Ciliberto, S. (S.)
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- Statistical properties of fracture precursors(American Physical Society, 1997) Ciliberto, S. (S.); Lebon, L. (L.); Montero, Á. (Ángel); Guarino, A. (A.)We present the data of a mode-I fracture experiment. The samples are broken under imposed pressure. The acoustic emission of microfractures before the breakup of the sample is registered. From the acoustic signals, the position of microfractures and the energy released are calculated. A measure of the clustering of microfractures yields information about the critical load. The statistics from energy measurements strongly suggest that the fracture can be viewed as a critical phenomenon; energy events are distributed in magnitude as a power law, and a critical exponent is found for the energy near fracture.
- Defects in roll-hexagon competition(American Physical Society, 1990) Perez-Garcia, C. (C.); Ciliberto, S. (S.); Lega, J. (J.); Pampaloni, E. (E.); Coullet, P. (P.)
- An experimental test of the critical behaviour of fracture precursors(1998) Ciliberto, S. (S.); Montero, Á. (Ángel); Guarino, A. (A.)The statistical properties and the localization of fracture precursors on heteregeneous materials is studied by recording their acoustic emission as a function of the applied load. It's found that the microcrack cluster together as the load increases and the instantaneous acoustic energy has an invariant power law distribution. The integrated acoustic energy presents a critical divergency close to the failure load for the sample. These result support the idea that fracture can be viewed as a critical phenomenon. Finally a measure of the concentration of microcraks, which allows us to predict the failure load, is introduced. These properties are studied also when a periodic load is applied to the sample. It's found that the Kaiser e ect is not strictly satis ed in heteregeneous materials.
- Finite-size effects in the transition from hexagons to rolls in convective systems(European Physical Society, 1990) Perez-Garcia, C. (C.); Ciliberto, S. (S.); Pampaloni, E. (E.)The transition thresholds between hexagons and rolls in convective patterns are obtained in the framework of the amplitude equations. We show that the discrepancies between the theoretical thresholds, calculated for unbounded systems, and the experimental ones, made in finite containers, can be partially corrected by a phenomenological argument. The finite-size effects are responsible for the decreasing in the efficiency of the heat transport across the cell. Using this fact we are able to approach the calculated thresholds to those observed in real experiments. The transition between different symmetries in convective
- Failure time and microcrack nucleation(1999) Ciliberto, S. (S.); Montero, Á. (Ángel); Guarino, A. (A.)The failure time of samples of heterogeneous materials (wood, ¯berglass) is stud- ied as a function of the applied stress. It is shown that in these materials the failure time is predicted with a good accuracy by a model of microcrack nucleation proposed by Pomeau. It is also shown that the crack growth process presents critical features when the failure time is approached.
- Intermittent origin of the large violations of the fluctuation-dissipation relations in an aging polymer glass(2003) Ciliberto, S. (S.); Buisson, L. (L.); Montero, Á. (Ángel)The fluctuation-dissipation relation (FDR)is measured on the dielectric properties of a polymer glass (polycarbonate)in the range 20 mHz–100Hz. It is found that after a quench below the glass transition temperature, the fluctuation-dissipation theorem is strongly violated. The amplitude and the persistence time of this violation are decreasing functions of frequency. At frequencies larger than 1Hz it persists for about 3 h. The origin of this violation is a highly intermittent dynamics characterized by large fluctuations. The relevance of these results for recent models of aging dynamics is discussed.
- Failure time and critical behaviour of fracture precursors in heterogeneous materials(2002) Ciliberto, S. (S.); Scorretti, R. (R.); Zei, M. (M.); Montero, Á. (Ángel); Guarino, A. (A.)