On the damping effect due to bolted junctions in space structures subjected to pyro-shock

The damping due to bolted or riveted joints in the dynamics of assembled structures subjected to pyro-shock has been studied. A relevant effect in this phenomenon is the micro-slip between the jointed surfaces. In order to verify the feasibility and the reliability of the numerical analyses performed on structures with junctions, the numerical results obtained by the finite elements method have been compared with those obtained experimentally. Several numerical analyses, in which friction forces have been represented as nonlinear loads, have been carried out for the FE models of two application cases: an electronic unit mounted within the Radarsat-2 satellite, and the complete Cosmo-Skymed spacecraft. Considering the load type, involving a typical high frequency response spectrum between 100 and 10 000 Hz, both numerical and experimental data have been reduced to the shock response spectrum form. After the comparative evaluation, taking into account also the damping effect, the agreement between numerical results and experimental data has been evaluated. The proposed numerical approach yields an effective and less expensive instrument, able to provide indications in the design phase, to allow the prevision of the dynamic behaviour of the structure for the prevention of failures in units or systems mounted within the spacecraft or launch vehicle. With the proposed model, it is possible to determine in a simple and direct way the characteristics of the damping due to the single bolted and riveted joints, and use them in similar multiple joints in the complete structure assembling or substructuring.