BS 2782-3 Method 352F-1996 Methods of testing plastics - Mechanical properties - Determination of impact resistance by the free-falling dart method (instrumented puncture test)《塑料试.pdf

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1、BRITISH STANDARD BS 2782-3: Method352F: 1996 ISO7765-2: 1994 Methods of testing plastics Part 3:Mechanical properties Method 352F: Determination of impact resistance by the free-falling dart method (instrumented puncture test) ICS 83.080BS2782-3: Method 352F:1996 This British Standard, having been p

2、repared under the direction of the Sector Board for Materials and Chemicals, waspublished under the authority of the Standards Board and comes into effect on 15 September 1996 BSI 10-1998 The following BSI references relate to the work on this standard: Committee reference PRI/75 Draft for comment 8

3、9/39133 DC ISBN 0 580 26301 0 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee PRI/75, Plastics and rubber films and sheets, upon which the following bodies were represented: British Plastics Federation Her Majestys Statio

4、nery Office Institute of Trading Standards Administration Ministry of Defence Packaging and Industrial Films Association PIRA International Amendments issued since publication Amd. No. Date CommentsBS2782-3: Method 352F:1996 BSI 10-1998 i Contents Page Committees responsible Inside front cover Natio

5、nal foreword ii 1 Scope 1 2 Normative references 1 3 Definitions 1 4 Principle 2 5 Apparatus 2 6 Test specimens 6 7 Procedure 7 8 Expression of results 7 9 Precision 8 10 Test report 8 Annex A (informative) General remarks 9 Annex B (informative) Bibliography 9 Figure 1 Force-deformation diagram for

6、 very tough materials (schematic) 2 Figure 2 Force-deformation diagram for tough materials (schematic) 3 Figure 3 Force-deformation diagram for brittle materials (schematic) 3 Figure 4 Test apparatus (schematic) 4 Figure 5 Clamping device 5 List of references Inside back coverBS2782-3: Method 352F:1

7、996 ii BSI 10-1998 National foreword This British Standard has been prepared by Technical Committee PRI/75. It is identical with ISO7765:1994 Plastics film and sheeting Determination of impact resistance by the free-falling dart method Part 2: Instrumented puncture test, published by the Internation

8、al Organization for Standardization (ISO). BS2782: Method 352F, together with BS2782: Method 352E, supersedes BS2782: Method 352D:1979, which is withdrawn. The Technical Committee has reviewed the provisions of ISO291:1977 to which normative reference is made in the text, and has decided that it is

9、acceptable for use in conjunction with this standard. 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

10、obligations. Cross-references Publications referred to Corresponding British Standard BS 2782 Methods of testing plastics ISO 4593:1993 Part 6 Dimensional properties Method 630A:1994 Determination of thickness by mechanical scanning of flexible sheet (Identical) ISO 6603-2:1989 Part 3 Determination

11、of tensile properties Method 353B:1991 Determination of multi-axial impact behaviour by the instrumented puncture test (Identical) ISO 7765-1:1988 Method 352E:1996 Determination of impact resistance by the free-falling dart method (staircase method) (Identical) Summary of pages This document compris

12、es a front cover, an inside front cover, pages i and ii, pages1 to 10, an inside back cover 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 theinside front cover.BS2782-3: Method 352F:199

13、6 BSI 10-1998 1 1 Scope 1.1 The impact-penetration test described in the two parts of this International Standard is used for the assessment of plastic films and thin sheets (herein-after referred to as films) under an impact stress applied at right angles to the plane of the film. 1.2 Part 1 of thi

14、s International Standard can be used if it is sufficient to characterize the impact behaviour of the film by an impact-failure energy. Part 2 is used if a force-deformation or a force-time diagram, recorded at practically constant velocity of the striker, is necessary for characterization of the imp

15、act behaviour. This applies if: measured quantities derivable only from this diagram are required or only a small number of test specimens are available. 1.3 The test method is applicable to films of up to1mm thickness and makes it possible to compare impact-penetration forces, biaxial deformabiliti

16、es and energy-absorption capacities of films. Furthermore, if required, the transition region between brittle and tough behaviour of the film under the conditions of testing can be determined by varying the temperature or the penetration velocity or the relative humidity (see also annex B). NOTE 1Fo

17、r thicknesses greater than 1mm, ISO6603-2 should be used. 1.4 The test results are comparable only if the conditions for preparation of specimens, their thickness and surfaces, and the test conditions are identical. Comprehensive evaluation of the reaction to impact stress requires that the determin

18、ations are made as functions of deformation rate and temperature for different material variables, such as crystallinity and moisture content. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO7765. At th

19、e time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO7765 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintai

20、n registers of currently valid International Standards. ISO 291:1977, Plastics Standard atmospheres for conditioning and testing. ISO 4593:1993, Plastics Film and sheeting Determination of thickness by mechanical scanning. ISO 6603-2:1989, Plastics Determination of multiaxial impact behaviour of rig

21、id plastics Part2: Instrumented puncture test. ISO 7765-1:1988, Plastics film and sheeting Determination of impact resistance by the free-falling dart method Part 1: Staircase methods. 3 Definitions For the purposes of this part of ISO7765, the following definitions apply. 3.1 peak force, F M the ma

22、ximum force exerted by the striker inthedirection of impact during the test (see Figure 1 to Figure 3) 3.2 deformation at peak force, s M the deformation in the direction of impact at the centre of the test specimen corresponding to the peak force. For materials exhibiting a peak-force plateau, the

23、deformation is taken at the centre of the plateau (see Figure 1) 3.3 energy to peak force, W M the area under the force-deformation curve bounded by the origin, the peak force and the deformation at peak force (see Figure 1 to Figure 3) 3.4 total penetration energy, W T the total energy expended in

24、penetrating the test specimen (see Figure 1 to Figure 3) in contrast to the instrumented puncture test applied to test specimens made of brittle plastic (seeISO6603-2), the force-deformation diagram of this test applied to film and sheeting frequently shows a clear point of first failure (failure po

25、int) indicated by a sharp drop in the force. If this is the case, and if the interested parties agree to use this point as a characteristic criterion, the following additional definitions may be used 3.5 failure force, F F the force exerted by the striker in the direction of impact, measured at the

26、failure point (see Figure 1 and Figure 2) 3.6 failure deformation, s F the deformation in the direction of impact at the centre of the test specimen, measured at the failure, point (see Figure 1 and Figure 2)BS2782-3: Method 352F:1996 2 BSI 10-1998 3.7 failure energy, W F the area under the force-de

27、formation curve bounded by the origin, the failure force and the failure deformation (see Figure 1 and Figure 2) NOTE 2If the force-deformation diagram as measured during the test is influenced strongly by dynamic resonance effects, a mean curve may be used to obtain the values of the parameters def

28、ined in 3.1 and 3.4. This, however, is seldom the case when plastic film is tested. NOTE 3When comparing films of slightly different thicknesses, it is advisable to relate F M , F F , W Mand W Fto the thickness d of the specimen. Though the normalized values F M /d, F F /d, W M /d and W F /d do not

29、allow a physically exact comparison between film specimens of different materials, the thickness dependence of these normalized values is negligible for similar materials (those with the same amount of crystallinity and the same orientation) provided the thicknesses do not differ by more than a fact

30、or of 1,5. 4 Principle The test specimen is penetrated normal to its plane by a striker at a nominally uniform velocity. The resulting force-deformation or force-time diagram is electronically recorded. The test specimen is firmly clamped during the test. The force-deformation diagram obtained in th

31、ese tests shows several features of the materials bahaviour under impact. For example, the fracture may be “brittle”, “ductile”, “tough” or characterized by initial damage or by crack initiation and propagation. In addition, dynamic effects may be present, such as load-cell/indentor resonance, speci

32、men resonance and initial contact/inertia peaks (see Figure 1 to Figure 3). In all cases care must be exercised in analysing these features because the operative mechanism and the trains of inference are not yet fully established, and are the subject of continuing research. 5 Apparatus The apparatus

33、 consists of a mechanical test device for applying the test force, instruments for measuring the force and the deformation produced, and a thickness gauge. 5.1 Test device The essential components of the test device are the energy carrier (normally a falling mass, but a pneumatically, hydraulically

34、or spring-driven mass or a pendulum impact-testing device may also be used), the striker, and the clamping device consisting of the test specimen support and the clamping ring (see Figure 4 and Figure 5). The apparatus shall permit the test specimen to be punctured at the centre at a nominally const

35、ant velocity, perpendicular to the specimen surface. The force exerted on the test specimen in the direction of impact and the deformation of the specimen in the direction of impact shall be measurable or derivable (see Figure 4). Equipment suitable for this are falling-dart machines, pendulums long

36、 enough for the penetration path to be regarded as approximately straight, or high-speed tensile-testing machines with suitable attachments. Figure 1 Force-deformation diagram for very tough materials (schematic)BS2782-3: Method 352F:1996 BSI 10-1998 3 Figure 2 Force-deformation diagram for tough ma

37、terials (schematic) Figure 3 Force-deformation diagram for brittle materials (schematic)BS2782-3: Method 352F:1996 4 BSI 10-1998 Figure 4 Test apparatus (schematic)BS2782-3: Method 352F:1996 BSI 10-1998 5 5.1.1 Energy carrier The impact energy (e.g. drop energy) available shall be large in compariso

38、n to the penetration energy absorbed W T . This is because the influence of the test velocity (over the range of velocities used in the test) on the viscoelastic behaviour of plastics is relatively small; a decrease in the velocity of the striker of 20% is acceptable. This energy requirement is met

39、by falling-dart machines if where The falling-dart system used shall be capable of holding and releasing a weighted striker so that the striker falls constrained by a guide or guide(s). The fall shall be largely without friction or losses through windage. Any friction shall be taken into account in

40、the calculations. NOTE 4In most cases, a weighted striker with a total mass m of 10kg is sufficient. NOTE 5A velocity-measuring sensor should be placed close to the point of impact to eliminate errors due to friction between the dart and the guides and to air resistance. With hydraulically driven hi

41、gh-speed tensile-testing machines, any deviation of the velocity during impact shall be proved, e.g. by plotting the deformation-time curves and checking their slope. Figure 5 Clamping device m is the falling mass, in kilograms; g is the acceleration due to gravity (9,81 m/s 2 ); H 0 is the height o

42、f fall, in metres; W T is the total penetration energy, in joules.BS2782-3: Method 352F:1996 6 BSI 10-1998 5.1.2 Striker The preferred striker has a polished, hardened, hemispherical striking surface with a diameter D 1 =20mm 0,2mm. Alternatively, a striking surface of 10mm 0,1mm diameter may be use

43、d. The striker shall be constructed of steel. The load cell on the striker shall be mounted as close as possible to the tip to minimize the effect of extraneous forces. An example is shown in Figure 4. The head of the striker may be powdered with talcum or lubricated with oil to reduce friction, pro

44、vided that the interested parties agree on this procedure and use identical material. In some cases, this can reduce the statistical scatter of the results. It should be borne in mind, however, that lubricating the striker may influence the test results considerably. The natural frequency f nof the

45、striker/load-cell assembly shall be higher than the value specifiedin5.2. 5.1.3 Clamping device The test-specimen clamping device shall have an inside diameter D 2of 40 mm2mm. The clamping device shall be constructed in such a way that the circular specimen can be clamped flat and held securely duri

46、ng the test. Moreover, the clamping device shall not cause any radial pre-stretching of the specimen greater than 0,01%. Both requirements can be met with manual or hydraulic clamping faces. Furthermore, placing a ring of fine emery paper on the specimen support has been found to be useful. Figure 5

47、 shows a recommended clamping-device design. 5.2 Instruments for measuring force, specimen deformation and specimen thickness The instruments for measuring force and deformation shall be capable of measuring the force and deformation to within 5% of their maximum value. EXAMPLE If an electronic devi

48、ce has an accuracy of 0,4% at full scale (FS) then, for a value of 20% FS, the accuracy is 2%. 5.2.1 Load cell Because of the very short duration of the impact, only electronic load cells with a high natural frequency can be used. The shortest time intervalDt F,minwhich the device shall be required

49、to measure shall be 5/f n , where f nis the natural frequency of the striker/load-cell assembly. For the bandwidth B Tof the amplifier train (direct-current or carrier-frequency amplifier) with a lower bandwidth limit of 0 Hz, the following applies by analogy: where B jis the individual bandwidth of the j thamplifier stage. NOTE 6An example of such a measurement train is a piezoelectric lead cell mounted between the striker and the shaft (see Figure 4) and connected to a charge amplifier. 5.2.2 Device for measuring the spec