UNCERTAINTY ANALYSIS IN MEASUREMENT OF CONTACT FRICTION PARAMETERS OF BOLTED JOINT INTERFACE

In the literature [1,2], a test apparatus was proposed for high-precision measurement of contact friction parameters based on piezoelectric actuator and laser vibrometer. Based on this test apparatus, five pairs of nominally identical bolted joint specimen were fabricated according to the same drawings and process, and they were assembled and tested using four test plans under two bolt preloads. The reassembly uncertainties of the test apparatus were taken into account to assess the variability of the test results and to analyse error sources. Then the influence of part-to-part differences of nominally identical specimen pairs on the contact friction parameters was investigated. Finally, the variability of contact parameters for rough surfaces and smooth surfaces were studied, which indicates that roughness has an important effect on the uncertainty of test results. The results in this paper suggest that the micro morphology of the contact interface has a significant effect on the tangential contact stiffness, followed by energy dissipation, and has less impact on the friction coefficient. Differences in mechanical properties of nominally identical joint structures caused by differences in micromorphology should be considered in the actual analysis.