Prediction of dimensional changes during fabrication of thin shell ship hull bottom units

Abstract

The cumulative effect of distortion resulting from the welding of butts and stiffeners during the fabrication of ship hull units leads to an overall change in dimensions. This dimensional inaccuracy causes further erection difficulties owing to mismatch and misalignment. This problem has been addressed in the present work using the far field–near field concept. The near field has been assumed to extend from the weld line to a location where the peak temperature attained is 350°C, and the rest of the plate is far field. Plastic deformation is expected only in the near field, whereas the far field behaves elastically throughout the heating and cooling cycle. Measurements carried out on two units show a fairly good agreement with the calculated values.