基于自适应点估计和最大熵原理的结构体系多构件可靠度分析

准确而高效地求解结构体系中多个构件的可靠度水准对结构维护和优化具有重要意义,目前已有学者将蒙特卡洛法和响应面法用于此类可靠度分析。然而,蒙特卡洛法所需结构分析次数取决于失效概率的量级,通常计算成本较高。而响应面法的所需结构分析次数取决于杆件数量,当其数量较多时同样有较高的成本。鉴于此,该文提出了一种基于自适应点估计和最大熵原理的结构体系多构件可靠度分析方法,其所需的结构重分析次数上限与杆件数量无关,计算过程简便无需迭代。首先,通过引入自适应交叉项判定和双变量降维近似模型求解各杆件的前四阶矩;然后,根据各杆件的前四阶矩,采用最大熵原理求解各杆件的可靠度指标;最后,通过多个算例对比了蒙特卡洛法、响应面法和建议方法的精度和效率。结果表明建议方法所需的结构重分析次数远少于蒙特卡洛法和响应面法,实现过程简便,且精度能够满足工程要求。     

堆焊熔合区成分和组织分析

利用电子探针，透射电镜对不锈钢堆焊熔合区的成分和组织进行了分析和研究，发现无论焊态还是焊后热处理态，熔合区中都存在一个马氏体组织带，熔合区铬、镍呈线性分布且存在一人成分梯度，焊后热处理碳在熔合区中集聚，从而熔合区出现大量碳化物析出。     

THE GROWTH OF SMALL FATIGUE CRACKS IN A LOW CARBON STEEL; THE EFFECT OF MICROSTRUCTURE AND LIMITATIONS OF LINEAR ELASTIC FRACTURE MECHANICS

The growth characteristics of small fatigue cracks were studied under rotary bending in a low carbon steel prepared with two ferrite grain sizes of 24 and 84 μm, and were compared with the growth characteristics of large through cracks in fracture mechanics type specimens. The effect of microstructure on crack growth rates and the interaction in growth behaviour between two neighboring small cracks were examined experimentally, and also the critical crack lengths above which linear elastic fracture mechanics (LEFM) is applicable were evaluated for small crack growth and for fatigue crack thresholds. It is found that small cracks grow much faster than large ones and also show growth rate perturbations due to grain boundaries. It is indicated that the critical crack lengths for fatigue crack thresholds are significantly shorter than those for small crack growth.     

缩聚反应体系对芳香－脂肪族共聚酰胺序列结构的影响

用ＮＭＲ分析配合计算机分峰，分析和计算共缩聚物序列结构参数的方法，研究了单体、酸吸收剂的加料顺序和两种二元胺的投料比对由已二胺和乙二胺为代表的脂肪族二胺，对苯二胺和对苯二甲酰氯合成的芳香－脂肪族共聚酰胺序列结构的影响。结果表明，在脂肪族二胺用量占二胺总量３３．３％（ｍｏｌ）时，所获得的共聚物具有最大的无规度和最短的数均序列长度。     

Al-ZrOCl2体系原位生成Al3Zr的孪晶生长

借助于XRD和TEM研究了Al-ZrOCl2体系熔体反应生成的原位复合材料，结果表明：内生增强体为Al3Zr和Al2O3颗粒，Al3Zr晶体形貌主要以多面体和长方体形状为主，其平均尺寸约为1．26μm，最大尺寸为4μm，纵横比在1.5-2.0之间。这两种形状的晶体表面均存在生长小面（facet)，首次发现Al3Zr晶体以孪晶方式生长，孪晶面为（1，1^-,4^-),孪生方向为[2,2^-,1]。对Al3Zr晶体的结构分析发现，该晶体存在四个密排面，它们分别是（1，1，4），（1^-,1^-,4),(1,1^-,4)和（1^-,1,4)。     

ON THE RELATIONSHIP BETWEEN LOW CYCLE FATIGUE AND CRACK GROWTH RATE PROPERTIES IN WELDED STEEL COMPONENTS

Previous investigations have shown that for plain materials, the crack growth rate constants applied in an elastic-plastic crack growth model may be obtained indirectly from the constants describing the low cycle fatigue capacity of the material. In the present study a simple EPFM crack growth model, based on bulk strain amplitude as the governing parameter, is assumed. The crack growth constants derived from the linear regression constants describing the LCF capacity of manually butwelded components are determined, and the validity of the resulting EPFM crack growth model is checked against measured LCF crack growth data.     

CRACK GROWTH BEHAVIOUR OF FATIGUE MICROCRACKS IN LOW CARBON STEELS

The behaviour of low carbon steels has been studied, in particular the initiation and growth of the major crack which led to final fracture of smooth specimens, via surface replica and photomicrograph techniques. From this study, the fracture process and fatigue life prediction characterized by the growth of surface microcracks have been analysed by a new approach unifying the conventional approaches based on the final fracture of materials with the fracture mechanics approach. Knowledge of fracture parameters is critical for non-destructive inspection during service life and the application of fracture mechanics to life prediction and assessment.     

新型HIRFL-800低温泵的设计及热负荷的计算

介绍了近代物理研究所自行研制的新型HIRFL－800低温泵，对其抽速、低温冷凝板和屏蔽板的热负荷进行了具体的分析和计算，肯定了新型HIRFL－800低温泵的设计方案。     

混凝土断裂及亚临界扩展的细观机制

通过模型和三点弯曲断裂SEM试验,详细研究了混凝土断裂全过程及亚临界扩展的细观机理。结果表明:混凝土断裂是一个复杂的不规则过程,存在明显的亚临界扩展现象。混凝土亚临界扩展路径是曲折的,并非经典断裂力学假定的平直路径,混凝土亚临界扩展和临界失稳扩展呈现分形特征。用起裂断裂韧性K_ICⁱ和分形等效断裂韧性K_IC^e,f来描述混凝土抵抗初裂和临界失稳扩展的能力。给出了考虑亚临界扩展弯折效应的混凝土亚临界扩展长度、混凝土起裂断裂韧性K_ICⁱ和分形等效断裂韧性K_IC^e,f的计算表达式。计算表明:混凝土失稳断裂时的分形等效断裂韧性K_IC^e,f与混凝土亚临界扩展的分维数D成正比。     

THE BEHAVIOUR OF FATIGUE CRACK GROWTH IN THE FRETTING-CORROSION-FATIGUE OF HIGH TENSILE ROPING STEEL IN AIR AND SEAWATER

Abstract— Fretting fatigue tests of high tensile roping steel, 1.5 mm in diameter, 1770 MPa grade, were carried out in air and seawater. S-N curves were completed in both the environments and under cathodic protection at-850 mV (SCE). The crack growth curves were determined at three different alternating stress levels. The coefficients of friction between the specimen and the fretting bridge, where the macro-slip occurred, were found to be 0.63 in air and 0.38 in seawater. The prediction of the fretting fatigue lives were made according to the Tanaka—Mutoh model, where the frictional force was taken into consideration. The predicted fatigue life agreed well with the experimental results in air but in seawater the prediction defined a much higher fatigue limit compared with the experimental results which showed the absence of the fatigue limit. These results indicate that the method of removing the electrochemical component is very promising for the prevention of fretting fatigue failure in seawater.     

ITER计划和核聚变研究的未来

ITER(国际热核聚变实验实验堆)是规划建设中的一个为验证全尺寸可控核聚变技术的可行性而设计的国际托卡马克实验堆。是由美国、日本、欧盟、中国、俄罗斯、韩国和印度在内的7方共同参与合作的目前世界上最大型的国际大科学合作计划。ITER计划的参与各国将通过这项大型国际科学计划,学习和积累大型核聚变堆的研制技术,并培养人才。日本、中国等国家都计划通过参与ITER计划的建设和实验运行,缩短自身与国际核聚变研究最前沿的距离,在未来建造自己的聚变示范堆。最终实现核聚变能源的商业应用。     

冰蓄冷系统优化与控制分析

在冰蓄冷系统运行优化和控制中，存在概念不清、系统分工糊涂、控制要求提法混乱等实际情况。本文借助于控制理论的大系统观点，剖析了优化和控制的层次、地位和作用。最后，通过部分蓄冰系统，提出了冰蓄冷系统优化和控制的解决办法和实施步骤。     

聚变第一壁新材料性能研究初步

对ＨＬ－１Ｍ的硅化石墨样品和北京科技大学研制的耐高温等离子体冲刷的功能梯度材料的真空性能和耐溅射性能进行初步比较研究。证明铜基上的碳化硼（Ｂ４Ｃ／Ｃｕ）和ＳｉＣ／Ｃ这两种梯度材料适于用作面向等离子体的聚变第一壁材料。     

除湿系统中直接蒸发式表面冷却器在结霜工况下的设计计算

本文分析了除湿系统中直接蒸发式表面冷却器在结霜工况下的换热特性 ,特别是结霜速度、结霜时间以及结霜时的换热计算。通过计算机模拟 ,得出了有实用价值的计算方法     

INITIATION AND GROWTH OF FRETTING FATIGUE CRACKS IN THE PARTIAL SLIP REGIME

Abstract— —Recent work addressing the problems of fretting fatigue crack initiation and propagation under a carefully controlled axi-symmetric Hertzian contact is described. Both experimental work, enabling the fretting damage, sites of initiation, and crack trajectory to be viewed, and theoretical work, permitting a prediction of those processes are presented. Good correlation between the two strands of work is found. In particular, the initiation criterion proposed by Ruiz, Boddington and Chen for a very different geometry is found to work well, and would seem to indicate its potential as a design tool.     

工程制图改革与机械基础系列课程新体系的探讨

从培养面向２１世纪机械类人才的角度，分析了现机械基础系列课程和工程制图教学中存在的向问题，从整体优化的角度，将原机械基础系列课程打散进行重组和安排，提出了一种机械基础系列课程新体系。     

碳—氢—氯体系金刚石薄膜生长条件预测

首次计算了一碳－氢－氯体系中生长金刚石膜的相图，研究了该体系中金刚石生长区随衬底温度及氯含量变化的趋势，与实验结果符合较好，计算结果表明，Ｃ－Ｈ－Ｃｌ系相图中金刚石生长区被限制在两个小三角形（ＣＨ４－Ｈ－ＨＣｌ和ＣＣｌ４－ＨＣｌ－Ｃｌ）中变化，可能生长金刚石薄膜的碳氢氯组分波严格地限制在金刚石生长区内，并随生长温度和压力等条件而变化，当气相中氯含量与氢的含量相近时，金刚石生长区趋于消失，金刚石生长     

中西方风格特色小镇的导向系统设计之比较

当今社会,小镇这一概念方兴未艾,但是说起一个优秀的特色小镇,人们首先想到的大多是小镇的规划设计、建筑设计、园林景观设计和室内设计等方面,这些设计组成了一个小镇最直观的形象,但是在一个小镇当中,作为艺术设计中的导向系统设计的作用同样不容小觑,它在小镇中处处可见,并与别的设计相辅相成,好的导向设计可为小镇画龙点睛,为整个小镇最终的展示形象加上亮丽的一笔. 随着经济的发展,全国各地著名房产企业都去打造特色和精品的小镇,涌现出如杭州绿城房地产开发的"桃李春风"小镇,以及由大型央企中国五矿集团投资开发的"哈斯塔特村"小镇,都试图在特色上创造自己的特点,特色小镇包罗万象.     

工程CAD中的归并模型及算法研究

归并问题是工程ＣＡＤ领域中的一项常见的设计问题。笔者从实践中提取并抽象成为归并的数学模型，根据该总是的实际特点提出了解决这一模型的算法思想和若干启发式规则。该研究应用于实际的工程ＣＡＤ系统开发，收到了良好的效果。