Vibration

Vibration refers to mechanical oscillation about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road. Vibration is occasionally "desirable". For example the motion of a tuning fork,the reed in the woodwind instrument or harmonica or the cone of the loudspeaker is desirable vibration, necessary for the correct functioning of the various devices. More often, vibration is undesirable, wasting energy and creating unwanted sound.For example, the vibrational motions of Engine, electrical Motor or mechanical device in operation are typically unwanted. Such vibrations can be caused by imbalances in the rotating parts, uneven friction the meshing of gear teeth, etc. Careful designs usually minimize unwanted vibrations. Types of vibration:free and forced Vibration.

Vibration testing is accomplished by introducing a forcing function into a structure, usually with some type of shaker. Generally, one or more points on the structure are kept at a specified vibration level. Two typical types of vibration tests performed are random- and sine test. Sine tests are performed to survey the structural response of the device under test (DUT). A random test is generally conducted to more closely replicate a real world environment.

Most vibration testing is conducted in the vertical axis. Some may be conducted horizontally, in multiple axes, or rotationally.