BS ISO 5348-1998 Mechanical vibration and shock - Mechanical mounting of accelerometers《机械振动和冲击 加速计的机械安装》.pdf

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1、BRITISH STANDARD BS ISO 5348:1998 Mechanical vibration and shock Mechanical mounting of accelerometers ICS 17.160BSISO5348:1998 This British Standard, having been prepared under the directionof the Engineering SectorBoard, was published underthe authorityof the Standards Board and comes intoeffect o

2、n 15 July 1998 BSI 05-1999 ISBN 0 580 29870 1 National foreword This British Standard reproduces verbatim ISO5348:1998 and implements it as the UK national standard. It supersedes BS7129:1989 which is withdrawn. The UK participation in its preparation was entrusted by Technical Committee GME/21, Mec

3、hanical vibration and shock, to Subcommittee GME/21/2, Vibration and shock measuring instruments and test equipment, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals fo

4、r change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this subcommittee can be obtained on request to its secretary. Cross-references The British Standards which implement internatio

5、nal or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include a

6、ll the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i an

7、d ii, theISO title page, page ii, pages 1 to 11 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date CommentsBSISO5348

8、:1998 BSI 05-1999 i Contents Page National foreword Inside front cover Foreword ii Introduction 1 1 Scope 1 2 Normative references 2 3 Definitions 2 4 Characteristics to be specified by manufacturers of accelerometers 2 5 Consideration in the selection of a mounting method 2 Figure 1 Accelerometer m

9、ounting 1 Figure 2 Accelerometers with axial and radial connectors 6 Figure 3 Accelerometer test arrangement 6 Figure 4 Accelerometer response to shock 7 Figure 5 Typical frequency response of a representative stud-mounted accelerometer with oil film relative to the absolute acceleration of the stru

10、cture at its attachment 7 Figure 6 Typical frequency response of a representative cement-mounted accelerometer relative to the absolute acceleration of the structure at its attachment 8 Figure 7 Typical frequency response of a representative accelerometer mounted by double-sided adhesive tape relati

11、ve to the absolute acceleration of the structure at its attachment 8 Figure 8 Typical frequency response of a representative hand-held probe relative to the absolute acceleration of the structure at the contact point 9 Figure 9 Typical frequency response of a representative magnetically mounted acce

12、lerometer relative to the absolute acceleration of the structure at its attachment 9 Figure 10 Typical frequency response of a representative accelerometer mounted with a thin layer of beeswax relative to the absolute acceleration of the structure at its attachment 10 Figure 11 Quick mount 10 Figure

13、 12 Vacuum mounting 11 Table 1 Criteria that affect selection of mounting methods (based on best practices) 4ii blankBSISO5348:1998 ii BSI 05-1999 Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of

14、 preparing 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

15、, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. P

16、ublication as an International Standard requires approval by at least75% of the member bodies casting a vote. International Standard ISO5348 was prepared by Technical Committee ISO/TC108, Mechanical vibration and shock, Subcommittee SC 3, Use and calibration of vibration and shock measuring instrume

17、nts. This second edition cancels and replaces the first edition (ISO5348:1987), which has been technically revised. Descriptors: Vibration, mechanical shock, accelerometers, characteristics, mountings.BSISO5348:1998 BSI 05-1999 1 Introduction The method most commonly used for determining the vibrato

18、ry motion, v S , of a structure or body S is that using an electromechanical transducer T. Vibration-monitoring transducers fall into two broad classes: contacting and non-contacting transducers. Non-contacting structural response transducers are placed in close proximity to the structure and includ

19、e such generic types as eddy-current probes and optical proximity probes. Contacting transducers are placed in mechanical contact with the structural system and include such generic types as piezoelectric and piezoresistive accelerometers and seismic velocity transducers. This International Standard

20、 is concerned with the contacting type of accelerometers which currently are in wide use. The concern with using such transducers is that the mechanical coupling between the accelerometer and the test structure may significantly alter the response of the accelerometer, the structure, or both. This I

21、nternational Standard attempts to isolate parameters of concern in the selection of a method to mount the accelerometer onto the structure. This International Standard deals with accelerometers which are connected to the surface of the structure in motion by means of a mechanical mounting F (seeFigu

22、re 1). The information supplied by such a transducer is the electric signal, u, generated by the action of its own motion, v T . The information desired is the vibratory motion, v S , at a specified location on the structure S. The electric signal, u, generated by the transducer deviates from what i

23、t would have been, if that particular accelerometer effectively measured the vibratory motion, v S , of the structure, owing to non-ideal transfer of motion from S to the sensitive elements of the accelerometer T. Deviations may also occur owing to misalignment of the sensitive axis of the transduce

24、r, base bending, temperature transients, mounting torque and cable whip. The mechanical mounting will change the useful frequency range for a given accuracy with regard to amplitude as well as phase response (see5.4.5). 1 Scope This International Standard describes the mounting characteristics of ac

25、celerometers to be specified by the manufacturer and makes recommendations to the user for mounting accelerometers. Application of this International Standard is limited to the mounting of accelerometers which are mounted on the surface of the structure in motion, as illustrated in the simplified di

26、agram shown in Figure 1. It is not applicable to other types of transducers, such as relative motion pick-ups. Key S F T v s v T is the structure; is a means of mounting; is an accelerometer; is vibratory motion of the structure; is vibratory motion of the accelerometer. Figure 1 Accelerometer mount

27、ingBSISO5348:1998 2 BSI 05-1999 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and par

28、ties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 2041:1990, Vibration and shock Vocabu

29、lary. ISO 2954:1975, Mechanical vibration of rotating and reciprocating machinery Requirements for instruments for measuring vibration severity. ISO 5347-14:1993, Methods for the calibration of vibration and shock pick-ups Part 14: Resonance frequency testing of undamped accelerometers on a steel bl

30、ock. ISO 5347-22:1997, Methods for the calibration of vibration and shock pick-ups Part22:Accelerometer resonance testing General methods. ISO 8042:1988, Shock and vibration measurements Characteristics to be specified for seismic pick-ups. 3 Definitions For the purposes of this International Standa

31、rd, the terms and definitions given in ISO2041 apply. 4 Characteristics to be specified by manufacturers of accelerometers The manufacturer shall specify the following characteristics: a) mounting-surface characteristics pertinent to the mounting device(s) furnished with the accelerometer, e.g.surfa

32、ce finish roughness, surface flatness, hole perpendicularity and tap class; b) the geometrical dimensions of the accelerometer including the position of the centre of gravity of the accelerometer as a whole, the position of the centre of gravity of the seismic mass of the accelerometer; c) the mount

33、ing technique used during calibration; d) the recommended and maximum (i.e.for less than 2% change in the useful frequency range) mounting torque; e) temperature limitations of the accelerometer and fastening device; f) pertinent mechanical characteristics, i.e. total mass, material of base, the low

34、est unmounted resonance frequency of the accelerometer, the frequency response characteristic under well-defined mounting conditions, describing the object on which the transducer is mounted in terms of mass, material and dimensions, the maximum transverse sensitivity, and the frequency at which it

35、was determined; g) a description of the various fastening devices provided for the accelerometer, i.e. diameter, thread, material; h) the frequency response curves of the accelerometer with the type of mechanical mounting recommended by the manufacturer and the effect of special mounting devices sup

36、plied with the accelerometer, in particular axial stiffness, with account taken of the state of the surface of the structure in contact with the accelerometer and the tightening torque of the accelerometer, transverse deflection stiffness, on the same basis. For other characteristics to be specified

37、 by the manufacturer, refer to ISO8042. 5 Consideration in the selection of a mounting method 5.1 General considerations 5.1.1 Procedures An accelerometer will achieve optimal performance only if the following general procedures are followed: a) the accelerometer shall perform as nearly as possible

38、the same motion as the structure under test at the accelerometer attachment; b) the motion of the structure shall be changed as little as possible by the addition of the accelerometer; c) the ratio of the signal from the accelerometer to the motion of the accelerometer shall not be distorted by oper

39、ating too near to its mounted fundamental resonance frequency.BSISO5348:1998 BSI 05-1999 3 5.1.2 Conditions In order to achieve these ideal conditions, it is necessary to ensure that: a) the accelerometer and its mounting are as rigid and firm as possible (the mounting surfaces shall be as clean and

40、 flat as possible); b) the mounting introduces minimum distorting motions of its own (for example, simple symmetrical mountings are best); c) the mass of the accelerometer and mounting are small in comparison with that of the dynamic mass of the structure under test (see ISO2954). 5.2 Specific consi

41、derations 5.2.1 Frequency range of operation The accelerometer shall be used well below its fundamental resonance frequency. If it is possible to use the manufacturers recommended mounting, then operation at frequencies not greater than 20% of their quoted mounted resonance should, in the case of un

42、damped accelerometers (resonance magnification factor Q greater than 30 dB), ensure in most cases that errors of only a few percent on the amplitude response occur. If an estimate of the approximate error is required, it may be made on the basis of an equivalent linear spring-mass system with a give

43、n value of damping. NOTEFor single shock measurements, one may expect errors of only a few percent if the mounted fundamental resonance frequency is ten times greater than the inverse of the pulse duration. 5.2.2 Mounting torque When screw thread mounting is used, the mounting torque shall be as rec

44、ommended by the manufacturer. 5.2.3 Cables Stiff cables can cause case strain when used with accelerometers with axial connectors. Careful clamping of the cables is required to avoid such problems (seeFigure 2). Loose cables may introduce tribo-electric effects for piezo-electric type transducers. 5

45、.3 Determination of the mounted fundamental resonance frequency It is very useful, though at times difficult in practice, to determine accurately the mounted fundamental resonance frequency of the accelerometer mounted on the structure under test. The following method may be of use in finding the ap

46、proximate resonance, thus ensuring that an adequate margin exists between it and the test frequency. 5.3.1 Vibration excitation method A suitable steel reference block with well-defined shape and surface finish is recommended, e.g.a stainless steel block of mass180g. The motion of the reference bloc

47、k is monitored close to the mounting surface of the accelerometer being tested using an accelerometer with a resonance frequency higher than that of the first bending mode of the steel block itself. The excitation force can be generated electrodynamically. The influence of the quality of mounting su

48、rfaces and materials may be investigated by introducing typical samples between the steel surface and the accelerometer being tested (seeFigure 3). For common mountings and representative mounted frequency curves, seeFigure 5 toFigure 10. For the method of determining the fundamental (resonance) fre

49、quency, see ISO5347-14 and ISO5347-22. NOTEThe frequency response curves given in the figures are typical; they are strongly influenced by the parameters that are indicated in the figures. 5.3.2 Shock excitation methods The ballistic pendulum, the drop test and a simple hammer blow are three ways of using shock excitation. In the first, the accelerometer is attached to an anvil mass suspended as a pendulum while a second hammer mass, similarly suspended, is used to provide the blow. In the drop test, the accele