Seif Eddine Hamdi

Numerical Fracture Analysis Under Temperature Variation by Energetic Method

It is known that temperature change can induce sudden crack propagation especially when the material is composed of fibers. In this fact, the crack growth process under mixed-mode coupling mechanical and thermal loads in orthotropic materials like wood is investigated in this work. The analytical formulation of A integral’s combines the real and virtual mechanical and thermal stress/strain fields under transient diet in 2D. The Mixed Mode Crack Growth specimen providing the decrease of energy release rate during crack propagation is considered in order to compute the various mixed mode ratios. By using three specific routines, the analytical formulation is implemented in finite element software Cast3m. The efficiency of the proposed model is justified by showing the evolution of energy release rate and the stress intensity factors versus crack length and versus temperature variation in time dependent material.

Impact of Hydro-Mechanical Loadings on Rupture Process in Wood Material

With the environmental impacts coupled with mechanical loadings, the micro-cracks can propagate and drive the collapse of wood materials or timber-based structures. In this case, the rupture in mixed mode coupling mechanical hydric and thermal loads for orthotropic materials is studied. The analytical formulation of the energy release rate is introduced by the T and A integrals generalized to mixed mode crack growth. The time dependent effects are introduced according to the generalized Kelvin Voigt model. This new formulation is based on conservation laws and real and virtual mechanical and thermal fields based on the Arbitrary, Lagrangian and Eulerian configurations. The Mixed Mode Crack Growth specimen, providing the decrease of energy release rate during crack propagation, is considered in order to compute the various mixed mode ratios. The analytical formulation is implemented in finite element software Cast3m and the crack growth is obtained by testing the Griffith criterion rewritten in time domain under orthotropic configuration. The efficiency of the proposed model is justified by showing the evolution of energy release rate and the stress intensity factors versus crack length and hydric variations within time dependent material. Also the path independency is proven for each mixed mode configuration.

Time delay estimation for acoustic source location by means of short-time cross-correlation

This article presents a method which can be used for online Acoustic Emission (AE) source location in a composite plate by means of time delay estimations. A short-time cross-correlation function from the envelope of the two signals, has been developed. This method allows to estimate the time delay in the early coherent part of the signals, which is especially suitable in a very dispersive medium such as composite material. Experimental results, obtained with a glass-fiber/epoxy plate equipped with piezoelectric transducers, show that a balance of simplicity, accuracy and robustness can be achieved by using this method.