Fatigue Life is defined as:

• A. The total energy absorbed during loading.
• B. The total number of stress cycles that will cause a fatigue failure at a specified stress amplitude.
• C. The time to fracture under static load.
• D. The maximum stress endured before fracture.

Answer: (B)

Fatigue life is the total number of stress cycles a material can endure before fatigue failure occurs at a specified stress amplitude. This is typically denoted as N and represented on an S-N curve, illustrating that higher stress amplitudes reduce the number of cycles to failure. It differs from the total energy absorbed during loading (toughness), the time to fracture under a static load (static fracture), and the maximum stress endured before fracture (strength). The statement that describes cycles to failure at a given amplitude captures the essence of fatigue life.