THE SIZING PROCESS: Sine

SELECT A SYSTEM WHICH YOU THINK IS THE CORRECT ONE THEN, PROVE IT.

Ideally with 20% - 30% spare. Do not size a system to the limit!

For this example we will use the system ratings for a V830-335 SPA10K and a Test Load of 20kg with the following Test Specification.

SWEPT SINE TEST

Is the frequency range within the range of the system?		Limit: 0 to 3000Hz Required: 5 to 1000Hz
| YES |		D-V cross over = 14.32Hz V-A cross over = 34.68Hz
Is the required travel less than the rated travel?		20mm is less than 50.8mm
| YES |
Is the required peak velocity less than the rated velocity?		900mm/s is less than 2000mm/s
| YES |
Is the required peak sine acceleration less than the rated peak sine acceleration?		20gn is less than 75gn
| YES |
Calculate the total moving mass (Note 2)		12.85kg + 20kg = 32.85kg
|
Will the load support system support the load? (Note 3)		32.85kg is less than 160kg
| YES |
Calculate the Peak Force required		32.85kg x 20gn = 657kgf
|
Is the required force less than the rated force?		657kgf is less than 1000kgf
| YES |
Is the vibrator rigidly mounted?		If the vibrator is not rigidly mounted, body motion will occur.
| YES |		If No, the maximum available travel must be calculated. In this case it would be 49.37mm
Would a smaller system do the test?
| NO |		If Yes, select a smaller system and repeat the process.
Perform checks for other loads and test specifications

Note 1 (Random tests)

Where a test specifications highest frequency is below 500Hz this test can be considered as narrow band random test. Full system force may not be achievable under these conditions. Refer the test specification to the factory for analysis.

Note 2

The mass involved is the total moving mass and as such must include everything that is attached to the armature:

• Test Item (payload)
• Armature
• Fixture (Jig)
• Bolts
• Head expander
• Head extender
• Thermal barrier
• Accelerometers
• Driver bar
• Slip table
• Slip table bearings

Note 3

Locating the payload in the mid position of the armature travel is normally done by using the internal load support system, but this may be supplemented by using an external load support such as bungies.