Search results for "Ceramic"
showing 10 items of 2129 documents
Exact 3D solution for static and damped harmonic response of simply supported general laminates
2014
International audience; The state-space method is adapted to obtain three dimensional exact solutions for the static and damped dynamic behaviors of simply supported general laminates. The state-space method is written in a general form that permits to handle both cross-ply and antisymmetric angle-ply laminates. This general form also permits to obtain exact solutions for general laminates, albeit with some constraints. For the general case and for the static behavior, either an additive term is added to the load to simulate simply supported boundary conditions, or the plate bends in a particular way. For the dynamic behavior, the general case leads to pairs of natural frequencies for each …
On the FE codes capability for tool temperature calculation in machining processes
2006
Abstract The applications of numerical simulation to machining processes have been more and more growing in the last years: today a quite effective predictive capability has been reached, at least as far as global cutting variables (for instance cutting forces) are concerned. On the other hand, the capability to predict local cutting variables (i.e. pressure on the tool, temperature distribution, residual stresses in the machined surface) has to be heavily improved and verified. At the same time, effective experimental procedures for validating numerical results have to be developed. In this work two different approaches were implemented for temperature measuring: a thermocouple based appro…
Out-of-plane elastic constants of curved cell walls honeycombs
2021
International audience; The work describes the out-of-plane properties of a curved wall honeycomb structure evaluated using analytical models and finite elements techniques. Out-of-plane properties are calculated using a theoretical approach based on energy theorems and validated using a fullscale<br>finite element technique to simulate transverse shear tests. The effects of the curvature of the walls and the depth of the honeycomb cells on the out-of-plane elastic constants are evaluated and excellent agreement is observed between theoretical and numerical models. These curved cell wall honeycombs feature specific (i.e., relative density weighted) highly tailorable upper shear bounds tha…
Flying Laser Spot Thermography technique for the NDE of Fibre Metal Laminates disbonds
2017
Abstract The present work investigates the features of an active Infrared-NDT Thermography technique derived from a Flying Laser Spot set-up for the analysis of interlaminar disbonds in layered structures in general and Fibre Metal Laminates in particular. The presented technique uses a laser-spot heat source, which moves at a constant speed, raster scanning the object surface. Interlaminar defects parallel to the surfaces act as barriers towards through-the-thickness heat diffusion. This produces some modifications over the surface thermal field which are well identified in the Standard Deviation calculated over a Reference Area following the heat source. The mechanisms leading to such def…
Kinetics of block-copolymer aggregation in super critical CO2
2002
Small angle X-ray and neutron scattering (SAXS and SANS) are used to obtain structural information on the aggregation behavior of block-copolymers dissolved in supercritical CO2. The SANS technique is used to provide a detailed structural model for the micellar aggregates, which form below the critical micellization density (CMD), that we defined in our previous work. The SAXS technique (with a synchrotron source) is used to provide the first experimental information concerning the kinetic features of both formation and decomposition of such aggregates as soon as pressure jumps are applied to the solutions across the CMD. 2002 Elsevier Science B.V. All rights reserved.
A high-resolution layer-wise discontinuous Galerkin formulation for multilayered composite plates
2020
Abstract In this work, a novel high-resolution formulation for multilayered composite plates is presented. The formulations is referred to as high-resolution since it combines (i) Layer-Wise plate theories, which are based on a per-layer, high-order expansion of the primary variables throughout the plate’s thickness, providing a detailed layer-level description of the sought solution; (ii) The discontinuous Galerkin method, a numerical approach based on a discontinuous representation of the unknown fields over the mesh elements and on the introduction of boundary integral operators enforcing inter-element continuity, which allow the natural treatment of high-order mesh elements and provide …
A non-linear Ritz method for the analysis of low velocity impact induced dynamics in variable angle tow composite laminates
2021
Abstract Variable angle tow (VAT) laminates feature composite layers reinforced by fibres following continuous curved paths and offer a wide structural design space for the manufacturing of composite components. In this work, a formulation for the analysis of the impact-induced dynamics in VAT laminated plates is proposed, implemented and tested in this work. The method is based on the adoption of first order shear deformation kinematics and includes von Karman non-linear strains. The discrete system is obtained by employing a pb-2 Ritz series expansion into the Hamilton’s variational statement, while the impact loading is modelled through Hertzian contact law. The resulting non-linear gove…
Numerical study of photolithography system: electromagnetic differential method
2004
The R-matrix propagation algorithm is incorporated into the differential method to achieve an extended capability for modelling a photolithography systems. We show throughout this work the ability of the R-matrix algorithm and differential method to analyse gratings of arbitrary depth, profile, and conductivity without encountering numerical instabilities. We calculate the field intensity and the transmitted amplitudes in the 0 and −1 orders below different masks. We study also the influence of the various parameters (incidence, groove spacing, groove depth and index of refraction) on the field intensity maps and the transmittivity power. These results agree with the experimental patent: we…
EXAFS studies on the local structure of Er3+ ions in silica xerogels co-doped with aluminium
2001
The local environment around Er3+ ions in wet and densified (at 900°C) silica xerogels (pure and co-doped with aluminium) has been studied at the Er L3-edge by X-ray absorption spectroscopy using the fluorescence detection technique. The radial distribution functions (RDF), reconstructed from X-ray absorption fine structure (EXAFS), show several changes in the local co-ordination of erbium ions upon densification: shortening of the Er-O and Er-Si/Al distances, decrease of the co-ordination numbers and broadening of the Er-O RDF. The effect of Al co-doping is clearly discerned by EXAFS in both the first and second co-ordination shells for densified gels and mainly in the second shell for wet…
Formation of nanostructures in Eu3+ doped glass-ceramics: an XAS study.
2012
We describe the results of x-ray absorption experiments carried out to deduce structural and chemical information in Eu(3+) doped, transparent, oxyfluoride glass and nanostructured glass-ceramic samples. The spectra were measured at the Pb and Eu-L(III) edges. The Eu environment in the glass samples is observed to be similar to that of EuF(3). Complementary x-ray diffraction experiments show that thermal annealing creates β-PbF(2) type nanocrystals. X-ray absorption indicates that Eu ions act as seeds in the nanocrystal formation. There is evidence of interstitial fluorine atoms around Eu ions as well as Eu dimers. X-ray absorption at the Pb-L(III) edge shows that after the thermal treatmen…