Special Seminar: Advances and Opportunities for Micromechanical Testing using High-Energy X-rays
Darren Pagan
2:30 PM on 2019-02-05
3-180 Keller Hall
Abstract: High-energy X-ray experiments performed at synchrotron X-ray sources provide a unique means to probe the microstructure and micromechanical response of structural materials, including engineering alloys, during in-situ deformation. This talk will give an overview of how these new diffraction-based techniques can probe and reconstruct the deformation state of crystalline materials. Example applications of these techniques being used to study relevant materials problems including strain localization, deformation-driven phase transformations, and damage initiation will also be provided. In addition, the unique benefits of these measurements in comparison to traditional macroscopic mechanical testing will be highlighted with a detailed description of how far-field high-energy diffraction microscopy measurements, combined with finite element modeling, are used to deconvolve various crystallographic slip mechanisms in a hexagonal phase titanium alloy. This talk will conclude with a discussion of future avenues of technical development and scientific research regarding X-ray experiments, micromechanical constitutive modeling, and application to materials processing and design.
Bio: Darren Pagan is the X-ray scientist overseeing the structural materials science program at the Cornell High Energy Synchrotron Source (CHESS). Darren earned a B.S. degree in mechanical engineering from Columbia University in 2010 and his Ph.D. in mechanical engineering from Cornell University in 2016. His dissertation research focused on developing crystal kinematic and X-ray scattering models for measuring heterogeneous plastic deformation in single crystals during thermo-mechanical loading from in-situ X-ray data. As a postdoctoral researcher at Lawrence Livermore National Laboratory, Darren developed new methods for integrating diffraction data with crystal plasticity finite element modeling and used X-ray techniques to characterize granular material deformation in-situ under quasi-static and dynamic loading conditions. Darren’s current research focuses on developing new methods for quantifying intra-crystal stress fields and new experimental capabilities for characterizing microstructure evolution during materials processing.