Numerical Simulation and Experimental Investigation of Residual Stress in Multi-Pass Butt-Welded Joints of Q235 Thick Plates for Engine Structures

Abstract

Localized heating and repeated thermal cycling during thick-plate multi-pass welding can produce a complex residual stress state, which may impair the structural reliability of welded components used in marine engines. This study investigates a 55 mm-thick Q235 steel butt joint with a K-groove deposited in 12 passes. Blind-hole testing was conducted on the joint after welding to determine its transverse and longitudinal residual-stress components, whereas the entire welding sequence was simulated using a three-dimensional sequentially coupled thermal–mechanical finite element model. A Goldak double-ellipsoidal formulation was adopted for the moving heat input, sequential element activation was used to represent weld-metal deposition, and the source dimensions were calibrated against the molten-pool geometry of the individual passes. The predicted stress field showed pronounced tensile concentrations in the weld metal and heat-affected zone. The asymmetric K-groove and the alternating placement of weld beads between the two groove flanks produced uneven thermal behavior and an asymmetric residual-stress field across the joint. After welding, the peak transverse and longitudinal residual stresses were approximately 256 and 302 MPa, respectively, and the maximum von Mises stress following the final pass was about 303 MPa. The measured data followed the overall surface-stress profiles obtained numerically, supporting the applicability of the model to residual stress assessment in thick Q235 multi-pass joints. These findings provide a basis for welding-procedure refinement, residual stress evaluation, and structural safety assessment of thick welded components in marine-engine applications.