Analysis of fretting fatigue initial crack path in Al7075-T651 using cylindrical contact.pdfVIP

Tribology International 108 (2017) 87–94 Contents lists available at ScienceDirect Tribology International journal homepage: /locate/triboint Analysis of fretting fatigue initial crack path in Al7075-T651 using cylindrical contact J. Vázquez?, C. Navarro, J. Domínguez Department of Mechanical Engineering, University of Seville, Camino de los Descubrimientos s/n, C.P. 41092 Sevilla, Spain MARK ARTICLE INFO Keywords: Fretting fatigue Cylindrical contact Al7075-T651 Crack initiation ABSTRACT This paper analyses the initial crack path in a fretting fatigue test of Al7075-T651 alloy with a cylindrical contact and compares the capability of some multiaxial fatigue criteria to predict the crack initiation path. The experimental crack initiation paths obtained in the tests are optically measured along the fracture surface using a focus variation technique. The Fatemi-Socie (FS) and Smith-Watson-Topper (SWT) multiaxial fatigue parameters obtained from an analytical model, allow us to determine the controlling parameters of the crack initiation process observed in the tests and to estimate the crack path during the early stage of the crack growth. 1. Introduction Fretting is a type of damage often found in mechanical joints subjected to time variable loads. In typical situations, these loads produce small relative displacements between contacting surfaces. These relative displacements, in conjunction with surface friction, lead to a contact stress/strain ?eld able to generate surface cracks. [1]. Worse circumstances occur in many actual cases, in which the mechanical joint is also subjected to a global ?uctuating load. This global load by itself may produce failure of the joint; however, in conjunction with the fretting-initiated cracks, failure becomes more likely [2]. There is much research on fretting fatigue related documentation and many agents have been identi?ed [3], many palliatives are available [4–6], many parameter in?uences have been investigated [2,10–12], and va