1. Laboratory of Strength and Materials, Department of Mechanics, Faculty of Applied Sciences, National Technical University of Athens, Zografou Campus, Theocaris Building, Athens 157 73, Greece
2. State Engineering University of Armenia, 105 Terian Street, Yerevan 375009, Armenia
3. Institute of Mechanics, National Academy of Sciences of Armenia, 24 Marshall Baghramian Avenue, Yerevan 375019, Armenia