École nationale supérieure des mines de Nancy

About: École nationale supérieure des mines de Nancy is a education organization based out in Nancy, France. It is known for research contribution in the topics: Seebeck coefficient & Thermoelectric effect. The organization has 148 authors who have published 174 publications receiving 4194 citations. The organization is also known as: Ecole nationale superieure des mines de Nancy & Mines Nancy.

Brittle‐ductile transition and associated seismicity: Experimental and numerical studies and relationship with the b value

Abstract: The acoustic emission (AE) and the mechanical behavior of granite samples during triaxial compression tests have been analyzed. The size of AE events displays power law distributions, conforming to the Gutenberg-Richter law observed for earthquakes, which is characterized by the b value. As the confining pressure increases, the macroscopic behavior becomes more ductile. For all different stages of the rock mechanical behavior (linear, nonlinear prepeak, nonlinear postpeak, shearing), there is a systematic decrease of the b value with increasing confining pressure. A numerical model based on progressive elastic damage and the finite element method allows simulations of the main experimental observations on AE and of a wide range of macroscopic behaviors from brittleness to ductility. The model reproduces a decrease in the b value that appears to be related to the type of macroscopic behavior (brittle-ductile) rather than to the confining pressure. Both experimental and numerical results suggest a relationship between the b value and the brittle-ductile transition. Moreover, these results are consistent with recent earthquake observations and give new insight into the behavior of the Earth's crust.

Physical analysis of the state- and rate-dependent friction law. II. Dynamic friction

Abstract: We report an extensive study of dynamic friction at nonlubricated multicontact interfaces between nominally flat bodies, rough on the micrometer scale, made of identical polymer glasses. This work, which complements a previous study of static friction on the same systems, has been performed at temperatures ranging from $20\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ to close below the glass transitions. The data are analyzed within the framework of the Rice-Ruina state- and rate-dependent friction model. We show that this phenomenology is equivalent to a generalized Tabor decomposition of the friction force into the product of an age-dependent load-bearing area and of a velocity-strengthening interfacial shear stress. Quantitative analysis of this latter term leads to associate velocity strengthening with thermal activation of basic dynamical units of nanometer dimensions. We interpret our results with the help of a model due to Persson, in which shear is localized in a nanometer-thick interfacial adhesive layer, pinned elastically at a low shear level. Sliding proceeds via uncorrelated depinning of ``nanoblocks'' which constitute the layer. It is the competition between the drive-induced loading of these blocks up to their depinning stress and the thermally activated premature depinning events which leads to the velocity-strengthening contribution to the interfacial strength. In our interpretation, friction therefore appears as the localized elastoplastic response of a confined amorphous interfacial layer.

Surface integrity of dry machined titanium alloys

Abstract: The study is focused on the machined surface integrity of titanium alloy under the dry milling process. Roughness, lay, defects, microhardness and microstructure alterations are investigated. The result of surface roughness shows that the CVD-coated carbide tool fails to produce better Ra value compared to the uncoated tool. Lay is found to be dependent on cutting speed and feed speed directions. Microhardness is altered down to 350 μm beneath the machined surface. The first 50 μm is the soft sub-surface caused by thermal softening in the ageing process. Down to 200 μm is the hard sub-surface caused by the cyclic internal work hardening and then it gradually decreased to the bulk material hardness. It was concluded that for titanium alloys, dry machining can be carried out with uncoated carbide tools as far as cutting condition is limited to finish and/or semi-finish operations.

Macrosegregation in steel strands and ingots : Characterisation, formation and consequences

Abstract: The paper presents a survey of the work that was carried out in Nancy on segregation in steel strands and ingots since 1985. The basic phenomena that were subject of intense research effort are the followings: origin, growth, and movement of equiaxed crystals, as concerns large ingots; deformation of the mushy zone just before completion of solidification, as concerns continuous casting slabs.