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2 Journal of Theoretical and Applied Mechanics

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Selection of viscous damping coefficients using the continuous wavelet transform method for a gear system

Yousfi Nourhaine, Zghal Bacem, Akrout Ali, Walha Lassaad, Haddar Mohamed

Journal of Theoretical and Applied Mechanics

2020

Vol. 58 nr 3

585--598

Viscous damping is frequently used in the equation of motion to present the dissipation mechanism of a mechanical system. The orders of frequencies can be easily selected to determine viscous damping coefficients (VDCs) when the degree of freedom of the structure is low. For complex structures, difficulties in selecting the orders of reference frequencies to obtain reasonable VSCs are encountered. This paper mainly discusses the capability of the CWT method to select optimum frequencies of viscous damping formulation. The proposed procedure considers both the classical Rayleigh, modal and the proposed full model modal damping. The method is validated using a numerical time domain response of a two-stage gear system.

Numerical modeling of uncertainty in acoustic propagation via generalized Polynomial Chaos

Dammak Khalil, Koubaa Sana, Elhami Abdelkhalak, Walha Lassaad, Haddar Mohamed

Journal of Theoretical and Applied Mechanics

2019

Vol. 57 nr 1

3--15

This work aims at increasing the performance prediction for acoustic propagation systems that will operate in the presence of the inevitable parameters uncertainty. In the present contribution, the finite element method is applied to solve an acoustic problem described by the Helmholz equation when the geometric and material properties present uncertainty. The influence of the uncertainty of physical parameters on the pressure field is discussed. The results using the polynomial chaos expansion method are compared with Monte Carlo simulations. It is show that uncertainty levels in the input data could result in large variability in the calculated pressure field in the domain.