BS ISO 7626-2-2015 en_2286 Mechanical vibration and shock Experimental determination of mechanical mobility Measurements using single-point translation excitation with an attached vibration exci.pdf

1、BSI Standards Publication BS ISO 7626-2:2015 Mechanical vibration and shock Experimental determination of mechanical mobility Part 2: Measurements using single-point translation excitation with an attached vibration exciterBS ISO 7626-2:2015 BRITISH STANDARD National foreword This British Standard i

2、s the UK implementation of ISO 7626-2:2015. It supersedes BS 6897-2:1990 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee GME/21/3, Mechanical vibration, shock and condition monitoring - Measurement and evaluation of mechanical vibration and shock in s

3、tationary structures. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2015.

4、 Published by BSI Standards Limited 2015 ISBN 978 0 580 83256 7 ICS 17.160 Compliance with a British Standard cannot confer immunity from legal obligations. This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 May 2015. Amendments/corrigenda is

5、sued since publication Date Text affectedBS ISO 7626-2:2015 ISO 2015 Mechanical vibration and shock Experimental determination of mechanical mobility Part 2: Measurements using single-point translation excitation with an attached vibration exciter Vibrations et chocs Dtermination exprimentale de la

6、mobilit mcanique Partie 2: Mesurages avec utilisation dune excitation de translation en un seul point, au moyen dun gnrateur de vibrations solidaire de ce point INTERNATIONAL STANDARD ISO 7626-2 Second edition 2015-04-01 Reference number ISO 7626-2:2015(E)BS ISO 7626-2:2015ISO 7626-2:2015(E)ii ISO 2

7、015 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2015 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet,

8、 without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Publish

9、ed in SwitzerlandBS ISO 7626-2:2015ISO 7626-2:2015(E)Foreword v Introduction vi 1 Scope . 1 2 Normative references 1 3 T erms and definitions . 1 4 Ov er all c onfigur ation of the measur ement s y st em 2 5 Support of the structure under test 3 5.1 General . 3 5.2 Grounded measurements 3 5.3 Ungrou

10、nded measurements 3 6 Excitation 4 6.1 General . 4 6.2 Excitation waveforms 4 6.2.1 General 4 6.2.2 Discretely dwelled sinusoidal excitation . 4 6.2.3 Slowly swept sinusoidal excitation 5 6.2.4 Stationary random excitation . 5 6.2.5 Other excitation waveforms . 5 6.3 Vibration exciters 5 6.4 Avoidan

11、ce of spurious forces and moments 8 6.4.1 General 8 6.4.2 Transducer mass loading 8 6.4.3 Transducer rotational inertia loading . 8 6.4.4 Exciter attachment restraints . 8 7 Measurement of the exciting force and resulting motion response .9 7.1 General . 9 7.2 Attachment of transducers . 9 7.3 Mass

12、loading and mass cancellation .10 7.4 Signal amplifiers .10 7.5 Calibrations .11 7.5.1 General.11 7.5.2 Operational calibration .11 8 Processing of the transducer signals 14 8.1 Determination of the frequency-response function 14 8.1.1 General.14 8.1.2 Sinusoidal excitation .14 8.1.3 Random excitati

13、on .14 8.2 Filtering 14 8.2.1 Sinusoidal excitation .14 8.2.2 Random excitation .14 8.3 Avoidance of saturation 15 8.4 Frequency resolution15 8.4.1 General.15 8.4.2 Sinusoidal excitation .15 8.4.3 Random excitation .15 8.4.4 Periodic excitation .15 9 Control of the excitation 16 9.1 General 16 9.2 T

14、ime required for sinusoidal excitation .16 9.2.1 General.16 9.2.2 Discretely dwelled sinusoidal excitation 16 ISO 2015 All rights reserved iii Contents PageBS ISO 7626-2:2015ISO 7626-2:2015(E)9.2.3 Slowly swept sinusoidal excitation .17 9.3 Time required for random excitation .17 9.4 Dynamic range18

15、 9.4.1 General.18 9.4.2 Sinusoidal excitation .18 9.4.3 Random excitation .18 10 Tests for valid data 18 11 Modal par amet er identification 19 Annex A (normative) Tests for validity of measurement results .20 Annex B (normative) Requirements for excitation frequency increments and duration 23 Annex

16、 C (informative) Modal par amet er identification 25 Bibliography .26 iv ISO 2015 All rights reservedBS ISO 7626-2:2015ISO 7626-2:2015(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparin

17、g International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liai

18、son with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Dir

19、ectives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives). Attention is drawn to the possibility that

20、some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent decl

21、arations received (see www.iso.org/patents). Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement. For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information

22、 about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT), see the following URL: Foreword Supplementary information. The committee responsible for this document is ISO/TC 108, Mechanical vibration, shock and condition monitoring. This second edition cancels and replaces t

23、he first edition (ISO 7626-2:1990), which has been technically revised. ISO 7626 consists of the following parts, under the general title Mechanical vibration and shock Experimental determination of mechanical mobility: Part 1: Basic terms and definitions, and transducer specifications Part 2: Measu

24、rements using single-point translational excitation with an attached vibration exciter Part 5: Measurements using impact excitation with an exciter which is not attached to the structure ISO 2015 All rights reserved vBS ISO 7626-2:2015ISO 7626-2:2015(E) Introduction General introduction to the ISO 7

25、626- series on mobility measurement Dynamic characteristics of structures can be determined as a function of frequency from mobility measurements or measurements of the related frequency-response functions, known as accelerance and dynamic compliance. Each of these frequency-response functions is th

26、e phasor of the motion response at a point on a structure due to a unit force (or moment) excitation. The magnitude and the phase of these functions are frequency-dependent. Accelerance and dynamic compliance differ from mobility only in that the motion response is expressed in terms of acceleration

27、 and displacement, respectively, instead of in terms of velocity. In order to simplify the various parts of ISO 7626, only the term “mobility” is used. It is understood that all test procedures and requirements described are also applicable to the determination of accelerance and dynamic compliance.

28、 Typical applications for mobility measurements are for: a) predicting the dynamic response of structures to known or assumed input excitation; b) determining the modal properties of a structure (natural frequencies, damping ratios and mode shapes); c) predicting the dynamic interaction of interconn

29、ected structures; d) checking the validity and improving the accuracy of mathematical models of structures; e) determining dynamic properties (i.e. the complex modulus of elasticity) of materials in pure or composite forms. For some applications, a complete description of the dynamic characteristics

30、 can be required using measurements of translational forces and motions along three mutually perpendicular axes as well as measurements of moments and rotational motions about these three axes. This set of measurements results in a 6 6 mobility matrix for each location of interest. For N locations o

31、n a structure, the system thus has an overall mobility matrix of size 6N 6N. For most practical applications, it is not necessary to know the entire 6N 6N matrix. Often it is sufficient to measure the driving-point mobility and a few transfer mobilities by exciting with a force at a single point in

32、a single direction and measuring the translational response motions at key points on the structure. In other applications, only rotational mobilities might be of interest. Mechanical mobility is defined as the frequency-response function formed by the ratio of the phasor of the translational or rota

33、tional response velocity to the phasor of the applied force or moment excitation. If the response is measured with an accelerometer, conversion to velocity is required to obtain the mobility. Alternatively, the ratio of acceleration to force, known as accelerance, can be used to characterize a struc

34、ture. In other cases, dynamic compliance, the ratio of displacement to force, can be used. NOTE Historically, frequency-response functions of structures have often been expressed in terms of the reciprocal of one of the above-named dynamic characteristics. The arithmetic reciprocal of mechanical mob

35、ility has often been called mechanical impedance. It should be noted, however, that this is misleading because the arithmetic reciprocal of mobility does not, in general, represent any of the elements of the impedance matrix of a structure. Rather, conversion of mobility to impedance requires an inv

36、ersion of the full mobility matrix. This point is elaborated upon in ISO 7626-1. Mobility test data cannot be used directly as part of an impedance model of the structure. In order to achieve compatibility of the data and the model, the impedance matrix of the model is converted to mobility or vice

37、versa (see ISO 7626-1 for limitations).vi ISO 2015 All rights reservedBS ISO 7626-2:2015ISO 7626-2:2015(E) Introduction to this part of ISO 7626 For many applications of mechanical mobility data, it is sufficient to determine the driving-point mobility and a few transfer mobilities by exciting the s

38、tructure at a single location in a single direction and measuring the translational response motions at key points on the structure. The translational excitation force can be applied either by vibration exciters attached to the structure under test or by devices that are not attached. Categorization

39、 of excitation devices as “attached” or “unattached” has significance in terms of the ease of moving the excitation point to a new position. It is much easier, for example, to change the location of an impulse applied by an instrumented hammer than it is to relocate an attached vibration exciter to

40、a new point on the structure. Both methods of excitation have applications to which they are best suited. This part of ISO 7626 deals with measurements using a single attached exciter; measurements made by impact excitation without the use of attached exciters are covered by ISO 7626-5. ISO 2015 All

41、 rights reserved viiBS ISO 7626-2:2015BS ISO 7626-2:2015Mechanical vibration and shock Experimental determination of mechanical mobility Part 2: Measurements using single-point translation excitation with an attached vibration exciter 1 Scope This part of ISO 7626 specifies procedures for measuring

42、linear mechanical mobility and other frequency- response functions of structures, such as buildings, machines and vehicles, using a single-point translational vibration exciter attached to the structure under test for the duration of the measurement. It is applicable to measurements of mobility, acc

43、elerance, or dynamic compliance, either as a driving- point measurement or as a transfer measurement. It also applies to the determination of the arithmetic reciprocals of those ratios, such as free effective mass. Although excitation is applied at a single point, there is no limit on the number of

44、points at which simultaneous measurements of the motion response may be made. Multiple-response measurements are required, for example, for modal analyses. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its a

45、pplication. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 2041, Mechanical vibration, shock and condition monitoring Vocabulary ISO 7626-1, Mechanical vibration and shock Experimenta

46、l determination of mechanical mobility Part 1: Basic terms and definitions, and transducer specifications 3 T erms a nd definiti ons For the purposes of this document, the terms and definitions given in ISO 7626-1 and ISO 2041 and the following apply. Note As this part of ISO 7626 deals with mechani

47、cal mobility, the notes to the definitions below provide more detail than is given in ISO 2041. 3.1 frequency-response function frequency dependent ratio of complex motion response to complex excitation force for a linear system Note 1 to entry: Excitation may be harmonic, random or transient functi

48、ons of time. The frequency-response function does not depend on the type of excitation function if the tested structure can be considered a linear system in a certain range of the excitation or response. In such a case, the test results obtained with one type of excitation may be used for estimating

49、 the response of the system to any other type of excitation. Phasors and their equivalents for random and transient excitation are discussed in Annex B. Note 2 to entry: Linearity of the system is a condition which, in practice, is met only approximately, depending on the type of system and on the magnitude of the input. Care has to be taken to avoid nonlinear effects, particularly when applying impulse excitation. Structures which are known to be nonlinear (e.g. structures with fluid elements) should not be tested wi