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采用电液伺服疲劳试验机对2205双相不锈钢进行不同过载比(1.0,1.5,2.5,3.5)下的疲劳裂纹扩展试验,研究了单峰过载对疲劳裂纹扩展速率的影响。结果表明:过载比越大,2205双相不锈钢裂纹扩展停滞的时间越长,疲劳裂纹扩展速率下降的幅度越大;当过载比小于3.5时,单峰过载引起裂纹尖端发生钝化或闭合,疲劳裂纹扩展速率明显下降甚至暂时停滞;当过载比为3.5时,裂纹尖端发生偏折及分叉,疲劳裂纹扩展完全停止。 相似文献
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应用弹塑性断裂力学和ΔJ参数 ,研究了原始状态与热渗氢后 3 4 7L不锈钢堆焊层短裂纹的疲劳破坏特性。并用 da/d N=C(ΔJ) n 计算了裂纹扩展速度和门槛值。结果表明 ,在氢的作用下 ,3 4 7L钢堆焊层裂纹扩展的门槛值 (ΔJth) ,从 3 55× 1 0 - 6 MN/m,下降为热渗氢后的 2 52× 1 0 - 6MN/m,da/d N~ΔJ曲线也比原始状态的向左移 ,提高了裂纹扩展速度。断口分析表明 ,氢既有在柱状晶界及滑移面上位错塞积处聚集 ,促进脆化的作用 ,同时还有与交变载荷的动态协同作用 相似文献
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以轧态2205双相不锈钢为研究对象,通过纳米压痕试验推算2205双相不锈钢各相的微观组织性能,并与微拉伸试验结果进行对比,证明该方法的有效性. 相似文献
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罗宏 《机械工人(热加工)》2007,(9):50-51
2205双相不锈钢(00Cr22Ni5Mo3N)是一种典型的含氮、超低碳、铁素体-奥氏体双相不锈钢,通过正确控制各合金元素比例和热处理工艺使其固溶组织中铁 相似文献
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《机械工程材料》2016,(6)
对热轧铁素体贝氏体双相钢FB60、铁素体马氏体双相钢DP600和铁素体珠光体钢SPFH590等三种汽车用高强钢板进行了扩孔试验,利用光学显微镜观察了扩孔裂纹的萌生和扩展,研究了不同钢的扩孔性能及开裂机理。结果表明:FB60钢的扩孔性能最优,DP600钢的最差;SPFH590钢与FB60钢具有相同的屈强比,但其扩孔性能却不及FB60钢的;组织对扩孔性能的影响与扩孔裂纹的萌生和扩展有关,FB60钢的裂纹萌生于铁素体内以及铁素体与贝氏体晶界,绕过贝氏体穿过铁素体扩展;SPFH590钢的裂纹萌生于铁素体与珠光体边界、珠光体内铁素体与渗碳体界面和铁素体内,极易沿铁素体与渗碳体片层扩展;DP600钢的裂纹萌生于铁素体与马氏体晶界,并沿晶界扩展。 相似文献
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分析了波形膨胀节爆炸失效的原因,发现304不锈钢冷加工成形时(液压)发生马氏体相变,在湿硫化氢环境下含形变马氏体的304奥氏体不锈钢发生了湿硫化氢引起的氢致开裂(HIC)或应力导向氢致开裂(SOCHIC),当裂纹扩展到某一临界尺寸时便发生了低应力脆断型的爆炸事故。 相似文献
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陈坚 《机械工人(热加工)》2008,(8):49-50,55
从探讨氧氯化反应器冷却管束国产化制造过程中SAF2205双相不锈钢的焊接问题入手,着重分析和制定了双相钢焊接工艺方案和质量保证措施,完成了SAF2205双相不锈钢管束的国产化研制,并且运行正常。 相似文献
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采用手工非熔化极惰性气体钨极保护焊将ERNiCrMo-3镍基合金焊丝堆焊于X70管线钢表面,分析了堆焊层/母材界面处的显微组织、元素分布和硬度分布,并采用电解充氢方法研究了氢致裂纹萌生位置和扩展方式。结果表明:X70管线钢表面镍基合金堆焊层/母材界面热影响区中细晶区的组织为细小铁素体和少量珠光体,靠近熔合线粗晶区的组织为粗大的铁素体,熔合区的组织为马氏体,堆焊层的组织为树枝状奥氏体;堆焊层冲击断口呈韧性断裂特征,母材断口呈解理或准解理脆性断裂特征,熔合区断口呈由浅韧窝+准解理组成的具有变形特征的混合过渡特征;堆焊层和熔合区的硬度均高于母材的;堆焊层表面氢致裂纹萌生于Al2O3和单质硅夹杂物处,扩展方式为沿晶和穿晶扩展。 相似文献
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A new methodology for predicting crack initiation life for rolling contact fatigue based on dislocation and crack propagation 总被引:1,自引:0,他引:1
C. Richard Liu 《International Journal of Mechanical Sciences》2008,50(2):117-123
A new methodology for predicting crack initiation life is presented and validated experimentally. The methodology considers that the total fatigue life is the summation of crack initiation life and crack propagation life, since fatigue failures are due to crack initiation and crack propagation. It has been established that the crack propagation life can be estimated based on a modified Paris’ law when the size of crack is larger than a certain value. However, there has been no verified method for estimating the crack initiation life with good accuracy. The proposed methodology for predicting the crack initiation life is based on a dislocation model, and the constants for the model are determined by the crack initiation lives obtained by a new approach. This new approach determines the crack initiation life by subtracting the predicted crack propagation life from the experimentally obtained total fatigue life. The developed crack initiation life model is combined with a crack propagation life model for the prediction of fatigue life. It is noted that the standard deviation in the ratios of experimental life to predicted life by the developed fatigue life model is only 14% of that by the International Standard. 相似文献
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根据球铁断裂过程中石墨及石墨-基体界面的微观力学行为,对球铁组织进行优化设计.以强相(马氏体)或强韧相(奥氏体-贝氏体组织)环包围石墨,基体组织为马氏体或奥氏体-贝氏体组织,加上适量的铁素体,并通过快速加热短时保温后淬火或等温淬火获得.实验结果表明,优化组织球铁具有很高的强韧性.采用扫描电镜动态拉伸观察优化组织球铁断裂过程,发现微裂纹在石墨-基体界面萌生并沿界面扩展,马氏体环或奥-贝环阻碍界面裂纹的萌生与扩展,基体中的硬相和软相分别提高球铁的强度和韧性,这些都有利于提高优化组织球铁的强韧性. 相似文献
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对开裂的天然气集气末站汇管进行了宏观形貌、显微组织、化学成分分析和力学性能测试、断口形貌观察以及腐蚀产物相组成确定,对其开裂原因进行了分析。结果表明:集气末站汇管开裂裂纹位于汇管的焊缝区,裂纹分为表面裂纹与隐藏裂纹,裂纹性质属氢致开裂和应力导向氢致开裂;设备内壁防腐涂层质量低劣是导致开裂的主要原因,焊接工艺不当对开裂有明显的促进作用。 相似文献
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The causes of anomalous cracking of bearing balls experienced on the main bearings of a liquid-butane pump were investigated. The characteristic features of the cracked balls were (1) no scoring on ball surfaces; (2) no structural defects; (3) subsurface crack generation and intergranular growth; (4) no inclusions at the origins of the cracks. We suspected hydrogen embrittlement to be the reason for this phenomenon and the hydrogen concentration of cracked balls was measured. Amounts of hydrogen sufficient to cause the embrittlement were detected. We also measured the hydrogen concentration of balls tested under research-grade liquid butane by the four-ball rolling contact configuration. Although the cracking of balls was not reproduced, increased hydrogen concentrations were detected. The mechanisms of hydrogen diffusion into the balls are also discussed. 相似文献
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Explicit finite element modeling of subsurface initiated spalling in rolling contacts 总被引:5,自引:0,他引:5
Trevor Slack 《Tribology International》2010,43(9):1693-1702
An explicit finite element model was developed to investigate crack initiation and spall formation in machine elements subject to rolling contact fatigue. The modeling approach utilizes continuum damage mechanics to capture the initiation and propagation of fatigue damage that leads to the formation of a surface spall. The material microstructure is modeled via a randomly generated Voronoi tessellation. The material parameters for the model were obtained independently from torsional fatigue life data for 52100 bearing steel. The life scatter (Weibull slope) and the spall geometry obtained from the model correlate well with experimental results available in the open literature. 相似文献
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通过对不同热处理后获得3种典型显微组织的粉末高温合金FGH96合金试样在650 进行保载90 s和5 s并恒载荷循环应力作用下的疲劳试验,研究组织特征对疲劳裂纹扩展速率的影响规律,确定不同载荷条件下孕育期、萌生期、扩展期及瞬断期所占的比率。结果表明,γ相特征显著影响疲劳裂纹扩展速率;疲劳行为对保载时间存在敏感性,随保载时间的延长,在疲劳-蠕变的交互作用下会明显加快合金疲劳裂纹扩展;在整个疲劳破坏过程中,萌生比率均高于扩展比率,说明该合金抗裂纹萌生的能力要高于抗裂纹扩展的能力;此外,该合金疲劳裂纹扩展四个阶段在整个断裂周次所占的比率分配上,孕育期比率一般较小,萌生期和扩展期比率较大,瞬断期的比率很小,表明该合金裂纹扩展一旦失稳将高速扩展并迅速断裂。 相似文献