Division 2 fatigue curves are based on which type of data?

• A. S-N data
• B. Creep data
• C. Fracture toughness data
• D. Elastic modulus data

Answer: (A)

Fatigue curves are built from S-N data, which plot how many cycles a material can endure at a given stress amplitude before fatigue failure. S-N tests measure life by cycling specimens at specified stress ranges and recording the number of cycles to failure, providing the direct link between stress and fatigue life that these curves represent. Division 2 uses these empirical relationships to estimate safe stress ranges for a target life, often with corrections for mean stress, surface finish, size, and notch effects. The other data types don’t track fatigue life: creep data relates to time-dependent deformation at high temperature, fracture toughness data concerns resistance to crack growth, and elastic modulus data reflects stiffness rather than how long a component lasts under cyclic loading.