Search results for "engineering.material"
showing 10 items of 2352 documents
An experimental and constitutive investigation on the chemo-mechanical behaviour of a clay
2013
Engineering issues for which the understanding of the chemo-mechanical behaviour of soils is relevant include wellbore stability problems, the salinification of groundwater, and nuclear waste storage. However, despite the vast number of situations in which couplings between chemistry and mechanics occur, the available constitutive models rely on limited experimental evidence. This paper presents the results of an experimental programme on the chemo-mechanical behaviour of a non-swelling illite. The osmotic suction is controlled through the ion concentration of sodium chloride in the pore water. Stress paths include mechanical loading at a constant osmotic suction, and an increasing osmotic …
Electrochemical Impedance Spectroscopy Study of the Behaviour of Lanthanide-Rich Films Formed on Aluminium-Magnesium Alloys
1998
The film covering formed on AA5083 aluminium-magnesium alloy by immersion treatments in solutions containing CeCl 3 has been characterized by means of electrochemical techniques. The measurement of linear polarization has enabled to establish that the treatments applied provide efficient protection against both uniform and pitting corrosion of alloy AA5083, used in shipbuilding, in solutions of NaCl. This study has been focused on the use of Electrochemical Impedance Spectroscopy as a characterization technique for these film coverings.
Laser induced decohesion of coatings: probing by laser ultrasonics.
2002
The aim of the present study is to investigate a conventional laser-ultrasonics technique for the determination of intrinsic properties of oxide coatings and their adhesion strength on a metallic substrate. The good agreement between experiments and computations in an epicenter configuration allows determining the longitudinal wave velocity as well as the Young's modulus of the oxide coatings versus the porosity. For a critical value of the laser energy, a breakdown at the coating-substrate interface is generated by the laser irradiation. The critical tensile stress field developed at the coating/substrate interface, which leads to the interfacial fracture, can be easily calculated. The val…
Simultaneous laser generation and laser ultrasonic detection of the mechanical breakdown of a coating–substrate interface
2001
Abstract The present study deals with information that could be obtained by real-time contactless monitoring of the normal displacement, due to the propagation of the longitudinal waves generated by nanosecond pulsed laser irradiation, through a transparent and porous ceramic coating deposited on a metallic substrate. These displacements were recorded in real-time at the rear surface of the specimens using a laser heterodyne interferometer and were correlated with the different steps of laser/material interaction (thermoelastic interactions, fracture of the coating–substrate interface and coating expulsion). An analytical model was developed to establish a relation between the longitudinal …
Modeling Atmospheric Turbulence via Rapid Distortion Theory: Spectral Tensor of Velocity and Buoyancy
2017
Abstract A spectral tensor model is presented for turbulent fluctuations of wind velocity components and temperature, assuming uniform vertical gradients in mean temperature and mean wind speed. The model is built upon rapid distortion theory (RDT) following studies by Mann and by Hanazaki and Hunt, using the eddy lifetime parameterization of Mann to make the model stationary. The buoyant spectral tensor model is driven via five parameters: the viscous dissipation rate ε, length scale of energy-containing eddies L, a turbulence anisotropy parameter , gradient Richardson number (Ri) representing the local atmospheric stability, and the rate of destruction of temperature variance . Model outp…
Aggregation and Gel Formation in Basic Silico−Calco−Alkaline Solutions Studied: A SAXS, SANS, and ELS Study
1999
Gelation of strongly basic silico−alkaline solutions was promoted by appropriate additions of calcium ions. The structure of the aggregates formed in the precursor sols and the resulting gels were studied, within a wide length scale, using small-angle X-ray, small-angle neutron, and elastic light scattering. The study of the kinetics of aggregation was performed in situ. The experimental results demonstrate that gels are composed of aggregates exhibiting a fractal structure, large particles formed in the solutions just after calcium addition and, in some cases, small primary particles remaining in the solution phase. The structural features of the gels are strongly dependent on the concentr…
Validation of buoyancy driven spectral tensor model using HATS data
2016
We present a homogeneous spectral tensor model for wind velocity and temperature fluctuations, driven by mean vertical shear and mean temperature gradient. Results from the model, including one-dimensional velocity and temperature spectra and the associated co-spectra, are shown in this paper. The model also reproduces two-point statistics, such as coherence and phases, via cross-spectra between two points separated in space. Model results are compared with observations from the Horizontal Array Turbulence Study (HATS) field program (Horst et al. 2004). The spectral velocity tensor in the model is described via five parameters: the dissipation rate (), length scale of energy-containing eddi…
Efficient Anodic and Direct Phenol-Arene C,C Cross-Coupling: The Benign Role of Water or Methanol
2012
C,C cross-coupling reactions for the synthesis of nonsymmetrical biaryls represent one of the most significant transformations in contemporary organic chemistry. A variety of useful synthetic methods have been developed in recent decades, since nonsymmetrical biaryls play an evident role in natural product synthesis, as ligand systems in homogeneous catalysis and materials science. Transformation of simple arenes by direct C,H activation belongs to the cutting-edge strategies for creating biaryls; in particular the 2-fold C,H activation is of significant interest. However, in most examples very costly noble metal catalysts, ligand systems, and significant amount of waste-producing oxidants …
Evaluation of thin film adhesion to a compliant substrate by the analysis of progressive buckling in the fragmentation test
2009
The interface toughness of a thin coating/compliant substrate system is estimated based on the evolution of coating buckle patterns in the fragmentation test. The linear density of coating buckles as a function of applied strain is determined experimentally for a SiOx coating deposited on a polyethylene terephthalate film. A three-dimensional non-linear finite element model is developed to simulate the process of buckle formation in a single narrow coating strip. The elastic energy released during buckling-driven delamination is obtained from the energy balance in the system before and after the buckling event. Both the interface adhesion and the total energy release rate, which includes th…
Endothelialization and Anticoagulation Potential of Surface-Modified PET Intended for Vascular Applications.
2018
In vascular tissue engineering, great attention is paid to the immobilization of biomolecules onto synthetic grafts to increase bio- and hemocompatibility-two critical milestones in the field. The surface modification field of poly(ethylene terephthalate) (PET), a well-known vascular-graft material, is matured and oversaturated. Nevertheless, most developed methods are laborious multistep procedures generally accompanied by coating instability or toxicity issues. Herein, a straightforward surface modification procedure is presented engineered to simultaneously promote surface endothelialization and anticoagulation properties via the covalent immobilization of gelatin through a photoactivate…