Dave123456789
Nuclear
- Nov 5, 2012
- 1
This question is with regards to surface plasticity correction factors applied when linearised stresses are less than 3Sm.
If for example I had a P+Q value of 0.99 and I had a 3Sm value of 1, I wouldn’t need a Ke correction. But if I had a feature on the surface that lead me to have a surface stress of 4 then the surface stress would be over 3Sm. If all of the stresses in this model were mechanical then ASME would say that there isn’t any correction factor on the surface stress as it is not a local thermal stress. Therefore according to ASME the elastic stress calculated would be the stress used in the fatigue assessment.
I’m a little unsure why this is the case as this appears to be a good example where a Neuber correction would be used, where there is a high local stress but the remaining section has a lower stress less than yield. I have also made a model and used the effective strain equations in ASME VIII and determined a correction for plasticity greater than 1.0. Does anyone know the theory behind not having a plasticity correction factor on local mechanical stresses when the linearised stress is less than 3Sm?
If for example I had a P+Q value of 0.99 and I had a 3Sm value of 1, I wouldn’t need a Ke correction. But if I had a feature on the surface that lead me to have a surface stress of 4 then the surface stress would be over 3Sm. If all of the stresses in this model were mechanical then ASME would say that there isn’t any correction factor on the surface stress as it is not a local thermal stress. Therefore according to ASME the elastic stress calculated would be the stress used in the fatigue assessment.
I’m a little unsure why this is the case as this appears to be a good example where a Neuber correction would be used, where there is a high local stress but the remaining section has a lower stress less than yield. I have also made a model and used the effective strain equations in ASME VIII and determined a correction for plasticity greater than 1.0. Does anyone know the theory behind not having a plasticity correction factor on local mechanical stresses when the linearised stress is less than 3Sm?
