Lamb Wave Imaging and V(Z) Using a Broadband System

The work reported here has been motivated by the need to characterise thin ceramic coatings on metallic substrates. In addition to measuring the elastic constants of the coating, which among other things is dependent on the deposition technique, it is desirable to inspect the condition of the interface between the coating and the substrate. One deposition technique involves plasma-spraying of the ceramic onto a grit-blasted metal surface. Although the top surface of the film can be polished for ultrasonic inspection, the film/substrate interface will be very rough. The Lamb wave V(z) technique has been demonstrated to be effective for the calculation of the elastic constants of thin films on substrates. The effect of surface roughness on the Lamb wave dispersion curves must be well understood however, before this method can be applied to the problem of interest here. As such, a series of tests have been performed on glass slides that have different degrees of roughness introduced on one surface

Three Ultrasonic Devices for the Elastic Moduli Determination at High Temperatures

The aim of this paper is the characterization of materials submitted to high temperatures (up to 3000 °C). In this field, some mechanical tests are available the experiments involve a lot of critical measurements which depends on the applied strength and on the temperature. An alternative solution is an ultrasonic method which advantages are a non destructive mechanism and a possible determination of the elastic moduli for a very weak strength to deformation ratio [1]. In that field, to determine the material behavior at high temperatures by a non destructive method, we propose three different devices. Two of them are based on contact measurement with delay-lines working up to 1000 °C and up to 3000°C respectively. The last device, which is composed of a laser excitation and an interferometric detection, constitutes a non contact method especially useful for materials submitted to temperature neir their melting point. This paper is divided into three parts. The first one presents the principle of the elastic moduli measurement. The second one describes the different experimental set-up and the last part gives some results on metallic and organic samples.</p

Coral cavernous angiomas in a child

Dural-based cavernous angiomas are rare intracranial vascular lesions. Most of the reported cases are located in the middle cranial fossa, and those located outside the middle fossa are even more uncommon. Thus far, only 3 pediatric cases have been reported and all of them were found outside the middle fossa of a neonate. We would like to add the fourth pediatric case of a dural-based cavernous angioma located in the posterior fossa of a 5-year-old boy.link_to_subscribed_fulltex