异种钢焊接接头残余应力和变形的数值模拟

发布时间：2018-06-23 13:25

本文选题：数值模拟 + 异种钢焊接　；参考：《重庆大学》2015年硕士论文

【摘要】：异种金属焊接接头,近年来被越来越广泛地应用到核电装备和工程机械设备等领域中以满足各种复杂和苛刻条件的要求。焊接过程中,在不均匀温度场的作用下,不可避免会产生焊接残余应力和变形。异种金属焊接接头中由于各材料的热物理性质和力学性能间存在着较显著的差异,因而容易导致异种金属焊接接头产生较大且不易被消除的焊接残余应力。此外,异种金属接头在焊接冷却后残余应力与变形的分布与同种金属接头相比更为复杂。焊接残余应力和变形对焊接结构的静载强度、疲劳强度、结构稳定性以及冷加工过程中的制造精度等都有非常不利的影响。因此,如何控制和减小焊接结构中的残余应力与变形已经成为备受关注的研究课题。作为基础研究,本文以ABAQUS软件为平台,开发了用于模拟多层多道焊接过程的热-弹-塑性有限元计算方法。利用所开发的计算方法,对板厚10 mm的Q345/SUS304异种钢平板对接接头的温度场、应力场和变形进行数值模拟,并通过试验方法验证了数值模拟结果的准确性。采用数值和试验的方法研究了Q345/SUS304异种钢接头残余应力和变形的分布规律,并研究了开口朝向和坡口形式对异种钢接头残余应力和变形的影响。为改善异种钢接头的焊接工艺、控制和减小异种钢焊接残余应力与变形提供理论基础。实验研究表明:1)Q345/SUS304异种钢对接接头SUS304侧的纵向拉伸应力区域大于Q345侧,同时在Q345/焊缝(Y309L)的熔合线附近纵向拉伸应力分布有明显的不连续特征;Q345/SUS304异种钢焊接接头的横向收缩和角变形都比较明显。异种钢焊接接头角变形的大小更趋近于易发生变形的同质SUS304不锈钢接头。2)K形坡口接头开口朝向Q345侧相较于朝向SUS304侧,焊缝附近的高拉伸残余应力区分布范围和应力峰值均明显小于后者。数值和实验结果表明,坡口形式(V形坡口和K形坡口)对接头的角变形有明显的影响。3)V形坡口接头左、右两侧高纵向拉伸应力区域均明显大于X形坡口,V形坡口的横向拉伸残余应力区域和峰值、横向收缩和角变形均大于X形坡口。另外,在前人研究的基础上,我们通过开发新的考虑加工硬化和退火的热-弹-塑性有限元计算方法,模拟研究了核电站喷嘴构件的焊接残余应力分布情况。这一实例研究对预测实际工程结构中的焊接残余应力具有一定的指导意义。
[Abstract]:In recent years, dissimilar metal welded joints have been more and more widely used in nuclear power equipment and construction machinery to meet the requirements of complex and harsh conditions. During welding process, welding residual stress and deformation will inevitably occur under the action of inhomogeneous temperature field. In the dissimilar metal welded joint, there are obvious differences between the thermophysical properties and mechanical properties of the materials, so it is easy to cause the welding residual stress of the dissimilar metal welded joint to be large and difficult to be eliminated. In addition, the distribution of residual stress and deformation of dissimilar metal joints after welding cooling is more complex than that of the same metal joints. The welding residual stress and deformation have very adverse effects on the static load strength, fatigue strength, structural stability and manufacturing accuracy during cold working of welded structures. Therefore, how to control and reduce the residual stress and deformation in welded structures has become a hot research topic. Based on Abaqus software, a thermo-elastic-plastic finite element method is developed to simulate multilayer and multi-pass welding process. Using the developed method, the temperature field, stress field and deformation of Q345 / SUS304 dissimilar plate butt joint with 10 mm thickness are numerically simulated, and the accuracy of the numerical simulation results are verified by the experimental method. The distribution of residual stress and deformation in Q345 / SUS304 dissimilar joints was studied by numerical and experimental methods, and the effects of opening direction and groove form on residual stress and deformation of dissimilar steel joints were studied. It provides a theoretical basis for improving welding process of dissimilar steel joint and controlling and reducing welding residual stress and deformation of dissimilar steel. The experimental results show that the longitudinal tensile stress region of SUS304 side of Q345 / SUS304 dissimilar steel butt joint is larger than that of Q345 side. At the same time, the longitudinal tensile stress distribution near the fusion line of Q345 / weld (Y309L) is obviously discontinuous. The transverse shrinkage and angular deformation of Q345 / SUS304 dissimilar steel welded joints are obvious. The angle deformation of dissimilar steel welded joints is closer to that of homogeneous SUS304 stainless steel joints which are prone to deformation. The distribution range and peak stress value of the high tensile residual stress region near the weld are obviously smaller than that of the latter. Numerical and experimental results show that the groove form (V-groove and K-groove) has a significant effect on the angular deformation of the joint. The region of high longitudinal tensile stress on the right side is obviously larger than the region and peak value of the transverse tensile residual stress of the V-shaped groove, and the transverse shrinkage and angular deformation are larger than that of the X-shaped groove. In addition, on the basis of previous studies, a new thermo-elastic-plastic finite element method considering work hardening and annealing is developed to simulate and study the distribution of welding residual stress in nozzles of nuclear power plants. This case study has certain guiding significance for predicting welding residual stress in practical engineering structures.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG404

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