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# Secondary Stress depends on the young’s modulus?

## Secondary Stress depends on the young’s modulus?

(OP)
Dear experts,
i have read plenty of codes, standards and posts related to the definition of Primary stress and secondary stress, just to figure out a simple statement to clarify their difference. and i find the following statement:
Primary Stress is independent of young’s modulus.
Secondary Stress depends on the young’s modulus.

the statement is so simple that i quite doubt if it is always valid .
so many question : is it universally correct, like NEWTON's laws of motion?

### RE: Secondary Stress depends on the young’s modulus?

Secondary stresses are strain induced stresses. If things remain elastic, what is the ratio of stress to strain?

### RE: Secondary Stress depends on the young’s modulus?

I guess that it depends on what you mean by "depends". I would rather phrase it this way:

Primary stresses are those necessary to satisfy equilibrium.
Secondary stresses are those necessary to satisfy compatibility.

If you are unable to discern, in any particular problem, which is which, then follow the guidance in ASME Section VIII, Division 2, Part 5, Paragraph 5.2.1.2.:

#### Quote (ASME Section VIII, Division 2, Part 5, Paragraph 5.2.1.2.)

For components with a complex geometry and/or complex loading, the categorization of stresses requires significant knowledge and judgment. This is especially true for three-dimensional stress fields. Application of the limit load or elastic-plastic analysis methods in 5.2.3 and 5.2.4, respectively, is recommended for cases where the categorization process may produce ambiguous results.

### RE: Secondary Stress depends on the young’s modulus?

(OP)
thanks for response, Maslov & TGS4。
TGS4, i read that you restate from time to time, that stress classification is complex needing significant knowledge and experience.
a silly idea suddenly comes into my head, now Artificial Intelligence seems so powerful, will it be applied in this field in the near future, which may endanger the position of engineers. Ansys/Abaqus may incorporate AI into their software.
do you think it is possible?
Thanks.

### RE: Secondary Stress depends on the young’s modulus?

Simply put, no. I don’t think that AI will replace the experience and judgement of an experienced engineer in these stress categorization questions.

It is much better to use the nonlinear methods and forego stress categorization completely.

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