Failure time and microcrack nucleation

Abstract

The failure time of samples of heterogeneous materials (wood, fiberglass) is studied 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.

Failure time and critical behaviour of fracture precursors in heterogeneous materials

“…In fig.12c (reproduced in fig.10 for the sake of clearness), E measured when a constant pressure is applied to the sample is plotted as a function of τ −t τ . A power law is found in this case too [21]. The exponent γ is, within error bars, the same in the three cases.…”

“…The global results of the measurements are the following: a list of the positions of microcracks, the strain of the samples and the energy released as a function of the control parameter P . Further details of the setup are described elsewhere [10,9,21,22]. …”

“…However it has to be stressed that eq.1 and 2 are certainly first order approximation because they neglect the tensorial nature of crack perturbations and their long range interactions [6]. These ideas are quite interesting and it is important to check experimentally whether they can be applied in heterogeneous materials, such as fiber glass and wood pannels [21]. In two recent papers [9,10], we have shown that in these materials the microcracks, preceding the main crack form something like a coalescence around the final path of the main crack.…”

Thermally activated fracture of porous media

“…When a constant stress is applied to a solid, it will eventually break, even if the applied stress is below the experimental breaking threshold [1][2][3][4][5][6][7]. This phenomenon is known as subcritical rupture.…”

Present patterns of decelerating–accelerating seismic strain in South Japan

“…Considering previous studies where a large number of worldwide observations was used (Bufe and Varnes 1993;Bowman et al 1998;Papazachos and Papazachos 2001;Papazachos et al 2005, among many others), theoretical considerations and laboratory results (Rundle et al 1996;Ben-Zion et al 1999;Guarino et al 1999;Rundle et al 2000;Ben-Zion and Lyakhovsky 2002), as well as stress transfer considerations (Mignan et al 2007), a typical value for exponent m equal to 0.3 was adopted in the present study. Bowman et al (1998) suggested the minimization of a curvature parameter, C, which is defined as the ratio of the root mean square error of the power law fit (relation 1) to the corresponding linear fit error.…”