低碳钢焊接接头碱脆破裂的研究

本文叙述了用多种试验方法测试评定低碳钢焊接接头对碱脆破裂的敏感性。提出低碳钢焊接结构防止碱脆破裂的基本措施是消除焊后残留应力。     

抽油杆在深井中的断裂及其预防措施

以中原石油勘探局文留油田抽油杆的断裂统计为基础，分析了抽油杆断裂的特点和原因，就整个抽油杆柱而言，４５．７９％的断裂发生在井下９００～１５００ｍ杆段；就单根抽油杆而言，５０％～８９．８％的断裂发生在抽油杆接头的圆弧过渡区。断裂的原因是抽油杆头部圆弧过渡区断面变化大，加工时镦锻造成加工缺陷和应力集中，使用时这一部分又是不稳定变形的施力点，因此成为抽油杆的易断裂区域。针对这一情况，提出预防措施一是改进抽油杆的结构或加工工艺；二是实现抽油杆使用管理系列化；三是改进抽油杆柱设计。     

Quantitative measurement of soil cracking patterns

A method for quantitatively measuring properties of soil cracking patterns is described. Photographs of a sample area of the surface were taken, but because of the nature of the soils, the cracks were blackened by hand. A computer program measured properties of the cracking patterns, particularly length and width, on scanned images of the photographs. Results are presented for a set of 100 photographs from 25 soils used in experiments to examine the effect of gypsum application.     

铂漏板砷中毒事故分析

本文通过铂漏板中毒案例的分析,提出铂催化反应和电化学反应生成单质砷使铂漏板"中毒"的假设.     

The application of optical fibres as witness devices for the detection of plastic strain and cracking

Low cost optical fibres have recently become readily available for telecommunications purposes. Silica fibres are characterised by high elastic strains to failure. The feasibility of using these fibres for structural integrity monitoring particularly for offshore structures is investigated. The basis of the technique is that a fibre may be bonded to a critical part of a structure and provides an optical path which will be broken if the fibre fails due to plastic strain or crack opening in the critical area.
Groups of fibres which have been given predetermined fracture strains by surface etching were encapsulated in special packs. These packs were bonded to steel and concrete tensile specimens. Strain transfer occurred successfully between the specimens and individual fibres. The distribution of strain to fibre fracture appeared to be uniform along the fibre. The use of several fibres with a range of fracture strains caused fibres to break progressively with increasing strain. For applications to offshore structures it has been found possible to use water-repellent adhesives which can be applied and cured in sea water and suffer no deterioration.
The advantages of this system include versatility, relatively low cost, adaptability to continuous monitoring and the possibility of being fitted retrospectively and refitted after repair operations.     

Hydrogen cracking of ferritic stainless steel thermal storage tanks

A ferritic stainless steel (SUS436L), which was subjected to various kinds of reduction ratio was precharged with hydrogen at 40°C in 15% HCl solution by employing galvanic reaction with zinc. Tensile tests were performed in air at room temperature on both uncharged and charge specimens. Finite element method (FEM) analyses were carried out to obtain strain at panel corners under various different internal radii in a thermal storage tank when it was subjected to internal pressure. As a result, it was found that the value of internal corner radius?thickness of the panel (R?t) should be more than about 2 in order to prevent hydrogen embrittlement cracking.     

混凝土界面开裂模型

本文利用Ｅｓｈｅｌｂｙ等效原理［１］．给出了混凝土骨料与砂浆之间由于温度升高或湿度损失而造成界面破坏的条件．并根据水化热传导和水份扩散造成的非均匀温度和湿度场性质，讨论了混凝土材料热源裂缝与干缩裂缝的分布特征。     

The failure of an armour faced conveyor connector

The combined use of modern metallurgical techniques for fracture examination, laboratory test data and fracture mechanics calculations allows metallurgical failures to be examined in a quantitative manner. Complex load histories and environments can result in more than one sub-critical cracking mechanism occurring in a component. Quantitative understanding of the rate determining cracking process is a necessary prerequisite to rectifying the problem. The following case study describes a connector from an armour faced conveyor which failed in service. The failure investigation involved fractography, stress analysis, material property evaluation and fracture mechanics calculations. Fractographic evidence indicated a stress corrosion failure mechanism. Calculations of critical crack sizes showed that stress corrosion cracking alone could not account for the fracture. It was concluded that the failure was due to a sequence of three cracking processes which preceded unstable ductile fracture. Firstly, frictional heating caused rubbing or quench cracks typically 0.5–1 mm deep. Secondly, corrosion fatigue cracks grew several millimetres allowing the third fracture process, stress corrosion cracking, (SCC) to initiate and grow. In the situation described here, this process was much faster than corrosion fatigue. The influence of defect size due to rubbing cracks and the influence of K_ISCC have been compared with the corrosion fatigue life of the component. An increase in K_ISCC and hence critical defect size for SCC has been shown to increase the corrosion fatigue life of the component by a large factor. A change in design would also alleviate the problem of SCC by reducing the static stress, which is the driving force for SCC.     

12Cr1MoVG钢焊接接头热裂纹原因分析及对策

针对12Cr1MoVG钢高压集箱焊接接头出现的热裂纹,随机抽查6个不同厂家批次的相同牌号的焊条,通过对外观质量、熔敷金属化学成分、性能评价及产品模拟试件的比较,分析了熔敷金属的Mn/Si比值、Mn/S比值及屈强比。优选了对母材适应性较强的焊接材料进行施焊,并采取必要的工艺措施,焊缝金相组织索氏体含量增高,块状铁素体含量减少,强度及韧性增加,抗裂纹生成及扩展能力增强,有效解决了焊接热裂纹问题。     

Nb-Cr X80管线钢冷裂敏感性分析

采用碳当量法、焊接冷裂纹敏感指数法、最高硬度HV10(max)公式法、SHCCT曲线图、焊接热影响区最高硬度试验、斜Y形坡口对接裂纹试验、残余应力的数值模拟和插销试验评价了Nb-Cr X80管线钢产生冷裂纹的敏感性。理论分析与试验结果表明,Nb-Cr X80管线钢的冷裂倾向性较小。综合理论分析和试验数据,并考虑到管道安装焊接施工中钢管湿度高、装配拘束应力大的实际情况,认为Nb-Cr X80钢管0℃以上环境温度焊接时,采用低氢型焊接材料或进行根焊时预热温度≥50℃即可,采用纤维素型焊条进行根焊时预热温度≥100℃即可。