Experimental Characterization of Fixtures Design: A comprehensive study on vibration minimization technique by using viscoelastic materials

Sammanfattning: Damping is a phenomenon which is obviously related with dissipation of vibration energy under relative motion in a mechanical system. Without changing excitation force in many cases vibration is reduced only by changing mass or stiffness of the system just with altering the resonance frequencies. Most of the cases tuneable device with vibration or damping materials minimizes mechanical vibration by absorbing vibration energy from structure. There are some damping methods investigated to control the vibration for example, active, semi-active, semi-passive and passive method. Actuators together with sensors and analog or digital controllers are involved in active damping control of vibration. Active method cancels the disturbance caused by vibration by producing an out of phase actuation. Passive control mechanism doesn’t include the real time active algorithm which must exist in active method. Passive method includes damping device within the structure aiming to control or isolate energy dissipated from vibration. There are several kinds of damping materials used as a passive control of vibration such as tuned mass dampers, shunted piezoelements dampers, viscous dampers and viscoelastic dampers. This thesis deals with the last one that is viscoelastic damping. Viscoelastic materials are used as the joint interface which has both viscous and elastic properties. To examine how this interface materials affect the whole structure a prototype design of different geometric shaped joints are made by solid edge software. The geometric shapes of joint interface are flat, conical and spherical. Two types of experiment (theoretically and experimentally) are done to find out the frequency response function of the structure. First one is finite element modeling with comsol multiphysics 4.3a and second one is with LMS Test Lab which consist high sensitivity accelerometer sensors. This is proved from the both experiments that joint interface material greatly affect the dynamic characteristics of the whole structure. Although there are some quantitative difference in results between the simulation and test lab, the results show similar trends. This conclusion is drawn from the comparative study between the simulation and test lab results.