Paul R. Dawson

A new algorithm for free surface corrections in Eulerian finite element computations is presented and applied to a steady state bar rolling process to predict lateral spread. A variety of rolling geometries are examined, including differing height to width ratios and reductions. The bulge profiles, as well as the maximum and mean bulge amounts, are compared in detail with experiments.

In this paper, we discuss a method to calculate the topology of the rate independent single crystal yield surface for materials with arbitrary slip systems and arbitrary slip strengths. We describe the general problem, as motivated by Schmid's law, and detail the calculation of hyperplanes in deviatoric stress space, $\mathbb{D}^5$, which describe the criteria for slip on individual slip systems. We focus on finding the intersection of five linearly independent hyperplanes which represent stresses necessary to satisfy the criteria for general plastic deformation. Finally, we describe a method for calculating the inner convex hull of these intersection points, which describe the vertices of the five dimensional polytope that represents the single crystal yield surface. Our method applies to arbitrary crystal structure, allowing for an arbitrary number and type of slip systems and families, considers plastic anisotropy via inter- and intra-family strength anisotropy, and further considers strength anisotropy between slip in the positive and negative direction. We discuss the calculation and possible applications, and share a computational implementation of the calculation of the single crystal yield surface.

To assist in the planning of in situ loading, HEDM experiments by generating synthetic diffraction images of virtual samples in loaded and unloaded states. The user designates a target grain in the virtual sample and specifies the set of reflections for which images are to be generated. The code generates several intermediate images, including: (1) the points of intersection between the diffracted beam direction vector the detector plane; (2) reflection-dependent frequency distributions of the diffraction angle, $ω$; and (3) plots of the diffraction volume-weighted intensity distributions for the specified set of reflections. The final sets of plots are facsimiles of pixelated detector images which take into account characteristics of specific detectors, including its pixel size and point spread behavior.