jharris3
Mechanical
- May 3, 2011
- 52
Which approach does compress use for compressive load design in Section VIII Division 2 when materials other than carbon and low alloy steel are considered?
Does compress use External Pressure Charts from Section II subpart 3 or does compress use Section VIII Div 2 part 3-D.5 to calculate tangent modulus?
If the method from VIII-2 part 3-D.5 is used then how are the calculations made?
I am following the rules in VIII-2 part 4.4.3, (and 4.4.5) for nickel alloy shells under external pressure and the instructions are to calculate tangent modulus "based on a stress equal to Fhe." So when I did that the result of using equation 4.4.6 was an allowable stress that was way lower than the Div 1 allowable stress. I am pretty sure I know where the problem is but I want to ask around in case there is something I am missing.
It seems like the instructions are wrong and that they should tell the user to calculate tangent modulus iteratively based on a STRAIN equal to Fhe / Ey. They would have to try out multiple values of stress to calculate Et until Stress / Et = Fhe / Ey.
Does compress use External Pressure Charts from Section II subpart 3 or does compress use Section VIII Div 2 part 3-D.5 to calculate tangent modulus?
If the method from VIII-2 part 3-D.5 is used then how are the calculations made?
I am following the rules in VIII-2 part 4.4.3, (and 4.4.5) for nickel alloy shells under external pressure and the instructions are to calculate tangent modulus "based on a stress equal to Fhe." So when I did that the result of using equation 4.4.6 was an allowable stress that was way lower than the Div 1 allowable stress. I am pretty sure I know where the problem is but I want to ask around in case there is something I am missing.
It seems like the instructions are wrong and that they should tell the user to calculate tangent modulus iteratively based on a STRAIN equal to Fhe / Ey. They would have to try out multiple values of stress to calculate Et until Stress / Et = Fhe / Ey.