1. Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, Leics. LE11 3TU, UK
2. Lehrstuhl fu¨r Mechanik und Christian-Doppler-Laboratorium fu¨r Moderne Mehrphasensta¨hle, TU Mu¨nchen, Boltzmannstr. 15, D-85747 Garching, Germany