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利用有限元法,对微小尺寸的镍基钎焊不锈钢板翅结构进行600 ℃下的蠕变有限元分析,讨论钎焊残余应力对蠕变变形的影响.结果表明,由于镍基钎料BNi-2和不锈钢母材SS304力学性能的差异以及钎焊夹具的约束作用,钎焊后在接头处产生了较大的残余应力,对不锈钢板翅结构高温下的蠕变行为产生很大影响,在强度设计中不能忽略.初始应力和蠕变应变的分布规律具有一致性.隔板和翅片具有不同的应力应变分布特征,隔板侧的蠕变开裂的倾向比翅片大.钎角处蠕变应力和应变集中,易萌生蠕变裂纹.研究结果为不锈钢板翅结构钎焊接头的高温强度设计提供参考. 相似文献
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由于影响不锈钢板翅结构在真空钎焊过程中产生的残余应力因素较多,这给残余应力的预测带来很大的困难,为此,本文提出一种基于神经网络的不锈钢板翅结构钎焊残余应力预测方法.通过对不锈钢板翅结构在真空钎焊过程中产生的残余应力进行有限元分析,获知影响残余应力的主要因素,以构造神经网络的输入向量,建立不锈钢板翅结构钎焊残余应力的预测模型,并采用该模型对不锈钢板翅结构钎焊工艺过程进行仿真,结果表明该预测方法较快速有效地预测不锈钢板翅结构钎焊残余应力. 相似文献
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利用有限元软件ABAQUS,对不锈钢板翅结构在钎焊过程中产生的残余应力及其高温下的蠕变松弛行为进行三维有限元分析,得到了残余应力的变化规律.结果表明,由于镍基钎料BNi-2和不锈钢母材304力学性能的差异以及夹具的约束作用,钎焊后在接头处产生了较大的残余应力.在高温环境下,由于蠕变松弛,残余应力大幅度下降.在蠕变稳态阶段,钎缝处仍然存在一定的残余应力;钎角处蠕变应力和应变集中,易萌生裂纹,成为最薄弱环节.研究结果为板翅结构的高温强度设计提供参考. 相似文献
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Jianming Gong Wenchun Jiang Qinshan Fan Hu Chen S.T. Tu 《Journal of Materials Processing Technology》2009,209(4):1635-1643
This paper presents a finite element modelling of brazed residual stress in a stainless steel plate-fin structure applied to recuperators in microturbines. The effects of nine influence factors on residual stress are investigated. The results show that the brazed joint creates large residual stresses due to the mechanical properties mismatching between base metal and filler metal. Strength in the middle joint is affected mainly by longitudinal stress. The residual stress gradient around the interface between base metal and filler metal is very large, which can have a great effect on interface strength. The material mismatching, brazing gap, pressure loading, fin pitch, fin thickness, fin height and plate thickness significantly affect the residual stress distribution, while the brazing temperature and the number of fin layers have little impact on residual stress. This work provides a reference for optimizing the brazing procedure and decreasing the residual stress for stainless steel plate-fin structures. 相似文献
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采用弹塑性有限元法计算了Q235碳钢与304不锈钢的焊接温度场和焊接残余应力,计算结果表明,由于二者物理性能的差异造成了焊接温度场和残余应力分布的不均匀,焊接残余应力的峰值出现在304不锈钢一侧,其值略低于304不锈钢的屈服强度.当焊接热源偏向Q235钢时,焊接残余应力峰值变化较小,但高应力区减小,焊接变形明显减小,当焊接热源偏向304不锈钢时结果相反.当焊接热输入增大时会导致焊后高应力区范围的扩大,残余应力的峰值略有降低.采用红外热像仪测量了焊接过程中焊接接头上表面的温度变化情况,有限元计算的结果与其符合较好. 相似文献
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铝合金与不锈钢钎焊用钎剂性能研究 总被引:3,自引:0,他引:3
针对Al及其合金与不绣钢钎焊中存在的因钎剂的腐蚀性及钎料的润湿性等引起钎焊接头强度下降的问题,研制出一种以LiCl-NaCl为基,并配以其它成分的Al基钎剂。对钎剂的配制机理进行了分析,并用试验的方法对其钎焊性能进行了研究。对钎焊接头及其界面作扫描电镜(SEM)、透射电镜(TEM)、X射线衍射和拉力试验等分析发现,钎剂对钎料的润湿性能良好,有效地阻止了钎料在钎焊期间的氧化。对接头进行腐蚀性试验,发现焊缝的抗腐蚀性较强,能够满足一般环境的使用要求。 相似文献
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向Al-Si钎料中添加锌研制开发了Al-Si-Zn钎料,在评价其工艺性能的同时,研究了不同含锌量钎料、不含锌钎剂对铝合金/不锈钢钎焊接头组织特征、力学性能的影响。结果表明:Al-Si-Zn钎料高温下氧化严重形成致密的氧化膜,熔炼浇注相当困难。解决措施为向Al-Si钎料中添加氯化钠和氯化钾形成保护膜,锌添加量对Al-Si-Zn钎料和用其钎焊铝合金/不锈钢接头力学性能的影响大于对工艺性能的影响。随锌含量增加,钎料对不锈钢的润湿性虽有所改善,但却促使Al-Si-Zn钎料与铝合金产生润湿且被其吸收的速度加快;加之Zn挥发易产生气孔,最终导致接头强度明显下降。这一结果验证了随锌含量增加,Al-Si-Zn钎料等温凝固进程加快的事实。 相似文献
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玻璃和金属焊接接头由于设计不合理,将致使接头存在较大的焊接残余应力,会严重削弱接头强度.应用顺次耦合有限元热应力计算方法,对平板玻璃和金属在真空条件下的钎焊过程进行了数值模拟,分析了玻璃、金属、钎料厚度、钎焊压力和钎焊温度等因素对应力集中区域残余应力的影响,并观察了焊接接头拉伸断裂后的形貌特征.结果表明,金属厚度增加会增大残余应力,并且其对残余应力影响最显著;钎焊压力和钎焊温度的增加可以降低残余应力;玻璃和钎料厚度对残余应力的影响不大;焊接接头的拉伸断裂区域位于玻璃和金属焊接接头界面贴近玻璃一侧. 相似文献
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基于计算机仿真技术,定义随温度变化的材料热物理属性,建立316不锈钢连续油管对接焊接轴对称模型,分析焊接速度对焊后油管接头的残余应力和变形的影响。结果表明,在连续管道焊接过程中,焊接速度影响焊接温度场和焊后残余应力的分布;油管内壁最大残余压应力出现在距离焊缝中心22 mm接近母材的位置处,且轴向应力和环向应力的变化同步,油管外壁环向应力和轴向应力变化不同步;随焊接速度的增加,油管外壁残余应力逐渐增大,内壁残余应力和焊接变形逐渐减小,焊接变形可释放部分焊接残余应力,在一定程度上可降低焊后残余应力。 相似文献
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铝合金与不锈钢的物化性能相差很大,两者的直接连接易于在界面上生成Al和Fe的脆性化合物。作者用试验的方法研究了LF3铝合金与0Cr18Ni9不锈钢的Ni/Cu过渡层钎焊的工艺方法以及接头的组织与力学性能,并对各连接界面进行了机理分析。对钎缝的界面做剪切试验、X射线衍射、扫描电镜(SEM)和透射电镜(TEM)等分析发现,镀层与钎料等各界面连接紧密,特别是钎缝与母材之间没有生成脆性Al-Fe金属间化合物。由此得出结论,面心立方结构的Ni/Cu电刷镀层能有效地阻挡Al、Fe等原子扩散,钎缝与镀Cu界面上虽然生成了少量的AlCu3,但由于组织不连续,没有大幅度降低钎缝的剪切强度。通过过渡层钎焊,实现了LF3铝合金与0Cr18Ni9不锈钢的复合连接.满足了工程需要。 相似文献
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Based on thermal-elasto-plastic finite element theory, a two-dimensional finite element model for calculating electron beam brazing temperature and residual stress fields of stainless steel radiator are presented. The distributions of temperature and residual stress are studied. The resuhs showed that temperature distribution on brazing surface is rather uniform, ranging from 1 026 ℃ to 1 090 ℃. The residual stresses are varied from initial compressive to tensile , and the variation of residual stress is very little in total zone of brazing surface. 相似文献
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Jordan T. Maximov Angel P. Anchev 《International Journal of Machine Tools and Manufacture》2003,43(12):1241-1251
Fatigue life of structural elements with bolt holes depends mainly on residual stress distribution law around these holes. Residual compressive circumferential normal stresses around the hole reduce operating stress magnitudes to minimum values for cyclic tension and this enhances fatigue life and load-carrying capacity of structures. The presence of residual stresses is a result of the manufacturing process. Residual stresses can also be induced deliberately around the holes by means of appropriate working with suitably chosen parameters. Quantitative knowledge of residual stresses is necessary to model the stress field after applying an external load to a structural element in order to assess static or dynamic strength, fatigue strength including. This paper presents a combined approach consisting of experimental and numerical modelling of residual circumferential normal stress distribution when forming holes in workpieces of medium carbon steel by spherical mandrelling (SM). Since the object of study is residual macrostresses (stresses of first type), a mechanical method of their determination has been employed. On the basis of experimental outcomes, a mathematical model has been built and it predicts mean integral value distribution of residual circumferential normal stresses. Since the range of the experimental technique employed is limited by the wall thickness of the bushing being worked, numerical modelling of residual stresses by means of FE simulation has been performed. The numerical results obtained allow this mathematical model to be applied to various wall thicknesses by introducing correction factors for the polynomial coefficients. At the same time, the adequacy of the proposed FE model can be evaluated only by the experimentally obtained mathematical model. The SM efficiency for enhancing the load-carrying capacity of structural elements with cylindrical holes subjected to tension has been proved by means of FE simulation. 相似文献