Normal vector from node

[Esmond chan]

Hi everyone,

I'm currently struggling somehow with apdl post-processing to obtain stress of a node beneath a surface Hotspot. This node is lying on a normal vector from this Hotspot(currently with known ID and its coordinates).

Mathematically speaking, i will need a tangent surface to this Hotspot before getting its normal vector. How should I write it here since I only has node ID known?

I appreciate your help and suggestions very much here. Thanks

 

[rb1957]

what code are you using ?
what elements ?
normal stress does not "normally" require the normal direction.

if you do want the normal, well, the node belongs to a surface element, and surfaces have easily defined normal (based on their surface equation.

another day in paradise, or is paradise one day closer ?

 

[Esmond chan]

Hi,
Thanks for your reply. I am writing snippets in ansys, planning to adapt it for batch analysis to export nodal value.

Elements type are generally tet and hex. The point of interest lies beneath a surface node from a known distance and tangent to this surface node.

I have tried with *get but unfortunately with x y z coordinates is insufficient, I need the node to be automatically orientated to the nodal tangent surface.

Do you know a way to do this?

 

[rb1957]

try posting in the ANSYS forum.

I'd've thought that you could find which nodes are on the surface, and so get the equation of the surface. From there, normal through a point is "easy".

another day in paradise, or is paradise one day closer ?

 

[Esmond chan]

Hi,
I do have the coordinate and the node ID of the node on surface. How do I get the surface equation and the normal to acquire the node at a certain depth on this normal vector?

Regards

 

[rb1957]

the surface is defined by some set of nodes.
It is "easy" (certainly 1st year uni math) to develop the equation of a plane from three points.
It is then also "easy" to find a normal vector, through a point,
and finally "easy" to find the co-ordinates of a point some distance along this vector.

another day in paradise, or is paradise one day closer ?

 

[Esmond chan]

Thank you for your reply. I understand that there is the math to create a plane equation and normal vector, but is there no function in apdl to do the job? And I do not have an even surface (non planar) I require a tangent surface to this point. Any suggestion?

 

[rb1957]

refer to previous post .. post in ANSYS forum.

If you underlying geometry is surfaces, then these can be interrogated for tangent surface at a point.

another day in paradise, or is paradise one day closer ?

 

[IRstuff]

Worst comes to worst, you should be able to find the three nearest points and use them for the surface

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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