Q. Has the tolerance for defining multilinear stress-strain data changed since ANSYS 7.1? It seems to be a tighter tolerance. What is the tolerance at ANSYS 9.0, and can it be changed by the user?
A. The tolerance is 0.001*E. This has not changed since ANSYS 5.7. What has changed is that prior to 7.1, ANSYS just issued a warning if the slope of stress-strain curve was lower then E by 0.001E and let you pass if it was greater then E. After 7.1, the warning was switched to an Error and it was issued for slopes either greater then or less then E by an amount of 0.001E. The reason for the tighter restriction was that there were applications sent to us in which results were considered inaccurate and questionable. The explanation for the discrepancy was traced back to the loose variation between E and the slope derived from stress-strain data. The tolerance is hard coded and justified for quality control reasons. There are no plans to tighten the restriction any further. One of the reasons we added the ability to define stress vs. plastic strain directly was to get around this difficulty.
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Q. Has the tolerance for defining multilinear stress-strain data changed since ANSYS 7.1? It seems to be a tighter tolerance. What is the tolerance at ANSYS 9.0, and can it be changed by the user? A. The tolerance is 0.001*E. This has not changed since ANSYS 5.7. What has changed is that prior to 7.1, ANSYS just issued a warning if the slope of stress-strain curve was lower then E by 0.001E and let you pass if it was greater then E. After 7.1, the warning was switched to an Error and it was issued for slopes either greater then or less then E by an amount of 0.001E. The reason for the tighter restriction was that there were applications sent to us in which results were considered inaccurate and questionable. The explanation for the discrepancy was traced back to the loose variation between E and the slope derived from stress-strain data. The tolerance is hard coded and justified for quality control reasons. There are no plans to tighten the restriction any further. One of the reasons we added the ability to define stress vs. plastic strain directly was to get around this difficulty. |
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