Abstract
A pneumatically driven elevated-temperature fatigue machine and its control are described briefly. The use of this machine to determine qualitatively the initial damping as well as the changes in damping of the test specimen during vibration are discussed. The variation in high-stress initial damping versus temperature has been determined qualitatively on four high-temperature alloys. The elevated-temperature damping has been checked qualitatively during continuous vibration at high stresses. Two materials with extremely high initial damping tended to lose a large portion of it with time. The other materials showed damping changes of as high as 25 per cent with some increasing and some decreasing. Most of the data were taken below the fatigue limit and at temperatures of 1200 F, 1350 F, and 1500 F.
