An ICME Modeling Application for the Optimization of a Tie-Down Weld Sequence in Ship Production

Abstract

Aircraft tie-downs have been widely used to secure airplanes, helicopters, and other transportation vehicles to a ship's deck. A multi-pass welding process is typically used for integrating tie-downs to the deck plate to develop the required strength at the joint. During and after welding, the surrounding deck material around the tie-downs must deform elastically to preserve dimensional continuity, creating residual stresses. Weld-induced residual stress is a major concern because the tie-downs are subject to cyclic, dynamic loading which could induce cracking and directly impact the fatigue life of the deck plate structures during services. To select an optimized welding sequence that minimizes weld-induced residual stress in the welded joint, an integrated computational materials engineering approach was used to evaluate the effect of welding sequences on residual stress distributions. Various deck materials (including ABS Grade DH36 and HSLA-100 steel alloys) and welding sequences were investigated to identify the optimized welding sequence which reduced radial residual stress distribution, resulting in lower final deck plate distortion. 1. Introduction Like many heavy industries, shipbuilding has a need for developing lightweight, high-strength, durable structures to improve payload capacity and mission performance, and reduce total ownership costs. The engineering design criteria and the thin-steel alloy material advancement developed to meet these requirements has outpaced the improvement of many manufacturing processes, necessitating a greater understanding of the influence of material properties on producibility issues during construction that could impact the performance of ship structures at sea. Residual stresses are "locked-in" stresses that develop in materials and structures because of welding or material handling processes during manufacturing that are independent of the presence of any external loads. Typical residual stress-induced buckling distortions in ship structures are developed as an elastic response to any incompatible local plastic strains that exist in the material after welding (Huang et al. 2003, 2004).