1. Dynamics and Vibrations Group Technical University of Darmstadt Dolivostr.15 64293Darmstadt Germany
2. Graduate School of Computational Engineering Technical University of Darmstadt Dolivostr. 15 64293Darmstadt Germany
3. Design and Production Engineering Dept., Faculty of Engineering Ain Shams University ElSarayat St. 1 11517Cairo Egypt
4. Mechanical Engineering Dept. Pontifícia Universidade Católica do Rio de Janeiro Rio de Janeiro Brazil