1. Fraunhofer Institute for Mechanics of Materials (IWMH), Heideallee 19, D-06120 Halle, Germany. Tel.: +49(0)345 / 5589 117, Fax: +49(0)345 / 5589 101, matthias.ebert@iwmh.fraunhofer.de
2. Fraunhofer Institute for Mechanics of Materials (IWMH), Heideallee 19, D-06120 Halle, Germany