9416775 Kassner This is a high-risk, small grant for exploratory research (SGER) to perform in-situ fatigue experiments in the transmission electron microscope. The classic metal-fatigue phenomenon is poorly understood, partially because the dislocation dynamics of reversed deformation has not been characterized. Only limited success has been achieved with direct observation of dislocations during cyclic deformation, such as observed in in-situ cyclic or reversed plastic deformation tests in the transmission electron microscope. The problem is associated with buckling of thin foils when the applied tensile or shear stress is reversed. Analysis shows that dislocation movement can be reversed by tensile stressing in alternating perpendicular directions, and buckling of the foil can be avoided. A new specimen holder has been designed by the principal investigator for performing such mechanical tests in-situ in the transmission electron microscope. A series of in-situ reversed deformation fatigue tests will be run and should provide new insights into reversed deformation phenomena. %%% Fatigue of metal alloys can lead to unanticipated failure of metal alloy components used in industrial machinery, transportation systems, and related infrastructure areas. This research should provide improved understanding in this field. ***
