Cavitation-induced force transition in confined viscous liquids under traction

We perform traction experiments on simple liquids highly confined between parallel plates. At small separation rates, we observe a simple response corresponding to a convergent Poiseuille flow. Dramatic changes in the force response occur at high separation rates, with the appearance of a force plateau followed by an abrupt drop. By direct observation in the course of the experiment, we show that cavitation accounts for these features which are reminiscent of the utmost complex behavior of adhesive films under traction. Surprisingly enough, this is observed here in purely viscous fluids.Comment: Submitted to Physical Review Letters on May 31, 2002. Related informations on http://www.crpp.u-bordeaux.fr/tack.htm

Geochemical assessment of thermal water in Bouhanifia aquifer system: suitability for touristic therapeutic treatment

Abstract The touristic balneology is an essential source to promote the economy of the region. Our study aims to identify the geochemistry, the typology and the nature of the thermal waters of Hammam Bouhanifia, a geochemical and bacteriological study was carried out in the region, 13 sources were studied. The geochemical analysis results show a high mineralization of the waters (EC varies between 1.28 and 3.26 mS/cm); high-temperature variation (26 to 65 °C) indicates a high depth emergence. The geochemical classification of waters by the piper diagram shows typical Ca–Mg waters with a dominance of sulphates. All the water points have good bacteriological quality with the exception of source No. 6, which may indicate an infiltration of domestic discharges. The thermal reservoir of Hammam Bouhanifia may represent an important source of geothermal energy in Algeria in addition to its role in the development of thermal tourism in the western region of the country

Deformation and Failure Modes of Adhesively Bonded Elastic Layers

Adhesively bonded elastic layers with thicknesses that are small relative to their lateral dimensions are used in a wide variety of applications. The mechanical response of the compliant layer when a normal stress is imposed across its thickness is determined by the effects of lateral constraints, which are characterized by the ratio of the lateral dimensions of the layer to its thickness. From this degree of confinement and from the material properties of the compliant layer, we predict three distinct deformation modes: (1) edge crack propagation, (2) internal crack propagation, and (3) cavitation. The conditions conductive for each mode are presented in the form of a deformation map developed from fracture mechanics and bulk instability criteria. We use experimental data from elastic and viscoelastic materials to illustrate the predictions of this deformation map. We also discuss the evolution of the deformation to large strains, where nonlinear effects such as fibrillation and yielding dominate the failure process

Peeling of Polydimethylsiloxane Adhesives : the Case of Adhesive Failure

International audienceThe adhesion properties of high molecular weight Polydimethylsiloxane adhesives are measured using 90°-peel adhesion tests, in the high velocity range. Such adhesives undergo mainly adhesive failure in this regime. The influence of viscosity (non-Newtonian), adhesive thickness, peeling velocity, and backing properties are studied, and new unexpected behaviours are shown. The role of rheology and peeling velocity can be explained by an extension of a model already presented for cohesive failure, by using a power-law fluid for the adhesive. On the other hand, the influence of the backing rigidity reveals to be coupled with the adhesive elastic properties, this effect being correlated to the introduction of a new parameter in the model, the Weissenberg number for viscoelasticity