Date of download: 12/31/2017 Copyright © ASME. All rights reserved. From: General Procedure for Selecting and Testing Materials and Coatings in Response to a Tribological Problem J. Tribol. 2016;139(3):031302-031302-12. doi:10.1115/1.4034331 Figure Legend: (a) Air compressor where a deformable four-piston kinematic chain rotor rotates inside a fixed ovoid shape stator leading to the volume variation of compression/admission chambers and (b) modeling of the contact geometry which is a linear contact