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《Science & Technology of Welding & Joining》2013,18(6):478-484
AbstractThe effect of the distance between loading points on a long brittle crack arrest behaviour was investigated in the ultrawide duplex ESSO tests. The effect of loading conditions was also analysed. Arrest of a long brittle crack was more facilitated in the tests with a distance between loading points of 5 m than in those with 10 m. A load drop was larger in the tests with a loading point distance of 5 m than in those with 10 m. If the specimen length is 6·8 m or more, or the distance between loading points are 10 m or more in the ultrawide duplex ESSO test, the effect of the unloading stress wave on the dynamic stress intensity factor of a crack penetrating into the test plate becomes negligible, within the range of brittle crack propagation rate between 500 and 800 m s?1. 相似文献
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Tsunehisa Handa Shinichi Suzuki Noboru Kiji Masanobu Toyoda Takashi Miyata 《Welding International》2013,27(9):640-647
In the large heat input weld joint of heavy gauge steel plate used for large container carriers, a brittle crack possibly propagates straight along a weld joint without diverging to the base metal. This phenomenon is discussed for its application to the large heat input weld of heavy gauge plate to ship structures. In this study, to arrest a brittle crack at the T-joint embedding unwelded face, the effect of the unwelded face on behaviour of brittle crack propagation/arrest in the T-joint structure was investigated and analysed. The ESSO test of the T-joint structure was carried out, supposing that a brittle crack which propagates along a weld joint of hatch coaming rush into T-joint of hatch coaming and strength deck. The test results showed that the brittle crack arrested at the T-joint embedding the unwelded face, and the brittle crack arrested easier, the longer the unwelded face. The results of static FEM analysis showed that the stress intensity factor of the brittle crack was increased by the unwelded face, until the brittle crack reached a flange. However, when the brittle crack propagated into the flange, the stress intensity factor of the brittle crack was decreased by the unwelded face. The crack-arrest effect of the unwelded face appears after the brittle crack propagates into the flange. 相似文献
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Ruimar Rubens de Gouveia Anderson Geraldo Marenda Pukasiewicz André Ricardo Capra Sérgio Luiz Henke Paulo Cesar Okimoto 《Welding International》2013,27(6):433-440
Mainly due to their great toughness, martensitic stainless steels are used for manufacturing hydraulic turbines. However, these steels have some restrictions regarding regions recovered by welding, mainly due to the formation of non-quenched martensite, which causes a reduction in toughness. Considering repair of hydraulic turbines, there is a great interest in developing welding procedures that increase impact toughness and avoid post-welding heat treatment (TTPS). This study aims to analyse the influence of interpass temperature on microstructure, impact toughness and fatigue crack propagation in multipass welded joints on martensitic stainless steel CA6NM, using AWS410NiMo filler metal and the gas tungsten arc welding (GTAW) process. In the sample with interpass temperature of 80°C, influence of the interpass temperature on the formation of ferrite δ, with intragranular formation in the two-phase δ field, was observed, while in the sample welded at 150°C, the formation of ferrite δδ occurred mainly in the single-phase field. The change in the formation of ferrite δ, with the low interpass temperature, promoted an increase in impact toughness and a decrease in the fatigue crack propagation when compared with the sample welded with a higher interpass temperature. The results obtained indicate that the TIG process is an excellent alternative for the repair of CA6NM steel, with a significant influence from the interpass temperature. 相似文献
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对低碳钢渗碳淬火试样进行表面水喷丸处理,研究水喷丸对渗层表面组织结构及其疲劳裂纹扩展速率的影响。结果表明:添加细玻璃丸的水喷丸处理能显著细化表层亚结构,提高小角度晶界密度,并为渗层带来有效的残余压应力。在300 MPa水压及600 mm/min扫描速率工艺下,可实现100 μm左右深度,最高达1244 MPa的残余压应力,其表面粗糙度Ra=0.195 μm。疲劳裂纹速率试验结果显示,经过水喷丸处理后裂纹扩展速率da/dN有增加的趋势,这主要是因为表面压应力形成,增加了心部拉应力,且表层的变形强化降低了裂纹尖端塑性区。 相似文献
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采用SEM和TEM对9Ni钢断裂过程中裂纹的扩展行为进行了研究,讨论了逆转变奥氏体在断裂过程中的作用。SEM观察结果表明,基体的塑性对裂纹尖端形状有重要影响,基体塑性较差时裂纹前端尖锐,加剧了应力集中,基体塑性较高时裂纹前端呈“钝角”,使应力集中松弛。TEM观察显示,9Ni钢裂纹的扩展有两种形式:一种是在带状薄区中呈“Z”形扩展,另一种是遇到逆转变奥氏体后偏离原来的扩展方向。研究结果也显示在两种条件下获得的逆转变奥氏体,经变形后又发生相变。这表明稳定性高的逆转变奥氏体能够在变形过程中保留下来,阻碍裂纹扩展促使9Ni钢低温韧性提高,而稳定性较低的逆转变奥氏体则在变形过程中很快发生相变。 相似文献
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厚规格管线钢板随其厚度的增加, 落锤撕裂性能控制难度急剧增加, 成为管线钢开发的关键技术。本文对厚规格管线钢板生产过程中铸坯厚度、未再结晶区压下率、变形速率及轧制规程优化设计对粗轧阶段的变形渗透及钢板落锤撕裂性能的影响规律进行了分析研究, 并进行了工业化轧制试验。结果表明: 轧制相同规格(22 mm厚)管线钢板时, 铸坯厚度由300 mm增加到400 mm, 钢板落锤剪切面积由85%~90%提高到90%~100%; 采用相同坯料(400 mm厚)轧制25 mm厚度管线钢板, 通过优化轧制规程, 钢板落锤剪切面积由85%~90%提高到90%~95%。 相似文献
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针对壁厚33 mm、管径φ1 422 mm管线用X70钢板在-30 ℃下DWTT性能异常问题,利用扫描电镜和背散射电子衍射技术,分析了两种不同控轧工艺下X70管线钢板的微观组织、晶粒大小及取向等因素对其低温止裂性能的影响。结果表明:粗轧采用7道次,道次压下量21~35 mm,轧后冷却速率19.4 ℃/s的条件下,钢板可获得细小的多边形铁素体、针状铁素体、以及弥散分布的M/A岛组织;同时,由于采用大压下率,提高了钢板心部变形渗透能力,可以细化心部奥氏体晶粒,增加了心部大角度晶界比例;还有,由于钢板厚度方向晶界取向差接近且心部存在38.2%的大角晶界,均有利于提高管线钢板的止裂性能。 相似文献
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通过焊接热模拟方法对X80双相管线钢不同焊接热影响区疲劳裂纹扩展行为进行了研究,并分析实际焊接试样与焊接热模拟试样的热影响区疲劳裂纹扩展行为的差异,讨论了焊接热模拟技术应用于疲劳裂纹扩展寿命预测的可行性。结果表明,当裂纹在粗晶热影响区(CGHAZ)和临界热影响区(ICHAZ)上扩展时,由实际焊接试样与焊接热模拟试样热影响区所测得的疲劳裂纹扩展速率曲线(da/dN-DK曲线)存在明显差异,其原因与显微组织变化引起的裂纹扩展阻力大小不同有关。因此,建议采用实际焊接试样完整的热影响区所测得的da/dN-DK曲线来评估疲劳裂纹扩展寿命。 相似文献
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The influence of hydrogen on the deformation ahead of the crack tip and the crack propagation were observed and studied in
situ under transmission electron microscopy with dynamic tensile deformation for
bridge steel. The results show that hydrogen can promote local plastic deformation ahead of the crack tip
and change the mode of crack propagation so that the crack will propagate in a zigzag path. 相似文献
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采用裂纹尖端张开位移(CTOD)实验方法对研究了不同热处理工艺对新型R5系泊链钢断裂韧性的影响,使用偏光显微镜、光学显微镜和扫描电镜等对CTOD试样裂纹扩展区组织及断口形貌进行分析,并用高低温材料试验机测试了R5系泊链钢低温-20℃下的力学性能。结果表明,回火温度对R5系泊链钢CTOD断裂韧性有显著影响。在570~600℃范围内回火,组织保留马氏体位向,碳化物呈片状及长条状不均匀分布在原奥氏体晶界、马氏体板条界及板条内部,应力作用下容易导致局部应力集中,裂纹扩展速率大,CTOD特征值接近零。随回火温度升高,在600~690℃范围内回火,碳化物逐渐聚集、球化并在基体中弥散均匀分布,应力作用下不易引起局部应力集中,并且在裂纹扩展时可使裂纹扩展方向发生偏转,裂纹扩展路径延长,裂纹扩展受到抑制,CTOD特征值随回火温度升高不断增大。经950℃淬火+630~660℃区间回火,R5系泊链钢同时具有高强度和良好的CTOD断裂韧性。 相似文献
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This paper studies the effect of electron beam (EB) surface hardening on the fatigue crack growth rate in AISI 4340 steel. The heat treatment conditions were varied to consider the influence of microstructure and residual stress. The results show that increasing the EB heat input increases the compressive residual stress in the hardened layer. Thus EB surface-hardening treatment improves the fatigue crack growth resistance. This effect increases with increasing EB heat input but disappears as the ΔK value increases. The fracture mechanism of the hardened layer is intergranular fracture, while that of the base material is transgranular quasi-cleavage. 相似文献
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I-Hsuang Lo 《Corrosion Science》2007,49(4):1847-1861
The effect of selective dissolution on fatigue crack initiation of 2205 duplex stainless steel (DSS) was investigated in this study. In mixed sulfuric and hydrochloric acid aqueous solution, there existed two distinctly separated anodic peaks in the active-to-passive transition region of the polarization curve. Either ferritic or austenitic phase was selectively dissolved at each characteristic anodic peak potential. Under sinusoidal cyclic loading condition, however, selective dissolution did not assist fatigue crack initiation instead resulting in the elimination of stress concentration site in the selectively dissolving phase. As a consequence, under selective dissolution condition, fatigue crack initiated in the phase while its dissolution rate was lower with respect to the other constituent phase in the duplex stainless steel. The microstructural evolution of the corrosion fatigue crack initiation in 2205 DSS in the mixed sulfuric and hydrochloric acid solution is highlighted in this investigation. 相似文献
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Mill-annealed AISI type 316LN stainless steels, received from two different sources (one indigenous (SS-2) and the other foreign (SS-1)), were tested for stress corrosion cracking (SCC) resistance in a boiling acidified environment of NaCl. SCC results indicated a remarkably lower value of plateau crack growth rate (PCGR) and higher values of KISCC and JISCC for SS-2, which was attributed to the lower effective grain boundary energy resulting from a higher amount of copper in it. Cold working reduced KISCC and PCGR; while thermal aging and welding decreased KISCC and increased PCGR vis-à-vis the annealed material. 相似文献
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Roman Bogdanov Andrey Marshakov Vasiliy Ignatenko Ilya Ryakhovskikh Diana Bachurina 《腐蚀工程科学与技术》2017,52(4):294-301
An investigation of the effect of hydrogen peroxide (H2O2) on corrosion crack growth can be considered as a necessary stage in a study of the SCC of pipeline steels in the presence of dissolved oxygen and other oxidants. It was found that the presence of hydrogen peroxide at a low concentration (5?mM) results in a deceleration of the crack growth. With an increase in the concentration of H2O2, the crack growth rate increases. The change in the steel corrosion rate at various H2O2 concentrations agrees with the dependence of the crack growth rate on the oxidant concentration. The conclusion has been made that the crack growth in a weakly acidic electrolyte (pH 5.5) is determined by the metal dissolution process. Hydrogen charging of the metal indirectly affects the crack growth by increasing the surface coverage with hydrogen, which decreases the steel dissolution rate. 相似文献
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采用纯铝作为中间层对铝合金与低碳钢进行了电阻点焊,分析中间夹层厚度对界面反应层厚度和接头抗拉强度的影响。在钢/中间夹层界面观察到有界面反应层生成,其主要由靠近钢侧的Fe2Al5和靠近中间夹层铝侧的FeAl3两种金属间化合物组成。与不加中间夹层相比,利用纯铝作为中间夹层点焊的铝合金与低碳钢的接头具有较薄的界面反应层和较高的接合强度。随着中间夹层厚度的增加,界面反应层厚度逐渐减小,而接头抗拉强度则呈增大趋势。结果表明,采用纯铝作为中间夹层点焊铝合金与钢具有一定的有效性。 相似文献
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ABSTRACTRecently, slow-release materials have attracted more attentions. In this work, a kind of the slow-release inhibitor was successfully synthesised to protect carbon steel from corrosion and the effect of temperature on the passivation behaviour was evaluated. The results indicated that boron was the main dissolution-release component, and the dissolution-release rate increased with the increasing temperature. Meanwhile, the evaporation volume significantly decreased after adding the inhibitor. Good passivation performances over 33-day and near 15-day were obtained at 30–40°C (95.56–98.02%) and 50–60°C (95.06–97.09%), respectively, which was confirmed by a series of electrochemical tests. A passive film with Fe–O–B structure and the buffering characteristic of borate solution together contributed to the good passivation performance. This work revealed the effect of temperature on the passivation behaviour of the slow-release inhibitor and provided a theory foundation of the application of the slow-release inhibitor in the practical condition. 相似文献