Shock Isolation Example
Illustrative worked example showing assumptions, equations, units, calculation and engineering interpretation.
Illustrative problem
Compare an equipment mount natural frequency of 25 Hz with a transient whose important response content is around 150 Hz, using a simple frequency-ratio screening concept. All numerical values are illustrative and are not qualification limits.
Governing relationship
r=f/fn = 150/25 = 6
Calculation
- Calculate r=6
- Recognise this is well above the mount resonance for a linear SDOF
- Check that displacement travel under the low-frequency/rigid-body part of the shock remains acceptable
- Use the actual transient and nonlinear mount curve for qualification rather than the ratio alone
Illustrative result
The ratio suggests isolation may be possible for the higher-frequency content, but mount travel and nonlinear response can still govern.
Engineering interpretation
The numerical result is useful only inside the assumptions stated above. For qualification work, replace the illustrative values with the controlled environment and verify the model or calculation against the applicable test/specification.
Checks
- Units are consistent
- The calculated quantity matches the physical requirement
- The result changes in the expected direction when the governing input is varied
- The example is not treated as a universal allowable