SIMULATION OF WELDING DEFORMATION FOR ACCURATE SHIP ASSEMBLING (3RD REPORT) - OUT-OF-PLANE DEFORMATION OF BUTT WELDED PLATE

A 3-D thermal-elastic-plastic FEM was developed to simulate the out-of-plane deformation caused by one-sided automatic submerged arc welding. Efforts have been made to improve the reliability and accuracy of the FEM calculation. To prevent the phenomenon of transverse-shear-locking, which is observed as over estimation of the stiffness of a plate for a bending problem when solid elements are used, the reduced integration method is employed and shown to be effective. A special type of spring-element is utilized to deal with the contact problem between the plate and the working table. Using the 3-D FEM, the effects of various factors, such as gravity, the method of supporting, magnetic constraint and force from the backing near the welding line have been investigated. The results of the numerical simulation explain the phenomena observed in an actual shipyard. In the case of FCB automatic submerged arc welding which features large heat input, out-of-plane welding deformation is mainly affected by the constraint condition. The gravity of the plate and the backing force have great influences on the shape of angular distortion. Magnetic constraint can reduce the welding deformation effectively.