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Pré-Publication, Document De Travail Année : 2023

Role of porosity in the induced failure mechanisms of isotropic ice under three-points flexural loading

Dominique Saletti
Pascal Forquin

Résumé

The knowledge of the flexural strength of ice is essential to prescribe the interaction with building structures in various environments such as off-shore platforms or icy roads in the Great North. Microstructural properties of polycrystalline ice, mostly grain size and porosity, can strongly vary in natural ice and impact the mechanical response. There exist currently no bending experimental results that incorporate a robust characterization of these microstructural properties. In most fragile materials, such as concrete and rocks, pores often act as critical defects to trigger failure. Therefore, the porosity (pore size and shape distributions, density) can be considered as a major characteristic of the microstructure. In the present work we aim at (i) providing a robust set of bending experiments on well-controlled polycrystalline ice microstructures and (ii) provide a robust and accurate method for accessing the bending properties of ice through defect characterization. To do so, bending experiments were done on isotropic polycrystalline ice with the same grain size and shape distribution and two different porosity properties. Porosity was characterized at a relatively high resolution (down to 7µm) by micro-computed X-ray tomography (µCT). As classically done, the bending failure stress measurements have been statistically analyzed by means of the Weibull model. It results that, in situations were porosity follows a multi-modal distribution or a distribution too far from a Weibull one, this statistical approach is not well appropriate. An alternative is suggested that makes use of the accurate microstructure characterization from µCT. Providing that the Griffith/Irwin failure criterion can be applied, the measured pore distribution gives access to the prediction of a critical stress for defect activation. When compared with experimentally measured failure stress, this prediction enables to discriminate the defect population responsible for failure and highlight a volume effect on the behavior. As a result, we show that care should be taken when attempting to use the Weibull model to calibrate mechanical tests with complex and heterogeneous loadings (such as dynamic loadings) and complex microstructures. To make direct use of high resolution characterizations of the defect microstructure, when available, offers a more robust, accessible, and accurate predictability of the flexural strength.
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hal-04207437 , version 1 (14-09-2023)

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  • HAL Id : hal-04207437 , version 1

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David Georges, Dominique Saletti, Maurine Montagnat, Pascal Forquin, Hubert Maigre. Role of porosity in the induced failure mechanisms of isotropic ice under three-points flexural loading. 2023. ⟨hal-04207437⟩
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