A technique for in-situ displacement and strain measurement with laboratory-scale X-ray Computed Tomography

Published

May 23, 2024

Author(s)

Orion Kafka, Alexander Landauer, Jake Benzing, Newell Moser, Elisabeth Mansfield, Edward Garboczi

Abstract

Purpose: Establish a technique for simultaneous interrupted volumetric imaging of internal structure and time-resolved full-field surface strain measurements during in-situ X-ray micro-computed tomography (XCT) experiments. This enables in-situ testing of stiff materials with large forces relative to the compliance of the in-situ load frame, which might exhibit localization (e.g., necking, compaction banding) and other inhomogeneous behaviors. Methods: The system utilizes a combination of in-situ XCT, 2D X-ray imaging, and particle tracking to both conduct volumetric imaging of the internal structure of a specimen with interrupted loading and surface strain mapping during loading. Critically, prior to the laboratory-scale XCT experiments, specimens are speckled with a high-contrast (X-ray opaque) powder that is bonded the surface. During in-situ loading, the XCT system is commanded to capture sequential 2D X-ray image orthogonal to the speckled specimen surface. A single particle tracking (SPT) or digital image correlation (DIC) algorithm is used to measure full-field surface strain evolution throughout the time-sequence of images. At specified crosshead displacements the motion and 2D image sequence is paused for volumetric XCT image collection. Results: We show example results on a micro-tensile demonstration specimen additive manufactured from Inconel 718 nickel-chrome alloy. Results include XCT volume reconstructions, crosshead-based engineering stress, and full-field strain maps. Conclusion: We demonstrate an in-situ technique to obtain surface strain evolution during laboratory-scale XCT testing and interrupted volumetric imaging. This allows closer investigation of, for example, the effect of micro-porosity in the localization habits of additive manufactured metal alloys. In addition to describing the method using a representative test piece, the dataset and code are published as open-source resources for the community.

Citation

Experimental Techniques

Pub Type

Journals

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https://doi.org/10.1007/s40799-024-00715-y

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Keywords

In-situ pore deformation, surface strain measurement, particle tracking, Laboratory X-ray micro Computed Tomography

Citation

Kafka, O. , Landauer, A. , Benzing, J. , Moser, N. , Mansfield, E. and Garboczi, E. (2024), A technique for in-situ displacement and strain measurement with laboratory-scale X-ray Computed Tomography, Experimental Techniques, [online], https://doi.org/10.1007/s40799-024-00715-y, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=957030 (Accessed June 30, 2024)