共查询到18条相似文献,搜索用时 187 毫秒
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采用粘弹塑性有限元方法从应力释放角度讨论了Cr-Mo钢局部热处理下各种优化加热条件.研究表明,局部热处理过程产生的瞬态和残余应力受蠕变性能和温度关系弹性模量等因素的影响.当加热宽度足够大时,局部热处理后的应力与炉中热处理的应力接近.通过与现有标准的比较,从应力释放角度位于焊缝中心5√Rt的加热宽度较为合理.提出了考虑焊接冷却过程Cr-Mo低温膨胀现象的相变模型.给出了焊接残余应力与局部焊后热处理应力的试验结果与模拟结果的对比. 相似文献
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借助有限元模拟X60管线钢对接接头3种不同焊趾优化工艺设计焊接过程,得到了周向和轴向残余应力分布。采用盲孔法残余应力分析仪,验证仿真结果的准确性。结果表明,周向和轴向残余应力总体变化趋势与典型接头的应力变化趋势一致。常规焊趾工艺设计得到的周向和轴向残余应力梯度和平均应力值均最大,圆滑过渡焊趾设计得到周向和轴向残余应力梯度和平均应力值均最小。常规焊趾工艺设计达到应力峰值的距离比其他2种焊趾优化设计更接近引弧位置和焊缝中截面。圆滑过渡焊趾设计周向和轴向残余应力仿真结果与盲孔法测量结果吻合度好,最大误差控制在9.37%。圆滑过渡焊趾设计对预防应力腐蚀开裂有指导意义。 相似文献
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通过X射线衍射法研究管线用20G焊接残余应力的分布和焊后热处理对焊缝残余应力的影响,择优选取了焊后热处理条件。结果发现,在焊缝区存在较高的焊接残余应力。焊后热处理可以显著降低焊接残余应力,其中以620℃加热温度、1 h保温时间的处理工艺为宜。此外,热处理细化了焊缝区域晶粒,降低了焊缝区域硬度,改善了焊接接头抗H2S腐蚀的能力。 相似文献
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以含有六个接管的1000MW级压水堆核电站反应堆压力容器中筒体与接管连接处马鞍形焊缝为研究对象,利用热弹塑性有限元数值模拟方法详细研究了不同焊接线能量下马鞍形焊接接头处温度场、残余应力场以及变形的大小和分布情况,并在焊后将构件进行高温回火处理,即整体加热到610℃保温3 h后空冷。结果表明,在满足焊接的条件下,2.57 kJ/mm的线能量焊后焊接残余应力和变形均小于线能量为2.75和2.89kJ/mm焊后,焊后热处理使得焊接残余应力和变形在一定程度上得到了改善。 相似文献
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利用大型有限元分析软件Abaqus的多次顺次耦合功能,先对P91钢高温主蒸汽管道焊接接头焊态和焊后热处理状态进行残余应力分析, 然后采用Norton蠕变本构关系,根据P91耐热钢在625℃下焊缝、热影响区和母材的不同蠕变参数,对内压以及内压与热处理后残余应力共同作用下的接头蠕变进行有限元分析,分别得到了焊接残余应力和焊后热处理残余应力的分布规律,同时预测了在高温环境下服役105h后蠕变应变分布. 结果表明,由于高温管道的壁厚以及约束等影响, 焊后产生了较大的焊接残余应力,通过焊后热处理可以有效地降低焊接残余应力.但由于热处理残余应力的存在, 仍对高温管道焊接接头的蠕变有较大影响,并且在焊缝与热影响区的交界处存在着较大的蠕变应变. 相似文献
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依托焊接数值模拟技术在转轮上的实际应用成果,对比分析了几种焊接残余应力控制手段在电机关键部件上的应用特点,探讨了数值模拟技术在电机关键部件焊接上的应用前景及意义。通过对比分析可知:焊后热处理消应力和振动时效消应力方法对焊接应力在一定程度上均能起到降低作用,但其效果均因条件限制而有一定的局限性。焊接数值模拟技术可以利用计算机及软件对应力场进行调控,具有高度的可重复性,缩短周期,降低成本,在焊接阶段将应力控制在低应力水平,该项技术在电机制造上将会有广阔的应用前景。 相似文献
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为了得到SA508-3钢特厚板焊接残余应力分布及焊后热处理对残余应力分布的影响,利用有限元方法对焊接及焊后热处理进行了模拟计算,计算结果表明:焊后热处理对试板焊接应力分布趋势影响较小,但焊后热处理可以大大减小接头应力数值,其中,纵向应力最大减小幅度为72%,横向应力最大减小幅度为70%;焊接接头存在应力分布准稳定区,且接头内部残余应力水平最小,其次为接头上表面,接头下表面应力水平最大;通过残余应力测定试验与模拟结果比对,两者结果吻合度很高,说明计算模型及计算方法可靠,可以指导实际SA508-3钢特厚板焊后热处理生产. 相似文献
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The residual stress evolution in a safe-end/nozzle dissimilar metal welded joint of CAP1400 nuclear power plants was investigated in the manufacturing process by finite element simulation. A finite element model, including cladding, buttering, post-weld heat treatment (PWHT) and dissimilar metal multi-pass welding, is developed based on SYSWELD software to investigate the evolution of residual stress in the aforementioned manufacturing process. The results reveal a large tensile axial residual stress, which exists at the weld zone on the inner surface, leads to a high sensitivity to stress corrosion cracking (SCC). PWHT process before dissimilar metal multi-pass welding process has a great influence on the magnitude and distribution of final axial residual stress. The risk of SCC on the inner surface of the pipe will increase if PWHT process is not taken into account. Therefore, such crucial thermal manufacturing process such as cladding, buttering and post-weld heat treatment, besides the multi-pass welding process, should be considered in the numerical model in order to accurately predict the distribution and the magnitude of the residual stress. 相似文献
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AbstractPost-welding heat treatment (PWHT) is carried out on 2.25Cr–1Mo steel used in pressure vessels, to relieve welding residual stress and diffused hydrogen and to soften the weld joint. However, it is known that reheating cracks often occur during PWHT. A standard specimen is available to pre-estimate the existence of cracks in pressure vessels according to rules such as those in Japanese Industrial Standard WES 3005. However, these specimens do not reflect the shape of the pressure vessels and do not reproduce the actual cracks correctly because of non-cylindrical welding. In the present paper, a numerical analysis has been conducted for various models, which can reproduce the occurrence of reheating cracks in the welded joint of a pressure vessel nozzle. The present paper also investigates mechanical behaviour such as the relief history of welding residual stress as well as the accumulated history of creep strains. Through the above processes, the mechanical behaviour of the welded pressure vessel nozzle joints has been elucidated and a model of reheating crack initiation has been selected. In addition, experiments on reheating crack initiation have been carried out for the WES 3005 specimen, and a new susceptibility assessment specimen has been proposed and developed to pre-estimate the existence of actual reheating cracks correctly. 相似文献
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Jingjing Wang Jian Sun Xinhai Yu Guohong Chen Qiuhua Fu Chao Gao Wenming Tang 《Journal of Materials Engineering and Performance》2017,26(10):4659-4666
Small-caliber, thick-wall 12Cr1MoVG seamless steel tube welded joints were fabricated in this study by gas tungsten arc welding and shielded metal arc welding techniques, then the microstructures, mechanical properties, and residual stress distributions of the joints with or without post-weld heat treatment (PWHT) were compared. The welded joints are mainly composed of bcc ferrite (F), Fe3C, and M7C3 carbides. PWHT did not cause an apparent microstructure evolution in the joints, but promoted granular pearlite decomposition and growth of F grains and carbides, therefore decreasing the yield, tensile strength, and hardness while increasing the impact toughness and elongation of the welded joints. PWHT also released the circumferential residual stress and altered the stress state in the joint from tensile to compressive. Although the mechanical properties and bending performance of the small-caliber, thick-wall 12Cr1MoVG seamless welded joints without PWHT are acceptable, our results show that the joints with PWHT are more reliable. 相似文献
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焊接残余应力对氢扩散影响的有限元模拟 总被引:6,自引:0,他引:6
利用ABAQUS有限元软件开发的氢扩散耦合计算程序,对焊态和焊后热处理状态下残余应力对氢扩散的影响进行了数值模拟,并与无应力状态下的氢扩散进行了比较.结果表明,存在焊接残余应力梯度时,氢向高应力区富集,在热影响区附近,有一个氢浓度低谷,这是氢向高应力区长程扩散所致.经过焊后热处理,应力松弛效果明显,残余应力大幅下降,对氢扩散的影响也大大降低,氢的最高浓度降低了近40%.因此,焊后热处理可以有效降低材料在氢环境下开裂的敏感性. 相似文献
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Abhishek Mitra N. Siva Prasad G. D. Janaki Ram 《Journal of Materials Engineering and Performance》2016,25(4):1384-1393
Ferritic steel weldments are invariably post-weld heat treated for relieving the residual stresses. However, the long duration of post-weld heat treatment (PWHT) required for very thick weldments can adversely affect the mechanical properties and fracture toughness. Thus, there is a need to establish the relative importance of temperature and time of PWHT with respect to stress relief. Accordingly, in the present work, the phenomenon of stress relief (due to PWHT) in an 800-mm-thick steel weldment was investigated using finite element analysis and the results were validated against experimental measurements. An analytical study was also carried out to determine the relative influence of temperature and time of PWHT on stress relief. It was found that time of PWHT plays a more significant role in case of relatively lower PWHT temperatures. It was also found that, for a given value of Hollomon parameter, different combinations of PWHT temperature and time can be employed to achieve the same level of stress relief. A mathematical relationship has been established between Hollomon parameter and magnitude of residual stress after PWHT. It has been shown that residual stress is a monotonically decreasing function of the Hollomon parameter. 相似文献