Experimental and numerical analysis of residual stresses and strains induced during cold bending of thick steel plates

The paper presents an experimental and numerical analysis of the residual stresses and strains induced during the cold bending of thick steel plates. Cold bending technique is widely used in the shipbuilding and offshore industry, and thus it is important to know about the changes in the material characteristics induced during the metal fabrication process. For this purpose, firstly, three-point cold bending experiments are conducted with a relatively small indenter on the specimens cut from a thick steel plate (54 mm), and afterwards, tension tests are carried out on tensile coupons cut from the already bent specimens. Thus, the mechanical properties (engineering stress-strain curve) of the tensile coupons cut from the loaded and unloaded locations are compared so that to determine the residual stresses and strains resulting from the bending process. A numerical simulation is performed with the explicit LS-DYNA finite element solver to replicate the experimentally determined residual stresses and strains. The simulation provides information of the distribution of the residual stresses and strains along the span and through the thickness of the specimens. It is found that the local deformation underneath the indenter harms severely the structural integrity, producing large residual stresses and strains during the bending process. This work illustrates the potential use of finite element analysis to evaluate the residual stresses and strains in metal fabrication processes.