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

1、BSI Standards PublicationBS ISO 7626-2:2015Mechanical vibration and shock Experimental determinationof mechanical mobilityPart 2: Measurements using single-pointtranslation excitation with an attachedvibration exciterBS ISO 7626-2:2015 BRITISH STANDARDNational forewordThis British Standard is the UK

2、 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 It supersedes BS 6897-2:1990 which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee GME/21/3, Mechanical vibration, shock and condition monitoring - Measurement and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 stationary

3、 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.Published b

4、y BSI Standards Limited 2015ISBN 978 0 580 83256 7ICS 17.160Compliance 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 issued since public

5、ationDate Text affectedBS ISO 7626-2:2015 ISO 2015Mechanical vibration and shock Experimental determination of mechanical mobility Part 2: Measurements using single-point translation excitation with an attached vibration exciterVibrations et chocs Dtermination exprimentale de la mobilit mcanique Par

6、tie 2: Mesurages avec utilisation dune excitation de translation en un seul point, au moyen dun gnrateur de vibrations solidaire de ce pointINTERNATIONAL STANDARDISO7626-2Second edition2015-04-01Reference numberISO 7626-2:2015(E)BS ISO 7626-2:2015ISO 7626-2:2015(E)ii ISO 2015 All rights reservedCOPY

7、RIGHT PROTECTED DOCUMENT ISO 2015All 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, without prior written permis

8、sion. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 7626-2:2015I

9、SO 7626-2:2015(E)Foreword vIntroduction vi1 Scope . 12 Normative references 13 Terms and definitions . 14 Overall configuration of the measurement system 25 Support of the structure under test 35.1 General . 35.2 Grounded measurements 35.3 Ungrounded measurements 36 Excitation 46.1 General . 46.2 Ex

10、citation waveforms 46.2.1 General 46.2.2 Discretely dwelled sinusoidal excitation . 46.2.3 Slowly swept sinusoidal excitation 56.2.4 Stationary random excitation . 56.2.5 Other excitation waveforms . 56.3 Vibration exciters 56.4 Avoidance of spurious forces and moments 86.4.1 General 86.4.2 Transduc

11、er mass loading 86.4.3 Transducer rotational inertia loading . 86.4.4 Exciter attachment restraints . 87 Measurement of the exciting force and resulting motion response . 97.1 General . 97.2 Attachment of transducers . 97.3 Mass loading and mass cancellation . 107.4 Signal amplifiers . 107.5 Calibra

12、tions . 117.5.1 General. 117.5.2 Operational calibration .118 Processing of the transducer signals 148.1 Determination of the frequency-response function 148.1.1 General. 148.1.2 Sinusoidal excitation .148.1.3 Random excitation .148.2 Filtering 148.2.1 Sinusoidal excitation .148.2.2 Random excitatio

13、n .148.3 Avoidance of saturation 158.4 Frequency resolution 158.4.1 General. 158.4.2 Sinusoidal excitation .158.4.3 Random excitation .158.4.4 Periodic excitation .159 Control of the excitation 169.1 General 169.2 Time required for sinusoidal excitation . 169.2.1 General. 169.2.2 Discretely dwelled

14、sinusoidal excitation 16 ISO 2015 All rights reserved iiiContents PageBS ISO 7626-2:2015ISO 7626-2:2015(E)9.2.3 Slowly swept sinusoidal excitation . 179.3 Time required for random excitation . 179.4 Dynamic range 189.4.1 General. 189.4.2 Sinusoidal excitation .189.4.3 Random excitation .1810 Tests f

15、or valid data 1811 Modal parameter identification 19Annex A (normative) Tests for validity of measurement results .20Annex B (normative) Requirements for excitation frequency increments and duration 23Annex C (informative) Modal parameter identification 25Bibliography .26iv ISO 2015 All rights reser

16、vedBS ISO 7626-2:2015ISO 7626-2:2015(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body

17、 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 liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotec

18、hnical 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 Directives, Part 1. In particular the different approval criteria needed for the different types of ISO

19、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 some of the elements of this document may be the subject of patent rights. ISO shall not be held respo

20、nsible 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 declarations received (see www.iso.org/patents).Any trade name used in this document is information given

21、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 about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT), see the following

22、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 the first edition (ISO 7626-2:1990), which has been technically revised.ISO 7626 consists of the following

23、 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: Measurements using single-point translational excitation with an attached vibration exciter Part 5: Measurement

24、s 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)IntroductionGeneral introduction to the ISO 7626- series on mobility measurementDynamic characteristics of structures can be determined as a function of

25、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 the phasor of the motion response at a point on a structure due to a unit force (or moment) excitation. The mag

26、nitude 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 and displacement, respectively, instead of in terms of velocity. In order to simplify the various parts of IS

27、O 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.Typical applications for mobility measurements are for:a) predicting the dynamic response of structures to kno

28、wn 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 interconnected structures;d) checking the validity and improving the accuracy of mathematical models of structures;e) deter

29、mining 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 can be required using measurements of translational forces and motions along three mutually perpendicular axes as we

30、ll 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 on a structure, the system thus has an overall mobility matrix of size 6N 6N.For most practical applications, it is no

31、t 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 a single direction and measuring the translational response motions at key points on the structure. In other applicati

32、ons, 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 rotational response velocity to the phasor of the applied force or moment excitation. If the response is measured with an a

33、ccelerometer, 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 structure. In other cases, dynamic compliance, the ratio of displacement to force, can be used.NOTE Historically, frequency-

34、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 mobility has often been called mechanical impedance. It should be noted, however, that this is misleading because the arith

35、metic 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 inversion of the full mobility matrix. This point is elaborated upon in ISO 7626-1.Mobility test data cannot be used direct

36、ly 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 versa (see ISO 7626-1 for limitations).vi ISO 2015 All rights reservedBS ISO 7626-2:2015ISO 7626-2:2015(E)Introduction to

37、 this part of ISO 7626For many applications of mechanical mobility data, it is sufficient to determine the driving-point mobility and a few transfer mobilities by exciting the structure at a single location in a single direction and measuring the translational response motions at key points on the s

38、tructure. 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 of excitation devices as “attached” or “unattached” has significance in terms of the ease of moving the excitation point to

39、 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 a new point on the structure. Both methods of excitation have applications to which they are best suited. This part of ISO 7

40、626 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 rights reserved viiBS ISO 7626-2:2015BS ISO 7626-2:2015Mechanical vibration and shock Experimental determination of mechani

41、cal mobility Part 2: Measurements using single-point translation excitation with an attached vibration exciter1 ScopeThis part of ISO 7626 specifies procedures for measuring linear mechanical mobility and other frequency-response functions of structures, such as buildings, machines and vehicles, usi

42、ng 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, accelerance, or dynamic compliance, either as a driving-point measurement or as a transfer measurement. It also applies to the dete

43、rmination 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 points at which simultaneous measurements of the motion response may be made. Multiple-response measurements are required, for ex

44、ample, for modal analyses.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced docu

45、ment (including any amendments) applies.ISO 2041, Mechanical vibration, shock and condition monitoring VocabularyISO 7626-1, Mechanical vibration and shock Experimental determination of mechanical mobility Part 1: Basic terms and definitions, and transducer specifications3 Terms and definitionsFor t

46、he 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 mechanical mobility, the notes to the definitions below provide more detail than is given in ISO 2041.3.1frequency-response functionfrequency depe

47、ndent ratio of complex motion response to complex excitation force for a linear systemNote 1 to entry: Excitation may be harmonic, random or transient functions of time. The frequency-response function does not depend on the type of excitation function if the tested structure can be considered a lin

48、ear 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 the response of the system to any other type of excitation. Phasors and their equivalents for random and transient excitation are discussed in

49、 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 with impulse excitation and great care is required when using random excitation for testing of such structures.INTERNATIONAL STANDARD ISO 7626-2:2015(E) ISO