Question

According to IS 800, the stress range for a category of detail, depending upon the number of cycles it is required to withstand during design life is called as
1. Cut-off strength
2. Yield strength
3. Fatigue strength
4. Plastic strength
5. Fire strength

Answer 1

Correct Answer - Option 3 : Fatigue strength

Explanation:

Fatigue:

• It has been found that materials behave differently under static and dynamic loading. In cyclic or reverse cyclic loading, if the accumulated strain energy exceeds the toughness then fracture failure may occur.
• Factor affecting fatigue are
  • Loading condition
  • Frequency of loading
  • corrosion
  • Temperature
  • Stress concentration
• The number of loads cycle required to initiated surface cracks is called fatigue initiation life and the additional number of load cycles required to propagate surface cracks is called fatigue life. 
• To prevent fatigue life the developed stress should be kept below endurance limit. Endurance limit is that stress below which a material has a high probability of no failure even at an infinite number of load cycles.
  • For mild steel endurance limit = 186 MPa
  • Aluminium endurance limit = 131 MPa

Endurance limit is lower than proportional limit.