Prediction of fretting crack location and orientation in a single crystal nickel alloy

Fretting is a structural damage mechanism that occurs when two clamped surfaces are subjected to an oscillatory loading. A critical location for fretting induced damage has been identified at the blade/disk and blade/damper interfaces of gas turbine engine turbomachinery and space propulsion components. The high-temperature, high-frequency loading environment seen by these components lead to severe stress gradients at the edge-of-contact that could potentially foster crack growth leading to premature component failure. Recently, a high-frequency, high-temperature load frame has been designed for experimentally investigating fretting damage of single crystal nickel materials employed in aircraft and spacecraft turbomachinery [Matlik, J., Farris, T., Haake, F., Swanson, G., Duke, G., 2007. High-frequency, high-temperature fretting experiments. Wear 261, 1367–1382]. A modeling method for characterizing the fretting stresses of the spherical fretting contact stress behavior in this experiment is developed and described. The calculated fretting stresses for a series of experiments are then correlated to the observed fretting damage. Results show that knowledge of the normal stresses and resolved shear stresses on each crystal plane can aid in predicting fretting fatigue initiated crack locations and orientations.