The fatigue limit value of an engineering material____________________?
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Answer: A. is greatly decreased by poor surface conditions
Explanation
Poor surface conditions introduce micro-notches and surface roughness that act as stress risers, greatly decreasing the material's fatigue limit. Cyclic loading concentrates high localized stresses at these microscopic surface imperfections, initiating premature fatigue cracks. Smoothing and polishing metal components removes these stress concentration sites, substantially improving their resistance to cyclic failure. The fatigue limit represents the maximum alternating stress level that a metal can endure for an infinite number of load cycles. Surface finish is one of the most critical factors influencing the endurance limit of structural steels and engineering alloys. Microscopic scratches act like tiny notches that multiply nominal applied stresses far beyond the yield strength of the material.
Option B is incorrect because surface texture directly impacts stress concentration and alters the endurance limit of engineering components. Option C is wrong because core composition alone cannot prevent surface crack initiation caused by poor external finishing. Option D is incorrect because fatigue limits correlate more closely with ultimate tensile strength than with static yield strength alone.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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