System Selection

The selection of a suitable Vibration Test System is the most important aspect of application engineering, as Electrodynamic Shaker System consists of various sub-systems which perform independent functions but affect the overall performance of the system.

To frame out ratings of a vibration testing system based upon test application calls for extensive calculations and analysis as all parametres are interlinked to each other very closely with specimen mass, dimension, frequency range and test axes playing a vital role.The system ratings are prepared as per directions of International Standards Organisation document ISO 5344.

Following information assists in selecting a suitable configuration for your intended application.

System force requirements is estimated using the following formula:

        Force (F) = Mass (m) × Acceleration (a)    where: 

Force (F) is in Kgf,  
Mass (m) is the total mass in Kg, shaker armature moving mass+mass of test specimen+ fixture mass+ payload support mass.
Acceleration (a) is the peak value in ‘g’ (acceleration due to gravity) which is equal to 9.80665 m/s.2

Sine force rating is computed with the test loads provided the maximum acceleration level for shaker. ‘Endurance’ by sweeping is an appropriate method for simulating the effect of stresses experienced by specimen. The value of displacement is associated with a corresponding value of acceleration in such a manner that the magnitude of vibration is same at the cross-over frequency. The frequency range is thus programmed and swept continuously changing from constant displacement to constant acceleration and vice-versa at the cross-over frequency.

Random ratings have been calculated as per the directions of International Standards Organisation document ISO 5344. The force ratings are based on flat spectrum of 100 Hz to 2000 Hz with a 20 db/decade roll-off from 1000 down to 20 Hz, with loads equal to or greater than twice the armature mass.

The shock capability of the system is determined by the test profile such as pulse duration, pulse mplitude, pre and post pulse percentage etc.