In the design stage of a part, in addition to taking general measures to improve its strength, the following design measures can also be used to improve its fatigue strength:
① Reduce the influence of stress concentration on the spindle as much as possible. This is the primary measure and main way to improve its fatigue strength. The sudden change of the structural shape and size of the spindle (such as the shoulder) is the source of the stress concentration.
Therefore, in order to reduce the stress concentration, the sudden change of the structural shape and size of the part (that is, the spindle) should be minimized to make the change as much as possible The smoothness and uniformity. For this reason, it is necessary to increase the fillet radius at the transition as much as possible; the rigidity changes at adjacent sections on the same section of the shaft should be as small as possible, and so on.
Where it is inevitable to produce greater stress concentration, relief grooves can be used to reduce the impact of stress concentration.
②Select materials with high fatigue strength and stipulate heat treatment methods and strengthening processes that can improve the fatigue strength of the materials.
③Improve the surface quality of the spindle. For example, the surface of the spindle in the higher stress area is processed to be smoother. Or, if some shaft sections work in corrosive media, proper surface protection should be specified for the shaft section.
④ Minimizing or eliminating the size of the initial cracks that may occur on the surface of the main shaft has a more significant effect on extending the fatigue life of the material and improving the performance of the material. Therefore, for important shaft sections, strict inspection methods and requirements should be specified on the design drawings.
⑤ Cooling and load-reducing, adopting a cooling design for the journal of the heating friction pair, can also significantly improve its fatigue life. Because the main shaft is a rotating part, it will gradually increase to the designed stress level after running for a certain number of cycles under low stress.
Because bearings, especially some commonly used bearings, mainly refer to some rolling bearings, most of them have been standardized. Therefore, we need to carry out a part of the design content and correctly select the type and size of the bearing according to the specific working conditions. The other is the design of the bearing assembly, which includes the design of a series of contents such as installation, adjustment, lubrication, and sealing.
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