1. Department of Mechanical and Mechatronics Engineering, Tshwane University of Technology, Pretoria, South Africa
2. Department of Mechanical and Industrial Engineering, University of Johannesburg, Doornfontein Campus, Johannesburg, South Africa
3. Centre for Nanomechanics and Tribocorrosion, School of Mining, Metallurgy and Chemical Engineering, University of Johannesburg, Johannesburg, South Africa