Determination of Resistance to Abrasive Wear. VII. Uniformity of Results Obtained with the Du Pont Machine

Abstract

Abstract (1) Tests have been made to investigate the variability of the abrasive papers used on the du Pont abrasion machine; the data obtained have also been examined to detect any variation in rate of abrasion during one test, and differences between the right- and left-hand specimens. (2) Differences in abrasiveness of 13 per cent were found between the different sheets of emery paper, even when compared with the differences between the rubber specimens, and it is considered that a solid disc of bonded abrasive, as used on the Akron machine, would be preferable to emery papers. (3) As there is no evidence of variation in rate of abrasion during a 20-minute run, there seems to be no objection to using different test-periods for different rubbers if circumstances render this desirable. (4) There are small, but not consistent, differences between the abrasion losses on the right- and left-hand specimens, which may arise from the 8-lb. load not being equally distributed between them. It is considered that the machine could be improved by making the arm that carries the specimens free to oscillate in a plane perpendicular to the abrasive, so that the loads on the specimens would be automatically equalized. The practice of rigidly fixing the arm parallel to the plane of the abrasive seems unsound because, if the parallelism were really rigid, the rates of wear on the two specimens would of necessity be equal, even if the rubbers had different abrasion resistances. Moreover, any suggestion to test the sample under examination and a standard rubber simultaneously is clearly unsound unless a freely oscillating arm is provided.