This work would not have been completed without the support and guidance of several people over the course of completing my Ph.D.First, I would like to sincerely thank my supervisor Professor Vassilios Kalpakides for his immense help in shaping this work. Professor Kalpakides was always near for any kind of problem that has arisen during the preparation of this thesis. He is the kind of teacher that inspires trust and close to him i have learned that research requires patience and dedication. I would also like to thank Pr. Evangelos Hadjigeorgiou for his guidance and valuable discussions through the preparation of my thesis. I also thank Professor Cristian Dascalu, who accepted to be an advisor and even though he was far away, he kept watching my progress with great interest. I sincerely thank my many colleagues in our mechanics of materials research group for their support and encouragement during my course of study. Most importantly, I would like to thank my family and all my good friends. I could not have achieved this goal without their love and support. I especially thank my brother Alexandros and my sister Peny for their encouragement and love.Finally, I would like to thank the Department of Materials Science and Engineering for its warm hospitality and the State Scholarships Foundation (I. K.Y.) of Greece for providing a scholarship which supported financially this research.