Hello everyone,
I'm working with the new rules in the ASME BPVC 2025, specifically the introduction of the Bree diagram for ratcheting assessment. I've encountered a situation that seems to conflict with my previous understanding of fatigue exemption.
Here's the scenario:
A component is subjected to cyclic loading. I've performed a preliminary analysis and determined that it qualifies for an exemption from fatigue analysis based on one of the initial screening methods (e.g., Method A, B, or C).
However, I've also performed a more detailed ratcheting assessment using the new Bree Diagram procedure (new subsection 5.5.5.2.2 of Section VIII, Division 2 Part.5). In this assessment, the loading conditions result in a point that falls within the P1, P2, or P3 regions.
The code text for this procedure states that if the point falls within these regions, "cyclic plasticity is predicted for the primary plus secondary equivalent stress range and a penalty factor, Ke,k [see 5.5.4.2.2, Step 4(c)], is introduced into the fatigue analysis."
My question is: Does the result from the Bree diagram analysis (falling into P1, P2, or P3) override the initial fatigue exemption? Is a full fatigue analysis now required, even though the component initially screened out?
My initial interpretation is yes, the Bree diagram result necessitates a fatigue analysis with the Ke,k penalty factor. I believe this is because the Bree diagram is a more refined assessment that reveals a condition (cyclic plasticity) with the risk of low-cycle fatigue that the initial screening methods might not have captured.
I would appreciate any insights from those who have already started to implement the 2025 code changes or have attended related training. What is the correct interpretation and best practice in this scenario?
Thanks!
I'm working with the new rules in the ASME BPVC 2025, specifically the introduction of the Bree diagram for ratcheting assessment. I've encountered a situation that seems to conflict with my previous understanding of fatigue exemption.
Here's the scenario:
A component is subjected to cyclic loading. I've performed a preliminary analysis and determined that it qualifies for an exemption from fatigue analysis based on one of the initial screening methods (e.g., Method A, B, or C).
However, I've also performed a more detailed ratcheting assessment using the new Bree Diagram procedure (new subsection 5.5.5.2.2 of Section VIII, Division 2 Part.5). In this assessment, the loading conditions result in a point that falls within the P1, P2, or P3 regions.
The code text for this procedure states that if the point falls within these regions, "cyclic plasticity is predicted for the primary plus secondary equivalent stress range and a penalty factor, Ke,k [see 5.5.4.2.2, Step 4(c)], is introduced into the fatigue analysis."
My question is: Does the result from the Bree diagram analysis (falling into P1, P2, or P3) override the initial fatigue exemption? Is a full fatigue analysis now required, even though the component initially screened out?
My initial interpretation is yes, the Bree diagram result necessitates a fatigue analysis with the Ke,k penalty factor. I believe this is because the Bree diagram is a more refined assessment that reveals a condition (cyclic plasticity) with the risk of low-cycle fatigue that the initial screening methods might not have captured.
I would appreciate any insights from those who have already started to implement the 2025 code changes or have attended related training. What is the correct interpretation and best practice in this scenario?
Thanks!