Ways to improve component fatigue strength
(1) In stress reduction concentration, one should pay attention to the change of the section on the part, such as holes, keyways, transition fillets, threads, etc. The change of the section should not be sudden. For example, the radius of the crank transition fillet should not be less than 5% of the diameter of the crank pin diameter, otherwise serious bending stress concentration will occur.
(2) Enhancing the strength of the surface layer-Surface chemical heat treatment such as carburizing, nitriding, and carbonitriding can effectively improve the surface fatigue strength of the part: cold machining of the surface of the component, such as shot peening, surface rolling, etc. The strengthening process can form a pre-stress layer on the surface, reduce the surface tensile stress that is prone to fatigue cracks, and significantly increase the fatigue of the surface of the part.
(3) Reduce the surface roughness-the surface processing quality of components has a great influence on fatigue strength. Components requiring higher fatigue strength should have lower surface roughness. High strength is more sensitive to surface roughness, and only after finishing can it be beneficial to exert its high strength performance. Otherwise, the durability limit will be greatly reduced, and the significance of using high-strength steel will be lost. In use, the surface of the component should be protected from mechanical damage (such as scratches) or chemical damage (such as corrosion, rust, etc.)