Analysis and evaluation of multi-state wear mechanism of elastic-flexible thin-walled bearings

Abstract

EFTWBs (Elastic-flexible thin-walled bearings) are mainly used in harmonic reducers. Under the condition of large reduction ratio and cyclic rotation, LFW (linear fretting wear), CFW (curve fretting wear) and CRF (complete rolling friction) appear in the bearing raceway. In this study, LFW and CFW experiments were carried out, and the relationship between coefficient of friction and surface hardness was analyzed. Meanwhile, the multi-dimensional analysis (surface hardness, residual stress, surface/subsurface retained austenite) of the raceway surface integrity of EFTWBs after 8000 h of high service was analyzed. Combined with the manufacturing process of EFTWBs and the above conclusions, the multi-state wear mechanism of raceway was comprehensively evaluated. The evaluation conclusions show that the raceway of EFTWBs contained CRF (including pitting and spalling) and sliding fretting wear (including LFW and CFW). The axial and tangential residual stresses of the untested and tested outer and inner ring raceways were compressive stresses. Grain delamination appeared on the tested outer and inner ring raceway subsurface (20 µm from the surface). The wear of the outer ring raceway of EFTWBs was greater than that of the inner ring, and the wear was multiple. A 430 nm nanocrystalline layer was found under FIB-TEM on the surface layer of the outer ring raceway, and the fracture and obvious dislocation appeared. The rolling-sliding wear mechanism of EFTWBs raceway was comprehensively evaluated. The accuracy of this analysis was verified by combining thin-walled ring and Hertz theories. There are many detailed conclusions which provide theoretical support and data analysis for relevant manufacturers of harmonic reducer and robot EFTWBs.