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4D X-ray Computed Tomography for Material Science

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Advanced Materials Characterization".

Deadline for manuscript submissions: closed (20 November 2022) | Viewed by 8805

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Dr. Daniel Vavřík

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1. Institute of Theoretical and Applied Mechanics, Czech Academy of Sciences, Prosecka 76, 19000 Prague 9, Czech Republic
2. Institute of Experimental and Applied Physics, Czech Technical University in Prague, Husova 240/5, 11000 Prague 1, Czech Republic
Interests: computed tomography hw and sw; fracture mechanics; experimental mechanics

Special Issue Information

Dear Colleagues,

High-resolution X-ray (and neutron) computed tomography (CT) is nowadays routinely used for the non-destructive inspection of various aspects of material structures. Besides the standard CT devoted to inspection of static objects, four-dimensional computed tomography (4DCT) has been developed in recent years for the study of material behavior during non-stationary (time dependent) physical or chemical processes, even with sub-second time resolution.

Regarding non-stationary processes, we can mention, for instance: evolution of the elastic and inelastic deformations caused by mechanical or thermal loading; crack and damage propagation during specimen testing; environmentally induced damaging of materials; fluid transportation and evaporation within porous materials; changes of crystalline structure; foam forming and collapsing etc. The tomographic inspection of such time dependent processes may require the processing of enormous data volumes, as a series of many CT reconstructions is needed to follow and study an entire process. Obviously, the long-term stability of the CT scanner is therefore preferred. Moreover, 4DCT data have to be recorded fast in many cases, therefore an intensive X-ray source and a high speed X-ray detector may be required, together with a specific data acquisition protocol, and specific CT data processing.

Especially for the 4DCT with micrometric scale resolution, each reconstructed volume has to be aligned to the referenced one with subvoxel precision, to be able to distinguish subtle changes in the object employing differential tomography. Therefore, high precision digital volume correlation (DVC) is often required.

In the dependence on the process studied, various loading end environmental devices which can be operated inside of the CT scanner are needed.

In this Special Issue, papers focused on innovative CT methods for the investigation of time-dependent processes caused by external or internal factors, and advanced data post-processing and analysis on any type of natural, artificial materials and meta-materials are welcome.

Dr. Daniel Vavřík
Guest Editor

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Keywords

time dependent material properties
in situ mechanical testing
in situ physical testing
four-dimensional computed tomography
digital volume correlation

Published Papers (4 papers)

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Research

16 pages, 4011 KiB

Open AccessArticle

Fast 4D On-the-Fly Tomography for Observation of Advanced Pore Morphology (APM) Foam Elements Subjected to Compressive Loading

by Michal Vopalensky, Petr Koudelka, Jan Sleichrt, Ivana Kumpova, Matej Borovinsek, Matej Vesenjak and Daniel Kytyr

Materials 2021, 14(23), 7256; https://doi.org/10.3390/ma14237256 - 27 Nov 2021

Cited by 2 | Viewed by 1547

Abstract

Observation of dynamic testing by means of X-ray computed tomography (CT) and in-situ loading devices has proven its importance in material analysis already, yielding detailed 3D information on the internal structure of the object of interest and its changes during the experiment. However, the acquisition of the tomographic projections is, in general, a time-consuming task. The standard method for such experiments is the time-lapse CT, where the loading is suspended for the CT scan. On the other hand, modern X-ray tubes and detectors allow for shorter exposure times with an acceptable image quality. Consequently, the experiment can be designed in a way so that the mechanical test is running continuously, as well as the rotational platform, and the radiographic projections are taken one after another in a fast, free-running mode. Performing this so-called on-the-fly CT, the time for the experiment can be reduced substantially, compared to the time-lapse CT. In this paper, the advanced pore morphology (APM) foam elements were used as the test objects for in-situ X-ray microtomography experiments, during which series of CT scans were acquired, each with the duration of 12 s. The contrast-to-noise ratio and the full-width-half-maximum parameters are used for the quality assessment of the resultant 3D models. A comparison to the 3D models obtained by time-lapse CT is provided. Full article

(This article belongs to the Special Issue 4D X-ray Computed Tomography for Material Science)

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15 pages, 3663 KiB

Open AccessArticle

Analysis of Advanced Pore Morphology (APM) Foam Elements Using Compressive Testing and Time-Lapse Computed Microtomography

by Matej Borovinsek, Petr Koudelka, Jan Sleichrt, Michal Vopalensky, Ivana Kumpova, Matej Vesenjak and Daniel Kytyr

Materials 2021, 14(19), 5897; https://doi.org/10.3390/ma14195897 - 8 Oct 2021

Cited by 4 | Viewed by 1640

Abstract

Advanced pore morphology (APM) foam elements are almost spherical foam elements with a solid outer shell and a porous internal structure mainly used in applications with compressive loading. To determine how the deformation of the internal structure and its changes during compression are related to its mechanical response, in-situ time-resolved X-ray computed microtomography experiments were performed, where the APM foam elements were 3D scanned during a loading procedure. Simultaneously applying mechanical loading and radiographical imaging enabled new insights into the deformation behaviour of the APM foam samples when the mechanical response was correlated with the internal deformation of the samples. It was found that the highest stiffness of the APM elements is reached before the appearance of the first shear band. After this point, the stiffness of the APM element reduces up to the point of the first self-contact between the internal pore walls, increasing the sample stiffness towards the densification region. Full article

(This article belongs to the Special Issue 4D X-ray Computed Tomography for Material Science)

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23 pages, 74030 KiB

Open AccessEditor’s ChoiceArticle

A Method for Evaluation the Fatigue Microcrack Propagation in Human Cortical Bone Using Differential X-ray Computed Tomography

by Petr Koudelka, Daniel Kytyr, Tomas Fila, Jan Sleichrt, Vaclav Rada, Petr Zlamal, Pavel Benes, Vendula Bendova, Ivana Kumpova and Michal Vopalensky

Materials 2021, 14(6), 1370; https://doi.org/10.3390/ma14061370 - 11 Mar 2021

Cited by 1 | Viewed by 2167

Abstract

Fatigue initiation and the propagation of microcracks in a cortical bone is an initial phase of damage development that may ultimately lead to the formation of macroscopic fractures and failure of the bone. In this work, a time-resolved high-resolution X-ray micro-computed tomography (CT) was performed to investigate the system of microcracks in a bone sample loaded by a simulated gait cycle. A low-cycle (1000 cycles) fatigue loading in compression with a 900 N peak amplitude and a 0.4 Hz frequency simulating the slow walk for the initialization of the internal damage of the bone was used. An in-house developed laboratory X-ray micro-CT imaging system coupled with a compact loading device were employed for the in situ uni-axial fatigue experiments reaching a μ

2 μ m

effective voxel size. To reach a comparable quality of the reconstructed 3D images with the SEM microscopy, projection-level corrections and focal spot drift correction were performed prior to the digital volume correlation and evaluation using differential tomography for the identification of the individual microcracks in the microstructure. The microcracks in the intact bone, the crack formation after loading, and the changes in the topology of the microcracks were identified on a volumetric basis in the microstructure of the bone. Full article

(This article belongs to the Special Issue 4D X-ray Computed Tomography for Material Science)

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13 pages, 3482 KiB

Open AccessArticle

4D In-Situ Microscopy of Aerosol Filtration in a Wall Flow Filter

by Matthew P. Jones, Malte Storm, Andrew P. E. York, Timothy I. Hyde, Gareth D. Hatton, Alex G. Greenaway, Sarah J. Haigh and David S. Eastwood

Materials 2020, 13(24), 5676; https://doi.org/10.3390/ma13245676 - 12 Dec 2020

Cited by 3 | Viewed by 2359

Abstract

The transient nature of the internal pore structure of particulate wall flow filters, caused by the continuous deposition of particulate matter, makes studying their flow and filtration characteristics challenging. In this article we present a new methodology and first experimental demonstration of time resolved in-situ synchrotron micro X-ray computed tomography (micro-CT) to study aerosol filtration. We directly imaged in 4D (3D plus time) pore scale deposits of TiO

_{2}

nanoparticles (nominal mean primary diameter of 25 nm) with a pixel resolution of 1.6

μ

m. We obtained 3D tomograms at a rate of ∼1 per minute. The combined spatial and temporal resolution allows us to observe pore blocking and filling phenomena as they occur in the filter’s pore space. We quantified the reduction in filter porosity over time, from an initial porosity of 0.60 to a final porosity of 0.56 after 20 min. Furthermore, the penetration depth of particulate deposits and filtration rate was quantified. This novel image-based method offers valuable and statistically relevant insights into how the pore structure and function evolves during particulate filtration. Our data set will allow validation of simulations of automotive wall flow filters. Evolutions of this experimental design have potential for the study of a wide range of dry aerosol filters and could be directly applied to catalysed automotive wall flow filters. Full article

(This article belongs to the Special Issue 4D X-ray Computed Tomography for Material Science)

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