Analysis of the Contact Area of Smooth and Rough Surfaces in Contact with Sphere Indenter Using Finite Element MethodKartini, E. Saputra, R. Ismail, J. Jamari and A.P. BayusenoMATEC Web of Conferences, 58 (2016) 04007DOI: https://doi.org/10.1051/matecconf/20165804007