My PIPE18 and PIPE60 models do not give the correct reactions when I set KEYOPT(8)=1=(Internal and external pressures do not cause loads on end caps). That is, when the endcaps are removed, the reactions are wrong. Why?

Defect 67196 was filed, which resulted in Class 3 Error 2008-11 being written (see below). Essentially, when these elbow elements are subjected to an internal and/or external pressure, the reactions in the direction connecting the two end nodes is correct, but the force normal to that direction has the opposite sign. the straighter the elbow, the less the error (i.e., PIPE16 does not have this error, since the pipe is straight). The Class 3 Error test case (ev18-13s.dat) is attached to this record, as well, showing the error and the corrected results.

ANSYS Class3 Error Report

ERROR NO: 2008-11



Description of Error:

The results are incorrect for the elbow elements PIPE18 and PIPE60 with no end caps (accessed with KEYOPT(8) = 1) and with internal and/or external pressure (applied on faces 1 and/or 5).

Typical GUI Path(s):

Other Comments:

The force in the direction connecting the two end nodes is correct, but theforce normal to that direction has the incorrect sign. Hence, the error diminishes as the subtended angle decreases.

First Incorrect Version:

Release 11.0

Corrected In:

Release 12.0

Suggested User Action For Running on Uncorrected Version:

Use KEYOPT(8) = 0 and then apply forces at each end in the direction of the pipe to negate the pressure over the end of the element.

Author Signature: Peter Kohnke 4/16/2008 17:19
Reviewed By QA: William J. Bryan 5/7/2008 8:34
Approval: Dave Conover 4/17/2008 9:55

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