Vibration of Mechanical Systems:

In previous units, you have studied several mechanisms and machines. The IC engine is one of them that translate thermal energy of fossil fuels to power. It generates highly fluctuating torque. Even the machines have rotating parts are never fully balanced. From static and dynamic analysis of such type machines, it is known that these machines transmit forces to the ground through structure that are periodic in nature.

You know that in a simple pendulum, bob begins to and fro motion or we might say oscillations while bob is disturbed from its equilibrium location. It executes oscillations at natural frequency. This keeps on oscillating till its motion dies out. If such a system is subjected to the periodic forces this responds to the impressed frequency that makes system to execute forced vibration at forcing frequency. If impressed frequency is equivalent to the natural frequency, resonance occur resulting high oscillations and it results in excessive dynamic stresses.

This unit deals with oscillatory behaviour of the dynamic systems. All of the bodies with mass and elasticity are competent of vibration. In learning mechanical vibrations, the bodies are treated like elastic bodies rather than rigid bodies. The bodies contain mass also and due to this they may possess kinetic energy by virtue of their velocity. They might possess elastic strain energy that is comparable to the potential energy (elastic strain energy) into kinetic energy and vice-versa remains the body vibrating without external excitation.

Vibration of a system is unwanted due to its, high stresses, unwanted noise ,undesirable wear, etc. It is of great significance also in diagnostic maintenance.

Objectives

After learning this unit, you must be able to

• study of a system for mechanical vibration,
• resolve degree of freedom of a system,
• resolve natural frequency of a system, and
• study and analyse dynamical behaviour of a system.