In mechanical phenomenon

In mechanical phenomenon, any oscillations motion of physical system about an equilibrium point is call as vibration. The amplitude varies with time will describe about the motion in form of harmonic or periodic oscillations 1. There have two classifications of mechanical vibration; free or force vibration. If there are no external forces act at the systems, it will be free vibration, while there are result of external excitations, it will be force vibration. In addition, free and force have damped and undamped vibration. For damped vibration, the energy of vibrating object will lose to surrounding, while undamped vibration, the energy of vibrating object does not dissipating to surroundings over time 2. Vibration experiences in many mechanical and structural applications like machines, building, bridges, vehicles and aircraft. This source of vibration can be come from engine, mechanical device or electric motor. The most vibration phenomena are forced vibration. One sees in everyday life, rotating machine like electric motor will produce force vibration when drive of imbalance rotating parts. When center of mass for the rotating parts is out from the center of rotation, this will produce centrifugal force and produce vibration excitation. In vibration system, if frequency of vibration excitation coincides with the natural frequency of the structure, resonance will occur. Resonance have the potential to damage the system and lead catastrophic failure. Before the failure happened, it is very important to implement the vibration control on the system to reduce or dissipate the vibration energy which transmitted from the source of vibration to the receiver such as base structure, body structure, etc. In field of mechanical, there have two vibration control that can be used; vibration isolator and vibration absorber. The aim for vibration isolator is to absorb the vibration energy that transmitted from one part to the other part of the structure. It is important to determine the performance of vibration isolators by using transmissibility method. Besides, for vibration absorber, it is tune spring-mass system attached on main structure to minimize the vibration amplitudes at a specific set of points. To determine and analyse the vibration system, mechanical structure systems are often classified as single degree of freedom systems, two degree of freedom systems, multi degree of freedom systems or continuous systems which have an infinite number of degrees of freedom.