ASTM D430:2006 pdf free download – Standard Test Methods for Rubber Deterioration- -Dynamic Fatigue.
13. hub Size and Flexing Force
13.1 Specimens from belts shall be tested using hubs
31.7 mm (1.250 in.) in diameter with a 445 N (100 ibI) flexing force.
13.2 Specimens from tires or tire specimen pads shall be tested using hubs 14.3 mm (0.563 in.) in diameter with a 445 N (100 lbf) flexing force.
14. Procedure for Belt Specimens
14.1 Bend the belt test specimens around the hubs with the pulley side of the belt against the metal and the ends clamped in the grips.
14.2 Carefully apply the flexing load without shock, set the counter to zero, and start the machine. Allow it to run until some fine particles, dislodged by friction, may be seen on the white plate beneath the hub, which indicates that separation of the plies has started.
14.3 Frequent inspection of the specimens undergoing test is imperative if reliable results are to he expected.
14,4 When the first indication of ply separation appears, note and record the counter reading. Thereafter watch the specimen more closely and increase the frequency of the inspection to ensure proper determination of the end point.
14.5 When there is a clear separation across the width of the specimen it shall be considered to have failed. Record the minimum counter reading for this failure as the end point. Also record the location of the separation.
14.6 When a test is started, continue to completion without interruption. However, for the purpose of examining the specimen. each hub may be released momentarily from its force by means of the foot lever provided.
15. Procedure for Tire Specimens
15.1 Mount the tire test specimens with the lengthwise outer ply cords against the hub of the machine and test in a manner similar to the procedure for belts (Section 14).
15.2 After the tire specimen has been run about 10 mm, but before separation begins, brush a thick coat of molten carnauha wax on the outer side of the specimen at the flexing region.
15.3 As soon as separation begins, the temperature of the flexing region increases very rapidly and the wax melts. The melting of the wax starts with a small area and gradually spreads as separation increases. This serves as a warning that complete separation will occur shortly thereafter. The interval between the melting of the wax (the time at which separation actually starts) and complete separation across the specimen may not always he the same.
Nom 1—A specimen with a short flexing life will show complete separation soon after the wax melts, whereas a sample with a greater flexing life might requiie a time interval two or three times as long. However, with specimens having similar flexing life, the time interval between the melting of the wax and complete separation is fairly constant.