The elastic and plastic equivalent strains stored in the .rst file do not match those using AVPRIN,,effnu.
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Prior to ANSYS 6.0, the "effnu" effective Poisson's ratio was used to calculate elastic, plastic, and total equilvalent strains, according to Ch. 19.12 of the ANSYS Theory Reference. At ANSYS 6.0, the equivalent strains are calculated and stored in the .rst results file (for example, elastic equivalent strains use material's NUXY or PRXY values whereas plastic equivalent strains assume effnu=0.5). This is much more accurate than the AVPRIN,,effnu method since each integration point will have different 'effnu' in the case of total equivalent strains. If AVPRIN,,effnu is issued, the pre-6.0 way of calculating equivalent strains is used. If comparing nodal results (such as PRNSOL or PLNSOL), the two methods may not match, even for a simple case of elastic or plastic equivalent strains. For the default method at 6.0, equivalent strains are stored in the .rst file. Hence, when looking at nodal (averaged) results, these equivalent strains are averaged directly. For the pre-6.0 method using AVPRIN,,effnu, the equivalent strains are calculated on-the-fly. Hence, when looking at nodal (averaged) results, the components of strain are averaged first, then the equivalent value is computed per Ch. 19.12 of the Theory Reference. This should explain any differences seen when comparing *averaged* equivalent strain results with stored values in the .rst file (6.0 and later, default) and calculated values (pre-6.0). |
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