Investigation of longitudinal bending distortion of a double-side edge welded fin plate by study of plastic zones

The Okerblom’s theory of double-side welded structures states that the resultant longitudinal bending distortion will not be zero in structures that are welded with equal heat input on both the sides of centre of gravity axis, on account of smaller plastically deformed zone near the second weld. However, investigations have not been performed thus far in exploring why such a phenomenon happens. This is the gap that this research work addresses. Accordingly, investigations were made by performing welding on both the edges of a rectangular fin plate using gas metal arc welding (GMAW) both by experimentation and by finite element (FE) simulation using SYSWELD software. Von Mises stress plots and transient strain plots of few elements near the first and second edge of the fin plate were analysed to study their relative influence in causing the plastic deformation of the elements. The analysis showed that the smaller size of the plastic zone formed near the second edge weld was mainly due to the presence of residual tensile strain on the second side elements, formed as result of the weld laid on the first edge of the fin plate.