techniques used for these measurements and the principle findings of studies implementing these techniques. The most significant findings are that grain boundary plane distributions are anisotropic, that they are scale invariant during normal grain growth, that the most common grain boundary planes are those with low surface energies, that the grain boundary populations are inversely correlated with the grain boundary energy, and that the coincident site lattice number is a poor predictor of the grain boundary energy and population.     

绩优问题生的成因分析及其教育对策初探

绩优问题生,指学业成绩优异、但心理有疾患的大学生。为增强教育的针对性,促进绩优问题生的健康成长和全面发展,本文从家庭、学校、个人三个方面对其进行成因分析,并提出相应教育对策。     

The atomic age challenge to steel

Some months ago the submarine Nautilus was in dock for refueling. It had traveled 60,000 miles, but the total uranium used would make a lump smaller than a light bulb. This is only one example that the Atomic Age is here with us, now! How and where does this incredible Atomic Age challenge the first and greatest of America’s basic industries?     

齿轮精锻的数值模拟与实验研究

本文对空心直齿圆柱齿轮的精锻成形过程进行三维刚塑性有限元模拟和实验研究。通过有限元数值模拟和实验研究 ,得出了直齿圆柱齿轮精锻过程的金属流动规律和变形力学特征 ,揭示了直齿圆柱齿轮精锻过程的变形机理 ,数值模拟结果与实验结果吻合较好