ASME BPVC VIII Div 2, ANNEX 3D.3, Proportional Limit, Stress Strain Curve

[Doodler3D]

Hi,

I am performing an elastic-plastic simulation on a vessel. I've correctly generated the elastic plastic stress strain curve but I'm lost on the calculation of the proportional limit. I read the comments by TGS4 on the parent topic, but I'm still confused with the iterative procedure for the proportional limit? There's the arbitrary true plastic strain to be taken as 10^-6. Is it simply based off true strain(total) = True Elastic strain. I feel that I am overthinking the process after being muddled up in the definitions.

File attached for reference.

Thank you.

 

[TGS4]

Actually - the ASME Code Committee has clarified that the plastic strain at the proportional limit is the value of ε_p from Table 3-D.1.

Calculate the plastic strain (γ₁+γ₂) and determine the stress at which this value equals approximately ε_p.

 

[DriveMeNuts]

By chance, I've been mulling over this for the last few weeks as well.
Perhaps in the next code update, the committee will improve the definition of ε_p.

I find it remarkable that when a stress equal to yield is exerted onto the spreadsheet, the plastic strain equals near enough exactly 0.2%, in line with ASME II Part D.

 

[Doodler3D]

Thank you TGS4. I was indeed overthinking the simple.

 

[TGS4]

I believe that the Code item improving the definition of the proportional limit with ε _p was passed and it should be published in the 2021 Edition.