Basic Concepts of Vibration

Mechanical Vibration- 4th year

Dr Ahmad S.M. Al-Azzawi
University of Babylon
College of Engineering / Al-Musayab
Department of Automobile Engineering

Lecture 1

Contents
1. Basic Concepts of Vibration
2. Vibration and its applications
3. Number of Degrees of Freedom
4. Types of Vibrations
4.1 Free and Forced Vibration
4.2 Undamped and Damped Vibration
4.3 Linear and Nonlinear Vibration
4.4 Deterministic and Random Vibration
1. Basic Concepts of Vibration
1.1 Vibration definition
Any motion that repeats itself after an interval of time is called vibration or oscillation. The swinging of a pendulum and the motion of a plucked string are typical examples of vibration. The theory of vibration deals with the study of oscillatory motions of bodies and the forces associated with them.

1.2 Elementary Parts of Vibrating Systems
A vibratory system, in general, includes a means for storing potential energy (spring or elasticity), a means for storing kinetic energy (mass or inertia), and a means by which energy is gradually lost (damper).
The vibration of a system involves the transfer of its potential energy to kinetic energy and of kinetic energy to potential energy, alternately. If the system is damped, some energy is dissipated in each cycle of vibration and must be replaced by an external source if a state of steady vibration is to be maintained.