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1、INTERNATIONALSTANDARD INTERNATIONAL ORGANIZATION FOR STANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATION MEMYHAPOAHAR OPTAHM3AMR IlO CTAHflAPTM3AqMM Plastics - Determination of hardness - Part 2: Rockwell hardness Plastiques - D the higher the Rockwell hardness number, the harder the materi
2、al. Due to a short overlap of Rockwell hardness scales by this procedure, two different Rockwell hardness numbers of different scales may be obtained on the same material, both of which may be technically correct. 1.3 For materials having high creep and recovery, the time- factors involved in applic
3、ation of the major and minor loads have a considerable effect on the results of the measurements. 1.4 An alternative method of using the apparatus to give hardness on the Rockwell-o hardness scale is specified in the annex which shows how this scale may be related to the hard- ness measurement of IS
4、0 2039-l. 2 References IS0 48, Rubber, vulcanized - Determination of hardness (Hardness between IO and 199 IRHDI, 1) IS0 291, Plastics - Standard atmospheres for conditioning and testing. IS0 868, Plastics - Deterinination of indentation hardness by means of a durometer (Shore hardness). IS0 2039-1,
5、 Plastics - Determination of hardness - Part 1: Ball indentation method. 3 Principle 3.1 This is a method for determining hardness in which a constant minor load is applied to a steel ball resting on the material to be tested, followed by application of a major load, and then followed by a return to
6、 the same minor load, all at specified limits for times of loading. The actual measurement is based on the total depth of penetration, minus the elastic recovery after a fixed time following removal of the major load, minus the penetration resulting from the minor load. The Rockwell hardness number
7、is derived from the net increase in depth of impression as the load on an indentor is increased from a fixed minor load to a major load and then returned to the same minor load. 3.2 Each Rockwell hardness scale division represents 0,092 mm vertical movement of the indentor. In practice, the Rockwell
8、 hardness number is derived from the following relationship : HR = 130 - e where HR is the Rockwell hardness number; e is the depth of impression after removal of the major load, in units of 0,002 mm. NOTE - This relationship only holds for the E, M, L and R scales. 4 Apparatus 4.1 The apparatus is
9、a standard Rockwell hardness tester which comprises essentially - a rigid frame supporting an adjustable platform fitted with a plate at least 50 mm in diameter to support the test specimen; - an indentor with its associated fittings; - a device for applying the appropriate loads to the indentor wit
10、hout impact. 4.2 The indentor comprises a polished hardened steel ball which rolls freely in its housing. The ball shall not deform dur- ing the test or show damage after a test. The diameter of the in- dentor depends upon the Rockwell scale in use (see 4.51, 1) At present at the stage of draft. (Re
11、vision of IS0 48: 1979, IS0 1400: 1975 and IS0 1818: 1975.) -,-,- km i!U3Y-2 : IYW it) 4.3 The indentor is equipped with a dial gauge or other suitable device to measure the depth of penetration of the indentor to within 0,001 mm. It is desirable but not essential for the dial gauge to be calibrated
12、 in Rockwell hardness numbers (one Rockwell scale division = 0,002 mm). When the machine is so directly calibrated, it is usual for the dial gauge to have a black and a red scale, the latter allowing automatically for the constant of 130 in the derivation of Rockwell hardness number on the M, L and
13、R scales (see 3.2). Alternative means of measurement of penetration and display of data may be used, provided that the accuracy is at least equal to that of the dial gauge. 4.4 The appropriate loads for the M, L and R scales are as given in 4,5. In each case the minor load is 98,07 N. Provision is u
14、sually made in the Rockwell.machine to apply the minor load to the specimen by means of a screw capstan which raises the platform supporting the test specimen until the latter contacts the indentor. In these circumstances the dial gauge has an in- dicated point to show when the minor load has been f
15、ully ap- plied; reference should be made to the manufacturer s hand- book before operating the machine. The adjustment of speed of load-application is of great importance. Adjust the dash-pot on the Rockwell tester so that the operating handle completes its travel in 4 to 5 s with no specimen on the
16、 machine or no load applied by the indentor to the anvil. The major load shall be 98Q7 N for this calibration. 4.5 The major and minor loads and indentor diameters for the Rockwell scales are as follows : Rockwell Hardness scale Minor load Major load lndentor diameter N N mm Both the major and minor
17、 loads shall be accurate to within 2%. NOTE - The E scale is used for calibration only for the purpose of this International Standard. 4.6 The machine should be mounted on a level, rigid base free from vibration, If the machine mounting is unavoidably subjected to vibration (for example, in the vici
18、nity of other test machines), the Rockwell tester may be mounted on a metal plate with sponge rubber at least 25 mm thick, or upon any other mountings which effectively damp the vibration. 4.7 The testing apparatus is calibrated periodically using a test block of metal (cast iron, aluminium and magn
19、esium alloys, bearing metals) of known Rockwell hardness, using the Rockwell E scale. In this way any faults due to malfunctioning of the load application device or frame deformation will be observed; these faults shall be corrected before use. Ancillary checks may be made at frequent intervals usin
20、g blocks calibrated for use when the machine is set up in the R, L or M test modes. 5 Test specimen 5.1 The standard test specimen shall be a flat sheet at least 6 mm thick. It shall be of a suitable area to meet the re- quirements of 7.4. The test specimen does not necessarily have to be square. It
21、 shall not show any evidence of imprint by the indentor on the supported surface after a test. 5.2 When specimens of the minimum thickness specified in 5.1 are not available, the test specimen shall be made up of a pile of thinner test specimens of the same thickness and the same material, provided
22、that the surfaces of the individual pieces are in total contact and not held apart by any form of surface imperfections (as, for example, sink marks or burrs from saw cuts). 5.3 All indentations shall be made on one surface only of the test specimen. 5.4 One test specimen is sufficient for the deter
23、mination of Rockwell hardness and at least five measurements shall be made on each test specimen of isotropic materials. 5.5 If the material under test is anisotropic, the direction of indentation shall be specified in relation to the axes of anisotropy. If results in more than one direction are req
24、uired, test specimens shall be prepared so that at least five Rockwell hardness measurements may be determined in each direction. 6 Conditioning The test specimens shall be conditioned before testing in the atmosphere specified in the appropriate International Standard relating to the material under
25、 test or in one of those specified in IS0 291. 7 Procedure 7.1 Unless otherwise specified, testing shall be performed in the same standard atmosphere as used for conditioning the test specimen. 7.2 Check that the major and minor loads and the indentor diameter are correct for the Rockwell hardness s
26、cale in use (see 4.5). Discard the first reading after changing a ball adjustment, as the indentor does not properly seat by hand-adjustment in the housing chuck, The full pressure of the major loads is re- quired to seat the indentor shoulder into the chuck. NOTE - See 4.7 for periodic calibration
27、of the apparatus. 7.3 Place the test specimen on the platform. Check that the surface of the test specimen and that of the indentor are free of dust, dirt, grease and scale and that the test specimen sutiace is normal to the direction of the applied load. 2 -,-,- IS0 2039-2 : 1987 (El Apply the mino
28、r load and set the dial gauge to zero. Within 10 s of applying the minor load, apply the major load (see 4.41. Remove the major load 15 + i s after the start of applying the major load. During this operation, avoid jerking the machine mechanism. Read the dial gauge to the nearest scale division 15 s
29、 after the start of removing the major load. NOTE - If the machine is directly calibrated in Rockwell hardness numbers, it is convenient to proceed as follows : Count the number of times the needle passes through zero on the red scale after application of the major load. Subtract this from the numbe
30、r of times the needle passes through zero upon the removal of the major load. If this dif- ference is zero, record the hardness number as the reading plus 100. If the difference is 1, record the reading as the scale reading without change and, if the difference is 2, record the reading as the scale
31、reading minus 100. If in doubt, consult the manufacturer s handbook for the machine. 7.4 Make five measurements on the same surface of the test specimen. No measurement shall be made within 10 mm of any edge of the test specimen, and no two measurements shall be made less than 10 mm apart, 7.5 Ideal
32、ly, Rockwell hardness numbers should lie between 50 and 115; values above this range are inaccurate and the determination shall be repeated using the next severest scale. NOTE - If a less severe scale than the R scale is required, the Rockwell test is not suitable and the material should be tested i
33、n accordance with IS0 868 (Shore hardness). 8 Expression of results 8.1 Express the Rockwell hardness as a number prefixed by the scale letter. 8.2 If the Rockwell hardness tester is directly calibrated in hardness numbers, record the Rockwell hardness after each test (see the note in 7.31. 8.3 If n
34、ecessary, calculate the Rockwell hardness number bee 3.21. 8.4 When required, calculate the estimated standard devia- tion as follows : i xx2 - nX2 CT= n-1 where 7 is the standard deviation (estimated); x is the individual value of Rockwell hardness; X is the arithmetic mean of the results; n is the
35、 number of results. 9 Test report The test report shall include the following particulars : al reference to this International Standard; b) complete identification of the material tested; cl description, dimensions and manner of preparation of the test specimen; d) conditioning and conditions under
36、which the test is car- ried out; e) number of tests; fl Rockwell hardness scale (either M, L or RI; g) Rockwell hardness numbers, individual values and average value; h) estimated standard deviation of the results, if required. 3 -,-,- km iiUY-Z : IS/ (t) Annex Determination of Rockwell-a hardness (
37、This annex forms an integral part of the Standard.) A.0 Introduction The Rockwell hardness test as described in this International Standard determines the hardness of plastics as a function of indentor depth of penetration after allowing for elastic recovery of the test specimen. As such, the Rockwe
38、ll hardness on the L, M and R scales cannot be related to the ball indentation hard- ness of IS0 2039-l since this derives hardness from the depth of penetration of the indentor under load (that is, not allowing for any elastic recovery of the material). However, the Rockwell apparatus may be used t
39、o determine hardness from the depth of penetration under load and this has been standardizedtll as the Rockwell-o test. The only suitable Rockwell scale for deter- mining the Rockwell-o hardness of plastics is the R scale, that is, 12,7 mm diameter indentor and 5894 N major load. A.1 Procedure A,1 .
40、I Use the 12,7 mm diameter indentor and 569,4 N major load. A.1.2 Determine the spring constant of the testing machine as follows : Place a soft copper block (at least 6 mm thick) on the platform and apply the minor load. Set the depth-indicating device to zero and apply the major load. Maintain the
41、 major load until the depth indicator is stationary. Note the reading, remove the major load and reset the depth indicator to zero. Repeat this sequence of operations until the reading of the depth indicator is constant after each application of the major load. This represents the point at which no
42、further penetration of the copper block takes places and therefore the constant depth reading is the movement of the depth-indicating device due to the spring of the apparatus. Note this constant reading and record it as the number of 0,002 mm units (d,). A.1.3 Replace the copper block by the test s
43、pecimen and proceed as in 7.3 except that after the application of the minor load the depth indicator shall be set to zero within 10 s and the major load immediately applied. During 15 s of application of the major load, observe and record the depth of penetration in units of 0,002 mm (d, = depth of
44、 penetration at 15 s). A.2 Expression of results Calculate the Rockwell-o hardness using the equation R a = 1% - (d, - d,) R CI is the Rockwell hardness number; d, and dh are as defined in A.1.2 and A,1,3. A.3 Relationship between Rockwell-a hardness and ball indentation hardness of IS0 2039-I FetW
45、established the mathematical relationship between Rockwell-a hardness and the ball indentation hardness of IS0 2039-l and demonstrated that the mathematical relation- ship holds good in practice for both thermosetting and ther- moplastic materials over the range of Rockwell-o hardness be- tween - 20
46、 and 190. This relationship is given with sufficient accuracy by the equation or 1,23 H= A graph of R a versus H in the range of R a from - 30 to 130 follows for ease of conversion. -,-,- Rockwell-a hardness number 130 120 - 110 - loo - 90 - 80 - 70 - 60 - 50 - 40 - 30 - 20 - 10 - O- -10 - -20 - -30
47、 I I I I I I I I I I I I I I 2 4 6 8 IO 12 14 16 18 20 22 24 26 28 30 32 IS0 2039-l hardness, daN/mm* Bibliography Ill ASTM D 785-65, Standard fast method for Rockwell hardness of plastics and electrical insulating materials. 121 FETT, THEO, Relation between Rockwell-a hardness ASTM D 785 and ball indentation hardness DIN 52456, Materialpriifung, Vol. 14, No. 5, pp. 151-153. 5 -,-,- IS0 2039-2 : 1987 (El UDC 678.W.8 : 620.178.162.42 Descriptors : plastics, tests, mechanical tests, hardness tests, determination, Rockwell hardness. Price based on 5 pages -,-,-
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