Prediction of formability extension in deep drawing when superimposing a thermal gradient

摘要

The stamping processes are up to now widely utilised in mechanical industries for producing several typologies of products, ranging from computer industry to automotive components, from house products to furniture production. Anyway, the research of the best process performance for reducing the number of manufacturing steps has been very active in these last years. In fact, some interesting innovations have been introduced in this scenario: hydro-assisted processes and incremental forming operations are just pregnant examples in this direction. On the other hand, some interesting studies have been proposed also on the traditional processes, introducing some improvements aimed to extend formability limits and, finally, to reduce the manufacturing costs. In this paper an interesting simple enhancing of formability in deep drawing processes is presented. In the above process, a localised heating of the blank is obtained by using an electric heater. In addition, a cooling equipment ensures a low temperature at the centre of the sheet, in correspondence of the punch acting zone. In this way a decreasing of the material strength is obtained on the flange, causing a reduction of the axial stress on the vertical wall of the part. At the same time the material strength does not change at the bottom part, where the principal stress is applied. In this way a formability enhancing is easily obtained. An accurate justification from a theoretical point of view and a suitable prediction of the limit conditions are given-by using a customised FE simulation. An experimental assessment of the analysis has been carried out by using a properly designed and manufactured equipment.