A few years ago, some authors have observed by X-ray diffraction analysis in metallic multilayers with small period an in plane expansion combined with a large perpendicular expansion. These trends differ from prediction based on simple continuum elasticity theory. This unexpected result has been the starting point of an experimental development in our laboratory for determining the Poisson's ratio in such systems. Applying the $\sin^{2}\psi$ method on film-substrate set which is elastically deformed in an X-ray diffractometer, it is possible to extract the Poisson's ratio of the film. In this paper, we first detail the theoretical principles of the method and, we show its application on 150 nm thick tungsten films elaborated by ion beam assisted deposition on duralumin substrates. The obtained results demonstrate the feasibility of the method and its good precision.

To determine the mechanical properties of materials in thin layers by the measure of Lamb waves velocities, the acoustic microscopy can be used in two different manners: by the spatial acoustic signature V(z), and, less widespread, by the frequency acoustic signature V(f). However, in this study, we show that for each of these signatures V(z) or V(f), there are complementary domains of use in which the detection and the efficiency of Lamb modes are optimized. A specific formalism permits to foresee each of these domains where the efficiency is optimized.

We investigated the behaviour in tension and at room temperature of TiNi shape memory alloys in martensitic state. Our first experimental results show that two deformation mechanisms are involved in the behaviour of such materials: martensite platelets reorientation and irreversible plasticity. Moreover when irreversible plasticity appears, we observe an increase in the martensite to austenite transformation temperatures. The present study is especially focused on the deformation mechanisms and intends to identify the nature of the irreversible phenomena. It is shown that the reorientation process and the appearance of interface dislocations are in perfect agreement with a kinematic hardening. Finally a two loading surface model is proposed which allows not only to account for the overall behaviour but also to predict the transformation temperatures under an internal and/or external stress field.

This paper presents a new experimental measurement method of the electrical parameters, shown from the stator, of a squirrel cage induction machine in accordance with its magnetic saturation level. It develops a new two-phase saturated model of the induction machine which uses these measured electrical parameters. This new measurement method has a very big advantage in the industrial domain. It avoids the use of a finite elements calculation program which takes much more time to calculate the electrical parameters. The experimental measurement method is applied on a 4 KW squirrel cage induction machine. A comparison between the real dynamic response of this machine, and the dynamic response of the new two-phase saturated model shows that the obtained results are very encouraging.

A formalism is defined to describe systems composed of several electrical machines with several electrical and/or mechanical converters. So, a first classification of multi-converter multi-machine systems is proposed in order to point out their influences on the global power conversion: cost reduction, conversion quality... Three examples are presented with this specific formalism.

The alterations of the resonance frequency of the vibrating tip of an acoustic sensor detect the density and the viscosity of liquids. The employed acoustic near-field sensor has several resonance frequencies which correspond to its different parts. We determined that the resonance of the body of the acoustic sensor is sensitive to the rheological characteristics of viscoelastic media. We carried out experiments with bitumens and we modified the acoustic load on the sensor in two ways: the immersion depth of the tip and the temperature of the bitumen specimens. Theoretical and experimental results are compared.

The lifetime of minority carriers in crystalline silicon wafers is determined by means of the contactless microwave phase-shift technique, when the surfaces of the samples are passivated using an iodine aqueous solution of polyvidone. The stability of the passivation is sufficient in order to obtain a lifetime scan map with spatial resolution of 50 µm, using a thin coaxial cable which directs 9.4 GHz microwaves onto the investigated samples and a fiber coupled laser diode which generates carriers in excess. In gold contaminated single crystals an acceptable correlation is found between the lifetime scan maps and the local concentrations of gold determined by deep level transient spectroscopy applied to an array of aluminium silicon diodes. For multicrystalline silicon wafers containing large densities of different extended crystallographic defects, a good correlation is obtained between the lifetime maps and the diffusion length maps obtained by the light beam induced current technique. Both the maps display the same features of extended crystallographic defects and are in agreement with optical micrographs of the scanned samples after they have been chemically etched.