Study On Welding Deformation And Mechanical Constraint Of A Curved Ship Bottom Block

Curved ship block is a very important intermediate product in the shipbuilding process.Owing to the less similarity of structures,the construction technologies differ from one another.As a result,most of them can only be constructed with pin jigs at fixed position.At present,there is little related research on the welding deformation and pin jigs of the curved ship block.Based on thermal elasto-plastic finite element method(FEM),the welding simulation of a large-scale ship bottom block was carried out in this article,several techniques are used to enhance the calculation efficiency.The main works in this article are as follows:(1)The building technologies for curved ship blocks and the usage of pin jigs are presented at first.Then,the common methods to control the welding deformation of ship blocks are summarized.A comprehensive review on the research methods and current situation about welding is also presented in the first chapter.(2)In order to realize the welding simulation of a transverse framing ship bottom structure,several methods are combined and used: shell/solid model,segmented moving heat source,static substructure,temperature field’s translation,automatic connection of DOFs.And the subprogram which can exert the heat flux in curved weld lines is also written with FORTRAN language.(3)The distribution of welding deformation and residual stress are studied.By comparing the results in different welding directions and mechanical boundaries,the influence of this two factors are studied.The calculations indicate that asymmetry weld direction will increase the torsion distortion significantly,while the pin jigs cannot improve the welding results effectively.(4)The changing process of constraint forces in connection plates during the welding of ship block,and the spring-back deflections after pin jig being removed are also analyzed and discussed.Considering the removal process of connection plates,this paper compared the deformation and constraint force in four removal sequences.The results show that the removal sequences have no influence on the final welding deformation;The maximum constraint forces of connection plate occur at the moments when welding torch approaches the adjacent structural components and the connection plates are more apt to damage during welding process than at final state.