Ultrahigh Cycle, High Frequency Fatigue

We have developed a unique capability for high temperature fatigue testing in the kHz frequency range for characterization of the refractory-rich metallic and CMC materials. The high temperature fatigue apparatus consists of a load line connecting a series of components tuned to 20 kHz, including an ultrasonic converter that provides a controlled sinusoidal displacement and an ultrasonic horn that amplifies the axial displacement. This assembly is located within a hydraulic load frame that can superimpose static loads. Testing can be conducted on conventional fatigue specimens or on small sheet samples using a carrier specimen that resonates, imposing a displacement on the thin specimen attached. This system has been utilized for high cycle fatigue testing of Ni-base single crystal specimens at temperatures up to 1000˚C with samples as thin as 150 μm. Various heating approaches have been utilized, including induction heating for larger samples and microtorch approaches for small sheet samples.


Tresa Pollock

Research interests include the mechanical and environmental performance of materials in extreme environments, unique high temperature materials processing paths, ultrafast laser-material interactions, alloy design and 3-D materials characterization.