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The design of disk assemblies requires the capability to predict their dynamic behavior. To achieve this objective, knowledge of friction damping on the contact between blade and disk is of paramount importance. This paper proposes an experimental technique to measure the loss factor and the dynamics, in terms of natural frequencies, of blade-disk attachment. The free decay is used to infer the dynamic parameters from dummy blades. The identification method is based on the Hilbert transform that allows extracting the dynamic parameters from non-linear system. This paper shows the test rig utilized in the experimental analysis and details the excitation system used to displace the dummy blade. This system must be a real or a “virtual” non-contact system to avoid injecting external damping into the blade under test. Tests were performed on both a dovetail and a fir-tree type attachments. On the dovetail, tests were performed both with dry contact surfaces and with contact surfaces covered by a film of lubricant to achieve a low coefficient of friction. This low coefficient of friction better simulates dry surfaces at high temperatures, as friction coefficients decrease with temperatures. This paper presents the results obtained on the first and second bending mode. The experimental results show the loss factor and the natural frequency for different axial loads. The measured loss factor depends on the amplitude of vibrations. As predicted with theoretical analyses the loss factor shows a maximum then approaching zero for large amplitude of vibrations. As a rule, it decreases with increasing centrifugal loads.

The stability under dynamic mechanical solicitation and with the temperature of the elastomagnetic composite made of Sm2Co7 particles embedded in a silicone matrix is investigated. The thermal stability was examined by DSC measurements. The thermal (up to congruent to 340 degrees C) and mechanical ageing effects on the material elastomagnetic response were investigated by measuring the amplitude, V-0, of the electromotive force induced in a pick-up coil during the dynamic mechanical solicitation of the sample. It was found that for the whole investigation range of temperatures, the V, dependence on the frequency, v, and amplitude, D, of the externally induced deformation is linear and its amplitude is not changing for treatments up to 150 degrees C; for higher temperature treatments the response amplitude is decreasing. The analysis of the response signal (registered at 1 h intervals) after dynamic mechanical solicitation carried out during 48 h, shows the excellent output reliability and no decrease in amplitude with time.

Pulsed laser deposition is a technique used since twenty years ago for the production of nanoparticles films. Laser pulses with a duration in the femtosecond, picosecond and nanosecond range have been employed for material processing as well as for ablation and deposition of semiconductors, superconductive materials, ceramics, magnetic layers and multilayers. Recently, results on the ultra-short pulsed laser deposition (uPLD) revealed this technique as particularly interesting for the deposition of magnetic nanogranular films. This review deals with the innovative findings and the potential developments related to the use of uPLD. The following points are addressed: first, the peculiar shape and orientation of the nanoparticles in the films obtained by the uPLD technique; second, the capability of uPLD to reproduce the stoichiometry in target material in the deposited film; third, the possibility to produce nanogranular amorphous film from polycrystalline target; fourth, the potentiality of uPLD in tailoring the magnetic softness of the film by means of a co-deposition of hard and soft magnetic nanoparticles. Finally, we briefly discuss the potential applications of the uPLD in the production of composite nanogranular films with interesting performances for improved magnetostrictive and magnetoresisitive micro-devices.