Thermo-mechanical Tensioning: A Distortion Mitigation Tool for Shipbuilding Industry

O P Sha; Amith Gadagi; Sharat Kumar; N.R. Mandal

Abstract

Thin plates are widely used in ship building to lower the weight of the hull structure so as to have a gain in pay load as well as to improve fuel efficiency. But the fabrication of the structures involving the thin plates suffers weld induced buckling because of their lower critical buckling strength. So, there is a need to mitigate these weld induced buckling distortions by employing proper distortion control techniques. In view of this, an active in-process distortion control technique called Thermo-Mechanical Tensioning (TMT) is developed. The weld induced buckling occurs when the compressive residual stresses in the far-field zone exceeds the critical buckling strength of the panels being fabricated. TMT aims at reducing the magnitude of peak tensile residual stresses, thereby reducing the corresponding self-equilibrating compressive residual stresses in the far-field zone. Thus the weld induced buckling gets mitigated. The developed TMT method proved to be simple yet effective technique in the mitigation of weld induced buckling distortions. In this study, the method of TMT is explained and a validated numerical model is used to demonstrate the effectiveness of TMT. The numerical results show that, there is a considerable reduction in the welding distortions and weld induced residual stresses by employing TMT.