1. College of Engineering, Department of Mechanical Engineering, Otterbein University 1 , Westerville, Ohio 43081, USA
2. Department of Mechanical Engineering, Texas Tech University 2 , Lubbock, Texas 79409, USA
3. Applied Mechanics Laboratory, Faculty of Science, University of Yaounde I 3 , P.O. Box 812, Yaounde, Cameroon
4. Faculty of Military Science, Stellenbosch University 4 , Private Bag X2, Saldanha 7395, South Africa