Abdelkader N., Youcef O., Nouredine C., Abderrahmane S.

Abstract This work concerns the characterization of the thermodynamic behaviour of the superalloy Airsist 215 (PN 3601669-7) containing cobalt. Such superalloys are used in aeronautical construction, in the hot parts of the turbine. They are frequently used for the production of the paddles. The parts in service are subjected to dynamic sillicitations and thermals fluctuating in the course of time. They are responsible of modifications and degradations of the properties of the material. This can lead to the appearance of splits and in a long term to the rupture of these parts. A preliminary physical study is made on the appearance of the splits, then experiments by shocks at ambient temperature and under heating situation which simulates combustion. Thus, these dynamic charges have a very significant impact on the development of the splits which appear on the segments of the Nozzle turbine. The study is devoted to the elastic shock of Hertz-Boussinesq extended to viscoelastic bodies by direct convolution of Riemann-Stielges. The interest resides in the local convolution and the distribution of stresses in the contact zone. The excitation method by shock is made by mean of a deduced force; in load and disload phases. This force is an impulse which approaches a Dirac function. The sample can be represented, in approached manner, by a system of one degree of liberty, for natural frequency, damping and the transfer function. The spectral response of the specified shock allows calculating the damping. Every point of this spectrum gives the response for the linear system of the transfer function. Then, we deduct some parameters intervening in viscoelastic shock. Keys words: Shocks / transfer function / damping / shocks and impact / Dynamic charges.