This standard specifies four methods for determining the hardness of vulcanized or thermoplastic rubber with flat surfaces (standard hardness method) and four methods for determining the apparent hardness of bent surface specimens (apparent hardness method). The hardness value is expressed in Rubber International Hardness (IRHD). The hardness range applicable to these measurement methods ranges from 10 IRHD to 100 IRHD. The main difference between these methods lies in the diameter of the spherical indenter and the magnitude of the applied force、 and the appropriate method should be selected based on the specific application. The applicability of each method is shown in Figure 1. This standard does not specify a method for measuring hardness using a portable hardness tester、 which is described in ISO 7619-2 p>
2 Normative References
The following documents are essential for the application of this document.
. For dated references、 only the dated version applies to this document. For undated references、 the latest version (including all modification orders) applies to this document. ISO 18898 Rubber Calibration and Verification of hardness testers ISO 23529 Rubber General procedures for pre testing and conditioning tests for physical test methods 3 Terms and definitions The following terms and definitions apply to this document p> 3.1 Setting of International Rubber Hardness Scale for IRHD: О The Young's modulus of elasticity of the material is 0100、 indicating that the Young's modulus of elasticity of the material is infinite. Note: Within the conventional hardness range、 there are usually the following characteristics: a) The increment of international hardness of rubber always approximates the increment of Young's modulus of elasticity in the same proportion; b) For high elastic rubber、 the values of international hardness and Shore A hardness are comparable. 3.2 Standard hardness shall be measured using the procedures specified in methods N、 H、 L、 and M、 using specimens of standard thickness and not less than the specified minimum transverse size. Note: The standard hardness value is rounded to the nearest integer and expressed in IRHD. 3.3 Apparent hardness is measured on non-standard size specimens using the procedures specified in methods N、 H、 L、 and M、 or using methods CN、 CH、 CL、 and CM. Note 1: The apparent hardness value is rounded to the nearest integer and expressed in IRHD. Note 2: The values measured using methods CN、 CH、 CL、 and CM give the apparent hardness、 as testing is usually conducted on the entire product with varying rubber thickness、 and in most cases、 the horizontal dimension cannot guarantee the minimum distance between the foot and the edge image. Therefore、 the measured values are usually inconsistent with those obtained using methods N、 H、 L、 and M on standard specimens or flat surface products of the same thickness. In addition、 the hardness value measured is also related to the supporting method of the product and whether foot pressure is used. The results measured on curved surfaces are only applicable to specimens or products with special shapes、 sizes、 and special support methods. The apparent hardness can differ by about 10 IRHD from the standard hardness value. In addition、 the hardness values obtained from polished surfaces or surfaces with cloth patterns removed by other methods may differ slightly from smooth molded surfaces P>Function of testing report:
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