Determination of permissible contact stress of case hardened raceway of roller slewing bearing

The permissible contact stress for the rolling bearing made of the through hardened bearing steel has been established based on experience, while there is no definite value or calculating formula of the permissible contact stress for the slewing bearings which are hardened only on the raceway surface yet. To determine the permissible contact stress of the case hardened raceway of roller slewing bearing, finite element analysis for the contact elasto-plastic characteristics between the loaded roller and the case hardened raceway was performed, and the contact plastic deformations corresponding to different roller diameter, roller load, and case depth were obtained. The contact stress produced by the roller load was calculated by using Hertz contact theory. Based on the nonlinear regression analysis between the input parameters and the output plastic deformations of the model, the relation equation between the contact plastic deformation and the roller diameter, contact stress, case depth was established. The formula for calculating the permissible contact stress of the case hardened raceway was obtained according to the regression equation further. The permissible contact stresses calculated by using the obtained formula show that the permissible contact stress of the case hardened raceway depends mainly on the case depth. Loaded compression tests between the roller and the case hardened specimens were conducted to verify the validity of the established calculation method for the permissible contact stress of the case hardened raceway. Permissible contact stress decreases slightly with the increase of the roller diameter and increases with the increase of the case depth significantly. As the case depth reaches 6 mm, the maximum permissible contact stress is 3758 MPa. As the case depth reaches 7 mm, the maximum permissible contact stress of the case hardened raceway is 3889 MPa.

[Structure Design of the Supporting Device of Proton Radiotherapy Equipment Based on Workbench]

To reduce contact deformation between the supporting device and the contact area of the rotating gantry rollers, this paper mainly uses the workbench to perform finite element analysis on the contact deformation from two aspects of the layout of the ribs of the rotating gantry roller and the contact width with the supporting roller of the supporting device. The results show that for the proton therapy equipment corresponding to this article, the contact deformation is relatively small and the structure is more reasonable when the ribs are close to the symmetrical position and the contact width between the rotating gantry roller and the supporting roller of the supporting device is 200 mm. This article provides theoretical basis for the design of the proton radiotherapy equipment supporting device.