EXPERIMENTAL FRETTING-WEAR STUDIES OF STEAM-GENERATOR MATERIALS

Flow-induced vibration of steam generator tribes results in fretting-w ear damage due to impacting and rubbing of the tubes against their sup ports. This damage can be predicted by computing tube response to flow -induced excitation forces ruing analytical techniques, and then relat ing this response to resultant wear damage using experimentally derive d wear coefficients. Fretting-wear of steam generator materials has be en studied experimentally at Chalk River Laboratories for two decades. Tests are conducted in machines that simulate steam generator environ mental conditions and tube-to-support dynamic interactions. Different tube and support materials, tube-to-support clearances, and tube suppo rt geometries have been studied. The effect of environmental condition s, such as temperature, oxygen content, pH and chemistry control addit ive, have been investigated as well. Early studies showed that damage was related to contact force as long as other parameters, such as geom etry and motion, were held constant. Later studies have shown that dam age is I-elated to a parameter called work-rate, which combines both c ontact force and sliding distance. Results of short and long-term fret ting-wear tests for CANDU steam generator materials at realistic envir onmental conditions are presented. These results demonstrate that work -rate is an appropriate correlating parameter for impact-sliding inter action.