1、m Lb24bb9 05Y5082 850 m BRITISH STANDARD Plastics - Determination of dynamic mechanical properties Part 3. Flexural vibration - Resonance-curve method The European Standard EN IS0 6721-3 : 1996 has the status of a British Standard ICs 83.080 NO COPYING WITHOUT BSL PERMISSION EXCEPT AS PERMITTED BY C
2、OPYRIGHT LAW BS EN IS0 i996 IS 2782 : art 3 : aethod 338A : 1996 6721-3 : - lb24669 0545083 797 W Amd. No. BS EN IS0 67213 : 1996 Date Text affectM EN IS0 67213 February 1996 ICs 83.080 Descriptors: Plastics, rigid plastics, tests, vibration tests, determination, mechanical properties, dynamic prope
3、rties, modulus of elasticity, test equipment English version Plasties - Determination of dynamic mechanical properties - Part 3: Flexural vibration - Resonanee-eurve method (IS0 6721-3 : 1994, including Technical Corrigendum 1 : 1995) Plastiques - Dtermination des proprits Kunststoffe - Bestimmung m
4、caniques dynamiques - dynamisch-mechanischer Eigenschaften - Partie 3: Vibration en flexion - Mthode en Teil 3: Biegeschwingung - rsonance Resonanzkuwen-verfahren (IS0 6721-3 : 1994, Rectificatif Technique 1 : 1995 (IS0 6721-3 : 1994, einschliefilich Technische inclus) Korrektur 1 : 1995) This Europ
5、ean Standard was approved by CEN on 1996-01-15. CEN members are bound to comply with the CENKENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-todate lists and bibliographical references concernin
6、g such national standards may be obtained on application to the Centrai Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own lang
7、uage and notified to the Central Secretariat has the same statut as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and
8、United Kingdom. GEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels O 1996 Copyright reserved to CEN members Ref. No. EN IS0 67213 : 1996 E H 3624bb 0545087 332 Page 2 EN IS0 6721-3 : 1996 F
9、oreword The text of the International Standard from Technical Committee ISOAC 61, Plastics, of the International Organization for Standardization (EO) has been taken over as a European Standard by Technical Committee CENAC 249, Plastics, the secretanat of which is held by IBN. This European standard
10、 shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by August 1996, and conflicting national standards shall be withdrawn at the latest by August 1996. According to the CENICENELEC Intemal Regulations, the national standards
11、organizations of the following countries are bound to implement this European standard Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. O BSI 1996 - W 3624669 0545088 27
12、9 W Page 3 EN IS0 6721-3 : 1996 Plastics - Determination of dynamic mechanical properties - Part 3: Flexural vibration - Resonance-curve method 1 Scope This part of IS0 6721 specifies a bending-vibration method based upon resonance curves for determining the flexural complex modulus E; of homogeneou
13、s plastics and the damping properties of laminated plastics intended for acoustic insulation, for example systems consisting of a metal sheet coated with a damping plastic layer, or sandwich systems consisting of two sheet-metal layers with an intermediate plastic layer. For many purposes, it is use
14、ful to determine these properties as a function of temperature and frequency. 2 Normative reference The following standard contains provisions which, through reference in this text, constitute provisions of this part of IS0 6721. At the time of publication, the edition indicated was valid. All stand
15、ards are subject to revision, and parties to agreements based on this part of IS0 6721 are encouraged to investigate the possibility of applying the most recent edition of the standard indicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. IS0 6721-1 :
16、1994, Plastics - Determination of dy- namic mechanical properties - Part 7: General prin- ciples. 3 Definitions See IS0 6721 -1 : 1994, clause 3 NOTE 1 As stated in IS0 6721-1, frequencies derived from resonance curves based on deformation-rate ampli- tude measurements can be exactly related to dyna
17、mic properties. For the recommended range of the loss factor of this part of the International Standard. .e. tan 6 i 01. resonance curves based upon deformation amplitudes can also be used. For highly damping materials, see IS0 6721-1 :1994, annex A. 4 Principle A specimen is submitted to forced ben
18、ding vibrations in the frequency range between about 10 Hz and 1 O00 Hz. The resonance curve (see IS0 6721-1 :1994, subclause 3.1 1) is determined and, from the curve obtained, the flexural storage modulus E, (see IS0 6721-1:1994, subclause 3.2) is calculated in the range above 0,5 MPa and the loss
19、factor given by tan 6 = E“,/E, (see IS0 6721-1:1994, subclause 3.6) is calculated in the range between about lov2 and lo- (see note 1). The test frequency can be varied by making measurements at more than one vibrational order. The measurement range for the flexural loss modulus E“f (see IS0 6721-1:
20、1994, sub- clause 3.3) is determined by that of the loss factor and by the value of the storage modulus. The mode of oscillation used is designated oscillation mode III (see IS0 6721-1:1994, table 2) and the type of modulus measured is designated Ef (see IS0 6721-1:1994, table 3). The test is perfor
21、med on rectangular bars, either mounted vertically with the upper end clamped and the other end free (method A) or suspended horizon- tally by fine fibres at vibrational nodes (method BI (see figure 1). Method A is suitable for testing specimens _ _ m Lb24669 0545089 LO5 m Page 4 EN IS0 6721-3 : 199
22、6 of most types of plastic, including relatively soft ma- terials, whereas method B is particularly suitable for testing rigid (.e. dimensionally stable) specimens, for example sheet metal covered by a plastic layer for damping purposes. 5 Test apparatus 5.1 General The apparatus consists of devices
23、 for clamping (method A) or suspending (method B) the specimen, electronic devices (frequency generator and recording device) for exciting the specimen to forced bending vibration and for measuring the frequency as well as the velocity ampiitude of the specimen (see note 1). For excitation and detec
24、tion of the vibrations two electromagnetic transducers are situated near the ends of the specimen. The specimen, the clamping or supporting device and the electromagnetic trans- ducers are enclosed in a temperature-controlled chamber (see figure 1). 5.2 Clamps or suspension fibres If the specimen is
25、 clamped at one end, the clamp shall be designed to hold the upper end of the speci- men securely and tightly see figure 1 a). It shall be constructed so that no additional damping of the sys- tem occurs. There are two causes of additional damping: - Friction between the test specimen and the clamp:
26、 This can be detected by stimulating freely decaying oscillations of the relevant vibrational or- der. As explained in IS0 6721-1:1994, annex B, the type of decay is indicative of different types of deviation from linear viscoelastic behaviour. - Vibration of the clamp: The clamp shall be rigidly mo
27、unted on a heavy mass, which acts as a counterweight to the oscillating test specimen. This requires a heavy rigid stand within the temperature-controlled chamber (see figure 1). If the specimen is tested in the horizontal position, it shall be supported by two fine fibres at vibrational nodes (see
28、9.3.2). 5.3 Exciter and detector The frequency generator shall be capable of exciting the specimen with the aid of the electromagnetic transducer to oscillations within the frequency range of 10 Hz to 1 O00 Hz with a constant force amplitude. The detector shall be capable of measuring the de- format
29、ion or deformation-rate amplitude (see note l) of the specimen and the frequency of the oscillation, thereby permitting the recording of the resonance curve (see IS0 6721-1:1994, subclause 3.11 and an- nex A). The amplitude of the exciter and the sensitivity of the detector shall not vary with frequ
30、ency by more than 0,5 %within the range of a single-resonance peak, .e. for any 10 % variation of the frequency. A tracking filter shall be used to minimize noise at the detector. Frequencies shall be measured with a res- olution of at least 0,l % (see 11.2). Two small, thin steel plates shall be ad
31、hesively bonded at the ends of the specimen to permit the excitation and detection of the vibrations by means of suitable electromagnetic transducers (see 6.2). 5.4 Temperature-controlled enclosure See IS0 6721-1:1994, subclause 5.3. 5.5 Gas supply Supply of air or other suitable inert gas for purgi
32、ng purposes. 5.6 Temperature-measurement device See IS0 6721-1 :1994, subclause 5.5. 5.7 Devices for measuring test specimen dimensions and density See IS0 6721-1:1994, subclause 5.6. The balance used for measuring the mass of the specimen shall be capable of weighing to 1 mg. W 1624669 0545090 927
33、W From To amplifier frequency generator Page 5 EN IS0 6721-3 : 1996 1 - . . - . . - . . - . . _ . . I Clamp Detector Temperature- enclosure Specimen Exciter -controlled a) Method A Tempera ture-controlled enclosure I i i i Y/ Specimen !p Vibrational nodes . From frequency generator To amplifier b) M
34、ethod8 Detector Figure 1 - Schematic diagrams of test apparatus for methods A and B D 3624bb9 0545093 863 Page 6 EN IS0 6721-3 : 1996 6 Test specimens See IS0 6721-1:1994, clause 6. 6.1 Shape and dimensions Specimens shall be rectangular bars or strips thick enough to give sufficient bending stiffne
35、ss, which is critical for the resonance frequency. On the other hand, the thickness shall be sufficiently small when compared to the wavelength of the bending vibration. The specimen thickness shall also be limited to avoid effects due to shear deformation and rotatory inertia if accurate values of
36、E are required. Length-to- thickness ratios of less than 50 shall be avoided if values of E are required to be accurate to within - + 5 %, from measurements up to the sixth order of homogeneous, isotropic specimens. The thickness of the layers of a multilayer system will depend on the purpose for wh
37、ich the system was designed. When comparing various systems by the bending-vibration test, the preferred ratio of the mass of the plastic layer to the mass of the basic sheet material is 1:5. The width of the specimens shall be less than one- half of the wavelength used in order to avoid lateral res
38、onance vibrations. A width of 10 mm should be suitable in most cases. The length of the specimens depends on the desired frequency. For specimens clamped at one end, the length shall be sufficiently large to avoid the clamp influencing the vibration significantly. Usually a free length of 180 mm wil
39、l be suitable. If the specimen is not clamped, its length shall be 150 mm. 6.2 Preparation See IS0 6721-1 :I 994, subclause 6.2. Small, thin, light steel plates shall be adhesively bonded to the specimens near their ends to allow excitation and detection of the vibrations by means of electromagnetic
40、 transducers. To avoid errors in E greater than 4 %, the ratio of the added mass to the specimen mass shall not exceed 1 %. To avoid the steel plates causing additional stiffness, they shall not extend along more than 2 % of the length of the specimen. The distance between the steel plates shall be
41、large enough to avoid cross-talk between exciter and detector. Multilayer specimens shall be fabricated with the thickness and by the production techniques to be used in the projected end-use. For example, for a plastic material on steel sheet, the plastic may be ap- plied to the metal by spraying,
42、as a mastic or as an adhesively bonded sheet. 7 Number See IS0 6721-1:1994, 8 Conditioning See IS0 6721-1:1994, 9 Procedure clause 7. clause 8. 9.1 Test atmosphere See IS0 6721-1:1994, subclause 9.1 9.2 Measurement of specimen cross-section and density See IS0 6721-1 :I 994, subclause 9.2. Determine
43、 the density of the specimen (.e. the mass of the free length per unit volume) to f 0,5 %. 9.3 Mounting the test specimens and adjustment of the tranducers 9.3.1 Method A Clamp the specimen so that the clamping force is high enough to avoid additional damping from friction between the specimen and t
44、he clamp (see 5.2). Measure the free length L of the specimen to Mount the specimen by fine, preferably non-metallic, fibres at the calculated positions of the vibrational nodes. D 3624hh9 8545892 TT m Page 7 EN IS0 6721-3 : 1996 9.3.3 Adjustment of the transducers After clamping or supporting the s
45、pecimen, adjust the detector and exciter transducers so that they are just far enough from the specimen to avoid any noticeatle effect on the resonance frequency. With the usual test apparatus, the recommended distance is greater than 3 mm for i = I. Gaps of 1 mm or less can be used with higher orde
46、rs. 9.4 Varying the temperature See IS0 6721 -1 :I 994, subclause 9.4. 9.5 Varying the frequency See IS0 6721-1:1994, subclause 9.5. 9.6 Recording the resonance curve Excite the specimen using the frequency generator and determine the amplitude (or the effective value) of the deformation or deformat
47、ion rate. By varying the frequency, record the resonance curve. Measure the amplitude to 10,5 %, the resonance frequency to at least 50,l % and the width of the resonance peaks to +I % of the value of the peak width (see 1 1.2). Usually, it is possible to measure the resonance curve in the range fro
48、m the first to the sixth or seventh order of the vibration. When a clamped specimen is used (method A), the first order is the one mostly affected by damping in the clamp, and the amplitudes of the vibrations of higher orders decrease rapidly with frequency. There- fore, intermediate orders shall be
49、 chosen for the measurements. Ensure that the type of amplitude decay measured does not include either friction between moving and fixed parts of the apparatus or non-linear behaviour of the materials under test (see IS0 6721-1:1994, an- nex 8). 10 Expression of results 10.1 Symbols E, flexural storage modulus. expressed in pascals E, flexural loss modulus, expressed in pascals tan f flexural loss factor (dimensionless number) e specimen density, expressed in kilograms per cubic metre 1 length of the specimen (method B), expressed in metres
