Tunable Auxiliary Mass Damper with Friction Joint: Numerical Assessment

Auxiliary Mass Dampers (AMD) are often used to reduce excessive vibration amplitude in mechanical systems. It is also known that their performances are susceptible to changes in the frequency or in the nature of the excitation force. Therefore, to improve the robustness of the AMD it is necessary to design new systems which are adaptable to the excitation, i.e., tunable devices that could be used over large frequency range. In this work a friction damper, which is the association of an elastic element and a scratcher, is used to tune the AMD by changing the normal force in the scratcher at the same time that it dissipates the mechanical energy of the principal mass. This AMD is named Tunable Auxiliary Mass Damper (TAMD). Three normal force control strategies, and two combinations of them, are studied: (i) The normal force is assumed constant; (ii) The normal force is obtained from the solution of the equation of motion assuming null displacement for the principal mass; (iii) The normal force is obtained based on the vibratory system’s movement, warranting that the direction of the friction force promotes the movement of the principal mass toward its static equilibrium position. The effectiveness of the proposed TAMD is numerically evaluated based on mass and frequency ratios variations for each strategy. Therefore, a multi-degree-of-freedom (MDOF) system analysis is made in order to verify the TAMD’s robustness and efficiency.