The bendability of sheet met is an important factor in the design of forming processes such as the hemming process.

Traditional assessment of the formability of sheet metal materials using an FLC has some limitations in case of small radius over thickness ratios, non proportional strain paths and non-traditional forming materials with less formability, such as aluminum, titanium and high-strength steels. Ductile damage models can be used to improve the failure predictions.

A nonlocal damage model is presented, which avoids the mesh dependency problems of local damage modesl. It is implemented for both implicit and explicit finite element codes. The advantages and disadvantages of this model will be discussed. It is shown that this damage model is able to describe the bending failure mechanism correctly.

The nonlocal damage model contains some extra paramters, which have to be determined experimentally. Methods to identify these paramters of the damage model will be described.

The damage model is validated with results from bending experiments on aluminium sheet, where the sheet is bent - using a three-point bending test - until fracture occurs. Sheets without and with pre-strain, due to previous forming steps will be used.