FE stress analysis in VIII-2 Part 5

[ep0319]

Hi everybody
I'm to perform stress analysis by FE of some details of a pressure vessel in VIII div. 2 in this way:

1. Thermal analysis -> temp map.
2. Mech analysis for primary stress: temp map from step 1 + mech loads giving primary stress (engineer judgment...). To not introduce thermal stress THE THERMAL EXPANSION COEFF ARE TO BE SET EQUAL TO 0.
3. Mech analysis for secondary stress: temp map from step 1 + mech loads giving secondary stresses. THERMAL EXP COEFF. SET TO ACTUAL VALUES.

I'd use these procedure for both linear analysis (steps 1 and 2) and non-linear analysis (steps 1 to 3).
Please let me know if I'm right
Thanks

 

[jte]

Nope. Simply put, the terms "secondary stress" and "nonlinear" should not be combined. Its either one (linear) or the other.

jt

 

[ep0319]

jte,
You'y right... I've been confused by the limits of the stresses...

But, despite that, my concern was about the way I split the calculation in steps 1 to 3.

Thanks again

 

[MrBTU]

I disagree. According to Bednar, page 24, secondary loads can be non-linear, causing local deformation, but they are self-limiting, so that they do not lead to failure even though they cause a slight deformation. Fig 2.1 on page 26 shows a stepwise deformation then return to the elastic range.

 

[TGS4]

MrBTU - in the context of performing a "nonlinear" analysis, the classification of stresses is irrelevant (that's what jte is saying). If you classify, then you have to do an elastic/linear analysis. If you do a nonlinear analysis, then no classification.