tailieunhanh - Failure Analysis Case Studies II Episode 13

Tham khảo tài liệu 'failure analysis case studies ii episode 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Fig. 1. Schematic illustration of counterformal a and conformal b surfaces in contact Reprinted from Engineering Failure Analysis 4 2 155-160 1997 Failure Analysis Case Studies II . Jones Editor 2001 Elsevier Science Ltd. All rights reserved 409 CONTACT FATIGUE IN ROLLING-ELEMENT BEARINGS p. J. L. FERNANDES Advanced Engineering and Testing Services CSIR Private Bag X28 Auckland Park 2006. South Africa Received 15 January 1997 1. INTRODUCTION In the paper entitled Surface contact fatigue failures in gears Fernandes and McDuling l discuss the mechanism of contact fatigue damage frequently encountered on the active flanks of gear teeth. This mode of failure operates not only on counterformal surfaces in contact as in matching gear teeth but also on conformal surfaces Fig. 1 . The latter are found in ball bearings in contact with the inner and outer raceways in roller or needle bearings in contact with the outer raceway and in shafts in contact with sliding bearings 2 In the case of gears three types of contact fatigue damage were identified depending on the relative movement of the contacting bodies and the resulting stress distribution in the surface and near-surface material 1 . The characteristics of each type of failure were discussed in detail in 1 Rolling-element bearings consist of balls or rollers positioned between raceways which conform to the shape of the rolling element. Depending on the bearing design the loads acting on the bearing may be radial angular or axial 3 . These loads lead to elastic deformation at the points of contact between the rolling elements and the raceways. The stress distribution in the surface and nearsurface material under these conditions depends on the loads and the curvature and relative movement between the contacting bodies. 2. ROLLING AND ROLLING SLIDING CONTACT FATIGUE When bearing operation leads to pure rolling contact between the rolling elements and the raceway the maximum shear stress occurs at some distance below .