Acoustics and vibration. Laboratory measurement of vibro-acoustic transfer properties of resilient elements - Driving point method for determination of the low-frequency transfer stiffness of resilient supports for translatory motion

Acoustics and vibration. Laboratory measurement of vibro-acoustic transfer properties of resilient elements - Driving point method for determination of the low-frequency transfer stiffness of resilient supports for translatory motion

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1   Scope

This part of ISO 10846 specifies a driving point method for determining the low-frequency transfer stiffness for translations of resilient supports, under a specified preload. The method concerns the laboratory measurement of vibrations and forces on the input side with the output side blocked, and is called the “driving point method”.
The stiffness resulting from measuring the input displacement (velocity, acceleration) and input force is the dynamic driving point stiffness. Only at low frequencies, where the driving point stiffness and the transfer stiffness are equal, can this method be used for determination of the dynamic transfer stiffness.

NOTE 1 In ISO 10846‑2, the direct method for measuring the dynamic transfer stiffness is covered. The direct method covers the determination of the low-frequency dynamic transfer stiffness and it covers, in principle, a wider frequency range than the driving point method. Nevertheless, the driving point method is covered in the ISO 10846 series of international standards as well. It is considered as a valuable option for owners of (often expensive) test rigs for driving point stiffness measurements, to extend the use of these rigs with the determination of low-frequency dynamic transfer stiffness.

The method is applicable to test elements with parallel flanges (see Figure 1).
Resilient elements, which are the subject of this part of ISO 10846, are those which are used to reduce
  1. a) the transmission of vibration in the lower part of the audible frequency range (typically 20 Hz to 200 Hz) to a structure which may, for example, radiate unwanted fluid-borne sound (airborne, waterborne or others), and
  2. b) the transmission of low-frequency vibrations (typically 1 Hz to 80 Hz) which may, for example, act upon human subjects or cause damage to structures of any size when vibration is too severe.

NOTE 2 In practice, the size of available test rig(s) determines restrictions for very small and for very large resilient supports.

NOTE 3 Samples of continuous supports of strips and mats are included in the method. Whether or not the sample describes the behaviour of the complex system sufficiently is the responsibility of the user of this part of ISO 10846.

Measurements for translations normal and transverse to the flanges are covered in this part of ISO 10846. The method covers the frequency range from f1 = 1 Hz to the upper limiting frequencyfUL. Typically 50 Hz ≤ fUL ≤ 200 Hz.
The data obtained according to the method specified in this part of ISO 10846 can be used for the following:
  • - product information provided by manufacturers and suppliers;
  • - information during product development;
  • - quality control, and
  • - calculation of the transfer of vibration through isolators.
Figure 1 — Example of resilient supports with parallel flanges
fig_1

NOTE 1 When a resilient support has no parallel flanges, an auxiliary fixture should be included as part of the test element to arrange for parallel flanges.

NOTE 2 Arrows indicate load direction.