Mechanical Properties And Fatigue Life Analysis Of Cylindrical Roller Bearings For Rolling Mills

Rolling mill bearings mostly work in low speed and heavy load conditions,bearings are prone to misaligned load and fatigue failure under the excessive external load.It will lead to rolling mill equipment shutdown,and affect rolling production,resulting in large economic losses.Therefore,the study of the mechanical properties and fatigue life of rolling mill bearings is of great significance to rolling production.In this thesis,four-row cylindrical roller bearing FC4056200 for rolling mills is studied.The basic structure and characteristics of the bearing are introduced.The distribution of contact load of single row bearing roller under different clearance is calculated by building a discrete bearing model.The results found that the bearing under the action of external load,the roller at the bottom of the bearing to bear the maximum load,and the load value decreased with the change of initial radial clearance from negative to positive,and increased with the increase of radial load.The hertz line contact theory and slicing method were combined to solve the contact problem of misaligned load bearings numerically.The static contact stress of bearings was analyzed using ANSYS Workbench and the obtained results were compared with the theory calculation results.The results show that the errors of roller-raceway contact stress calculated by the finite element analysis and the contact mechanics model are less than 10 %,and the solution results are in good agreement.In addition,it is found that the contact between the roller and the inner raceway and the outer raceway appears stress concentration at both ends of the roller under the condition of unbiased load.Under misaligned load condition,the contact stress of rollers presents asymmetric distribution.The fatigue life numerical model of bearing with misaligned load was established,and the effect of misalignment load on bearing fatigue life was discussed.It was found that the fatigue life decreased with the increase of radial load under unbiased load condition.Under off-load,the fatigue life varied with load similar to the condition of unbiased load,and increased first and then decreased with the increase of misalignment load angle.Subsequently,ANSYS Workbench was used to simulate the fatigue life of cylindrical roller bearings on the basis of statics,and it was found that the earliest fatigue location appeared near the top and bottom of the bearing inner ring and the contact areas of the rollers with the inner and outer rings and the cage.The accuracy of the finite element results is illustrated by comparing the finite element results with the theory results.Modified cylindrical rollers of full convex arc curve,arc tangent curve and logarithmic curve with different convex measurements were designed.According to the contact stress and fatigue life model of bearing,the influence of different modification methods on the mechanical properties and fatigue life of off-load bearing was studied.It was found that the roller have better mechanical properties and fatigue life after being modified by full convex arc curve with arc radius R of 15000 mm,tangent arc curve with R=9000 mm and l=24 mm,and logarithmic curve with shape factor f of 0.002.