船体大型结构件焊接变形预测

发布时间：2018-06-05 23:37

本文选题：焊接变形预测 + 船体大型结构件　；参考：《江苏科技大学》2016年硕士论文

【摘要】：船舶工业是为水上交通、海洋开发和国防建设等行业提供技术装备的现代综合性产业。大型船舶结构件体积庞大,一次整体制造困难,国内外的造船厂建造的大型船舶往往将其分成几段或十几段相对较小的结构件分别焊接制造,最后再把各个分段拼装焊接起来。焊接局部不均匀的加热和冷却使得船舶与海洋工程等重要结构件产生各种焊接变形。结构件的焊接变形不仅导致船体焊接和装配的难度加大同时也会造成焊接精度问题,降低结构的承载能力。所以在建造大型船舶的每个分段时需要研究焊接结构件的残余应力和焊接变形问题。为了掌握焊接变形的规律,就应对焊接温度场及焊接过程中的应力变形进行准确的分析。常用的焊接应力变形数值模拟方法有热弹塑性有限元法和固有应变法,热弹塑性计算是典型非线性过程(材料非线性、几何非线性等),矩阵方程奇异性大,计算结果收敛困难需要多次迭代才能达到必要的精度,不适用于大型结构件应力变形预测,故本文采用固有应变法预测大型结构件应力变形。针对大型船体结构件(底板、纵骨和肋板焊接结构),本文选取其中一个典型小结构件(T型接头双边开45°角V形坡口)进行熔化极气体保护焊(MAG)焊接实验,使用盲孔法对典型小结构件(T型接头)进行焊后残余应力实验,并绘制出残余应力分布规律图;建立典型小结构(T型接头)的数学模型,确定材料热物性参数、边界条件、热源模型及约束条件等;使用ANSYS仿真软件进行热弹塑性有限元分析,计算小结构的温度场、应力应变、变形的分布;下一步采用固有应变的有限元分析方法,将小结构热弹塑性有限元计算得到的固有变形转化为固有应变加载到大型结构上,使用大型焊接变形仿真软件预测大型船体结构的焊接变形。研究结果表明:底板与纵骨八条长焊缝焊接后,整个结构件的横向收缩最大值为13.056mm,底板左下端和右上端横向收缩较大。左侧的三根纵骨向右侧横向收缩变形,右侧的三根肋骨向左侧横向收缩变形,中间两根纵骨横向收缩量较小。整个结构件纵向最大收缩量为16.9 mm且底板和纵骨上端的纵向收缩量较下端的大;底板与肋板、肋板与侧板八条长焊缝焊接后,整个大结构件产生纵向收缩,最大收缩量为19.28mm,底板和侧板的两端沿着长度方向向中间收缩变形,底板和肋板分别沿着各自的宽度方向发生横向收缩,横向收缩最大量为6.47mm。计算结果表明,基于固有应变的有限元分析方法能够比较合理地预测大型结构件的焊接变形,使得大型结构件焊接变形情况预测成为可能,对于实际焊接生产有一定的指导作用。
[Abstract]:Shipbuilding industry is a modern comprehensive industry which provides technical equipment for water transportation, marine development and national defense construction. Because of the large size of large ship structural parts, it is difficult to be manufactured at one time. Large ships built by shipyards at home and abroad are often welded into several sections or more than a dozen relatively small structural parts, and finally each segment is welded together. Welding local uneven heating and cooling cause various welding deformation of important structures such as ship and ocean engineering. The welding deformation of structural parts not only makes it more difficult to weld and assemble the hull, but also causes the welding precision problem and reduces the bearing capacity of the structure. So it is necessary to study the residual stress and welding deformation of welded structure when building each section of large ship. In order to master the rules of welding deformation, the welding temperature field and stress deformation in welding process should be analyzed accurately. The commonly used numerical simulation methods for welding stress and deformation are thermoelastic-plastic finite element method and inherent strain method. Thermoelastic-plastic calculation is a typical nonlinear process (material nonlinearity, geometric nonlinearity, etc.) The convergence of calculation results requires several iterations in order to achieve the necessary accuracy and is not suitable for the prediction of stress and deformation of large structural parts, so the inherent strain method is used to predict the stress and deformation of large structural parts in this paper. Aiming at large hull structure (bottom plate, longitudinal frame and ribbed plate welding structure), this paper selects one of typical small structure parts as T joint with 45 掳angle V groove to carry out gas shielded welding (MAG) welding experiment. Using blind hole method, the residual stress of typical small structure parts is tested after welding, and the distribution pattern of residual stress is drawn, the mathematical model of typical small structure T joint is established, and the material thermal physical parameters and boundary conditions are determined. The thermal source model and constraint conditions, ANSYS simulation software for thermoelastic-plastic finite element analysis, to calculate the temperature field, stress, strain, deformation distribution of small structures, the next step is to use the natural strain finite element analysis method, The thermal elastoplastic finite element analysis of small structures is transformed into inherent strain loading on large structures, and the welding deformation of large hull structures is predicted by large welding deformation simulation software. The results show that the maximum transverse shrinkage of the whole structure is 13.056mm after welding between the bottom plate and the longitudinal bone eight long welds, and the transverse shrinkage of the bottom plate at the left lower end and the right upper end is larger. The three longitudinal bones on the left contracted and deformed laterally to the right, the three ribs on the right contracted and deformed to the left, and the transverse contraction of the two longitudinal bones in the middle was relatively small. The maximum longitudinal shrinkage of the whole structure is 16.9 mm, and the longitudinal shrinkage of the bottom plate and the upper end of the longitudinal bone is greater than that of the lower end, and the longitudinal shrinkage of the whole large structure is produced after the welding of eight long welds between the bottom plate and the rib plate, the rib plate and the side plate. The maximum shrinkage is 19.28 mm. The two ends of the bottom plate and the side plate contract and deform along the length direction. The transverse shrinkage of the bottom plate and the ribbed plate is 6.47 mm. The calculation results show that the finite element analysis method based on inherent strain can reasonably predict the welding deformation of large structural parts, which makes it possible to predict the welding deformation of large structural parts. It has certain guiding function for actual welding production.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U671.83;TG404

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