1、BRITISH STANDARD BS3424-10: 1987 Testing coated fabrics Part 10: Methods 12A and 12B. Determination of surface drag IMPORTANT NOTE. It is recommended that this Part be read in conjunction with the information in Part 0 “Foreword and general introduction”. UDC 677.077.652:678.066.2:677.017.48:531.43B
2、S3424-10:1987 This British Standard, having been prepared under the directionof the Rubber StandardsCommittee, was published under the authority ofthe Board of BSI and comes intoeffect on 30January 1987 BSI03-1999 The following BSI references relate to the work on this standard: Committee reference
3、RUM/13 Draft for comment85/37596DC ISBN 0 580 15517 X Foreword The frictional properties of coated fabrics are important for many applications. In clothing, footwear, upholstery, industrial belting, constructional applications and other end uses as well as during processing, friction is an important
4、 consideration. In some cases it is the frictional behaviour of the coating with itself that is of prime importance. In others it is the frictional behaviour of the coating with another surface that is the major consideration. Invariably the static coefficient of friction is required to be known but
5、 also the kinetic coefficient can be as important. Similarly the differences between the two may, in some cases, have to be as small as possible, whilst the absolute value, be it high or low, may not be significant. The methods included in this Part of BS3424 will provide essential information on bo
6、th static and kinetic coefficients of friction. Method A will provide both coefficients in a single operation. A means of quantifying the frictional properties is also provided. Method B on the other hand has been included because the instrument is simple and cheap to fabricate, both the method and
7、equipment are well known within the industry and, if different modes of operation are employed, can give a measure of the static and kinetic coefficient of friction. The determination of frictional coefficients of coated fabrics requires somewhat different considerations to be taken into account tha
8、n is the case when testing other materials, for example metals. For a more detailed discussion of these considerations it is recommended that reference be made to BS4618-5.6 including the bibliography. This Part supersedes method12 of BS3424:1973. A British Standard does not purport to include all t
9、he 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 iand ii,
10、 pages1 to10, 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 the inside front cover. Amendments issued since publication Amd. No. Date of issue CommentsBS 3424-10:19
11、87 BSI 03-1999 i Contents Page Foreword Inside front cover 1 Scope 1 2 Definitions 1 3 Method A. Flat bed method 1 4 Method B. Inclined plane method 4 Appendix A Graphical representation of friction test results onidenticalmaterials using method A and method B, Mode1 and Mode2 9 Appendix B Examples
12、of autographic traces of friction tests on coatedfabricsanddetermination of variability of kinetic friction 9 Figure 1 Illustration of flat bed test apparatus 2 Figure 2 Autographic trace illustrating the method of plotting values for 4 k 3 Figure 3 Autographic trace illustrating a coated fabric to
13、meltonfrictiontestand the method of plotting values for V k % 4 Figure 4 Autographic trace illustrating a coated surface to coated surfacefriction test and the method of plotting values for V k % 5 Figure 5 Specimen holder for method12B 6 Figure 6 Apparatus for method12B Mode1 7 Figure 7 Apparatus f
14、or method 12B Mode2 7 Publications referred to Inside back coverii blankBS3424-10:1987 BSI 03-1999 1 1 Scope This Part of BS3424 describes two methods of assessing the frictional properties of coated fabrics. NOTEThe titles of the publications referred to in this standard are listed on the inside ba
15、ck page. 2 Definitions For the purposes of this Part of BS3424 the following definitions apply. 2.1 coefficient of static friction (4 s ) the ratio of the force necessary to cause the tangential separation of two stationary surfaces to the perpendicular force acting upon the two surfaces 2.2 coeffic
16、ient of kinetic friction (4 k ) the ratio of the force necessary to maintain a constant velocity between two surfaces in contact to the perpendicular force acting upon the two surfaces 2.3 kinetic angle of surface drag (D k ) the angle of the inclined plane at which the test sled will slide down the
17、 inclined plane when sliding is initiated by a standard impulse 2.4 static angle of surface drag (D s ) the angle of the inclined plane at which the test sled will slide down the inclined plane under its own mass and momentum 3 Method A. Flat bed method 3.1 Principle A rectangular strip of the coate
18、d fabric is mounted with the coating outermost on a sled to which is attached a strain gauge and autographic recording device. The sled is caused to move over a rigidly mounted horizontal bed to which is fastened the comparator material (either a melton cloth or the coated fabric itself). The force
19、necessary to initiate movement of the sled and thereafter maintain a constant velocity is measured 3.2 Apparatus 3.2.1 A sled, 1501mm long 1001mm wide having a mass of700 15g to which is attached the coated fabric test specimen (see3.3.1) and a test specimen support of cellular rubber or plastics ma
20、terial3mm thick and of medium apparent density. The surface of the sled is flat and smooth or polished. The edges of the sled do not contain any burrs or roughnesses. When laid upon the horizontal bed of the test instrument the sliding surface of the sled is parallel with the horizontal bed and in f
21、ull planar contact and without distortion. 3.2.2 A driving mechanism, to move the sled or horizontal bed in such a manner that the relative movement of one with the other can be maintained at a constant velocity of800 80mm/min. The drive mechanism is automatically disengaged or de-energized at the e
22、nd of the test run (see3.2.3). 3.2.3 A flat bed of rigid construction, having a smooth or polished surface to which the comparator material (see3.3.2) is fixed in such a manner that the comparator material is not stretched more than a necessary minimum to remove wrinkles or other non-permanent disto
23、rtions. The flat bed is of a length to permit a relative surface travel during the test of approximately400mm and of a width to permit approximately50mm of clearance between the edge of the sled and any edge obstructions. 3.2.4 A measuring device, in the form of a strain gauge, is employed with an a
24、ssociated autographic recording instrument to determine accurately the force necessary to initiate movement and the force necessary to maintain a constant velocity thereafter. The response time of the recording instrument is less than0.25s. 3.3 Preparation of test specimens and comparator material 3
25、.3.1 Cut two coated fabric specimens each measuring250mm 100mm, one in the longitudinal direction of the coated fabric and one in the transverse direction of the coated fabric. 3.3.2 Cut two comparator specimens each not less than550mm long 200mm wide, from either the coated fabric under test or fro
26、m a woollen melton cloth 1)similar to OC7 of BS1771-1:1984. 3.4 Procedure Determine the mass in grams of the coated fabric test specimen(3.3.1). Mount the coated fabric test specimen on the sled(3.2.1) with the coated surface to be evaluated outermost (see Figure 1). Ensure that the coated fabric te
27、st specimen is not unduly stretched but is under sufficient tension to prevent the material wrinkling or creasing during test as this would affect the results. Mount the comparator specimen(3.3.2) on the flat bed(3.2.3) in a similar manner. 1) Information concerning sources of supply for the woollen
28、 melton cloth and the apparatus can be obtained by sending a stamped addressed envelope to Enquiry Section, BSI, Linford Wood, Milton Keynes MK146LE.BS3424-10:1987 2 BSI 03-1999 NOTEIt has been found convenient to overlap the comparator specimen over the edges of the flat bed and secure it underneat
29、h using adhesive tape. Alternatively the comparator may be taped securely within the vacuum channel, or, if the comparator is a thin single face coated fabric, it may be secured by vacuum suction as indicated in Figure 1. Ensure that both surfaces are free of irregularities and foreign matter. Witho
30、ut exerting any additional downward force, place the sled on the flat bed, ensure that the autographic recording device(3.2.4) is registering zero and that the chart speed is approximately600mm/min. Measure and record the ambient relative humidity and temperature. Engage or energize the driving mech
31、anism(3.2.2). 3.5 Calculation and expression of results 3.5.1 Coefficient of static friction (4 s ). From the autographic record determine the maximum value necessary to initiate movement between the test surfaces. Calculate the coefficient of static friction (4 s ) according to the following equati
32、on: where F is the maximum value necessary to initiate movement between the test surfaces (in a); W is the mass of the sled and coated fabric test specimen (in g). s F W - = Figure 1 Illustration of flat bed test apparatusBS3424-10:1987 BSI 03-1999 3 3.5.2 Coefficient of kinetic friction (4 k ). Fro
33、m the autographic record determine from the central50% of the trace (i.e.the 2nd and3rd quartiles), the maximum and minimum deflections of the trace and calculate their mean value S (in g). (See Figure 2.) Calculate the mean coefficient of kinetic friction (4 k ) according to the following equation:
34、 where 3.5.3 Percentage variability of kinetic friction (V k ) (see Figure 3 and Figure 4). At ten equispaced positions along the length of the autographic trace, record the value (in g) of the maximum and minimum deflections on the autographic trace and calculate the percentage variability of kinet
35、ic friction (V k ) according to the following equation: where The percentage value of V kprovides an indication of the amount by which the kinetic frictional value oscillates about the mean kinetic friction value. Examples of different values of V k % related to different autographic traces are give
36、n in Appendix B. 3.6 Test report The test report shall include the following information: a) the description of the coated fabric; b) the ambient relative humidity and temperature in which the test was conducted; c) reference to this method of test, i.e.method12A of BS3424-10:1986; d) the descriptio
37、n of the comparator material used (see3.3.2) and the relative orientation of the specimen under test and comparator material, where these are the same; e) the coefficients of static friction in both tests; f) the mean coefficients of kinetic friction in both tests; g) the variability of kinetic fric
38、tion in both tests; h) details of any deviation from the standard test procedure. S is the mean value necessary to maintain a constant relative velocity between the test surfaces (in g); W is the mass of the sled and coated fabric test specimen (in g). M n are the maximum values of the kinetic frict
39、ional values at M 1 , M 2 , M 3 , . M 10 ; k S W - = m n are the minimum values of the kinetic frictional values at m 1 , m 2 , m 3 , . m 10 ; S is the mean value necessary to maintain a constant relative velocity between the test surfaces (in g) (see3.5.2). Figure 2 Autographic trace illustrating t
40、he method of plotting values for 4 kBS3424-10:1987 4 BSI 03-1999 4 Method B. Inclined plane method 4.1 Principle A sled on which is mounted a coated fabric test specimen is placed on a bed of melton fabric that can be raised at an angle to the horizontal. The angle of the inclined plane is gradually
41、 increased until the sled slides down the inclined plane. The angle of inclination of the inclined plane is measured and reported as the angle of surface drag. 4.2 Apparatus 4.2.1 Instrument for determination of static angle of surface drag (D s ) 4.2.1.1 General. The instrument for determination of
42、 D sshall consist of the items detailed in4.2.1.2 to4.2.1.6. 4.2.1.2 Rigid platform, not less than300mm long and not less than100mm wide and hinged at one end to a baseboard provided with levelling screws. The rigid platform is provided with a spirit level and means for measuring the angle of inclin
43、ation with an accuracy of 0.5. 4.2.1.3 A piece of woollen melton cloth, similar to BS1771-1, OC7 and measuring approximately250mm long and100mm wide with its length in the cross direction and fixed under slight tension to the platform(4.2.1.2). NOTEThe melton cloth should be covered when the apparat
44、us is not in use. It should be replaced at intervals, or if contaminated. 4.2.1.4 Specimen carrier, which is of metal, and which has dimensions as illustrated in Figure 5. The total mass of the carrier including the clamping screw is adjusted to300g by balanced boring out of the upper section of the
45、 carrier. 4.2.1.5 Electric motor, suitably geared to tilt the plane of the platform mechanically at a rate of15 2 /min. 4.2.1.6 Microswitch (see BS9562) included in the circuit in series with the electric motor(4.2.1.5). This is so positioned at the top end of the platform(4.2.1.2) that the actuatin
46、g lever of the switch may be depressed by the back edge of the specimen carrier(4.2.1.4) resting on the melton cloth. A suitable stop is provided such that the distance of travel of the specimen carrier between the stop and the contact breaking position of the switch is4.5 0.5mm. The force required
47、to depress the actuating lever of the microswitch is between40mN and80mN. A suitable apparatus is shown schematically in Figure 6. Figure 3 Autographic trace illustrating a coated fabric to melton friction test and the method of plotting values for V k %BS3424-10:1987 BSI 03-1999 5 4.2.2 Instrument
48、for determination of kinetic angle of surface drag (D k ). A suitable apparatus is shown in Figure 7. The rigid platform(4.2.1.2) and the specimen carrier(4.2.1.4) are suitable. Means are provided for tilting the rigid platform so that it may be positioned accurately to within 0.5 of a required degr
49、ee of inclination. Provision is made to impulse the back of the specimen carrier by a force of approximately3N in order to initiate sliding. (See4.4.2) NOTEThe impulse force of3N on the back of the specimen carrier can be achieved by a metal cylinder of appropriate dimensions and mass. This method is however subject to changes in resultant force at different inclinations of the platform. Figure 4 Autographic trace illustrating a coated surface to coated surface friction testandthe method of plotting values for V k %BS3424-10:
