ASTM D624-2020 pdf free download

ASTM D624-2020 pdf free download.Standard Test Method for Tear Strength of Conventional Vulcanized Rubber and Thermoplastic Elastomers
3. Terminology
3.1 The tear of rubber is a mechanical rupture process initiated and propagated at a site of high stress concentration caused a cut, defect, or localized deformation. The following definitions define different techniques for measuring the resis- tance to tear, i.e. the tear strength, required for use with this standard. 3.2 Definitions ofTerms Specific to This Standard: 3.2.1 Type A tear strength—the maximum force required to cause a nick or cut in a Type A (nicked crescent) test piece to grow by tearing the rubber, divided by the thickness of the test piece. 3.2.2 Type B tear strength—the maximum force required to cause a nick or cut in a Type B (nicked tab end) test piece to grow by tearing the rubber, divided by the thickness of the test piece. 3.2.3 Type C tear strength—the maximum force required to cause a rupture of a Type C (right angle) test piece, divided by the thickness of the test piece. 3.2.4 Type T or trouser tear strength—the mean or median force, calculated in accordance with procedures in this method, required to propagate a tear in a Type T (trouser) test piece, divided by the thickness of the test piece. 3.2.5 Type CP or constrained path tear strength—the mean or median force, calculated in accordance with procedures in this method, required to propagate a tear in a type CP (constrained path) test piece, divided by the thickness of the torn section.3.2.6 complete trace—the section of a graphical plot of force versus jaw separation distance between the point at which the first peak occurs and the point at which the test is terminated. 3.2.7 peak—a point at which the slope of a trace changes from positive to negative. 3.2.8 range—the difference between the greatest and the smallest observed test values. 3.2.9 valley—a point at which the slope of a trace changes from negative to positive.
4. Summary of Test Method
4.1 A tearing strain (and stress) is applied to a test specimen by means of a tensile testing machine operated without interruption at a constant rate of crosshead traverse until the specimen is completely torn. 4.2 This test method measures the force per unit thickness required to rupture, initiate, or propagate a tear through a sheet of rubber in the form of one of several test piece geometries: 4.2.1 Type A, a razor-nicked test piece with a crescent shape, as shown in Fig. 1, Die A. The force in this test piece acts in a direction substantially along the major axis (length) and perpendicular to the “nick”, or razor cut. Type A is used to measure tear propagation and is normally cut from smaller test specimens that can not accommodate other test types. 4.2.2 Type B, a razor-nicked test piece with a crescent shape and with tab ends, as shown in Fig. 1, Die B. The force in this test piece acts in a direction substantially along the major axis (length) and perpendicular to the “nick”, or razor cut. Type B also measures tear propagation and is preferred over Type A when the test sample allows. 4.2.3 Type C, an un-nicked test piece with a 90° angle on one side and with tab ends, as shown in Fig. 1, Die C. The force acts on the test piece in a direction substantially parallel to the tab ends of the specimen (45° to the 90° center angle) in the direction of grip separation. Type C measures rupture, or tear initiation strength at the stress concentration located at the 90° apex. Iftear initiation does not occur at the apex, the results are more indicative of tensile strength than tear strength. 4.2.4 Type T, a trouser tear test piece, as shown in Fig. 2. Type T measures tear propagation in a direction parallel to the length of both legs.