victor6397
Military
Hello, sorry if the question is very basic (I'm starting with ASME) but need to perform a fatigue analysis of a pressure vessel between 0 and 25 MPa according to ASME VIII-2.
I have compared the two elastic-plastic methods (Twice Yield and Cycle-by-cycle) and the results are very different, so I am probably doing something wrong.
For the Twice yield method I have used the strain range vs stress range curve, added in the Multilinear isotropic hardening option in Ansys. Then, I have applied the formulas (5.45) and (5.46) of section 5.5.4 for the calculation of the alternating stress.
For the cycle-by-cycle method, I have used the strain amplitude vs stress amplitude curve added in the Multilinear kinematic hardening option of Ansys and applied the same equations as before for the calculation of the alternating stress.
The alternating stress results are 25% higher in the cycle-by-cycle method for a range of pressures between 0 and 25 MPa.
Can someone tell me if the procedure i have used is correct? Or is there one method more correct than another for this case? I understand i have made something wrong because i doesn't seem very consistent to apply the same Salt equation when the equivalente plastic strain is significantly different between the two method.
I Hope you can help me. Thanks
I have compared the two elastic-plastic methods (Twice Yield and Cycle-by-cycle) and the results are very different, so I am probably doing something wrong.
For the Twice yield method I have used the strain range vs stress range curve, added in the Multilinear isotropic hardening option in Ansys. Then, I have applied the formulas (5.45) and (5.46) of section 5.5.4 for the calculation of the alternating stress.
For the cycle-by-cycle method, I have used the strain amplitude vs stress amplitude curve added in the Multilinear kinematic hardening option of Ansys and applied the same equations as before for the calculation of the alternating stress.
The alternating stress results are 25% higher in the cycle-by-cycle method for a range of pressures between 0 and 25 MPa.
Can someone tell me if the procedure i have used is correct? Or is there one method more correct than another for this case? I understand i have made something wrong because i doesn't seem very consistent to apply the same Salt equation when the equivalente plastic strain is significantly different between the two method.
I Hope you can help me. Thanks
