What is ISO 7626‑5- Experimental determination of mechanical mobility on mechanical vibration and shock about?
ISO 7626‑5 is a safety standard on the experimental determination of mechanical mobility on Mechanical vibration and shock.
ISO 7626‑5 specifies procedures for measuring mechanical mobility and other frequency-response functions of structures excited by means of an impulsive force generated by an exciter that is not attached to the structure under test.
ISO 7626‑5 is applicable to the measurement of mobility, acceleration, or dynamic compliance, either as a driving point measurement or as a transfer measurement, using impact excitation. The signal analysis methods covered are all based on the discrete Fourier transform (DFT), which is performed mostly by a fast Fourier transform (FFT) algorithm. This restriction in scope is based solely on the wide availability of equipment that implements these methods and on the large base of experience in using these methods. Impact excitation is also widely used to obtain uncalibrated frequency-response information. ISO 7626‑5 is limited to the use of impact excitation techniques for making accurate mobility measurements.
NOTE 1: ISO 7626‑5 is not intended to exclude the use of other methods currently under development.
NOTE 2: When a multi-axis transducer is used at a fixed location for a modal test and if the impact is applied in one direction of the transducer at each point, then only the mode shape components in that direction are obtained.
NOTE 3: The mass of the multiaxial transducer can change the mass properties of the structure leading to an inconsistent set of measured transfer functions. This can cause serious problems in using the FRFs for experimental modal analysis.
Who is ISO 7626‑5 - Experimental determination of mechanical mobility on mechanical vibration and shock for?
ISO 7626‑5 on the experimental determination of mechanical mobility is relevant to:
- Testing authorities
- Manufacturers of mechanical devices
- Mechanical engineers and electromechanical engineers
Why should you use ISO 7626‑5 - Experimental determination of mechanical mobility on mechanical vibration and shock?
Impact excitation has become a popular method for measuring the frequency response of structures because of its inherent speed and relatively low cost to implement. However, the accuracy of mobility measurements made by using impact excitation is highly dependent upon both the characteristics of the test structure and the experimental techniques employed.
ISO 7626‑5 provides a guide to the use of impact excitation for mobility measurements. Accurate mobility measurements always require careful attention to equipment selection and to the measurement techniques employed; these factors are especially important when using impact excitation. Furthermore, the characteristics of the test structure, especially its degree of nonlinearity, limit the accuracy which can be achieved. ISO 7626‑5 describes these limitations on the use of impact excitation. Because the exciter is not attached to the structure, this method makes it practical to measure a series of transfer mobilities of a structure by moving the excitation successively to each desired point on the structure, while the response motion transducer remains at a single fixed location and direction. Due to the principle of dynamic reciprocity, such measurements are equal, assuming linearity, to the results obtained using an attached exciter at the same fixed location and direction with the response transducer relocated to each desired point on the structure. ISO 7626-5 covers mobility measurements using impact excitation with an exciter which is not attached to the structure.
Overall, ISO 7626-5 is useful as it assists the user with mechanical mobility that provides the frequency-response function formed by the ratio of the phasor of the linear or rotational velocity response to the phasor of the applied force or moment excitation.
What’s changed since the last update?
BS ISO 7626‑5:2019 supersedes BS 6897‑5:1995, which is withdrawn.
BS ISO 7626‑5:2019 replaces the first edition (ISO 7626-5:1994), which has been technically revised.
The main changes compared with the previous edition are as follows:
- Updating of normative and informative references in the bibliography
- Redrawing of figures and graphs