Flanging and Hemming of Auto Body Panels using the Electro Magnetic Forming technology
Electro Magnetic Forming (EMF) technology has a great number of potential applications for the automotive industry. LABEIN-Tecnalia has worked with this technology for six years and has a good understanding of the automotive industry’s needs and challenges. LABEIN-Tecnalia is currently developing new applications with EMF technology. Taking into account the advantages and limitations of EMF, bending and hemming processes present good geometric conditions for the use of this technology. The study presented is based largely on hemming circular configurations which are simplifications of those commonly used on hemmed automotive parts. The parameters of this new EMF bending and hemming processes have been studied, as well as their influence on the final quality of the parts obtained. Conclusions obtained from the basic geometries were tested on a more complicated geometry in order to apply the knowledge acquired. Parallel to the experimental work, fully coupled electromechanical software by LS-DYNA has been used to simulate and extend the present hemming results.
Study and Simulation of Critical Factors Affecting Final Quality in Electromagnetically Hemmed Automotive Aluminum
A previous study on electromagnetic forming (EM) hemming technology carried out in TECNALIA showed the real capability of this high speed deformation method to produce quality hemmed parts (Jimbert et al., J. Mater. Process. Technol. 211:916–924, 2011). Continuing with the development of this promising new application for the EM technology, some new experiments were run. The objective of this study is to focus on the critical processing factors that affect the final quality of the electromagnetically hemmed parts. For this purpose, an experimental plan was designed changing different input parameters and output quality parameters measured to quantify the results. The flange height limit was obtained for the studied experimental setup and was established at 10 mm. The bending radius and the gap between the inner and the outer part have to be keep to the minimum to increase final quality. In parallel to the physical experiments, EM hemming simulations were carried out using an EM loose coupling simulation method. An EM hemming process simulation of a circular whole part was carried out using shell elements. Results were compared with cross section simulations of the hemmed union using solid elements in order to analyze the importance of the type of element used for EM hemming simulation. Simulations revealed that solid elements reproduce quality aspects better than shell elements.
Improvement of hem quality by optimizing flanging and pre-hemming operations using computer aided die design
Abstract Flanging and hemming of straight edge-flat surface (plane strain) aluminum killed-draw quality steel was investigated restricting the study to the radius flat hem with an inner sheet. The major process parameters in straight edge hemming were determined and relations between them and some forming defects were established. Among these parameters were flanging die corner radius, pre-hem path, pre-hem stroke and final hemming force. Possible process and tool design modifications, which may lead to quality improvements in hemming were tested experimentally and using FEM. The commercial finite element program DEFORM was used to simulate the flanging and hemming operations including springback, and the predictions were compared with limited experimental results. Results of the experiments and simulations were summarized in the form of trend-lines for the use of process and die designers.