Numerical simulation of T-bend of multilayer coated metal sheet using solid-shell element

The main aim of this paper is to model the T-bend test performed on multilayer coated metal sheets in order to measure the coating flexibility. Because of important uses of polymer coatings in many industrial applications and higher requirement on the quality of products, an accurate modeling of the T-bend process is therefore essential.
During the modeling with the finite element method, the large thickness ratio between the different layers is likely to produce elements with an unfavorable aspect ratio. Therefore, to avoid obtaining inaccurate results linked to the shape of the elements, solid-shell elements are used in this study. These elements are based on the Enhanced Assumed Strain (EAS) technique and the Assumed Natural Strain (ANS) technique. These techniques permit to avoid locking problems even in very bad conditions (nearly incompressible materials, very thin elements conducting to large aspect ratios, distorted element geometry…). The EAS technique artificially introduces additional degrees of freedom (DOFs) to the element. They permit to increase the flexibility of the element which is very efficient for several locking issues. On the other hand, the ANS technique modifies the interpolation scheme for particular strain components. The ANS technique proved to eliminate the transverse shear locking from the element in bending dominated situations. Besides, a numerical integration scheme dedicated to Solid-Shell elements was implemented. It uses a user-defined number of integration points along the thickness direction, which permits to increase the element accuracy with a mesh containing a reduced number of elements along the thickness direction.
The results obtained from numerical simulations are compared with some analytical results in order to check the strain predicted in the coated layer by FEM. This information helps to investigate the coating layer ductility in the real process.