Question

Fatigue failure occurs due to

• A. Extended constant loading
• B. Extended cyclic loading
• C. Diffusion of atoms
• D. Movement of dislocations

Hint:

Fatigue failure can occur at stress levels much lower than the yield strength of a material, making \textbf{design against fatigue} crucial in engineering applications.

Answer 1

The Correct Option is B

Fatigue failure refers to the gradual weakening of a material caused by repeated or cyclic loading, even if the stress is below the material's ultimate tensile strength. Step 1: Understanding Fatigue Failure - Fatigue occurs when a material is subjected to repeated loading and unloading, typically at stresses that are much lower than the material's tensile strength. - Over time, these cyclic stresses cause the material to develop small cracks, which propagate and eventually lead to failure, even without a large amount of plastic deformation.


Step 2: Evaluating the Options - Option (A) - Incorrect: Extended constant loading leads to creep failure, which is a different type of time-dependent deformation. - Option (B) - Correct: Fatigue failure is caused by extended cyclic loading where stress is repeatedly applied and removed. - Option (C) - Incorrect: Diffusion of atoms is more related to high-temperature deformation (creep) than fatigue failure. - Option (D) - Incorrect: Dislocations move during deformation, but fatigue failure is primarily caused by cyclic loading rather than just dislocation movement.


Step 3: Conclusion Extended cyclic loading is the primary cause of fatigue failure, which is why option (B) is the correct answer.