This paper presents the results of a study to develop a methodology for predicting torsional fatigue damage to a turbine-generator rotor subjected to transient electrical disturbances. This methodology used torsional properties obtained from constant amplitude tests on 25.4-mm-diameter specimens. The predictions were verified with constant amplitude and variable amplitude tests of specimens up to 127 mm in diameter.

The constant amplitude tests gave the following results:

1. Fatigue reduction factors for notched specimens were readily estimated from Neuber's rule.

2. Size effect could be approximated by lowering the strain-life curve by a function of the diameter ratio.

3. Uniaxial and torsional fatigue properties and cyclic stress-strain properties correlated on octahedral shear stress and strain using a deformation theory of plasticity.

Variable amplitude loading tests indicated that range pair cycle counting technique and linear damage rule predicted fatigue lives within a factor of two of actual test results. In addition, the predicted lives were generally conservative.