An energy approach for impact wear in water environment

Abstract

Wear induced by repetitive impacts between steam generator tubes and anti-vibration bars in pressurized water reactors is studied with an analytical impact wear apparatus. Repetitive impacts between an Inconel tube sample and a stainless steel flat bar target are performed in water environment at ambient temperature. Incident energy and angle of impacts are controlled, normal and tangential loads during impact are measured as well as rebound energy and angle of impacts. Impacts characteristics are deeply analyzed and interdependences are highlighted. In particular, the evolution of restitution coefficient, ratio between tangential and normal impulses during impacts, energy loss and sliding distance during impacts versus incidence angle are identified. Impact wear is found to be strongly dependent to impact dynamics, in particular it is observed to be proportional to energy loss during impacts and dependent to incidence angle with a maximum near 20° to the tangential axis. Microscope observation of the wear scars shows the existence of numerous abrasive scratches whose length corresponds to the sliding distance during impact. An impact model is introduced to express energy loss and sliding distance as functions of incidence angle, incident energy, restitution coefficient and impulse ratio. Experimental wear is observed to be dependent on both incidence angle and energy loss.