1,721,014 research outputs found
Pierro (Elena). Ceramica «ionica» non figurata e coppe attiche a figure nere. {Materiali del Museo Archeologico Nazionale di Tarquinia. VI).
No full textLaffineur Robert. Pierro (Elena). Ceramica «ionica» non figurata e coppe attiche a figure nere. {Materiali del Museo Archeologico Nazionale di Tarquinia. VI).. In: Revue belge de philologie et d'histoire, tome 66, fasc. 1, 1988. Antiquité - Oudheid. pp. 218-219
Erratum: Loading-unloading hysteresis loop of randomly rough adhesive contacts (Physical Review E - Statistical, Nonlinear, and Soft Matter Physics (2015) 92 (062404))
No full textThis corrects the article DOI: 10.1103/PhysRevE.92.062404
Does roughness make elastic-adhesive contacts dissipative?
Full text linkIn this paper we investigate the adhesive contact between a rubber block and rigid randomly rough profiles, in loading and unloading conditions. The roughness is assumed to be described by a self-affine fractal on a limited range of wave-vectors. We employ a spectral method to generate such randomly rough surfaces with different root mean square roughness values and fractal dimensions. Calculations are performed for each profiles by means of an ad hoc numerical code previously developed by the authors.The calculated data are then statistically averaged, and the contact area, the applied load are shown as a function of the penetration, both for loading and unloading conditions. It is found that the combination of adhesion forces and roughness leads to a hysteresis loading-unloading loop, which might be unexpected for perfectly elastic materials. This result is very interesting as it shows that energy can be lost simply as a consequence of roughness and van der Waals forces. Our calculations enable us to numerically quantify such an energy loss and, in particular, to assess the influence of the surface statistical properties and the energy of adhesion on the hysteresis process
Microcantilever dynamics: effect of Brownian excitation in liquids
No full textNowadays dynamic atomic force microscopes (dAFM) are being extensively investigated because of the so different and novel applications where dAFM are employed, e.g. to study biological targets as cells, proteins, DNA. In such cases the micro-cantilever tip often needs to operate in a liquid environment to extract the required information from the sample. However, tip dynamics is strongly affected by the presence of the liquid itself, so that understanding the actual microcantilever response in such conditions, has become one of the most challenging problems the researchers are trying to face. A deep knowledge of the degree of interaction between the cantilever dynamics and the fluid is extremely important to avoid misleading information. Because of the micro-scale size of the cantilever, thermal noise due to Brownian forcing of liquid particles cannot be neglected and therefore proper insights about this effect are required. This is why different numerical approaches have been presented in literature, which only approximatively describe the liquid - cantilever interaction. In this paper the authors provide a useful and relatively simple tool to describe the fluid-structure interaction. In particular we present an analytical heuristic formulation of the force the liquid exerts on the cantilever, which can be successfully utilized to investigate the AFM cantilever dynamics under the action of both linear and non linear forces. In particular we show that the liquid response consists of three terms: (i) a viscous term, (ii) a velocity-diffusive term, and (iii) an inertial term. The novelty of the model is mainly represented by the velocity-diffusive term, that to the best of our knowledge has never been taken into account before. We show indeed, that neglecting this term leads to large errors in the estimation of the cantilever response and , hence, of its thermal response, which is often used to calibrate the instrument
Loading-unloading hysteresis loop of randomly rough adhesive contacts
Full text linkWe investigate the loading and unloading behavior of soft solids in adhesive contact with randomly rough
profiles. The roughness is assumed to be described by a self-affine fractal on a limited range of wave vectors.
A spectral method is exploited to generate such randomly rough surfaces. The results are statistically averaged,
and the calculated contact area and applied load are shown as a function of the penetration, for loading and
unloading conditions. We found that the combination of adhesion forces and roughness leads to a hysteresis
loading-unloading loop. This shows that energy can be lost simply as a consequence of roughness and van der
Waals forces, as in this case a large number of local energy minima exist and the system may be trapped in
metastable states. We numerically quantify the hysteretic loss and assess the influence of the surface statistical
properties and the energy of adhesion on the hysteresis process
- …
