GATE ME 2022 Set 1 — Question 29

MSQ+1 / -0MediumFatigue, S-N Diagram & EnduranceStatic & Dynamic LoadingMachine Design

Machine Design → Static & Dynamic Loading → Fatigue, S-N Diagram & Endurance

Last updated 5 September 2026

Question

Which of the following methods can improve the fatigue strength of a circular mild steel (MS) shaft?

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Correct answer (A) Enhancing surface finish; (B) Shot peening of the shaft; (D OR A); (B) Shot peening of the shaft Solution Fatigue strength is significantly affected by surface conditions. (A) Enhancing surface finish: A smoother surface reduces stress concentration points (e.g., scratches, machining marks), which are common sites for fatigue crack initiation. This improves fatigue strength. (B) Shot peening of the shaft: Shot peening is a cold working process that introduces compressive residual stresses on the surface of the material. These compressive residual stresses counteract the tensile stresses that cause fatigue cracks, thereby increasing fatigue life and strength. (C) Increasing relative humidity: Environmental factors like humidity can influence corrosion fatigue, but increasing humidity generally does not improve the intrinsic fatigue strength of the material; it can often accelerate corrosion. (D) Reducing relative humidity: While reducing humidity might mitigate corrosion fatigue in some environments, it's not a direct method to improve the material's inherent fatigue strength in the same way surface treatments do. It's more about preventing degradation. Therefore, enhancing surface finish and shot peening are direct methods to improve the fatigue strength of the shaft. Turn this into a strength. Explore AI-powered practice and doubt support with Success Tracker.

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Correct answer (A) Enhancing surface finish; (B) Shot peening of the shaft; (D OR A); (B) Shot peening of the shaft Solution Fatigue strength is significantly affected by surface conditions. (A) Enhancing surface finish: A smoother surface reduces stress concentration points (e.g., scratches, machining marks), which are common sites for fatigue crack initiation. This improves fatigue strength. (B) Shot peening of the shaft: Shot peening is a cold working process that introduces compressive residual stresses on the surface of the material. These compressive residual stresses counteract the tensile stresses that cause fatigue cracks, thereby increasing fatigue life and strength. (C) Increasing relative humidity: Environmental factors like humidity can influence corrosion fatigue, but increasing humidity generally does not improve the intrinsic fatigue strength of the material; it can often accelerate corrosion. (D) Reducing relative humidity: While reducing humidity might mitigate corrosion fatigue in some environments, it's not a direct method to improve the material's inherent fatigue strength in the same way surface treatments do. It's more about preventing degradation. Therefore, enhancing surface finish and shot peening are direct methods to improve the fatigue strength of the shaft.

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