ASTM D623-07(R2019) pdf free download

ASTM D623-07(R2019) pdf free download.Standard Test Methods for Rubber Property—Heat Generation and Flexing Fatigue In Compression
6. Nature of Test
6.1 In this test method, which uses the Goodrich Flexometer, a definite compressive load is applied to a test specimen through a lever system having high inertia, while imposing on the specimen an additional high-frequency cyclic compression ofdefinite amplitude. The increase in temperature at the base of the test specimen is measured with a thermo- couple to provide a relative indication of the heat generated in flexing the specimen. Specimens may be tested under a constant applied load, or a constant initial compression. The change in height of the test specimen can be measured continuously during flexure. By comparing this change in height with the observed permanent set after test, the degree of stiffening (or softening) of the test specimen may be estimated. Anisotropic specimens may be tested in different directions producing measurable differences in temperature rise due to the anisotropy.
7. Apparatus
7.1 The essential parts of the apparatus are shown in Fig. 1. The test specimen is placed between anvils faced with inserts of a black NEMA Grade XX Paper-Phenolic, for heat- insulation purposes. The top anvil or hammer is connected to an adjustable eccentric usually driven at 30 6 0.2 Hz (1800 rpm). The static load is applied by means of a lever having a fulcrum point consisting of a low friction bearing cartridge block or resting on a knife edge. The moment of inertia of the lever system is increased, and its natural frequency reduced, by suspending masses of approximately 24 kg (53 lb) at each end of the lever system. The lower anvil may be raised or lowered relative to the lever by means of a calibrated micrometer device. This device permits the lever system to be maintained in a horizontal position during the test as determined by a pointer and a reference mark on the end of the bar or a gear motor mounted to the end of the lever system to automatically drive the micrometer device based on sensors indicating the level position of the system.
8. Adjustment
8.1 Locate the machine on a firm foundation. Adjust the leveling screws in the base to bring the machine into a level position in all directions at a point just to the rear of the fulcrum of the loading lever. With the loading lever locked in place with the pin, place a level on the lever bar and verify the level setting. 8.2 Adjust the eccentric to give a stroke of 4.45 6 0.03 mm (0.175 6 0.001 in.) (Note 1). This is best accomplished by means ofa dial micrometer resting on either the cross bar ofthe upper anvil or by means ofadapters attached to the loading arm of the eccentric. N OTE 1—The 4.45-mm (0.175-in.) stroke is selected as the standard for calibration purposes. When strokes other than 4.45 mm (0.175 in.) are to be used, the displacement of the lower anvil should be maintained within the tolerance specified for its height above the loading lever. The tolerance for all stroke settings shall be 60.03 mm (60.001 in.). 8.3 Raise the top anvil as far as the eccentric will permit by its rotation. Place a calibrating block (Note 2) 25.40 6 0.01 mm (1.000 6 0.0005 in.) in height on the lower anvil. Raise the anvil by means of the micrometer until the bottom side of the metal cup holding the thermocouple is 67 6 3 mm (2.625 6 0.125 in.) above the top of the loading lever. The loading lever is to be in the locked position. Adjust the cross bar ofthe upper anvil, maintaining a parallel setting with the lower anvil and a firm contact with the calibrating block. The micrometer should now be set at zero. This may require disengagement ofthe gear train nearest the vernier scale of the micrometer.