ASME 5.3.2 | Local failure criteria | negative value of sum of principal stresses

Question

ASME 5.3.2 | Local failure criteria | negative value of sum of principal stresses

shiraz883 (Automotive)

(OP)

25 Apr 23 09:05

HI,

If the sum of principal stresses is coming to be negative (considering principal stresses with their respective signs "+ or -") and if this negative value magnitude i.e., absolute value is greater than the limit of 4S, will the local failure criteria be satisfied or not? The code does not say anything about the absolute values but mentions about the algebraic sum of linearized primary principal stresses which can be negative or positive.

Shiraz
Sr. Engineer

IdanPV (Mechanical) · Answer 1 · 2023-04-25 10:45:42

Refer to ASME PTB-3, Example E5.3.2 - That should answer your questions. Here and in the previous: thread https://www.eng-tips.com/viewthread.cfm?qid=506228

Basically:
- You can use the "Sum Principals" plot of your FEA software and make sure it is less than 4S.
- Local failure will not occur with negative stress.

TGS4 (Mechanical) · Answer 2 · 2023-04-25 17:29:37

IdanPV is correct. The intent is algebraic values of the sum of principal stresses. And the value must be less than 4S - negative values, regardless of magnitude, are less than 4S and therefore satisfy the criteria.

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ASME 5.3.2 | Local failure criteria | negative value of sum of principal stresses