Study of the mechanical properties of sheet metals drawn through drawbeads

Abstract

The use of modern materials leads to a need for detailed knowledge of the material flow. Drawbeads are one common way to control serial forming processes. Although they are already well investigated, the effect on the resulting mechanical properties after a drawbead passage is not analysed in detail yet. This work is showing the influence of a drawbead geometry used in deep drawing on typical mechanical properties. Therefore, different sheet metal materials are preloaded in a modified strip drawing test with commonly used drawbeads. In testing, three different levels of pressure between 2.5 MPa and 7.5 MPa and of drawing speed between 10 mm/s and 50 mm/s are combined to nine variations and are examined. Afterwards, specimens are cut out by a laser cutting machine of the drawn strips. Those specimens are then tested with the use of an optical measurement system. Results are discussed in relation to blankholder pressure, drawing velocity and drawbead geometry to work out the main effects. Overall it can be stated, that variations of blank holder pressure and drawbead height lead to significant changes for the material properties. A variation of the drawing velocity in the observed range does not show significant effects.

Robust Optimization and Kriging Metamodeling of Deep-Drawing Process to Obtain a Regulation Curve of Blank Holder Force

“…To control material flow during drawing operation in order to achieve the optimal forming of a part without cracks and wrinkles, it is generally necessary to slow down the sliding of the blank regions that flow more easily. This can be achieved by calibrating the blank holder force and eventually by drawbeads, which are rib-like projections mounted on the binder and designed with the aim of improving the metal flow control [2]. For better effectiveness, during the stamping phase, the action of the drawbeads and the force on the blank holder can be differentiated in the different regions of the sheet.…”