Abstract: Fatigue remains to be a critical and challenging issue for engineers and scientists.  During cyclic loading, the stress state and structure of the material are evolving, which results in a dynamic problem with many variables to consider.  Given the vast microstructure variations in structural engineering materials, it poses a problem of how the uncertainty in the microstructure propagates to variability in the fatigue response of the material.  Of greater interest to our community, is how do we account for the uncertainty in defect/microstructure distributions within our material in our life predictions and analysis.  The focus of this talk will be an overview of research efforts to understand, model, and verify activities for crack nucleation resulting from persistent slip bands.  Results from in situ fatigue experiments, in the form of (i) concurrent digital image correlation and electron backscatter diffraction and (ii) high energy x-ray diffraction microscopy, are discussed to map strain evolution relative to the materials microstructure.  Finally, we note that as a result of fatigue life limitations in gas turbine applications, many components are overdesigned leading to increased weight and lower operating temperatures of the engine.  Thus, significant energy efficiency benefits exist with better fatigue life prognosis.

Bio: Michael D. Sangid received his B.S. (2002) and M.S. (2005) in Mechanical Engineering from the University of Illinois at Urbana-Champaign (UIUC).  After his Master’s degree, Dr. Sangid spent two years working in Indianapolis, IN for Rolls-Royce Corporation, specializing in material characterization, fatigue, fracture, and creep of high temperature aerospace materials before resuming his education in 2007.  He received his PhD in Mechanical Engineering from UIUC in 2010 and continued as a post-doctoral associate.  In the spring of 2012, Dr. Sangid started as an assistant professor at Purdue University in the School of Aeronautics and Astronautics with a courtesy appointment in Materials Engineering, where he continues his work on building computational materials models with experimental validation efforts.  He is a recipient of the TMS Young Leaders Award, the ASME Orr Award, and the AFOSR, ONR, and DARPA Young Investigator/Faculty Awards.