Determination of Residual Stress and Elastic Strain Fields During Cold Expansion Processing Using Complementary Diffraction Techniques

Monday, October 20, 2025: 11:20 AM
Dr. Nicholas A. Bachus , University of California, Davis, CA
Dr. Donald W. Brown , Los Alamos National Laboratory, Los Alamos, NM
Dr. Christopher Budrow , Budrow Consulting LLC, Loudonville, NY
Dr. Michael E. Burba , Air Force Research Laboratory, Dayton, OH
Dr. Bjørn Clausen , Los Alamos National Laboratory, Los Alamos, NM
Dr. Adrian T. DeWald , Hill Engineering, LLC, Rancho Cordova, CA
Dr. Peter Ko , Cornell High Energy Synchrotron Source, Ithaca, NY
Dr. Kelly Nygren , Cornell High Energy Synchrotron Source, Ithaca, NY
Dr. Mark Obstalecki , Air Force Research Laboratory, Wright-Patterson AFB, OH
Robert T. Pilarczyk , Hill Engineering, LLC, Rancho Cordova, CA
Dr. Renan L. Ribeiro , Hill Engineering, LLC, Rancho Cordova, CA
Dr. Paul Shade , Air Force Research Laboratory, Wright-Patterson AFB, OH
Dr. Matthew Shultz , Fatigue Technology Inc, Seattle, WA
Prof. Michael R. Hill , University of California, Davis, Davis, CA
Synchrotron x-ray and time-of-flight neutron diffraction measurements are used to determine elastic residual strain and stress fields in the vicinity of geometrically large holes in 7050-T7451 aluminum plate samples caused by cold expansion (Cx) processing. Cx is widely used in the aircraft industry to improve the fatigue resistance of critical components containing fastener holes. Recent model development reveals a large discrepancy between computed and measured residual stress fields. The Los Alamos SMARTS and Cornell FAST diffractometers are used to determine the residual stress and strain fields in partially (50%) and fully (100%) processed samples. Consistent strain trends are observed in both samples for the two types of measurements, with the datasets being complementary: neutrons offering determination of stress, and x-rays revealing fine spatial variations of strain. Together these data provide opportunities for improving process models of Cx.
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