Research Of Large Structure Welding Deformation Prediction

Shipbuilding industry is a modern and comprehensive industry which provides technical equipment for water transportation, ocean development and national defense construction. The volume of large ship structure is huge, an overall manufacturing is difficulty. Both at home and abroad, shipbuilding plant construction of large ships are often divided into several or more segments of the relatively small structure in the welding manufacturing, and finally assembled the various segments together.Fast and local uneven heating and cooling makes the ship and ocean engineering structure produce a variety of welding deformation,The welding deformation of the structure not only leads to the difficulty of welding and assembling, but also causes the problem of welding precision, which can reduce the bearing capacity of the structure. So it is of great need to study the residual stress and the welding deformation of the welded structure in the construction of each segment of the large ship.In order to grasp the characteristics of welding deformation, the welding temperature field and stress deformation in the welding process should be analyzed accurately. Thermal elastic plastic finite element method and inherent strain method are usually used as welding stress deformation numerical simulation methods, the thermal elastic-plastic analysis is typical nonlinear process(material nonlinear, geometric nonlinear, etc.) with singularity matrix equation, requires several iterations to achieve the necessary precision, not applicable to large structural stress deformation prediction. Therefore, in this paper the inherent strain method is used to predict the stress and deformation of large structure.In view of the large hull structure(bottom plate, longitudinal and ribs welding structure), we selected a typical small structure(T joint, bilateral open angle of 45°, V groove) for gas metal arc welding(MAG) welding experiments. A typical small structure(T Joint) was used to measure the residual stress after welding experiment with blind hole method, and the residual stress distribution map has been drawn out; We established the mathematical model of a typical small structure(T Joint), and determined the material properties, boundary conditions, heat source model, constraint conditions and so on; We used ANSYS to do finite element analysis of thermal elastic plastic, calculating temperature field, stress and deformation distribution of small structure; The inherent deformation of small structure calculated by thermal elastic plastic finite element was transformed into the inherent strain which was loaded to the large structure using inherent strain finite element analysis method. Welding deformation of large ship structure was predicted with the WELD-STA large welding deformation simulation software.Research results show that: In the welding of bottom plate and longitudinal bone, the largest transverse shrinkage of the whole structure is 13.056 mm,and the largest transverse shrinkage appears in the left lower end and the upper right end of the bottom plate. Three longitudinal bones in the left side shrink to the right side, and three longitudinal bones in the right side shrink to the left side. The transverse shrinkage of the two longitudinal bones in the middle is little. The largest longitudinal shrinkage is 16.9mm, and the longitudinal bone shrinkage in the upper end of bottom plate and longitudinal is larger than that in the bottom end of the bottom plate and longitudinal. Bottom plate, a ribbed plate and the side plate structure with eight long weld after welding, the maximum longitudinal shrinkage is 19.28 mm and both ends of the bottom plate and the side plate are contracted to the middle along the length direction;Bottom plate and ribbed plate and the side plate of the eight long weld after welding, the whole structure of parts produced longitudinal shrinkage, maximum diameter shrinkage 19.28 mm, at both ends of the bottom plate and the side plate along the length direction to the middle of the shrinkage deformation; floor and floor respectively along the width direction of the respective occurred transverse shrinkage, transverse shrinkage the lots for 6.47 mm. Calculation results show that, based on the inherent strain finite element method(FEM) can be used to predict welding deformation of large structure and the results of welding deformation is reasonable. It makes it possible to predict the welding deformation of large structure, which has a certain guiding role in the actual welding production.