A multi-step assembly process: drawing, flanging and hemming of metallic sheets
LIMATB, Université de Bretagne-Sud,
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This paper presents hemming tests on complex geometries, combining curved surfaces and radii of curvature in the plane. The samples are ﬁrstly prestrained in order to obtain a strain history prior to ﬂanging and hemming. The choice of the sample geometries as well as prior plastic strains is based on a survey of current geometries hemmed in automotive doors. A device has been designed to hem these samples both by classical and roll-hemming processes and to allow a comparison between both technologies. Roll-in, which characterizes the change of geometry of the hemmed zone between ﬂanging and hemming, and loads are obtained during this multistep process. Results show that roll-in observed in roll-hemming is lower than in classical hemming and that its evolution greatly diﬀers between the two processes. The analysis of the results on diﬀerent samples shows that it is diﬃcult to establish rules on the variation of other parameters in such a complex multistep process and that it requires an intensive use of numerical simulation.
© Owned by the authors, published by EDP Sciences, 2010