ISO 48-4:2018 pdf download – Rubber, vulcanized or thermoplastic – Determination of hardness
10.2 Checking using standard rubber blocks 1)
Press the instrument against a suitable flat, hard surface (e.g. glass) and adjust, where possible, the reading on the scale to give a value of 100. Continue the instrument check using a set of standard rubber blocks covering the measurement range. All adjustments shall be made in accordance with the manufacturer’s instructions. The set of standard rubber blocks used shall consist of at least three reference blocks in a suitable covered container away from light, heat, oil and grease. The reference blocks shall be recalibrated once a year, or if the mean value deviates more than one unit compared with the certificate of the reference blocks. The calibration of the reference blocks needs to be done with a reference measurement device of an accredited laboratory. Instruments in regular use shall be checked at least each week against standard rubber blocks.
Rubber Hardness Degrees (Micro IRHD) was also evaluated for the purposes of comparison. ISO 48-2 includes the additional set of precision results for IRHD 3) . The repeatability, or local domain precision, for each of the hardness test methods was established for each material as the values found in Table A.2. Two individual test results (obtained by the proper use of this document) that differ by more than the tabulated values of r (in measurement units) and (r) (in percent) should be considered as suspect, i.e. as having come from different populations, and should suggest that some appropriate investigative action be taken. The reproducibility, or global domain precision, for the type AM durometer hardness test method was established for each material as the values found in Table A.2. Two individual test results obtained in different laboratories (by the proper use of this document) that differ by more than the tabulated values of R (in measurement units) and (R) (in percent) should be considered as suspect, i.e. as having come from different populations, and should suggest that some appropriate investigative action be taken.
A.3.2 A type 1 precision was evaluated (for both tests) using cured test pieces prepared from four different rubber compounds, A, B, C and D (with a range of hardness values), supplied to each of the six laboratories participating in the ITP. On each of two test days, two weeks apart, the following test sequence was carried out. Three test pieces were furnished for each compound, and the median value of five hardness measurements on each of the three test pieces was obtained for each of two operators. For each operator, the median value was selected for all three test pieces. The two median values were then averaged to obtain a single value designated as the test result for that test day. Shore AM measurements were made on one side of the test piece and IRHD measurements were made on the reverse side. The precision analysis was based on test result data, i.e. two test result values per laboratory. The ISO/TR 9272:2005 option 2 outlier treatment procedure, outlier replacement, was adopted since the ITP had the minimum number of six participating laboratories. This option 2 procedure replaces each outlier declared as significant with a value that is consistent with the data value distribution for the non-outlier data for that material. See ISO/TR 9272:2005 for the rationale behind this concept and for other details. The precision results as determined by this ITP may not be applied to acceptance or rejection testing for any group of materials or products without documentation that the results of this precision evaluation actually apply to the materials or products tested.