POLYFLOW - transient viscoelastic calculation may fail at early steps, because of lack of precision


Running a transient viscoelastic calculation from scratch (i.e. vanishing stress state) often fails. The most typical symptom is a reduction of the time step below the minimum value assigned. What can be done for fixing this?
When running a transient viscoelastic calculaiton, the viscoelastic stresses often start from zero, and usually grow exponentially. This is especially true in a situation involving extension or compression. This may hinder the evaluation of the precision, especially at the beginning of the calculation, where stress values are small, but show a rather fast growth. It is therefore important to make sure that the viscoelastic stresses are not considered for the evaluation of the precision . By default, viscoelastic stresses are discarded from this evaluation. If the keyword PRECISIONSTRESS is not included in a .p3rc file for the POLYDATA session, then only the convergence for hte viscoelastic stress will be checked, while they will be skipped for the precision evaluation. This feature can also be activated via POLYMAN as an option in the .p3rc configuration file for POLYDATA.
N.B. In former version, the keyword CONVSTRESS had just the opposite effect.





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