BRITISH STANDARD AUTOMOBILE SERIES BS AU 142 1968 Methods of test for Brake linings materials UDC 629 113 59 BS AU 142 1968 This British Standard, having been approved by the Automobile Industry Stand[.]
BRITISH STANDARD AUTOMOBILE SERIES Methods of test for Brake linings materials UDC 629 1 3- BS AU 142:1968 BS AU : 968 Fore word This British Standard, which is published under the authority of the Automobile Industry Standards Committee of the BSI, is based upon data sheet SMMT C- 3E: 964 (as revised in February 967) of the Society of Motor Manufacturers and Traders Limited It should be noted that the tests in this standard are not intended to replace the testing of brakes on a vehicle or dynamometer, it being accepted that a full assessment of a lining can be made only under operating conditions The tests may, however, be used for checking the consistency of manufacture For this purpose, the supplier and the purchaser should reach agreement on the selection of the tests, the sampling procedures and the limits to apply to the results The test procedures described are for the determination of certain physical and chemical properties; they can be used for any lining material, and as a quality control check on that material The properties should be identified with a particular brake lining and not with the brake or vehicle on which this lining is used The test procedures are not intended to assist the designer to find suitable materials for any particular application since the properties not necessarily bear any direct relationship to the performance of the lining in service 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 C o mpliance with a British S tand ard does not o f itse lf co nfe r immunity fro m le gal ob ligations S ummary o f p ages This document comprises a front cover, an inside front cover, pages i and ii, pages to and a back cover This British Standard, having been approved by the This standard has been updated (see copyright date) and may have had Automob ile Industry amendments incorporated This will be indicated in the amendment table on Standards Committee and the inside front cover endorsed by the Chairman of the Engineering Divisional Council, was published under the authority of the General Ame ndments issued since p ub lication Council of the Institution on 30 January 968 © BSI 02 - 2000 The following BSI reference relates to the work on this standard: Committee reference AUE/- IS B N 0 0 X Amd No Date Comments BS AU 142:1968 Contents Page Foreword Ins ide front cover S cop e Terms and definitions Tes ts Ass es s ment of friction and wear for quality control p urp os es Presentation of tes t data Figure — S chematic diagram of typ ical friction materials test machine © BS I - 00 10 Figure — Typ ical friction materials tes t drum 11 Figure — S tandard drum heating curve, friction materials test machine 12 Figure — S tandard drum cooling curve, friction materials test machine 13 Figure — Recommended mas ter form p lot sheet 14 Figure — Recommended master form log sheet 15 Tab le — Brinell hardnes s numb ers S cale A Tab le — Brinell hardnes s numb ers S cale B Tab le — Brinell hardnes s numb ers S cale C i ii blank BS AU : 968 S cop e This British Standard gives methods for testing brake lining friction materials to determine certain physical and chemical properties The tests given include: 1) Density 2) Hardness (Brinell and Rockwell) 3) Crossbreaking strength, for drum brake linings 4) Acetone extract 5) Loss of weight by ignition 6) Assessment of friction and wear Te rms and definitions For the purposes of this British Standard the following definitions apply: 2.1 b rake li ning a piece of friction material made to a shape specified by a brake manufacturer 2.2 sample a selection of brake linings taken from any batch or delivery of a particular material 2.3 sp e cimen that part of a sample brake lining on which tests are performed Te sts Specimens taken from samples of brake linings shall be subjected to the tests described in this standard The size of the sample and the number of specimens tested from the sample shall be agreed between the purchaser and the manufacturer Where alternative methods of testing are given the manufacturer shall, unless otherwise agreed with the purchaser, select the method he considers most suitable for the particular material Two alternative methods are given: Method ) The weight in grammes of the specimen shall be determined within an accuracy of ± 0.1 % The mean dimensions of the specimen shall be determined within an accuracy of ± 0.25 % and the volume computed in cubic centimetres The shape of the specimen will determine how this is done; in the case of an undrilled specimen which is in the form of an arc, the volume V is given by: A + A bt V= where, V = volume in cm3 A1 = mean length of outer curved surface in centimetres A2 = mean length of inner curved surface in centimetres b = mean width The mean values in centimetres shall be determined by measurements equally spaced along the specimen t = mean thickness The density of the specimen shall be computed as follows: Density = W g/cm3 V where W = weight of specimen in grammes Ge ne ral D e nsity 3.2.1 ( ) © BSI 02-2000 BS AU : 968 Suspend the specimen from a balance pan hook by means of a length of thin thread and determine the weight of the specimen in air within an accuracy of ± 0.1 % Immerse the specimen in water at a temperature between 18 °C and 24 °C in such a way that it is freely suspended and does not touch the surface of the water or the walls of the water-container, and re-weigh within an accuracy of ± 0.1 % If the weight of the thread is small (less than 0.05 %) compared to the weight of the specimen, it may be ignored In weighing the specimen in water, air bubbles adhering to the specimen shall be removed Their removal can be facilitated by the presence of a trace (e.g one part in 10 000) of detergent in the water, or by dipping the specimen momentarily into industrial methylated spirit, provided that it is known that the material is not affected by this treatment If the latter procedure is adopted, care shall be taken that the minimum amount of spirit is transferred to the water in which the specimen is weighed The specimen must be weighed as quickly as possible after immersing in water The density of the specimen shall be computed as follows: 3.2.2 Method a g/cm3 – a b where, a = weight in air in grammes b = weight in water in grammes Two alternative methods are given: This test which is based on the Brinell principles described in BS 240-1 1) , shall be carried out with a hardness testing machine fitted with a ball indenter of or 10 mm diameter The test shall be applied to the working surface of the specimen If necessary, a small amount of material may be removed from this surface by grinding in order to provide a smooth surface for the test The ambient temperature at the machine shall be between 18 °C and 24 °C The specimen shall be firmly held in position with adequate support from below with the working surface normal to the direction of application of the load, and a piece of aluminium foil 0.020 mm thick, located on the surface of the specimen so that the result may be observed on the foil The indenter shall be applied with the specified load for a period of 15 seconds The load and ball size, selected from one of the following scales, shall be such that the impressed diameter is between one quarter and half of the ball diameter: Density = W W W W W H ardness 3.3.1 Method Brinell hardness S cale A B C B all d iame te r Lo ad mm kgfa 10 10 a kgf = 9.806 65 N 30 100 75 Where two of these scales will give results within the above limitation, the scale selected shall be that which gives the greater diameter of impression The impression created on the foil shall be examined and its mean diameter, taken as the average length of two diameters taken at right angles to each other, measured in millimetres The specimen underneath the foil shall also be examined; if it is evident that the indenter has struck a hard inclusion or other particle liable to falsify the result, the reading shall be discarded and another obtained The result for each specimen shall be determined from the arithmetic mean of the measurements from at least three indentations These indentations shall be at least 12 mm from any edge and uniformly spaced along the specimen The hardness shall then be determined as the quotient of the applied load divided by spherical area of the impression For the scale used and the average diameter of impression obtained in millimetres the Brinell hardness number can be obtained from Table 1, Table or Table 1) BS 240, “ Method fo r Brinell h ardness tes t ”, Part 1, “ Tes ting o f m etals ” © BSI 02-2000 BS AU : 968 Table — Brinell hard ness numbe rs S cale A D iameter of ball = mm; load = kgf D i ame te r o f imp re ssi o n 0.00 01 02 03 04 05 06 07 08 09 01 97 92 87 82 78 73 69 64 60 60 55 51 47 43 38 34 30 26 2 70 5 07 03 99 95 92 88 85 81 80 77 74 71 67 64 61 57 54 51 48 90 44 41 38 35 32 29 23 4 00 4 09 06 04 01 98 95 93 90 3 88 85 83 80 78 75 73 70 68 66 20 63 61 59 56 54 52 50 47 45 43 30 41 39 37 35 33 31 26 23 40 21 3 1 09 07 06 04 50 02 00 98 97 95 93 92 90 88 86 60 85 83 82 80 78 77 75 74 72 71 70 69 68 66 65 63 62 60 59 57 56 80 55 53 52 50 49 48 46 45 44 42 90 41 40 39 37 36 35 34 32 31 30 00 29 28 2 25 2 23 2 2 21 18 17 12 1 10 09 08 20 07 05 04 03 02 01 00 99 98 98 30 97 96 95 94 93 92 91 90 89 88 40 87 86 85 85 84 83 82 81 80 79 50 79 78 77 76 75 74 73 73 72 71 60 70 70 69 68 67 67 66 65 64 64 70 63 62 61 61 60 59 58 58 57 56 80 56 55 54 54 53 52 52 51 50 50 90 49 48 48 47 46 46 45 44 44 43 00 43 42 41 41 40 40 39 38 38 37 mm 50 © BSI 02 - 000 BS AU : 968 Table — Brinell hardness numbe rs S cale B D iameter of b all = mm; load = 00 kgf D i ame te r o f imp re ssi o n 0.00 01 02 03 04 05 06 07 08 09 mm 50 0 9 9 9 1 8 60 8 8 1 7 7 70 1 6 6 6 80 5 5 1 90 4 4 1 00 5 3 3 1 3 1 12 8 12 12 3 2 20 12 11.9 11.8 11.7 11.7 11.6 11.5 11.4 30 11.4 11.3 11.2 11.2 11.1 11.0 11.0 8 40 6 4 2 1 50 1 0 95 89 83 77 72 66 61 55 60 50 44 39 33 28 23 9 07 02 70 97 92 87 82 77 72 68 63 58 53 80 49 44 39 35 30 26 21 8 08 90 04 00 95 91 87 83 79 75 71 67 00 63 59 55 51 47 43 39 35 32 28 7 20 7 7 06 02 99 95 92 20 88 85 82 78 75 71 68 65 62 58 30 55 52 49 46 42 39 36 33 30 27 40 6 21 6 09 06 04 01 98 50 95 92 90 87 84 81 79 76 73 71 60 68 65 63 60 58 55 53 50 48 45 70 43 40 38 35 33 30 28 26 5 21 80 5 5 07 05 03 01 98 90 06 94 92 90 88 86 83 81 79 77 00 75 73 71 69 67 65 63 61 59 57 07 08 09 Table — Brinell hardness numbe rs S cale C D iameter of b all = mm; load = 75 kgf D iame te r o f i mp re ssi o n 0.00 01 02 03 04 05 06 mm 20 65 64 63 62 61 60 59 58 57 56 30 55 54 53 53 52 51 50 49 49 48 40 47 47 46 45 45 44 43 43 42 42 50 41 40 40 39 39 38 38 37 37 36 60 36 35 35 35 34 34 33 33 32 32 70 32 31 31 30 30 30 2 29 29 2 8 80 28 27 27 26 6 26 26 1 90 5 25 24 24 24 23 23 00 2 22 22 2 21 21 21 21 21 2 20 20 2 0 9 9 1 20 8 8 7 7 2 30 6 6 1 40 5 5 4 50 4 1 3 © BSI 02 - 000 BS AU 42:1 968 3.3.2 Method Rockw ell hardnes s This test is based on the Rockwell principles described in BS 891 - 2) Rockwell hardness is defined in terms of the depth of penetration of a spherical indenter into the specimen The ball shall be applied to the working surface of the specimen If necessary, a small amount of material may be removed from the surface by grinding in order to provide a smooth surface for the test, but the specimen may be flat or radiused provided that it is firmly held in position, with the working surface normal to the direction of application of the load, and with adequate support from below The ambient temperature at the machine shall be between ° C and 24 ° C The machine shall be capable of applying loads of 0, 60, 00 and 50 kgf, of utilising balls of 75 mm, 35 mm and mm diameter and of indicating the depth of penetration of the indenter in units of 002 mm A direct reading Rockwell hardness testing machine, verified in accordance with BS 891 - 2) is suitable A preliminary load of kgf shall be applied and the depth measuring device set to 30 (reading on the Rockwell B scale for the direct reading machine) after seconds An additional load, in accordance with the scale used, shall be applied for a period of seconds and then removed The Rockwell hardness number shall be read directly from the scale of the direct reading machine seconds after the removal of the additional load and with the preliminary load still applied If a direct reading machine is not available the depth of penetration, e , shall be taken seconds after the removal of the maj or load and with the minor load still applied The Rockwell hardness = (1 30 – e ) where e is the observed depth of penetration in units of 002 mm The result for each specimen shall be taken as the arithmetic mean of the readings from at least three indentations The indentations shall be not less than mm from any edge and uniformly spaced along the specimen The load and indenter size shall be chosen from the following scales: Scale Ball diameter mm R Load kgf 60 L 35 60 M 35 00 P 35 50 K 75 50 The choice of scale shall depend on the hardness of the specimen and shall, where possible, be such that the Rockwell hardness number lies between 40 and 90 units Scale R would be used for soft materials with a reading less than 40 units and K for the hardest materials In cases where a material can be tested on two scales within the limitation the one selected shall be that giving the smaller numerical value of hardness It is essential always to use the same scale for any particular material 3.4 Crossbreaking strength (drum brake linings) This test is to determine the ultimate stress, due to bending, of a specimen with a rectangular cross section which is regular throughout the gauge length The width of the specimen shall not be less than mm and shall be uniform (± 25 mm) over the gauge length In the case of linings exceeding 50 mm width, a specimen 50 mm wide shall be cut from the centre of the lining and the cross-breaking strength measured across the specimen The ambient temperature at the machine shall be 20 °C ± ° C The mean width and mean thickness of the specimen shall be determined by at least three measurements across the lining The specimen shall be placed, with the concave surface upwards, symmetrically across two parallel supports with ± 25 mm radius supporting edges The length of the supports shall be at least the width of the specimen For specimens up to and including mm thickness, the supports shall be set 25 ± 25 mm apart For specimens of greater thickness than this, the gauge length shall be 00 ± 25 mm If a specimen tested on the 25 mm gauge length fails to break when the load reaches 225 kgf a new specimen shall be taken and tested on the 00 mm gauge length 2) BS 891 , “Meth od © BSI 02- 2000 fo r Ro ckw ell h ardness test ”, Part , “ Tes ting of m etals ”, Part 2, “Verificatio n o f the testing m achine ” BS AU : 968 The load shall be applied squarely across the width of the specimen by means of a third block, with 3.175 ± 0.125 mm radius bearing edge, which is parallel to and mid-way between the supporting blocks The load shall be increased steadily so that the specimen fractures in to 15 seconds The load in kgf at failure shall be noted Any tests in which the fracture occurs at rivet holes shall be disregarded The cross breaking strength of the specimen shall be computed as follows: Crossbreaking strength = 150 WL2 kgf/cm2 3.4.1 BD where, W = load at failure in kgf L = gauge length in mm B = mean width of specimen in mm D = mean thickness of specimen in mm Three tests per brake lining are recommended, one test at each end and one in the centre Each result shall be recorded In the following method, the specimen is extracted by acetone and the extract is isolated and weighed A Soxhlet extraction apparatus comprising an extractor complying with BS 2071 3) and a suitable flask and condenser, all connected with ground glass joints shall be used The acetone used in the extraction shall comply with BS 5094) A specimen of fine particles of the friction material shall be prepared by drilling with a 10 mm drill, using conditions which not produce visible overheating The samples shall be drilled perpendicular to the working face, but not nearer than mm from the edges The depth of drilling shall be such as to obtain a representative sample of the friction material, uncontaminated with any separate backing layer should this be present, or with the material of the backplate in the case of disc brake pads For the latter, this will normally mean that the depth of drill holes will be about 60 % of the pad thickness The weight of drillings required for the specimen is ± 0.2 g and sufficient holes should be drilled to give this weight It is not advisable to drill a much larger weight and to take a part of it for the required specimen The time between drilling the specimen and extracting shall not exceed hours The specimen shall be weighed to 0.001 g, and shall be wrapped securely in a filter paper The wrapped specimen shall be placed in an extraction thimble, (previously fat extracted) 25 mm by 80 mm single thickness and transferred to the Soxhlet extraction apparatus Sufficient acetone shall be added to fill the extraction unit plus a further 25 ml Extraction shall proceed for six hours, or a shorter period by agreement between manufacturer and purchaser The cycling rate during extraction shall be 10 to 20 cycles per hour On completion of the extraction period the flask shall be removed at a stage when the extraction unit is nearly filled with acetone This should leave about 15 ml of acetone in the extraction flask The contents of the flask shall be transferred to a preweighed vitreous silica crucible, the flask washed out with approximately ml of acetone and the washings transferred to the same crucible The crucible shall then be placed on a water bath and the acetone evaporated Suitable precautions against accidental ignition of the acetone should be taken The crucible shall finally be dried for ten minutes in an oven at 80 to 85 °C, and shall then be transferred to a desiccator, allowed to cool and reweighed 100 ( W3 – W2 ) The percentage acetone extract = W Aceto ne e xtract where, W1 = weight of specimen W2 = weight of crucible empty W3 = weight of crucible plus extract 3) BS 2071, “Soxhlet extractors ” 4) BS 509, “Acetone ” © BSI 02-2000 BS AU : 968 This test is not applicable to some materials which contain fillers for which the reaction is ill defined during the process of ignition The validity of the method in any particular case should be agreed between manufacturer and purchaser A specimen of fine particles of the friction material shall be prepared by drilling with a 10 mm drill, using conditions which not produce visible overheating The samples shall be drilled perpendicular to the working face, but not nearer than mm from the edges The depth of drilling shall be such as to obtain a representative sample of the friction material, uncontaminated with any separate backing layer should this be present, or with the material of the backplate in the case of disc brake pads For the latter this will normally mean that the depth of the drill holes will be about 60 % of the pad thickness The weight of drillings required for the specimen is g ± 0.1 g and sufficient holes should be drilled to give this weight It is not advisable to drill a much larger weight and to take part of it for the required specimen The material shall be weighed into a previously ignited crucible Weighing to 001 g is considered adequate The crucible and its contents, without lid, shall be placed in a muffle furnace at 825 ± 24 °C and left for two hours In some cases it may be desirable to extend or reduce the period of ignition; such cases will be negotiated individually In some cases, direct introduction of the crucible into the muffle may cause a minor explosion with loss of some of the contents In these instances the bulk of the volatile matter shall be carefully removed over a bunsen burner prior to the introduction of the crucible into the muffle After ignition the crucible shall be removed, cooled in a desiccator and reweighed (W – W ) The percentage loss on ignition = 100W –2 W where, W1 = weight of crucible W2 = weight of crucible and specimen before ignition W3 = weight of crucible and its contents after ignition Lo ss o f we ight b y ignitio n Asse ssme nt of friction and we ar for quality control p urp ose s This describes a procedure for determining and reporting the friction characteristics and wear rate data of brake linings The procedure is designed to verify that the tolerances established for a friction material are maintained The sampling procedure and test result limits for each material shall be agreed between the manufacturer and the purchaser The data obtained from this procedure is not recommended as a suitable basis for the selection of a friction material for a specific application Ge ne ral NOTE The procedure given in this Standard is similar to standard No J661 a, “Brake lining quality control test procedure ”, of the Society of Automotive Engineers (S.A.E) The test machine shall be equipped with suitable means for: 1) Measuring the drum temperature 2) Heating the drum 3) Controlling the drum heating rate 4) Cooling the drum 5) Controlling the drum cooling rate 6) Measuring the friction force 7) Measuring the drum rotational speed Means shall also be provided for measuring specimen thickness and weight The means for heating the drum shall be capable of ensuring that the “free running” temperature rise of the drum follows the heating curve in Figure within ± 14 degC The means for cooling the drum shall be capable of ensuring that the maximum drum temperature of 93 °C specified in is not exceeded, and that the “free running” cooling curve of the drum follows the cooling curve in Figure within ± 14 degC Ap p aratus 4.4.3 © BSI 02-2000 BS AU : 968 The temperature measuring system shall be accurate to within ± % of the full scale The friction force measuring system shall be accurate to within ± % of the full scale The drum speed measuring system shall be accurate to within ± % of the full scale A typical machine for carrying out this test procedure is shown in Figure and Figure Actual tests for performance shall be started when preliminary preparations and lining bedding given in have been completed All drum speeds, in rev/min, are based on a nominal 280 mm diameter drum with the specified loads applied to the specimen Te st conditions 4.4 Proced ure Preparation of test specimen The number of segments of linings to be selected for the test shall be as agreed between the manufacturer and the purchaser The test specimen shall be taken from the centre of the lining segment equidistant from each end The specimen shall be 25 mm square and flat on the bottom; the radius of the working surface shall conform to the radius of the test drum Not less than 0.25 mm nor more than 0.50 mm shall be removed from the working surface of a curved specimen The specimen thickness (or specimen plus shim) shall be approximately mm measured in the centre of the specimen Excess of material shall be removed from bottom side of the specimen cut from 6.3 mm or greater nominal thickness linings In cases where nominal lining thickness is less than 5.3 mm remove a minimum amount of material from the bottom surface to produce flatness The working surface of the specimen should not be handled and should be kept free of foreign matter Preparation of test drum surface After grinding the drum surface of new or resurfaced drums (in position on the test machine), remove all grinder marks and finish with No 320 grit (wet or dry) abrasive paper or cloth Remove dust from the drum with clean dry air and/or wiping with a clean cheese cloth or equivalent Complete the surface preparation by running a reference specimen continuously at kgf/cm2, 417 rev/min (6 metres/second) and at not over 93 °C until the coefficient of friction has stabilized Prior to each test, finish the drum surface with No 320 grit (wet or dry) abrasive paper or cloth Remove dust from the drum with clean dry air and/or wipe it with clean cheese cloth or equivalent Conditioning of test specimen The specimen is run-in at kgf/cm2, 312 rev/min (4.5 m/s) and at a maximum drum temperature of 93 °C, for 20 minutes If the specimen does not show at least 95 % contact after 20 minutes, the specimen is to be discarded and another prepared Initial thickness and weight measurements Specimen thickness measurements are taken in three places along the axis parallel to the drum axis (open centre and closed edges) and recorded Weigh (in grammes) to 0.001 mg and record Reseat the specimen by running continuously for at 3.5 kgf/cm2 and 208 rev/min (3 m/s) The initial clearance between the specimen and the drum should be 0.25 mm to 0.38 mm in the OFF position Initial wear measurement With the drum stationary and at 93 °C and with 10.5 kgf/cm2 loading on the specimen, obtain an indicator reading of height of specimen holder, and record 4.4.1 4.4.2 4.4.3 4.4.4 4.4.5 Te st runs Base line run Run for 10 seconds ON (load applied) and for 20 seconds OFF (load removed), at 10.5 kgf/cm2 and 417 rev/min (6 m/s) for 20 applications Start the run at a drum temperature of 93 ± 11 °C and maintain within these limits during this part of the test First fade run With the heater voltage adjusted so that the “free running” temperature rise curve of the drum follows the heating curve in Figure within ± 14 degC run under a continuous load of 10.5 kgf/cm2 at 417 rev/min (6 m/s) with the heater ON and cooling means OFF Start the run at 93 °C and run for either 10 minutes or until 233 °C obtained, whichever occurs first Take simultaneous readings of friction force and drum temperature at 36 second intervals and record the time required to reach 233 °C First recovery run Immediately following completion of first fade run in , turn off heater and turn on cooling means (adjusted so that the “free running” cooling curve of the drum follows the cooling curve in Figure within ± 14 degC and make a 10 second application at each 55 degC interval during cooling from 260 °C to 93 °C 4.5 4.5.2 4.5.3 © BSI 02-2000 BS AU : 968 4.5.4 4.5.5 Second wear measurement Repeat the initial wear measurement in Wear run Run for 20 s ON and s OFF , at kgf/cm 4.4.5 and 41 rev/min (6 m/s) for 00 applications Start the run at a drum temperature of 205 ± 1 ° C and maintain the average of the maximum and minimum temperature for each application at 205 ± 1 ° C 4.5.6 Third wear measurement Immediately upon completion of the wear run in repeat the initial wear measurement in 4.5.7 Second fade run Immediately upon completion of the third wear measurement in heater voltage adj usted, as specified in the first fade run in at 41 rev/min (6 m/s) with the heater cool to 93 ° C and 4.5 , 4.4.5 ON , and the cooling means 4.5.6 and with the run at a continuous lead of kgf/cm OFF Start the run at 93 ° C and run for either minutes or until 288 ° C is reached, whichever occurs first Take simultaneous readings of friction force and drum temperature at 30 s intervals and record time required to reach 288 ° C 4.5.8 Second recovery run Immediately following the completion of the second fade run in the heater, turn on the cooling means (adj usted as specified for the first recovery run in 4.5 7, 4.5 3) turn off and make a s application at each 55 degC interval during cooling from 31 °C to 93 °C 4.5.9 Baseline re-run Repeat the base line run in 4.5.1 4.5 Final wear measurement Repeat the initial wear measurement in 4.5 1 Final thickness and weight measurements Measure and weigh as described in 4.4.5 4.4.4 S e le ction o f p lot p o int fo r coefficie nt of frictio n value During the intermittent application runs, the coefficient of friction values are taken at the end of each application Pre se ntation of te st data 5.1 Figure shows a recommended form of plot sheet for uniformity in the presentation of test data 5.2 Figure shows a recommended form of data sheet for use by the test operator © BSI 02- 2000 BS AU 142:1968 Figure — Schematic diagram of typical friction materials test machine 10 © BSI 02 - 000 BS AU 142:1968 Figure — Typical friction materials test drum © BSI 02 - 000 11 BS AU 42 : 968 Figure — S tandard drum heating curve, friction materials test machine 12 © BSI 02 - 000 BS AU : 968 Figure — S tandard drum cooling curve, friction materials test machine © BSI 02 - 000 13 Figure — Recommended master form plot sheet BS AU 142:1968 14 © BSI 02 - 000 BS AU 142:1968 Figure — Recommended master form log sheet © BSI 02 - 000 15 BS AU 142:1968 BSI — British Standards Institution BS I is the independent national b ody res p ons ib le for p rep aring Britis h S tandards It p res ents the UK view on s tandards in E urop e and 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