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MAE Publications and Papers

Sibley School of Mechanical and Aerospace Engineering

New article: Analyzing Shear Band Formation with High Resolution X-ray Diffraction

Article: Pagan, DC; Obstalecki, M; Park, JS; Miller, MP; “Analyzing Shear Band Formation with High Resolution X-ray Diffraction”, ACTA Materialia, 147: 133-148


Abstract:  Localization of crystallographic slip into shear bands during uniaxial compression of a copper single crystal is studied using very far-field high-energy diffraction microscopy (vff-HEDM). Diffracted intensity was collected in-situ as the crystal deformed using a unique mobile detector stage that provided access to multiple diffraction peaks with high-angular resolution. From the diffraction data, single crystal orientation pole figures (SCPFs) were generated and are used to track the evolution of the distribution of lattice orientation that develops as slip localizes. To aid the identification of ‘signatures’ of shear band formation and analyze the SCPF data, a model of slip-driven lattice reorientation within shear bands is introduced. Confidence is built in conclusions drawn from the SCPF data about the character of internal slip localization through comparisons with strain fields on the sample surface measured simultaneously using digital image correlation. From the diffraction data, we find that the active slip direction and slip plane are not directly aligned with the orientation of the shear bands that formed. In fact, by extracting the underlying slip system activity from the SCPF data, we show that intersecting shear bands measured on the surface of the sample arise from slip primarily on the same underlying single slip system. These new vff-HEDM results raise significant questions on the use of surface measurements for slip system activity estimation. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Funding Acknowledgement:
Cornell High Energy Synchrotron Source (CHESS); Lawrence Livermore National Laboratory; National Science Foundation under NSF [DMR-1332208]; U.S. Department of Energy [DE-AC52-07NA27344 (LLNL-JRNL-683851)]; DOE Office of Science [DE-AC02-06CH11357]

Funding Text:
The authors would like to thank Dr. Peter Kenesei, Dr. Sarvjit Shastri, and Dr. Jon Almer for their help performing the experiment and Professor Armand Beaudoin for many helpful discussions. DCP was supported by a GRA position at the Cornell High Energy Synchrotron Source (CHESS) during his graduate work and by Lawrence Livermore National Laboratory as a post-doc. CHESS is supported by the National Science Foundation under NSF Award No. DMR-1332208. This work was performed partially under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 (LLNL-JRNL-683851). This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

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