Physics Colloquium: Using high energy X-ray diffraction and finite element models to understand multiscale material behavior

Event Details

  • Speaker(s): Matthew Miller
  • Date:
  • Time: 3:30 PM
  • Location: SCIE 1511

Abstract

The macroscopic behavior of polycrystalline alloys are a product of their single crystal properties and the cumulative response of each crystal within an aggregate.

This talk presents different diffraction-based methods for understanding microscale deformation within a polycrystalline aggregate and for using these data hand-in-hand with crystal scale material models. Diffracted intensity distributions provide a link to the distorted shape and orientation of an individual crystal. High energy synchrotron x-rays enable penetration through bulk specimens – each crystal within a deforming aggregate can be probed. The use of high speed detectors enables acquisition of thousands of lattice strains in a matter of minutes. We’ve developed a method of inverting lattice strain pole figures for the underlying strain tensor as a function of orientation, then ultimately the orientation-dependent stress. These data can then be employed to validate a crystal-scale finite element model for multiscale deformation behavior. Examples from in situ loading experiments and from residual stress measurements are given. If the crystal is larger compared to the diffraction volume, we acquire individual reflections (diffraction spots) from each crystal and determination of its individual stress state using lattice strains is then possible. The diffracted intensity data contains multiple layers of information about the crystal and these data are invaluable when used together with a multiscale material model. In current research we employ results from virtual diffraction experiments on the model microstructure and compare these directly to experimental data from in situ experiments to understand model performance and ultimately underlying material behaviors.