A new Device for Determination of Forming-Limit-Curves under Hot-Forming Conditions

Forming-Limit-Curves (FLCs) are widely used to characterize the forming behaviour of materials. Nevertheless, the determination of FLCs for hot forming processes is a challenging and time-consuming procedure. At the Chair of Automotive Lightweight Design, a new device for the determination of FLCs under hot forming conditions was developed. In a sealed isothermal oven atmosphere, blank holder, die and punch are used for the FLC determination relying on the DIN EN ISO 12004-2. External hydraulic forces actuate the punch and blank holder. To ensure insulation from the thermal load set inside the hot oven atmosphere an innovative cooling system with extensive use of additively manufactured components with integrated cooling channels is used. For the feed of the different deep drawing tests geometries an airlock is installed, which allows keeping the temperatures constant during the testing procedure. Afterward the forming limits for the different geometries are evaluated with optical measurement systems. The developed test rig proved the ability to determine FLCs for isothermal temperatures up to 800 degrees C.