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Materials (Basel). 2018 Mar 15;11(3). pii: E427. doi: 10.3390/ma11030427.

Digital Image Correlation of 2D X-ray Powder Diffraction Data for Lattice Strain Evaluation.

Author information

1
Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, UK. hongjia.zhang@eng.ox.ac.uk.
2
Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, UK. tan.sui@eng.ox.ac.uk.
3
Department of Mechanical Engineering Sciences, University of Surrey, Guildford GU2 7XH, UK. tan.sui@eng.ox.ac.uk.
4
Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, UK. enrico.salvati@eng.ox.ac.uk.
5
Beamline I15, Diamond Light Source, Didcot OX11 0DE, UK. dominik.daisenberger@diamond.ac.uk.
6
Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, UK. alexander.lunt@cern.ch.
7
CERN, CH-1211 Geneva 23, Switzerland. alexander.lunt@cern.ch.
8
Singapore Institute of Manufacturing Technology (SIMTech), 73 Nanyang Drive, Singapore 637662, Singapore. ksfong@simtech.a-star.edu.sg.
9
Singapore Institute of Manufacturing Technology (SIMTech), 73 Nanyang Drive, Singapore 637662, Singapore. xsong@simtech.a-star.edu.sg.
10
Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, UK. alexander.korsunsky@eng.ox.ac.uk.

Abstract

High energy 2D X-ray powder diffraction experiments are widely used for lattice strain measurement. The 2D to 1D conversion of diffraction patterns is a necessary step used to prepare the data for full pattern refinement, but is inefficient when only peak centre position information is required for lattice strain evaluation. The multi-step conversion process is likely to lead to increased errors associated with the 'caking' (radial binning) or fitting procedures. A new method is proposed here that relies on direct Digital Image Correlation analysis of 2D X-ray powder diffraction patterns (XRD-DIC, for short). As an example of using XRD-DIC, residual strain values along the central line in a Mg AZ31B alloy bar after 3-point bending are calculated by using both XRD-DIC and the conventional 'caking' with fitting procedures. Comparison of the results for strain values in different azimuthal angles demonstrates excellent agreement between the two methods. The principal strains and directions are calculated using multiple direction strain data, leading to full in-plane strain evaluation. It is therefore concluded that XRD-DIC provides a reliable and robust method for strain evaluation from 2D powder diffraction data. The XRD-DIC approach simplifies the analysis process by skipping 2D to 1D conversion, and opens new possibilities for robust 2D powder diffraction data analysis for full in-plane strain evaluation.

KEYWORDS:

2D X-ray powder diffraction; 3-point bending; Digital Image Correlation; strain measurement

Conflict of interest statement

The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.

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