Correlation between the internal length, the fracture process zone and size effect in model materials

Abstract

International audienceIn this paper, we examine the correlation between the width of the fracture process zone, the parameters entering in the description of size effect (related to the dimension of the specimen especially), and the internal length in non local constitutive relations for a model mortar material with a controlled macro-porosity. Experimental investigations on this material in compression, bending, acoustic emission measurements and their analysis are detailed. The experiments show a good agreement between the evolution of Bažant's size effect parameter d0 and the evolution of the width of the FPZ. The internal length obtained with the help of inverse finite element analysis is also proportional to these quantities. This correlation provides a reasonable approximation of the internal length, from an experimental test on specimens of a single size directly, equipped with acoustic emission localization devices.Dans cet article, nous examinons les corrélations entre la largeur de la zone de microfissuration (FPZ), les paramètres entrant dans la description de l'effet d'échelle et la longueur interne du modèle d'endommagement non local pour un mortier à macro-porosité contrôlée. Des résultats expérimentaux sur ce matériau en comparession, en flexion ainsi que des mesures d'émission acoustiques et leur analyse sont présentés. Les résultats d'essais montrent une bonne corrélation, entre l'évolution du paramètre d0, paramètre de la loi d'effet d'échelle de Bažant, et la largeur de la PFZ. La longueur interne obtenue numériquement par analyse inverse est aussi proportionnelle à ces paramètres. Une bonne approximation de la longueur interne à partir d'essais sur une seule taille d'éprouvette équipée d'un système d'émission, acoustique est aussi obtenue

Acoustic emission from the initiation of plastic deformation of Polyethylenes during tensile tests

“…However, the in situ determination of the initiation of micro-structural plastic events such as shearing of crystallites or cavitation remains problematic and requires complex devices such as SAXS or tomography [9][10][11][12][13][14][15]. As an in situ and convenient technique, acoustic emission (AE) is often used to analyze plastic deformation and damage of materials such as metals, ceramics and composites [16][17][18]. AE is defined as "the class of phenomena whereby transient elastic waves are generated by the rapid release of energy from localized sources within a material, or the transient elastic waves so generated" (ASTM 1982).…”

Comparison between thick level set (TLS) and cohesive zone models

“…The equality of each one of these three quantities for both models leads to (26) and (27). In order to close the system, we need to remind the normality rule for one of the models (28).…”

“…The system (45) writes now This choice is motivated by a damage distribution obtained from non-local damage and fracture equivalence [18], damage profiles obtained by lattice model simulations [24] and their similarity with some acoustic emission profiles [25,26].…”

Evolution of the fracture process zone in high-strength concrete under different loading rates

“…The extention and location of the FPZ is often dominated by complicated mechanisms, such as micro-cracking, crack bridge and friction. Due to the close relationship between the FPZ size and the characteristic length of a material, the FPZ evolution under different loading conditions has been the object of countless research efforts for decades [1][2][3][4][5][6].…”

“…Moreover, acoustic emission (AE) is also an experimental technique well suited for monitoring fracture process. Haidar et al [4] and Maji et al [5] have studied the relation between acoustic emission characteristics and the properties of the FPZ. Compared with the extensive research on properties of the FPZ under quasi-static loading conditions, much less information is available on its dynamic characterization, especially for high-strength concrete (HSC).…”