The operational fatigue life of a mechanical part can be successfully enhanced by_____________________?
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Answer: D. shot peening
Explanation
Shot peening bombards component surfaces with hard spherical media to induce beneficial compressive stresses. These surface compressive residual stresses counteract applied tensile loads that drive fatigue crack propagation. Delaying surface crack initiation and growth significantly enhances the operational fatigue life of parts. The mechanical impact causes localized plastic yielding of the surface layer while underlying metal resists. This process creates a thin, highly stressed outer layer containing high levels of compressive residual stress. Standard peening intensity is measured using Almen strips to ensure consistent surface treatment quality.
Shot peening is widely applied to automotive gears, aircraft landing gear, and high-performance connecting rods. Components subjected to severe cyclic bending or torsional loads benefit immensely from this surface treatment. It provides a cost-effective method to improve fatigue performance without changing component bulk dimensions. Electroplating deposits metal layers but can introduce hydrogen embrittlement and tensile residual stresses instead. Polishing removes surface scratches but fails to generate the deep compressive residual stresses of peening. Standard heat treatments alter bulk material microstructure rather than establishing surface compressive residual stress fields.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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