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

Developments in Shell Surface Characterizations Using Holography

International audienceThe Digital Holographic Microscopy (DHM) technology allows fast three-dimensional (3-D) surface image acquisition in order to characterize and quantify defects on microshell outer surface. This device captures holograms and reconstructs a double image, one for the intensity and another for the phase. Depending on the used objective lens (20× or 50×) and the microshell diameter, several hundred or thousand pictures must be taken to cover both hemispheres (1170 pictures for a 2200-$\mu$m-diameter capsule). A specific handling system using two rotation axes has been developed to acquire automatically all 3-D hemispherical data without any manipulation.A new version of the 3-D surface rebuilding (using images stitching) and analyzing software is used to characterize (diameter and height measurement) and to localize individual defects, such as bumps or pits. Using a new version of the dedicated software, the pictures are filtered and stitched together to perform a 3-D surface mapping of the capsule. Postprocessing routines are able to detect defects and to sort them out. Specific tools are also dedicated to the characterization of polishing defects, such as concave or clustered defects.In addition to this, a study of the DHM metrology capabilities, including a comparison with a calibrated atomic force microscope, has been led