【作者】 高飞；

【导师】 刘玉君； 赵东升；

【作者基本信息】 大连理工大学 ， 船舶与海洋结构物设计制造， 2010， 硕士

【摘要】 异种材料的焊接结构能够充分发挥组成材料的性能优势,而且能够节省贵金属材料因而具有较大的成本优势。随着造船技术不断进步,异种钢焊接的应用愈加广泛。焊接残余应力是影响船舶建造质量的重要因素,异种材料连接时,由于材料之间的性能差异尤其是热物理性能的差异导致焊接残余应力的问题更为突出。因此有必要研究异种钢结构的残余应力分布情况,为改善焊接工艺,提高船舶建造水平,减少异种钢的焊接残余应力提供理论基础。首先本文采用弹塑性有限元法计算了Q235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。其次改变了焊接工艺条件,探索了热源偏移及热输入改变对残余应力的影响。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。最后采用红外热像仪测量了焊接过程中焊接材料表面的温度变化情况,有限元计算的结果与其符合较好。并将所采用的参数模型推广到异种钢管管对接焊算例中,得到管管焊接中内表面残余应力大于外表面的结论,及其轴向和周向残余应力的分布规律。更多还原

【Abstract】 The welding structure of dissimilar steels can fulfill the performance advantage of each material fully and save the noble metal. Thus result in a cost advantage. With the development of the shipbuilding technology, the application of dissimilar steels welding has become more and more widely.The influence of welding residual stress is an important factor of the quality of the shipbuilding. The residual stresses are complex and difficult to predict because of the differences between mechanical and physical properties of the different materials. Therefore, it is necessary to do researches on the residual stress distribution of the dissimilar steels welding structure, providing a theoretical basis for improving the welding process, raising the level of shipbuilding and reducing the residual stress of welding.Firstly, in this paper Elasto-plastic finite element method is used for measuring the welding temperature field and the residual stress in butt-welded Q235 and 304 Stainless Steel. The results indicate that differences between their physics property caused the inhomogeneous distribution of the welding temperature field and the residual stress. And the peaks of the residual stress show on 304 Stainless Steel side, and the peak value is slightly less than the yield strength of 304 Stainless Steel.Secondly, the welding parameters were changed in this paper to explore the influences of the offsetting of heat resources and the changing of heat input on the welding residual stress. When the heat source was moved towards Q235, the peak value has small changes, but the high-stress was reduced as well as the welding distortion. On the contrary, when the heat source was moved towards 304 Stainless Steel, the high-stress area would be expanded with higher welding heat, and the peak value of the residual stress was slightly decreased.Finally, an infrared thermal imager was also applied to measure surface temperature changing of welding materials during welding, the results are accordant with that drawn from elasto-plastic finite element measurement. Meanwhile the same finite element model were used on residual stresses in dissimilar butt-welded pipes, the results indicate that the residual stress on inner surface is larger than outer surface of dissimilar joint. And the axial and hoop distribution of residual stress were shown in the results.更多还原