VIBRATION TESTING TECHNOLOGY

Basic units used for vibration test

There are four important units for a vibration test:

- Force [N]

- Acceleration [m/s2]

- Velocity [m/s] and

- Displacement [mm peak-to-peak (p-p)]

Calculating Required Force requires application of Newton’s Second Law of Motion:

F (Force) = M (Mass) x A (Acceleration)

That is to say, when a mass of 1 kg is accelerated to an acceleration of 1 m/s2 the required force is 1N.

The mass value (M) must include all moving masses attached to the shaker armature surface including the armature mass itself: shaker armature + head expander or slip plate with its driver bar + test specimen + specimen interface fixture, including bolts and bearing friction if the system is driving horizontal plate using hydrostatic bearings.

The maximum acceleration (A) is derived from the customer test specification:

• for Sine Vibration (G-peak)

• for Random Vibration (G-rms)

• for Classical Shock Pulse (G-peak)

The user must know the maximum displacement and velocity of any given test parameters to ensure they choose the right system and they don’t exceed the system capabilities.

Suitability of a specific test system can be evaluated in terms of the following:

- Force requirement (lbf or kgf )

Unit Under Test (UUT) + Fixture Weight + Armature Weight x G = F x 1.30 (30% safety margin)

The result will give you the required Force for shaker system selection

- Maximum Displacement (determined by test environment)

- Maximum Velocity (determined by test environment)