Numerical Simulation Of Welding Distortion Of Large Hull Structure

It is well known that welding technology is playing a more and more important role inship industry, which can improve productive efficiency in welding of ship, shorten theproduction cycle, reduce cost and enhance the competitiveness of enterprise. Weldingdistortion, however, not only has been taken into consideration. But also it is tough tocontrol the welding distortion in the whole welding procedure. Welding distortion existedmay lead to shape and size of the ship structure to vary, what’s more, the additional bendingmoment and phenomenon of stress concentration which were generated by weldingdistortion under working load is the main reason leading to the premature failure of hullstructure. For the reason above mentioned, the prediction and control of welding distortionhas been a significant and emergent problem to be resolved in actual production.There are two problems in predicting welding distortion of large and complicated shipstructure. One is how to ensure enough distortion tolerance; another is how to savecalculation time and cost. Thermal elastic-plastic finite element method is widely used innumerical simulation of welding, which needs computer memory of large capacity and takesmore time to calculate and now is not applicable to research of other large-scale andcomplicated structures apart from welded joint and small structures.The paper adopted the inherent strain theory that Japanese scholars brought forwardand studied the prediction of the distortion of the large and complicated ship structure on thebasic of inherent strain theory. Inherent strain method is a kind of relatively fast andeffective and approximate method, what’s more, it can make sure to get values of weldingdistortion accurately, which offers a strong and new tool in calculating values ofanti-deformation. Hence, this method must be really very important in practical significanceand be with pretty good future.This paper takes the seven examples as object, those examples adopted inherent strainmethod and finite element method of plastic shell element. Then, numerical simulating thewelding distortion of ship structures by special software Weld_sta. In the method on thebasic of inherent strain theory, getting a simplified formula is about a thickness parameter ofplates through a pretty large number of calculating and measuring datas and establishing aninherent strain database of ship structures welding. It is pretty possible to predict thewelding distortion of large hull structure on the basic of above mentioned.The study shows that the exclusive welding software Weld_sta on the basic of inherentstrain successfully predict welding distortion of hull structure, which provides a powerful and new tool for confirming value of anti-deformation and accuracy shipbuilding to achieve,providing a kind of new idea and method for predicting the welding distortion of large-scaleand complicated structure.Though the inherent strain finite element method can predict successfully the weldingdistortion of the large-scale and complicated ship structure, the more further research needgo on, because the effect factors of the welding were not all taken into account.