Introduction of vibrations

Vibration is the oscillatory motion of a body about its equilibrium position. When a system is displaced from its rest position and allowed to move, it tends to swing back and forth due to internal restoring forces. This repeated motion is called vibration.

Vibrations are present everywhere in engineering systems—machines, vehicles, structures, engines, turbines, bridges, and even in the human body.

What Causes Vibrations?

Vibrations occur when three basic elements interact:

• Mass – provides inertia

• Stiffness – provides restoring force

• Damping – dissipates energy

When a mass attached to a spring is disturbed, the spring tries to bring it back to equilibrium, and the mass overshoots due to inertia, creating oscillatory motion.

Examples of Vibrations in Daily Life

• A plucked guitar string vibrating

• Vehicle suspension moving on a rough road

• Fans and motors vibrating during operation

• Buildings vibrating during earthquakes

• Washing machine shaking during spin cycle

Types of Vibrations (Basic Idea)

• Free vibration – occurs after an initial disturbance without continuous force

• Forced vibration – caused by continuous external force

• Damped vibration – amplitude decreases with time due to resistance

• Undamped vibration – ideal case with no energy loss

Important Terms

• Cycle: One complete oscillation

• Time period (T): Time for one cycle

• Frequency (f): Number of cycles per second (Hz)

• Amplitude: Maximum displacement from mean position

• Natural frequency: Frequency at which a system vibrates freely

Why Study Vibrations?

Understanding vibrations is crucial because excessive vibration can:

• Cause noise and discomfort

• Lead to fatigue failure of components

• Reduce machine life

• Cause structural damage

At the same time, controlled vibrations are useful in:

• Sieving and screening machines

• Compaction equipment

• Musical instruments