The fatigue limit of material is defined as stress that would cause failure after a specified number of stress reversals. The factors affecting the fatigue strength of materials and the ways of improving the fatigue strength are discussed here.
Factors controlling Fatigue strength:
- Stress Concentration: Fatigue strength is reduced by presence of stress raisers
- Surface Roughness: Smoother the surface finish of metal sample, higher the fatigue strength
- Surface Treatment: Carburizing and nitriding increase fatigue life. Decarburzing lowers the fatigue life.
- Environment: corrosive environment accelerates rate at which fatigue cracks propagate
Improving Fracture Limit
- Good design, avoiding sharp corners, avoiding regions of stress concentration.
- Polishing to give good finish & thereby removing surface irregularities helps
- Short peening of metals introduces compressive stresses at surface and helps in raising the fatigue limit
- A fine grain size improves the fatigue resistance
- Carburzing and Nitriding will be highly helpful
The above information is taken from Material Science Study Material provided by IEI and from Material Science and Engineering by Raghavan. Don't forget to grab a copy of Material Science and Engineering book, which is essential for preparing for AMIE, Material Science.
with warm regards
AllMyPosts
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