Visualization of the Evolution of the Fracture Process Zone in Sandstone by Transmission Computed Radiography

Vavro, Leona; Souček, Kamil; Kytýř, Daniel; Fíla, Tomáš; Keršner, Zbyněk; Vavro, Martin

doi:10.1016/j.proeng.2017.05.233

Cited by 19 publications

(10 citation statements)

References 9 publications

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“…However, since the FPZ is essentially a non-linear three-dimensional region, it is imperative that a method capable of assessing the volumetric FPZ characteristics has to be employed to ensure the sufficient reliability and repeatability of the results. We have already shown in a paper by Vavro et al that a time-lapse high-resolution micro-tomography under three-point bending load conditions (a 4D micro-CT) provides sufficient insight into the crack formation process and the FPZ evolution mechanisms [3]. Additionally, we have demonstrated that the modification of the standard flexural arrangements into the four-point bending of a vertically oriented specimen brings significant advantages of the in-situ experiments in terms of uniform X-ray attenuation during tomographic scanning, improved resolution around the stress-concentrators, and the possibility to enhance the loading device mechanically, so that it is possible to perform intermittent loading with an arbitrary number of tomographic scans throughout the force-displacement (P-d) curve of the material.…”

Section: Introductionmentioning

confidence: 99%

In-situ X-ray Differential Micro-tomography for Investigation of Water-weakening in Quasi-brittle Materials Subjected to Four-point Bending

et al. 2020

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Several methods, including X-ray radiography, have been developed for the investigation of the characteristics of water-saturated quasi-brittle materials. Here, the water content is one of the most important factors influencing their strength and fracture properties, in particular, as regards to porous building materials. However, the research concentrated on the three-dimensional fracture propagation characteristics is still significantly limited due to the problems encountered with the instrumentation requirements and the size effect. In this paper, we study the influence of the water content in a natural quasi-brittle material on its mechanical characteristics and fracture development during in-situ four-point bending by employing high-resolution X-ray differential micro-tomography. The cylindrical samples with a chevron notch were loaded using an in-house designed four-point bending loading device with the vertical orientation of the sample. The in-house designed modular micro-CT scanner was used for the visualisation of the specimen’s behaviour during the loading experiments. Several tomographic scans were performed throughout the force-displacement diagrams of the samples. The reconstructed 3D images were processed using an in-house developed differential tomography and digital volume correlation algorithms. The apparent reduction in the ultimate strength was observed due to the moisture content. The crack growth process in the water-saturated specimens was identified to be different in comparison with the dry specimens.

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Section: Introductionmentioning

confidence: 99%

In-situ X-ray Differential Micro-tomography for Investigation of Water-weakening in Quasi-brittle Materials Subjected to Four-point Bending

et al. 2020

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“…It is equipped with an X-ray flat panel detector having a number of 2,000  2,000 pixels with a pixel size of 200 μm. The basic technical parameters of the XT H 225 ST inspection machine are given, for example, in [17]. The scanning parameters were as follows: a reflection target, 160 kV voltage, 126 μA current, 0.5 mm thick aluminium filter, 3,141 projections with two images per projection, 1,000 ms exposition, a scanning time of ca.…”

Section: X-ray Ct Imaging Devicementioning

confidence: 99%

“…Previous research [17], [18] has focussed on the study of the crack propagation processes in quasi-brittle materials, such as silica-based composites or sandstones; these have shown some limitations when the conventional three-point bending tests were used in combination with the X-ray CT technique. The main disadvantage of such an arrangement of the experiment can be seen in particular in the horizontal orientation of the sample perpendicular to the rotational axis of the CT scanner, which, together with the loading supports covering parts of the radiograms (see Figure 1A) significantly reduces the quality of the acquired data.…”

Section: Loading Devicementioning

confidence: 99%

Study of fracture processes in sandstone subjected to four-point bending by means of 4D X-ray computed micro-tomography

Vavro

Souček

et al. 2022

ACTA IMEKO

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<p class="Abstract">High-resolution X-ray computed micro-tomography (CT) is a powerful technique for studying the processes of crack propagation in non-homogenous quasi-brittle materials such as rocks. To obtain all the significant information about the deformation behaviour and fracture characteristics of the studied rocks, the use of a highly specialised loading device suitable for the integration into existing tomographic setups is crucial. Since no adequate commercial solution is currently available, a completely newly-designed loading device with a four-point bending setup and vertically-oriented scanned samples was used. This design of the loading procedure, coupled with the high stiffness of the loading frame, allows the loading process to be interrupted at any time and for CT scanning to be performed without the risk of the sudden destruction of the scanned sample.</p>This article deals with the use of the 4D CT for the visualisation of crack initiation and propagation in clastic sedimentary rocks. Two types of quartz-rich sandstones of Czech provenance were used for tomographic observations during the four-point bending loading performed on chevron notched test specimens. It was found that the crack begins to propagate from the moment that ca. 80 % of the maximum loading force is applied.

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“…The concept for 4D micro-CT of the bending experiments was developed based on experience from measurements presented in [12,13], where conventional three-point bending tests (see fig. 2 left) were employed.…”

Section: Loading Devicementioning

confidence: 99%

Instrumentation of Four-Point Bending Test During 4d Computed Tomography

Kytýř

Fíla

Koudelka

et al. 2018

APP

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High-resolution time-lapse micro-focus X-ray computed tomography is an effective method for investigation of deformation processes on volumetric basis including fracture propagation characteristics of non-homogeneous materials subjected to mechanical loading. This experimental method requires implementation of specifically designed loading devices to X-ray imaging setups. In case of bending tests, our background research showed that no commercial solution allowing for reliable investigation of so called fracture process zone in quasi-brittle materials is currently available. Thus, this paper is focused on description of recently developed in-situ four-point bending loading device and its instrumentation for testing of quasi-brittle materials. Proof of concept together with the pilot experiments were successfully performed in a CT scanner TORATOM. Based on results of the pilot experiments, we demonstrate that crack development and propagation in a quasi-brittle material can be successfully observed in 3D using high resolution 4D micro-CT under loading.

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Visualization of the Evolution of the Fracture Process Zone in Sandstone by Transmission Computed Radiography

Cited by 19 publications

References 9 publications

In-situ X-ray Differential Micro-tomography for Investigation of Water-weakening in Quasi-brittle Materials Subjected to Four-point Bending

In-situ X-ray Differential Micro-tomography for Investigation of Water-weakening in Quasi-brittle Materials Subjected to Four-point Bending

Study of fracture processes in sandstone subjected to four-point bending by means of 4D X-ray computed micro-tomography

Instrumentation of Four-Point Bending Test During 4d Computed Tomography

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