Computation of impact-friction interaction between a vibrating tube and its loose supports

Maintaining PWR components in reliable operating condition requires complex design to prevent various damaging processes including flow-induced vibration and wear mechanisms. To improve prediction of tube/support interaction and wear in PWR components, EDF has undertaken a comprehensive program involving both calculations and experiments. This paper describes EDF numerical development with the Aster mechanics computer code to calculate the non-linear dynamics of tubular structures with loose supports. Both numerical and experimental validations of this computer code are given. The numerical technique for dynamic simulation is based on a Ritz decomposition method, including the modal superposition method as used in some other computer codes. The explicit expression of impact and friction forces allows a fast, explicit integration scheme to be used. Different projection bases are compared. Some can improve significantly the resolution of the dynamic problem. The code numerical validations consist in simulations of some mechanical configurations (analytical or computed) provided in the literature. The comparison of the Aster calculation results with the available data of the literature shows the high accuracy of the computer code. A validation on some experimental data is also provided. The experiment used for this validation consists in a multi-supported U-tube, with four loose supports in the U-bend and submitted to harmonic and broad band excitation forces. Three of them correspond to a small gap Gs, and the fourth one to a large gap G1 (G1 = 15 Gs). In this experiment, the excitation forces are varied. For each configuration, the tube response is computed and compared to the experimental results. The analysis of the parameters governing wear concludes to a good accordance between the calculated and measured values. (authors). 13 figs., 4 tabs., 10 refs