Hello Everybody
I'm new in this Forum and I've read some very interesting threads in here. Therefore I thought someone could probably help me with a problem I have in meshing a human intervertebral disc (IVD) in Ansys WB 13.
First i might explain you some basics about an IVD (see picture). The Disc is composed of mainly 4 different structures. The cartilaginous endplates on the bottom and the top of the disc (green), the incompressible - jelly like "nucleus pulposus" in the center of de IVD (red) and the "anulus fibrosus" (orange). As you can see in the picture, the IVD has already been meshed with mostly Hex-Elements.
The materials of the nucleus and the endplates are represented by two different mostly incompressible, linear material laws.
The anulus fibrosus is based on a hyper-elastic mooney-rivlin material law. Because the ground substance of the anulus can't bearly take any tractive forces (in truth), the substance is reinfoced by tensional fibres in a criss-cross pattern of 30 resp. 150 degrees to the horizontal (transversal plane) (see picture http://www.juliawilliams.co.uk/Prolapsed_intervertebral_Disc_files/Disc%20fibres.jpg).
My problem ist now, that i want to implement this fibres all around the anulus fibrosus. This means that every orange Hex-Element needs to be reinforced by these fibres. For that reason I wrote some APDL Code (I'm just learning this script language and I'm still a beginner in writing this kind of code...):
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/prep7
!Materialmodell für die eingebetteten Fasern
MP,EX,1500,500
MP,PRXY,1500,0.3
!Reinf265 Elemente
SECTYPE,100,REINF,SMEAR
!Material ID 150, A = 0.03 , S = 0.2, KCN = 20, THETA = 30/150, PATT = ELEf
SECDATA,1500,0.03,0.2,20,30,ELEf,3,0.5
!SECDATA,1500,0.03,0.2,20,150,ELEf,3,0.5
!Fasern sollen nur Zugkraefte aufnehmen
SECCONTROLS,1
secn,100
*DO,i,1,48,1
esel,s,mat,,IVDL2L3_%i%
EREINF
*ENDDO
etlist,all
alls
/solu
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The code works and the Reinf265 elements will be created. But, the problem is now, that the "planes" in the HEX-Elements, where the reinf elements will be created in, are not alligned all the same. That means that some fibres lie in the horizontal plane, some in the side plan and so on (see picture above).
I think the problem can be solved by line up the Hex-Elements respectively the sides of the HEX-Elements all in the same direction. This must be done during or right before the meshing of the IVD I think.
Can somebody help me with that? I would appreciate every help, hint and comment smile.
Greetings from Switzerland,
Christian S.
PS: You can reply me in german :-)
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