ASTM D3527 Test Method for Life Performance of Automotive Wheel Bearing Grease
12. Report
12.1 Report the hours to failure.
13. Precision and Bias
13.1 The precision of this test method was determined by statistical examination of interlaboratory results. Research Report D02-1007 procedures were followed in the round-robin testing and statistical analysis of data. In 1988 a more precise description of the bearing packing procedure was included in 10.3. The precision data shown in Table X2.1 was obtained earlier using a less detailed packing procedure.
13.1.1 Repeatability - The difference between two test results obtained by the same operator with the same apparatus under constant operating conditions on identical test material would, in the long run, in the normal and correct operation of the test method, exceed the following values in only one case in twenty:
Repeatability = (0.8)X
where:
X = the average of the two test results.
13.1.2 Reproducibility - The difference between two single and independent results obtained by different operators working in different laboratories on identical test material would, in the long run, in the normal and correct operation of the test method, exceed the following values in only one case in twenty:
Reproducibility = (1.2)X
where:
X = the average of the two test results.
13.2 Bias - The procedure in this test method has no bias because the value of grease life can be defined only in terms of the test method.
NOTE 5 - A round robin of twelve cooperators testing five greases has resulted in the precision statement shown above. The data are shown in Table X2.1. In this round robin, determinations were made using testers by PAM, Koehler, and Falex. No distinction was made as all testers gave equivalent results.
14. Keywords
14.1 automotive wheel bearing grease; grease life performance; lubricating grease
