Research On Large Ship Structure Welding Deformation Simulation Using Shell Element

Welding method is the most widely used and effective method to join metal materials in shipbuilding industry.Material was heated rapidly and unevenly during welding processing.This may usually cause large deformation and residual stress.Using finite element method to simulate welding process can predict the deformation and residual stress.Simulation of welding process is carried out using the finite element method with solid element.Calculation scale of the simulation using solid element can be extremely large and takes a lot of time.The ship hull structure is mostly made of thin plates.Using shell element to simulate the welding process of the ship hull structure can be more efficient.In this research,4-node shell element was used based on ANSYS FEM software to simulate the welding process of the hull.Calculation scale of the simulation is reduced and higher efficiency is obtained due to a less amount of elements and degrees,is of great significance to improve the calculation efficiency of welding process simulation of large ship hull structures,The main content of this research is as follow:1.Aiming at the problem of flat butt welding,both solid element and shell element are used to simulate the same model using Gaussian moving heat source.Layer feature of the shell element was used to apply different heat load along thickness direction.Same loading method is used on solid element model.In the postprocess,temperature field,deformation and residual stress of both models were analyzed.Finally,feasibility of welding simulation using shell element is verified by comparing the results of verification experiments.2.In order to solve the problem of convergence of shell elements in welding process simulation,the factors that influence the convergence of shell elements are discussed.Effect of tangent modulus and Young’s modulus in the properties of model materials were analyzed and optimal reference values were given.Effects of shell element layer feature on the simulation of plate welding process and its result of deformation and residual stress are also analyzed.3.Research on a ship hull structure sub-assembly by-pass current welding method was carried out with shell element model.Heat source loading model of by-pass current welding method is investigated and given based on the mechanism of the hybrid arc.The sub-assembly model was applied respectively with BC-MIG welding heat source and conventional MIG welding heat source.After the simulations,effect of these two processes on the welding deformation and residual stress of the sub-assembly stiffened plate structure of ship was compared,and the improving of the heat input on the welding deformation was proved.