New parameter for characterizing and correlating impact-sliding fretting wear to energy dissipation-experimental investigation

Accurate prediction of fretting wear of heat exchanger tubes is critical for safe and economical operation of nuclear power plants. The 'work rate' parameter is commonly used to correlate wear losses to the integral effect of the contact load and the relative sliding distance between the tube and its support. The wear rate-work rate relationship is not unique, strongly dependent on the tube orbital motion, and exhibits unacceptable scatter in the data. In recent years, a weighted work rate parameter was proposed to reduce this scatter and improve the wear prediction. This parameter was, however, unsuccessful in correlating wear loses under normal impact conditions and is shown to be inconsistent. A new physically-meaningful parameter is developed in this investigation to characterize fretting wear under complex impact-sliding motions, and to correlate wear losses to energy dissipation in the contact zone. The derivation of this parameter is based on fracture mechanics analysis of the subsurface crack initiation and propagation processes. Experimental validation of the proposed parameter was carried out for different tube orbital motions. The results showed this parameter can significantly reduce the scatter in the correlation data, and accurately describe the wear mechanism.