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1.
采用二维有限元数值方法分析了焊接热影响区粗晶区（ＣＧＨＡＺ）中局部硬化区（ＬＨＺ）的作用。当含有ＬＨＺ时，大大提高了ＬＨＺ内的应力并引起应变在ＬＨＺ和基体界面处产生不连续分布。ＬＨＺ的形状强烈影响ＬＨＺ内部的应力，在细长ＬＨＺ内几乎整体均呈现高应力分布，而块状ＬＨＺ仅在边缘区域出现应力集中。即使ＬＨＺ含量相同，随ＬＨＺ细长比的增大，ＬＨＺ内峰值应力及高应力区面积增加，说明细长ＬＨＺ容易在低应力水平下诱发断裂。这一结果在高强钢焊接热影响区ＣＴＯＤ试验中得到证实。含细长ＭＡ组元的ＣＧＨＡＺ在低得多的ＣＴＯＤ水平下发生断裂，因此控制ＭＡ组元的形状能够大大改善ＣＧＨＡＺ的韧性。 相似文献
2.
研究了变形速率对低合金结构钢 3 5CrMo磨擦焊接头组织与力学性能的影响 .结果表明 ,增加变形速率可改善焊缝韧性 .焊缝韧性改善的机理为近缝区晶粒细化和硬度降低 .采用金相法、TEM法对近缝区粒状组织精细结构进行了观察 ,粒状组织小岛由M -A组成 .指出增加变形速率使近缝区金属强化机制为位错强化、一定数量的岛状第二相强化和细晶粒强化 .通过测试异种金属焊缝界面近区碳浓度的分布 ,探讨变形速率对磨擦焊最高加热温度的影响 ,增加变形速率可使磨擦焊界面的最高加热温度下降 相似文献
3.
滨海新区行政区成立以来,新区教育系统广大教职工按照区委区政府总体安排部署,紧紧围绕"争当教育排头兵"的总体目标,发扬"五加二、白加黑"的拼搏奉献精神,深化教育改革,推进教育均衡发展,加强队伍建设,提高教育教学质量,办好人民满意教育。 相似文献
4.
滨海新区行政区成立以来,新区教育系统广大教职工按照区委区政府总体安排部署,紧紧围绕＂争当教育排头兵＂的总体目标,发扬＂五加二、白加黑＂的拼搏奉献精神,深化教育改革,推进教育均衡发展,加强队伍建设,提高教育教学质量,办好人民满意教育。 相似文献
5.
The definition of J-integral of interfacial crack was introduced. The three-point bending tests were carried out to obtain the critical loading
values when the interfacial crack initiation occurred between coatings and substrates. The finite element analysis (FEA) was
adopted to analyze the stress distribution in the specimens and compute the J-integral of the interfacial crack between LX88A coating and Chinese Q345 steel. The results showed that the average value
of critical J-integral is 0.70 N/m, which can be taken as the fracture parameter to evaluate the interfacial fracture behavior for the
three-point bending specimens of LX88A coating/Q345 steel system.
Supported by Tianjin Natural Science Foundation (No.08JCYBJC09100), New Teacher Research Fund for the Doctoral Program of
Higher Education of China (No.20070056096) and New Century Outstanding Talented Person Plan of China.
XU Lianyong, born in 1975, male, Dr. 相似文献
6.
The fracture behavior of a ceramic reinforced metal-base coating prepared by high velocity arc spraying (HVAS)technology in three-point bending test was studied.Moreover,finite element analysis(FEA)was adopted to analyze the stress distribution in the crack front.It can be found that the crack norrnal to the interface in the coatings occurred at the location where a fixed moment of force was reached.So the critical moment can be taken as thecoating cracking criterion,which was confirmed by FEA results.In addition,the stress levels at three different locations where cracks occurred near the interface are almost the same.The results will provide reference for the design of coatings and the structure integrity evaluation of coating/substrate systems. 相似文献
7.
2020年是《天津教育》创刊70周年。《天津教育》创刊伊始,便得到了党和政府、教育界前辈和读者的厚爱。郭沫若、马叙伦、叶圣陶等亲笔为创刊号题词致信,陆定一在创刊号上发表了署名文章,广大读者也纷纷寄语,表达了他们对这份刊物的殷切期望。70年来,《天津教育》始终秉承“引领教育教学改革、促进教师专业发展”的办刊理念,全面宣传贯彻党的教育方针,坚持立德树人根本任务,与教育同行,与时代同步,积极反映天津教育动态,在传播教育教学经验、宣传教改实验成就、开展教育学术讨论、提升学校管理水平、推动教育改革发展等方面发挥了重要作用。 相似文献
8.
建设“大思政课”是新时代推进思政课改革发展的重大理论和实践创新。聚焦新时代“大思政课”建设任务要求,要通过改革思政课教学、善用社会大课堂、搭建大资源平台、构建大师资体系、拓展大工作格局等方式,推动习近平新时代中国特色社会主义思想入脑入心,培养担当民族复兴大任的时代新人。 相似文献
9.
High-Temperature Corrosion of Protective Coatings for Boiler Tubes in Thermal Power Plants 总被引：4，自引：0，他引：4
High-temperature corrosion is a serious problem for the water-wall tubes of boilers used in thermal power plants. Oxidation, sulfidation and molten salt corrosion are main corrosion ways.Thereinto, the most severe corrosion occurs in molten salt corrosion environment. Materials rich in oxides formers, such as chromium and aluminum, are needed to resist corrosion in high-temperature and corrosive environment, but processability of such bulk alloys is very limited. High velocity electric arc spraying (HVAS) technology is adopted to produce coatings with high corrosion resistance. By comparison, NiCr (Ni-45Cr-4Ti) is recommended as a promising alloy coating for the water-wall tubes, which can even resist molten salt corrosion attack. In the study of corrosion mechanism, the modern material analysis methods, such as scanning electron microscopy ( SEM ), X-ray diffractometry (XRD) and energy dispersive spectrometry (EDS), are used. It is found that the corrosion resistances of NiCr and FeCrAl coatings are much better than that of 20g steel, that the NiCr coatings have the best anti-corrosion properties, and that the NiCr coatings have slightly lower pores than FeCrAI coatings. It is testified that corrosion resistance of coatings is mainly determined by chromium content, and the microstructure of a coating is as important as the chemical composition of the material. In addition, the fracture mechanisms of coatings in the cycle of heating and cooling are put forward. The difference of the thermal physical properties between coatings and base metals results in the thermal stress inside the coatings. Consequently, the coatings spall from the base metal. 相似文献
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