1. CEMMPRE Mechanical Engineering Department, University of Coimbra 1 , 3030-788 Coimbra, Portugal
2. LED&Mat-IPN, Instituto Pedro Nunes, Laboratório de Ensaios Desgaste e Materiais 2 , Rua Pedro Nunes, 3030-199 Coimbra, Portugal
3. Walker Department of Mechanical Engineering, The University of Texas at Austin 3 , Austin, Texas 78712