Dry Sliding Friction Experiments at Elevated Velocities A. Lodygowski*, L. Faure † , G. Z. Voyiadjis* and S. Philippon ‡ * Department of Civil and Environmental Engineering, Louisiana State University (L.S.U.), 3508-B Patrick F. Taylor Hall, Baton Rouge, LA 70803, USA † Laboratory of Physics and Mechanics of Materials (La.P.M.M.), University of Metz (U.P.V.M.), Ile du Saulcy, 57045 Metz, France ‡ Laboratory of Mechanics, Biomechanics, Polymers and Structures (La.B.P.S.), National Engineering School of Metz (E.N.I.M.), Ile du Saulcy, 57045 Metz, France ABSTRACT: An enhancement of an existing tribometer device developed by Philippon et al. (2004, Wear 257, 777–784) is presented in this work. This experimental device is made up of a dyna- mometer ring and a specific load sensor allowing to apply an apparent normal force on specimens and to measure frictional forces respectively. Problems such as static calibration of both distinct parts supported by conducted numerical simulations is given and described in detail. Further dis- cussion, again supported by numerical analysis, validates the placing of the strain gauges and explains the problems of sensitivity of loading surface and cross-sensitivity. The entire experimental setup is then discussed explaining the mounting of the strain gauges located on the tribometer device, showing the configuration of the Wheatstone quarter-bridges, presenting the signal conditioning amplifier system and the digital oscilloscopes which all together create one uniform data acquisition system. The set up is adapted on a gas gun to carry the Steel 1080 on Steel VascoMax 300 experiments. The main set of experiments with sliding velocities varying from 10 to 60 m s )1 are performed in the same tested setup. The recordings of normal and tangential forces leading to the friction coefficient determination are discussed. The values of dry friction coefficient l according to the experimental parameters are in good agreement with those observed in the literature. Using this new configuration, the effects of the sliding velocity on the surface roughness changes and on the dry fiction coefficient are also investigated. Moreover, very interesting relations between wear and sliding velocity are observed. KEY WORDS: dry friction, high velocity, roughness, wear Introduction The setup used in this research represents a signifi- cant evolution of an original friction apparatus developed by Philippon et al. [1] and used by Sutter et al. [2] for high-speed machining investigation. Dry friction coefficient l for a sliding pair of materials, defined in 17th century by G. Amontons and later in 18th by C.A. Coulomb, is obtained by the ratio between the tangential (or frictional) force F T because of friction and the apparent normal force F N applied on the sliding surface S. In the original configuration [1, 2], the value of F N , calibrated before the test, is applied by the use of a dynamometer ring and is assumed to be constant during all the friction process. Tangential force F T is determined with a specific load sensor based on the elastic deformation of a thin tube where a set of two strain gauges are glued. The new configuration, presented here, allows controlling and measuring the value of apparent normal force F N during the friction process. A new dynamometer ring whose stiffness has been increased in comparison with the original version is also equipped by addi- tional two strain gauges; each of them is connected to form a Wheatstone quarter-bridge. Therefore, a possible variation of the apparent normal force F N can be recorded and observed. The higher velocities (V > 30 m s )1 ) and higher normal pressure (p > 5 MPa), not possible to obtain on commonly used pin-on-disc method, can be generated by modified torsional pressure Split- Hopkinson bar [3, 4], pressure-shear plate impact [5–7] or with a spun steel ball grabbing with other samples [8]. In particular, for investigating friction behavior, the torsional Kolsky bar designed to monitor high strain rate behavior [3] can be modified 436 Ó 2010 Blackwell Publishing Ltd j Strain (2011) 47 (Suppl. 2), 436–453 doi: 10.1111/j.1475-1305.2010.00785.x An International Journal for Experimental Mechanics