Dynamic Characteristics Of Rolling Bearings Based On Sliding Non-Ideal Hertz Contact

With the development of modern industrial science and technology,the requirements for the safety and stability of rotating machinery are higher and higher,and the demand for rolling bearings is also more and more strict.At present,it is possible to judge whether a bearing faults by observing the vibration response of the bearing when it is working.Therefore,many researchers have explored the vibration characteristics of rolling bearings.But they are based on Hertz’s pure rolling contact theory,and rolling bearings are often in complex environments and varied working conditions,and sliding contact always exists between the internal components of bearings.Therefore,the study of bearing vibration characteristics based on Hertz pure rolling contact has an appropriate amount of errors.To solve this problem,the dynamic characteristics of rolling bearings with sliding non-ideal Hertz contact are studied in this paper.The main contents are as follows:(1)Theoretical analysis of sliding non-ideal contact of rolling bearings.Based on Hertz theory of pure roll on the basis of the rolling element bearings and they are adding a proper relative slip between the combination of wheel-rail creep theory and shear Hooke theory,analyzed considering slip after contact between the roller and outer contact force changes,and will be under pure rolling contact Hertz contact with the sliding contact of characteristics were compared.A theoretical load-displacement formula considering the slip contact is obtained.(2)The values of coefficients k and n in the load-displacement formula for the theoretically derived slip contact was determined.A local contact finite element model of NU306 cylindrical roller bearing was established,and the validity of the model was confirmed by comparing the calculated contact deformation values with those in Hertz pure rolling theory.A series of contact force and contact deformation data sets were obtained by adding the relative slip between the rolling element and the outer ring to the finite element model of rolling bearing.The coefficients k and n in the load-displacement formula under the slip contact were obtained by using the nonlinear fitting method.(3)Research on vibration characteristics of fault-free rolling bearings under sliding contact.A two-degree-of-freedom dynamic model of rolling bearing was established to analyze the differences and laws of vibration characteristics between sliding contact and Hertz contact under different loads and speeds.The results show that under different working conditions,the inner ring vibration signal considering slip contact will lead or lag the signal under Hertz contact.And at high speed,the maximum value of inner ring vibration under slip contact is considered to be less than that under Hertz’s contact.(4)Research on vibration characteristics of fault bearings under sliding contact.Three dynamic models of rolling bearings with different degrees of freedom were established,and the relationship between different fault sizes and vibration characteristics of rolling bearings was explored by considering slip contact,time-varying displacement,stiffness,and other factors.Among the three models,the vibration signal of the bearing dynamic model considering the rolling body motion has the highest sensitivity to the fault and the highest fluctuation at the moment of impact,and the attenuation rate of the vibration signal is faster.