Amortissement d'une poutre par traitement viscoelastique contraint et analyse du regime transitoire suite a un impact

The effects of a viscoelastic partial constrained layer damping (PCLD) treatment on the initial transient response of all impacted beam are studied using an analytical model. The viscoelastic properties of the core are frequency dependent and the shear modulus is modelled using a Prony Series. The equations of motion (EOM) of the system are obtained using Lagrange's equations. The forces used are characterized by a quick increase up to a maximum value of approximately 10 Newtons and a slower decrease until the force disappears. The EOM are converted in the frequency domain using Fourier Transform and they are solved for frequency displacements using the assumed modes method. Displacements are then converted back in the time domain using an inverse Fourier Transform. The technique is validated for natural frequencies and for transient responses using experimental impact signals. The numerical results are in good agreement both with open literature and experimental data. These data are obtained by exciting different beams with various PCLD configuration using an impact hammer. The displacements are measured over different positions. Four PCLD parameters are studied: the length, the placement, the viscoelastic layer thickness and the constraining layer thickness. It turns out that (1) the longer is the PCLD, the smaller are the initial transient displacements; (2) a thicker constraining layer leads to smaller transverse displacements; (3) the viscoelastic layer thickness has little effect on the displacements when the constraining layer is thick; (4) a thick viscoelastic layer leads to smaller displacements if the PCLD is long; (5) combining a short PCLD and a placement far from the clamped edge may result in non causal diplacements. It is shown that the added mass does not change the above-mentioned behaviors.