Operator-split damage-plasticity applied to groove forming in food can lids

This paper presents a numerical–experimental analysis of damage engineering applied to a well-known industrial problem. Many food cans are manually opened by raising a tab on the lid, thus initiating a crack, which is propagated along a circumferential groove. The influence of the groove geometry and depth on the opening force and the resistance against premature opening is investigated for some packaging materials, by making use of dedicated experimental techniques and an operator-split damage-plasticity framework. Attention is focused on a small part of the groove at a location halfway the circular crack-path, 90⁰ from the crack initiation point. First, the groove manufacturing is analyzed by pressing a punch into a thin sheet of the material. Grooved specimens are loaded in tension, simulating the internal pressure during sterilization, and in shear, simulating the opening. Experiments have been carried out using a miniaturized tensile/compression stage located in the objective field of an optical microscope. For the computational analysis, an operator-split damage-plasticity model is proposed, where ductile damage is easily operated in conjunction with standard plasticity models. Simulations are done within a geometrically non-linear context, using a hypo-elasto-plastic material model with non-linear hardening and a contact algorithm to simulate the contact bodies in the groove forming process. An arbitrary–Lagrange–Euler (ALE) technique and adaptive remeshing are used to assure mesh quality during the large deformation process. The operator-split procedure used for the solution of the governing equations, allows to make easy use of a non-local damage operator as an extra feature within a commercial FEM package. Experimental results reveal that a reduction up to 20% for the opening force with unchanged pre-opening resistance can be reached with the use of an asymmetric punch for the groove forming. Numerical and experimental results are in good agreement. Simulations show that the industrial process of can lid production can be optimized considerably by controlling damage evolution in the first stage of the process.