Fatigue evaluation in Division 2 relies on which method?

Fatigue evaluation in Division 2 relies on which method?

• A. Paris' law
• B. Rainflow counting
• C. S-N curves
• D. Goodman diagram

Answer: (C)

Fatigue evaluation in Division 2 relies on S-N curves. These curves provide the relationship between the stress range a component experiences and the number of cycles it can endure before fatigue failure, based on test data for the material and weld detail. In practice you determine the critical section, compute the stress range (and any mean stress), and then compare the expected life under those cycles to what the S-N curve allows. If needed, a mean-stress correction (such as a Goodman-type adjustment) can be applied to convert the actual loading to an equivalent stress range before using the curve. The other methods play different roles: Paris’ law describes crack growth rate once a crack exists, rainflow counting helps convert a complex load history into simple cycles for life assessment, and the Goodman diagram is a mean-stress correction tool used with fatigue data but not the primary life-estimation method itself.

Fatigue evaluation in Division 2 relies on S-N curves. These curves provide the relationship between the stress range a component experiences and the number of cycles it can endure before fatigue failure, based on test data for the material and weld detail. In practice you determine the critical section, compute the stress range (and any mean stress), and then compare the expected life under those cycles to what the S-N curve allows. If needed, a mean-stress correction (such as a Goodman-type adjustment) can be applied to convert the actual loading to an equivalent stress range before using the curve. The other methods play different roles: Paris’ law describes crack growth rate once a crack exists, rainflow counting helps convert a complex load history into simple cycles for life assessment, and the Goodman diagram is a mean-stress correction tool used with fatigue data but not the primary life-estimation method itself.