1、BRITISH STANDARD BS 2782-3: Method 323E: 1997 ISO 6721-8: 1997 Methods of testing plastics Part 3: Mechanical properties Method 323E: Longitudinal and shear vibration Wave-propagation method ICS 83.080.01BS2782-3:Method 323E:1997 This British Standard, having been prepared under the directionof the
2、Sector Board forMaterials and Chemicals, waspublished under the authorityof the Standards Boardand comes into effect on 15August 1997 BSI 09-1999 ISBN 0 580 28057 8 National foreword This British Standard reproduces ISO 6721-8:1997 “Plastics Determination of dynamic mechanical properties Part 8: Lon
3、gitudinal and shear vibration Wave-propagation method” and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee PRI/21, Testing of Plastics, which has the responsibility to: aid enquirers to understand the text; present to the respon
4、sible international/European committee any enquiries on the interpretation, or proposals for 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 committee can be obtained on req
5、uest to its secretary. Cross-references The British Standards which implement international 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 using the “Find” facility of the
6、 BSI Standards Electronic Catalogue. A British Standard does not purport to include all 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. Summ
7、ary of pages This document comprises a front cover, an inside front cover, pages i and ii, theISO title page, pages ii to iv, pages 1 to 9 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
8、the inside front cover. Amendments issued since publication Amd. No. Date CommentsBS2782-3:Method 323E:1997 BSI 09-1999 i Contents Page National foreword Inside front cover Foreword iii Text of ISO 6721-8 1ii blankBS2782-3:Method 323E:1997 ii BSI 09-1999 Contents Page Foreword iii 1 Scope 1 2 Normat
9、ive references 1 3 Definitions 1 4 Principle 1 5 Testing device 2 6 Test specimens 3 7 Number of specimens 3 8 Conditioning 3 9 Procedure 3 10 Expression of the results 4 11 Precision 6 12 Test report 6 Figure 1 Measurement of ultrasonic wave velocity using the immersion method (a) with both a trans
10、mitting and a receiving transducer and (b) with a single transducer acting as a transmitter and a receiver 7 Figure 2 Measurement of ultrasonic wave velocity using the transducer contact method (a) with both a transmitting and a receiving transducer and (b) with a single transducer acting as a trans
11、mitter and a receiver 8 Figure 3 Waveform of a suitable pulse for the measurement of velocity 9BS2782-3:Method 323E:1997 BSI 09-1999 iii Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing
12、 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 liais
13、on 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. Publication
14、 as an International Standard requires approval by at least75% of the member bodies casting a vote. International Standard ISO6721-8 was prepared by Technical Committee ISO/TC61, Plastics, Subcommittee SC2, Mechanical properties. ISO 6721 consists of the following parts, under the general title Plas
15、tics Determination of dynamic mechanical properties: Part 1: General principles; Part 2: Torsion-pendulum method; Part 3: Flexural vibration Resonance-curve method; Part 4: Tensile vibration Non-resonance method; Part 5: Flexural vibration Non-resonance method; Part 6: Shear vibration Non-resonance
16、method; Part 7: Torsional vibration Non-resonance method; Part 8: Longitudinal and shear vibration Wave-propagation method; Part 9: Tensile vibration Sonic-pulse propagation method; Part 10: Complex shear viscosity using a parallel-plate oscillatory rheometer. Descriptors: Plastics, rigid plastics,
17、tests, mechanical tests, determination, mechanical properties, dynamic properties, shear modulus, test equipment.iv blankBS2782-3:Method 323E:1997 BSI 09-1999 1 1 Scope This part of the International Standard ISO6721 describes an ultrasonic wave propagation method for determining the storage compone
18、nts of the longitudinal complex modulus L* and the shear complex modulus G* of polymers at discrete frequencies typically in the range0.5MHz to5MHz. The method is suitable for measuring materials with storage moduli in the range0.01GPa to 200GPa and with loss factors below0.1at around1MHz. With mate
19、rials that have a higher loss, significant errors in velocity measurement are introduced through waveform distortion and can only be reduced using procedures that are outside the scope of this standard. The method allows measurements to be made on small specimens, typically 50mm 20mm 5mm, or small r
20、egions of larger specimens or sheets. It is therefore possible to obtain information on the homogeneity or anisotropy (seeclause10.5) of modulus in a specimen. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this Inter
21、national Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to use the most recent editions of the standards listed below. Members of IEC and ISO maintain regist
22、ers of currently valid International Standards. ISO 1183:1987, Plastics Methods for determining the density and relative density of non-cellular plastics. ISO 6721-1:1994, Plastics Determination of dynamic mechanical properties Part 1: General principles. 3 Definitions See ISO6721-1, 4. 3.1 longitud
23、inal modulus the ratio of a uniaxial tensile or compressive stress applied to a specimen to the resulting uniaxial strain when the strain in a plane transverse to the axis of applied stress is zero. See Table 5 in ISO6721-1 for relationships between this and other moduli 3.2 longitudinal acoustic wa
24、ve a sound wave in which the particle displacement is in the direction of wave propagation 3.3 transverse acoustic wave a sound wave in which the particle displacement is perpendicular to the direction of wave propagation 3.4 bulk wave the mode of propagation of an acoustic wave in a material whose
25、boundaries normal to the direction of propagation are infinitely remote. This mode is realised in practice for waves whose wavelength is much less than the dimensions of the specimen transverse to the direction of propagation. In practice, the acoustic wave frequency is then ultrasonic 4 Principle M
26、easurements are made of the velocity of longitudinal and transverse acoustic waves in a specimen and the specimen density. The frequency of the wave is chosen so that its wavelength in the specimen is significantly less than the specimen dimensions in a plane transverse to the direction of wave prop
27、agation. The wave then propagates as a bulk wave. The longitudinal and shear storage moduli are given by the product of the material density and the square of the longitudinal and the shear wave velocities respectively. Two methods are described in this International Standard for measuring wave velo
28、cities. In the immersion method, the specimen intercepts a beam of longitudinal acoustic wave pulses passing between a transmitting and receiving transducer in a bath of a suitable liquid. At normal incidence, longitudinal wave pulses are excited in the specimen. As the angle of incidence is increas
29、ed, the amplitude of the longitudinal refracted wave decreases and a refracted transverse (shear) wave is generated. Longitudinal and transverse wave velocities are deduced from measurements of differences in pulse transit times with and without the specimen in the beam and a knowledge of the veloci
30、ty of sound in the liquid. In the transducer contact method, the specimen is sandwiched between two transducers, one launching and the other receiving acoustic wave pulses. For the determinaion of longitudinal and transverse wave velocities, transducer pairs having longitudinal and transverse polari
31、sations, respectively, are used. Wave velocities are again obtained from measurements of differences in pulse transit times with and without the specimen in the beam.BS2782-3:Method 323E:1997 2 BSI 09-1999 5 Testing device 5.1 Apparatus The requirements of the apparatus are that it shall enable meas
32、urement of the velocities of longitudinal and transverse ultrasonic waves in a specimen. Two methods are described in this International Standard. 5.1.1 Method A: Immersion method Figure 1(a) shows, schematically, suitable apparatus for measuring velocity by an immersion method. Two ultrasonic trans
33、ducers are mounted coaxially in a bath containing a liquid, one acts as a transmitter T of longitudinal ultrasonic wave pulses and the other as a receiver R. The transmitter is driven by a series of high-voltage, short-duration electrical pulses from the transducer drive unit. A pulse repetition int
34、erval of about1ms is satisfactory. Acoustic pulses launched by the transmitter travel through the liquid and the specimen and are detected by the receiving transducer. The specimen is mounted on a turntable, located between the transducers T and R, such that the angle of incidence of the acoustic be
35、am can be varied and measured to +0.5 . The specimen can be removed from the beam. The receiving transducer is connected to electronic equipment that will enable measurement of the difference in the arrival times of pulses received with and without the specimen in the beam. An oscilloscope, whose ti
36、mebase is accurately calibrated and triggered by the transducer drive unit, is suitable for this purpose. The receiving transducer may be replaced by a reflecting surface, such as a metal block, positioned normal to the axis of the transmitter as shown in Figure 1(b). The transmitting transducer is
37、now used to detect the beam of pulses reflected back through the liquid and the specimen and is connected to the transit-time measuring equipment (see note 1). (NOTE 1This test arrangement may be more appropriate if the specimen is only available as a thin sheet since the transit time in the specime
38、n is twice that obtained using the transmitter and receiver arrangement.) 5.1.2 Method B: Transducer contact method Figure 2(a) shows a method for measuring wave velocity by direct contact between the transmitting and receiving transducers and the surfaces of the specimen. For the determination of t
39、he longitudinal wave velocity, transducer pairs that launch and receive longitudinal acoustic waves are used whilst, for the determination of the transverse wave velocity, shear (transverse) wave transducers are employed. The transducer separation can be varied to accommodate specimens of different
40、thickness including direct contact between the two transducers. A coupling fluid is necessary to maximise the pulse amplitude transmitted to the specimen and to the receiver. The receiver may be replaced by a reflecting surface in contact with the specimen as shown inFigure 2(b). The transmitting tr
41、ansducer is now used to detect the beam of pulses reflected back through the specimen and is connected to the transit time measuring equipment (see note1). 5.2 Transducers When driven by the transducer drive unit, the transmitter should produce a short pulse at its natural frequency that has a durat
42、ion of around three or four cycles. A suitable waveform is shown inFigure 3. Pulses of longer duration are satisfactory but may not allow measurement of wave velocities by timing the interval between pulses that have been internally reflected by the specimen surfaces owing to an overlap of those pul
43、ses. In either of the test arrangements shown inFigure 2, the transmitter should possess a suitable buffer material located between the acoustic resonating device and the surface of the transmitter in order to prevent the contact with the specimen, the receiver or the reflector from influencing the
44、acoustic performance of the transmitter and hence the shape of the pulses generated. 5.3 Transit-time measuring equipment Data processing equipment shall be capable of measuring the time interval between two received pulses to an accuracy of 0.5% of the time interval (see note2). (NOTE 2The time int
45、erval between received pulses will depend upon the thickness of the specimen and the wave velocity in the material. For attenuating materials, such as most polymers, where specimens of only a few millimetres in thickness can be used, time intervals will be in the region of one microsecond.) The use
46、of a digital storage oscilloscope having a high sampling rate or an oscilloscope whose time base is triggered by the transducer drive unit through an accurate digital delay circuit are suitable for this purpose.BS2782-3:Method 323E:1997 BSI 09-1999 3 5.4 Temperature measurement and control See ISO 6
47、721-1, sub clause5.5 and note3. (NOTE 3The determination of wave velocity using the methods described in this standard involve measuring the time interval between two received pulses. When these pulses are obtained with and without the specimen in the acoustic beam, it is important that the temperat
48、ure of the apparatus has not changed significantly between the two measurements. As general guidance, any temperature change should be less than0.5 K using the transducer contact method and less than0.2 K using the immersion method.) 6 Test specimens See ISO6721-1, clause 6. 6.1 Shape and dimensions
49、 Test specimens in the shape of a bar or plate are suitable. The surfaces normal to the wave direction must be smooth, plane and parallel over an area comparable with the area of the faces of the transmitter and receiver. The dimension d of the specimen in the wave direction shall not vary by more than 0.2% over this area. In order to ensure that it is the bulk wave velocity that is measured (see clause4.4) the dimensions transverse to the wave direction shall be greater than3 the longitudinal pulse waveleng
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