Estimation of the coefficient of friction in partial slip contacts between contacting nickel superalloys.pdfVIP

Tribology International 108 (2017) 156–163 Contents lists available at ScienceDirect Tribology International journal homepage: /locate/triboint Estimation of the coe?cient of friction in partial slip contacts between contacting nickel superalloys R.M.N. Fleury?, R.J.H. Paynter, D. Nowell Department of Engineering Science, University of Oxford, Parks Road, OX1 3PJ Oxford, UK MARK ARTICLE INFO Keywords: Friction Fretting Partial slip Contact mechanics ABSTRACT Standard methods for measuring the coe?cient of friction between two objects are not appropriate for partial slip contacts, since less damage occurs at the interface. A discussion on the di?erent methods for measuring the coe?cient of friction in partial slip contacts is carried out. Results of the coe?cient of friction between Nickel superalloys, measured by a non-sliding technique, are presented. The e?ect of crystal orientation of singlecrystals on the friction coe?cient was found to be small. A study for using the energy dissipated in twodimensional partial slip contacts is also presented. An approach for measuring the friction coe?cient using the dissipated energy is proposed and the challenges and di?culties in measuring friction through the dissipated energy at the contact are discussed. 1. Introduction Fretting fatigue occurs primarily in partial slip contacts. Although the surface wear in partial slip is not as signi?cant as in gross sliding contacts, the small slip region in the contact may accelerate crack initiation and propagation, reducing the fatigue life of components. Vingsbo and S?derberg [1] have shown through their map of di?erent fretting regimes that wear may inhibit crack initiation in gross sliding contacts, when material is removed before cracks can initiate. In partial slip contacts, on the other hand, cracks are more likely to initiate and propagate. One of the main di?culties in analysing partial slip problems is that the coe?cient of friction is generally unknown inside the contact z