Semi-Analytical Methodology for Fretting Wear Evaluation of the Pitch Bearing Raceways Under Operative and Non-Operative Periods

Current methodologies for the evaluation of fretting in pitch bearing raceways only consider damage induced by oscillating control movements. However, pitch bearings can remain static for long operative and non-operative periods, and previous works have shown that load fluctuations cause fretting damage due the small movements and deformations at the contact. In this work a semi-analytical methodology is presented and an analysis of the fretting phenomenon in pitch bearing raceways under both productive and non-productive periods of static pitch control is accomplished. The analysis is performed following the energy-based wear model and the calculation of a total 30 times series of 10 minutes of duration concerning winds speeds from 3 m/s to 25 m/s. As result, critical locations, and critical times, defined as the maximum allowable time in the same position before the damage is developed, are presented for the different wind speeds. Additionally, a cumulative method is proposed for simplified calculations of variable winds.