Initiation and propagation of complex 3D networks of cracks in heterogeneous quasi-brittle materials: Direct comparison between in situ testing-microCT experiments and phase field simulations

Nguyen, Thanh Tung; Yvonnet, Julien; Bornert, Michel; Chateau, Camille

doi:10.1016/j.jmps.2016.06.004

Cited by 110 publications

(51 citation statements)

References 46 publications

(55 reference statements)

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“…Finally, a noteworthy morphology of the crack network is shown in Figure , where three crack surfaces are observed to propagate separated by approximate angles of 120°, from the bottom of a spherical pore (EPS bead), which is located just above another spherical pore. This typical cracking morphology has already been observed in lightweight plaster under compression and captured by numerical simulation in Nguyen et al…”

Section: Qualitative Characterisation Of Microcracking In Lightweightsupporting

confidence: 61%

“…This corresponds to the limit case addressed in Section 3.2.3, where the grey‐level variation generated by the cracks is similar to the image noise. To unambiguously follow qualitatively the damage evolution during the compression test and compare it to the microstructure of the material, an alternative technique could be used as in Nguyen et al It consists in only transforming the deformed images back to the reference frame, without performing the subtraction. The so‐called transformed image would be defined as t ( X ) = g ( ϕ 1 ( X )).…”

Section: Qualitative Characterisation Of Microcracking In Lightweightmentioning

confidence: 99%

“…Detailed experimental characterisation is still needed for a better understanding of fracture mechanisms, in terms of initiation, propagation, or localisation leading to macroscopic failure. Such data are also necessary to develop and to validate predictive models of crack nucleation and propagation at microscale . The increasing use of X‐ray computed tomography (XRCT) in material science makes it possible to characterise both microstructure and damage mechanisms in three‐dimensional (3D) space within the bulk of materials.…”

Section: Introductionmentioning

confidence: 99%

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DVC‐based image subtraction to detect microcracking in lightweight concrete

Chateau

Nguyen

Bornert

et al. 2018

Strain

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This paper presents an image subtraction technique based on digital volume correlation to detect and extract the complex network of microcracks that progressively developed in a lightweight concrete sample submitted in situ to uniaxial compression and imaged by X‐ray computed tomography. From local digital volume correlation measurements, performed only on positions with sufficient image contrast, the mechanical transformation is estimated at all voxels within the whole sample using an adjusted interpolation procedure that computes an affine approximation of the local transformation. The deformed image (containing cracks) is thus transformed back to the same frame as the reference image (without cracks) to compute the difference between both images, taking into account possible brightness and contrast adjustments. The resulting subtracted image reveals the path of cracks, which is clearly visible without the underlying heterogeneous microstructure of the concrete. The detection accuracy is here estimated to one tenth of a voxel, allowing early‐age cracks to be detected while they would barely have been noticed on the X‐ray computed tomography images. Segmentation of the crack network is also made much easier. To overcome a low signal‐to‐noise ratio for the tiniest cracks, a Hessian‐based filter is used to extract the complex crack network. The cracks can be directly located in the microstructure segmented in the reference image and compared for all loading steps to characterise their initiation and propagation.

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Section: Qualitative Characterisation Of Microcracking In Lightweightsupporting

confidence: 61%

Section: Qualitative Characterisation Of Microcracking In Lightweightmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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DVC‐based image subtraction to detect microcracking in lightweight concrete

Chateau

Nguyen

Bornert

et al. 2018

Strain

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“…Phase field simulations were validated against experiments through the comparison of crack patterns in lightweight concrete and plaster [166].…”

Section: Identification and Validationmentioning

confidence: 99%

Digital Volume Correlation: Review of Progress and Challenges

et al. 2018

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3D imaging has become popular for analyzing material microstructures. When time lapse series of 3D pictures are acquired during a single experiment, it is possible to measure displacement fields via digital volume correlation (DVC), thereby leading to 4D results. Such ForewordThe present paper aims at reviewing the major developments in Digital Volume Correlation (DVC) over the past ten years. It follows the first review on DVC that was published in 2008 by its pioneer [11]. In the latter, the interested reader will find all the general principles associated with what is now called local DVC. They will not be recalled hereafter. In such approaches the region of interest is subdivided into small subvolumes that are independently registered. In addition to its wider use with local approaches, DVC has been extended to global approaches in which the displacement field is defined in a dense way over the region of interest. Kinematic bases using finite element discretizations have been selected. To further add mechanical content, elastic regularization has been introduced. Last, integrated approaches use kinematic fields that are constructed from finite element simulations with chosen constitutive equations. The material parameters (and/or boundary conditions) then become the quantities of interest.These various implementations assume different degrees of integration of mechanical knowledge about the analyzed experiment. First and foremost, DVC can be considered as a stand-alone technique, which has seen its field of applications grow over the last ten years. In this case the measured displacement fields and post-processed strain fields are reported. With the introduction of finite element based DVC, the measured displacement field is continuous. It is also a standalone technique. However, given the fact that it shares common kinematic bases with numerical simulations, it can be easily combined with the latter. One route is to require local satisfaction of equilibrium via mechanical regularization. Another route is to fully merge DVC analyses and numerical simulations via integrated approaches. Different examples will illustrate how these various integration steps can be tailored and what are the current challenges associated with various approaches.

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“…In comparison with numerical models using idealised microscale morphologies [14][15][16] or assumed stochastically random field properties [17], the image-based models faithfully reproduce the intrinsic heterogeneity of the material, such as shape, size, and distribution of inclusions and pores [18]. Moreover, the simulated results at different loading steps can be quantitatively validated by in situ experimental images (e.g., XCT) [9,19].…”

Section: Introductionmentioning

confidence: 80%

Three‐Dimensional In Situ XCT Characterisation and FE Modelling of Cracking in Concrete

et al. 2018

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Three-dimensional (3D) characterisation and modelling of cracking in concrete have been always of great importance and interest in civil engineering. In this study, an in situ microscale X-ray computed tomography (XCT) test was carried out to characterise the 3D microscale structure and cracking behaviour under progressive uniaxial compressive loading. The 3D cracking and fracture behaviour including internal crack opening, closing, and bridging were observed through both 2D tomography slices and 3D CT images. Spatial distributions of voids and cracks were obtained to understand the overall cracking process within the specimen. Furthermore, the XCT images of the original configuration of the specimen were processed and used to build microscale realistic 3D finite element (FE) models. Cohesive interface elements were inserted into the FE mesh to capture complicated discrete crack initiation and propagation. An FE simulation of uniaxial compression was conducted and validated by the in situ XCT compression test results, followed by a tension simulation using the same image-based model to investigate the cracking behaviour. The quantitative agreement between the FE simulation and experiment demonstrates that it is a very promising and effective technique to investigate the internal damage and fracture behaviour in multiphasic composites by combining the in situ micro XCT experiment and image-based FE modelling.

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Initiation and propagation of complex 3D networks of cracks in heterogeneous quasi-brittle materials: Direct comparison between in situ testing-microCT experiments and phase field simulations

Cited by 110 publications

References 46 publications

DVC‐based image subtraction to detect microcracking in lightweight concrete

DVC‐based image subtraction to detect microcracking in lightweight concrete

Digital Volume Correlation: Review of Progress and Challenges

Three‐Dimensional In Situ XCT Characterisation and FE Modelling of Cracking in Concrete

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