Analytical description of the forming process of a double curvature shipbuilding plate
J. van Cappellen (TU Delft - Mechanical Engineering)
C. L. Walters – Mentor (TU Delft - Ship Hydromechanics and Structures)
JFJ Pruijn – Graduation committee member (TU Delft - Ship Design, Production and Operations)
Wei Jun Wong – Graduation committee member (TU Delft - Ship Hydromechanics and Structures)
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Abstract
The forming of double curvature shipbuilding steel plates is performed by experienced craftsmen at IHC Metalix. Their experience will get lost when they retire; therefore, it can be valuable for future metal workers to capture the forming process of a double curved plate theoretically. An analytical description and understanding of the forming process will help craftsmen. In the future, it could even lead to the development of automatic forming machines.
This research investigates plastic deformation initiated by a rolling and a three point bending machine forming a saddle shaped plate. A 2Doptimization for the three point bending process is performed using beam theory. A single bend is validated by a 2D Finite Element Analysis (FEA). The rolling process is analytically described by equations obtained from literature. These equations are used to find a relation between the material stretching/membrane strains and the rolling forces. Furthermore, an elastic perfectly plastic stress strain curve is used. Material hardening and residual stresses due to repeated bending or rolling operations are not taken into account.
The bending optimization resulted in the least number of bending operations needed over a cross section, assuming the cross section behaves like a beam. The rolling equations resulted in required rolling forces for a desired membrane strain. The craftsmen know by experience that bending operations should be performed first to initiate a first curvature. Thereafter, the plate is rolled to initiate the second curvature and form the saddle shape.
In this thesis, the first steps are taken to capture and predict the manual forming process of double curvature steel plates. Future work on this topic should take the 3D-effects of the three point bending into account which lead to more accurate analytical descriptions. Furthermore, other assumptions could be analyzed to get better understanding of their contribution.