Characterization of a cracked specimen with full-field measurements: direct determination of the crack tip and energy release rate calculation

Pitti, Rostand Moutou; Bădulescu, Claudiu; Grédiac, Michel

doi:10.1007/s10704-013-9921-5

Cited by 21 publications

(6 citation statements)

References 31 publications

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“…Beams were tested in three‐point and four‐point bending, and the cracking pattern was deduced in each case, enabling to analyze the cracking evolution during the test, and establish the link between the crack pattern and the global response of the tested specimens. An aluminium notched specimen was tested in . Interestingly, the specimen was tested in an Arcan device beforehand, with a load direction inclined with respect to the normal direction of the notch, causing a crack to initiate along a direction also inclined with respect to the notch.…”

Section: Examplesmentioning

confidence: 99%

See 1 more Smart Citation

The Grid Method for In‐plane Displacement and Strain Measurement: A Review and Analysis

Grédiac

Sur

Blaysat

2016

Strain

139

162

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The grid method is a technique suitable for the measurement of in-plane displacement and strain components on specimens undergoing a small deformation. It relies on a regular marking of the surfaces under investigation. Various techniques are proposed in the literature to retrieve these sought quantities from images of regular markings, but recent advances show that techniques developed initially to process fringe patterns lead to the best results. The grid method features a good compromise between measurement resolution and spatial resolution, thus making it an efficient tool to characterise strain gradients. Another advantage of this technique is the ability to establish closed-form expressions between its main metrological characteristics, thus enabling to predict them within certain limits. In this context, the objective of this paper is to give the state of the art in the grid method, the information being currently spread out in the literature. We propose first to recall various techniques that were used in the past to process grid images, to focus progressively on the one that is the most used in recent examples: the windowed Fourier transform. From a practical point of view, surfaces under investigation must be marked with grids, so the techniques available to mark specimens with grids are presented. Then we gather the information available in the recent literature to synthesise the connection between three important characteristics of full-field measurement techniques: the spatial resolution, the measurement resolution and the measurement bias. Some practical information is then offered to help the readers who discover this technique to start using it. In particular, programmes used here to process the grid images are offered to the readers on a dedicated website. We finally present some recent examples available in the literature to highlight the effectiveness of the grid method for in-plane displacement and strain measurement in real situations.

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Section: Examplesmentioning

confidence: 99%

“…Strain field near a crack tip in aluminium specimen (see ). dimensions in pixels, 1 pixel represents 40 μ m on the specimen.…”

Section: Examplesmentioning

confidence: 99%

The Grid Method for In‐plane Displacement and Strain Measurement: A Review and Analysis

Grédiac

Sur

Blaysat

2016

Strain

139

162

View full text Add to dashboard Cite

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“…Shortly afterwards, Huntley [20] determined the SIF from a full field displacement field, obtained by double exposure laser speckle photography, via a least square fit to the Williams' series. Other techniques to obtain the displacement field, such as the grid method [21] that tracks a pattern drawn at the surface of the sample, have also been used to extract stress intensity factors.…”

Section: Introductionmentioning

confidence: 99%

“…Often implemented as a line integral, the J-integral can be formulated as a surface or area integral using Green's theorem, and this is convenient to implement in finite element analyses. An example of the direct evaluation of the J-integral from the measured crack field is the JMAN method [41,42], which implements the area integral with DIC measurements, and the implementation of other integrals with full-field displacement data can be found in the literature, such as [21]. Importantly, these methods do not rely on fitting a presumed field (e.g.…”

Section: Introductionmentioning

confidence: 99%

J-Integral Calculation by Finite Element Processing of Measured Full-Field Surface Displacements

et al. 2017

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A novel method has been developed based on the conjoint use of digital image correlation to measure full field displacements and finite element simulations to extract the strain energy release rate of surface cracks. In this approach, a finite element model with imported full-field displacements measured by DIC is solved and the J-integral is calculated, without knowledge of the specimen geometry and applied loads. This can be done even in a specimen that develops crack tip plasticity, if the elastic and yield behaviour of the material are known. The application of the method is demonstrated in an analysis of a fatigue crack, introduced to an aluminium alloy compact tension specimen (Al 2024, T351 heat condition).

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“…The grid method features however a better compromise between spatial resolution and displacement resolution than DIC, as recently shown in [31]. This is illustrated in [32] for instance, where crack propagation is studied in notched aluminium specimens. This technique is therefore used here again in the case of wood specimens.…”

Section: Introductionmentioning

confidence: 97%

Mode I fracture of tropical woods using grid method

Odounga

Pitti

Toussaint

et al. 2018

Theoretical and Applied Fracture Mechanics

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The cracking properties in opening mode of three tropicals species from the Gabonese forest, namely Iroko (Milicia Excelsa), Okume (Aucoumea klaineana Pierre), and Padouk (Pterocarpus soyauxii), were investigated in this study. Various tests were performed at room temperature and for two different thicknesses. A full-field measurement technique, namely the grid method, was used in order to obtain the displacement and strain maps near the crack during the tests. The mechanical parameters, the specificities of the wood species, the Arcan system and the grid transfer method are first described. For all the specimens, the initial crack length was oriented along the fiber direction (RL). The instantaneous failure tests were performed using two types of specimens: the modified Compact Tension Shear (CTS) and the Mixed Mode Crack Growth (MMCG) specimens. The images of the grid were recorded and analyzed to obtain the displacement maps. The crack opening, the location of the crack tip as well as the strain fields on the surface of the specimens were deduced from these displacement maps. The experimental critical energy release rate Gc was evaluated by the compliance method in imposed displacement. In the case of instantaneous crack with CTS specimens, the comparison of the initial value of Gc for all the samples show that this quantity strongly depends on the thickness and density of the species under study. Crack propagation was observed for a thickness equal to 20 mm only. The results of the crack propagation with the MMCG specimens show the same dependence, and confirm the quasi-brittle fracture behavior of Iroko. The experimental results are scattered, but clear trends can be observed concerning the fracture parameters of the in previous studies described in the literature on wood species with wood species under study. The results are finally compared with those given densities similar to those studied here.

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Characterization of a cracked specimen with full-field measurements: direct determination of the crack tip and energy release rate calculation

Cited by 21 publications

References 31 publications

The Grid Method for In‐plane Displacement and Strain Measurement: A Review and Analysis

The Grid Method for In‐plane Displacement and Strain Measurement: A Review and Analysis

J-Integral Calculation by Finite Element Processing of Measured Full-Field Surface Displacements

Mode I fracture of tropical woods using grid method

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