Interlaboratory comparison: Round robin test for the damage reproduction of white etching crack in cylindrical roller thrust bearings

Abstract

White Etching Cracks (WEC) is a damage pattern in roller bearings characterized by sub-surface crack networks within local microstructural changes. Nowadays, neither the causes of occurrence are clarified, nor are there commercial calculation methods for damage prediction. The comparability of current research results is hampered by the use of different testing methods and their transferability is, therefore, limited. Until today, there is no generally accepted test method for the risk assessment of predefined tribological systems regarding WEC occurrence. To establish such a test method, the statistically valid transferability of experimental results with a commercially available test rig is necessary. The present work, therefore, concentrates on the transferability of the WEC occurrence using cylindrical roller thrust bearings, a standardized test rig, and a detailed test guideline. The statistical validation of the WEC occurrence and therefore of the proposed reference test method was carried out using an interlaboratory comparison of 20 tests in 10 laboratories. Subsequent metallographic examinations confirmed that all failures were caused by surface anomalies related to WEC. Furthermore, the WEC's position and orientation were systematically and extensively analyzed. The high reproducibility (Weibull coefficient of correlation of 0.975) and low variance (Weibull exponent of 6.4) show the suitability of the test method for risk assessment of predefined tribological systems.