Some Observations on the Relationship Between Fatigue and Internal Friction

Abstract

An investigation has been conducted to determine the internal friction and fatigue strength of commercially pure 1100 aluminum under repeated stressing in torsion at various temperatures and stress levels in an effort to find if there exists any correlation between internal friction and fatigue characteristics. For this investigation a torsional fatigue-testing machine of the resonant type was designed with facilities for measuring internal friction at low stress levels. Results indicate the existence of a critical temperature at which the fatigue life of the specimens appears to reach a minimum value. The effect of this temperature on the internal friction at various stress levels was quite substantial. In addition, the phenomenon of the recovery of internal friction during brief periods of rest was discussed. The recovery of internal friction was observed to depend upon the stress level and temperature of testing.