Title: X-Ray Stereo Digital Image Correlation

Abstract

Digital Image Correlation (DIC) is a well-established, non-contact diagnostic technique used to measure shape, displacement and strain of a solid specimen subjected to loading or deformation. Yet, measurements using standard DIC can have significant errors or be completely infeasible in challenging experiments, such as explosive, combustion, or fluid-structure interaction applications, where beam-steering due to index of refraction variation biases measurements or where the sample is engulfed in flames or soot. To address these challenges, we propose using X-ray imaging instead of visible light imaging for stereo-DIC, since refraction of X-rays is negligible in many situations, and X-rays can penetrate occluding material. Two techniques of creating an appropriate pattern for X-ray DIC are presented, both based on adding a dense material in a random speckle pattern on top of a less-dense specimen. A standard dot-calibration target is adapted for X-ray imaging, allowing the common bundle-adjustment calibration process in commercial stereo-DIC software to be used. High-quality X-ray images with sufficient signal-to-noise ratios for DIC are obtained for aluminum specimens with thickness up to 22.2 mm, with a speckle pattern thickness of only 80 μm of tantalum. The accuracy and precision of X-ray DIC measurements are verified through simultaneous optical and X-ray stereo-DICmore » measurements during rigid in-plane and out-of-plane translations, where errors in the X-ray DIC displacements were approximately 2–10 μm for applied displacements up to 20 mm. Finally, a vast reduction in measurement error—5–20 times reduction of displacement error and 2–3 times reduction of strain error—is demonstrated, by comparing X-ray and optical DIC when a hot plate induced a heterogeneous index of refraction field in the air between the specimen and the imaging systems. Subsequently, these findings show the feasibility of using X-ray-based stereo-DIC for non-contact measurements in exacting experimental conditions, where optical DIC cannot be used.« less

Authors:

Jones, E. M. C.  ^[1];

• Search DOE PAGES for author "Jones, E. M. C."
• Search DOE PAGES for ORCID "0000-0001-6093-6458"
• Search orcid.org for ORCID "0000-0001-6093-6458"

Quintana, E. C. ^[1]; Reu, P. L. ^[1]; Wagner, J. L. ^[1]

---

+ Show Author Affiliations

1. Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

Publication Date:

2019-08-26

Research Org.:

Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:

1559523

Report Number(s):

SAND-2019-9806J
Journal ID: ISSN 0732-8818; 678668; TRN: US2000360

Grant/Contract Number:  

AC04-94AL85000; NA0003525

Resource Type:

Accepted Manuscript

Journal Name:

Experimental Techniques

Additional Journal Information:

Journal Volume: 44; Journal Issue: 2; Journal ID: ISSN 0732-8818

Publisher:

Wiley

Country of Publication:

United States

Language:

English

Subject:

47 OTHER INSTRUMENTATION; Digital Image Correlation (DIC); Index of refraction; X-ray