1. INM - Leibniz Institute for New Materials; Campus D2 2 66123 Saarbrücken Germany
2. Department of Materials Science and Engineering; Saarland University; Campus D2 2 66123 Saarbrücken Germany
3. Fraunhofer Institute for Nondestructive Testing (IZFP); Campus E3 1 66123 Saarbrücken Germany
4. Department of Mechanical Engineering; University of California; Santa Barbara CA 93106 USA