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mg rover group engineering standards issue no:mgr es: title: page 1 of 2 date: - printed copy is uncontrolled - check issue is current - 3 hardness of elastomeric materials august 1991 30.hx.903 1scope these methods are applicable to all elastomeric materials, giving a direct reading or apparent hardness value. methods a and c measure hardness in the range 30 - 90 irhd. method b measures hardness in the range 10 - 90 irhd. method d measures hardness above 20 shore d. standard hardness values can only be obtained by using test pieces of standard dimensions as hardness value is dependent on the dimensions of the test pieces, the thickness usually being the most critical dimension. bs.903: part a26 and astm d2240 have been used as a basis. 2apparatus 2.1method a - durometer hardness tester irhd to bs 903 part a57. 2.2method b - suitable deadweight hardness tester, to bs 903. 2.3method c - micro-hardness tester, to bs 903. 2.4method d - durometer hardness tester shore d to astm d2240. 3.specimen preparation (applicable if moulded sheet material is not available). if fabric is attached to or embedded in the samples it shall be removed before cutting test pieces. the method of removal shall be mechanical. surface irregularities shall be removed by means of buffing. tests intended to be comparable shall be made on test pieces of similar thickness, where the sample thickness is below that specified for the procedure, but not less than 2 mm thick, a maximum of two test pieces may be superimposed to obtain the test thickness; the disparity of thickness between any two pieces shall not exceed t2/30. (where t is the mean thickness in mm). 4test selection 4.1it is recommended that measurement is mane with methods a, b or c as applicable. measurements are made using method d only when values greater than 90 irhd are obtained using methods a, b or c. 5procedure 5.1method a - applicable to materials of thickness greater than 4mm. 5.1.1calibrate the hardness tester using standard test blocks. 5.1.2 support the specimen on a horizontal rigid surface and apply the durometer. mg rover group engineering standards issue no:mgr es: title: page 2 of 2 date: - printed copy is uncontrolled - check issue is current - 3 hardness of elastomeric materials august 1991 30.hx.903 5.1.3read off the hardness value given in irhd (international rubber hardness degrees) immediately after the foot is in contact with the specimen. 5.1.4carry out the test at five points distributed over the test specimen on each of three test pieces. 5.2method b - applicable to materials of thickness greater than 4 mm. 5.2.1switch on the apparatus vibrator. 5.2.2lower the foot so that it presses on the test piece with the requisite force. 5.2.3immediately afterwards lower the indentor to apply the pre-load and maintain this force for five seconds. 5.2.4after this period apply the major load and maintain for 30 seconds. 5.2.5read off the hardness value in irhd. 5.2.6carry out the test at five points distributed over the test specimen on each of three test pieces. 5.3method c - applicable to materials of thickness less than 4 mm but greater than 1 mm. 5.3.1switch on the apparatus. 5.3.2adjust the platform so that it presses on the test piece with the requisite force. 5.3.3immediately afterwards lower the indentor to apply the pre-load and maintain this force for five seconds. 5.3.4after this period apply the major load and maintain for 30 seconds. 5.3.5read off the hardness value in irhd. 5.3.6carry out the test at five points distributed over the test specimen on each of three test pieces. 5.4method d - applicable to materials of thickness greater than 4mm. 5.4.1check calibration of hardness tester using a calibration block. 5.4.2support the specimen on a horizontal rigid surface and apply the durometer. 5.4.3read the hardness value given
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