An evaluation of parameters for predicting fretting fatigue crack initiation

There are numerous fatigue parameters that can be used to determine the onset of crack initiation in a component subjected to constant amplitude plain fatigue, This study evaluated how well some of these parameters predict fretting fatigue crack initiation in titanium alloy, Ti-6Al-4V. The following crack initiation parameters were evaluated; the strain-life parameter, the maximum strain corrected for strain ratio effects, the maximum principal strain corrected for principal strain ratio effects, the Smith-Watson-Topper (SWT) parameter, the critical plane SWT parameter and the Fatemi and Socie (F-S) parameter. The Ruiz parameters, which are specific to fretting fatigue condition, were also evaluated. The evaluation was based on the parameter's ability to predict the number of cycles to initiation and location for crack initiation. The results indicated that the maximum strain amplitude at the contact interface was an important parameter for fretting fatigue crack initiation. Furthermore, the results indicated that when the applied loading was corrected for the effects of contact and mean stress or strain ratio, titanium alloy, Ti-6Al-4V exposed to the fretting fatigue condition behaved in a manner similar to the plain fatigue condition. (C) 2000 Elsevier Science Ltd. All rights reserved.