RF axisymmetric with OUTPUT 3D

Analysis issues
1

Hi,

Reactions in an axisymmetric model when OUTPUT 3D is requested do not deliver the overall section reaction but the Reaction in just 2º. I couldn’t find this behaviour documented in the manual and could lead to error.

Input 2000N

RF with OUTPUT=2D

2000N

RF with OUTPUT=3D

-11.11112N (2000N*2/360)

*NODE
1,0.009,0.01,0
2,0.01,0.01,0
3,0.01,0,0
4,0.009,0,0
5,0.011,0,0
6,0.011,0.01,0
7,0.01,0,0
*ELEMENT,TYPE=CAX4
1,3,5,6,2
2,4,3,2,1
*NSET,NSET=BASE
3
*ELSET,ELSET=DEFAULT
1
2
*MATERIAL,NAME=MATERIAL
*ELASTIC,TYPE=ISOTROPIC
210000000000,0.3
*SOLID SECTION,ELSET=DEFAULT,MATERIAL=MATERIAL
*BOUNDARY
3,2,,0
*STEP
*STATIC
*CLOAD
2,2,2000
*NODE FILE,GLOBAL=YES,OUTPUT=3D
U,RF
*EL FILE
S,NOE,E,ENER
*END STEP
2

Right, it’s not explicitly mentioned there (the manual only mentions the expansion angle and interpretation of some other quantities). It’s also different than the way input forces are treated and different than in Abaqus, so it can be counterintuitive. The user basically has to figure out that the reaction force is taken directly from the expanded segment. Here’s a subtle hint from the manual:

For axisymmetric structures the concentrated forces are assumed to apply for the whole 360◦ . Since the expansion is done for a small sector only (must be small to keep enough accuracy with only one layer of elements, the size of the sector is specified by the user underneath the *SOLID SECTION card) the force is scaled down appropriately.

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