A Dynamic Model of Outer Race Defective Bearing Considering the Unbalanced Shaft-Bearing System With Experimental Simulation

Abstract

In this study, the effects of the evolution of bearing outer race defect size and increase in speed on the vibration characteristics of a shaft-bearing system under unbalanced conditions. The contact stiffness between the races and the balls is considered as a series of springs is also incorporated in the model. Hertzian contact deformation theory is used to obtain the contact stiffness. This model considers the contact deformation between the balls and the races, the additional displacement between the balls and the inner race due to radial clearance, and due to defect geometry. The maximum possible radial displacement of the ball into the defect is calculated analytically using the groove radius, ball radius and defect diameter. The rectangular function is used for modelling the defect. MATLAB codes are developed for modelling the shaft-bearing system and for solving the differential equations of motion using the Runge-Kutta method. The vibration responses obtained by modelling and by experimentation show similar vibration characteristics. The investigation shows that the values of statistical parameters initially increase with the increase in defect size and then decrease with a further increase in defect size. While peak and RMS increase with the speed and crest factor and kurtosis decrease with an increase in speed. Peak is more sensitive for diagnosing spalls on outer race and its evolution. This study helps as an effective diagnosis of antifriction bearings having spalls on the outer race under unbalanced conditions.

Comparison of non-linear vibration of outer race defective ball bearing using two defect functions

“…In this study, the constant equivalent contact stiffness K between ball and races in terms of elliptic integrals and ellipticity parameters is obtained by using Hertzian contact deformation theory. This theory is explained by Harris 33 and used by some researchers 12,17,22,24,34,35 in their studies to calculate the value of K . In this study, the value of K obtained for SKF 6305 DGBB is 9.67814753014 × 10 9 N/m 3/2 by using bearing parameters given in Table 1: D b = 11.5 mm, D o = 55 mm, D i = 32 mm, D c = 43.5 mm, f o/i = 0.53, r go = 6.095 mm, r gi = 6.095 mm, E = 206 GPa and ν = 0.3.…”

Dynamic modeling and analysis of rolling bearing faults under time-varying excitations considering defect deformation

“…However, in actual working conditions, the contact between the rolling element and the cage and the outer ring will cause bearing deformation [26]. Whether it is a cage fault [27] or an outer ring fault [28], when the rolling element passes through the defect, the impact force will change due to contact deformation. The variation in impact force caused by contact deformation can be illustrated using Fig.…”