# Eigenvalue along normal direction of surfaces

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Hi,

I performed a modal analysis on a train gearbox with complex geometry, I obtain values for 170 000 nodes and I need to see or export eigen values of nodes along normal direction of their local surfaces. I saw in contour panel that it possible to display the magnitude or values along of x, y  and z axis, but, I would like know if it's possible to display values (like eigen value or displacement) along normal direction of surfaces in HyperView ? Or a solution (like a local system for each node) before the computation with optistruct to display values along normal direction in HV ?

BR,

Karl

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Please check with  user defined local coordinate system option.Refer below post for same.

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ok, but how can I make 170 000 different local coordinate systems, 1 per node, where one of three axis is the local normal vector ? I need to extract values along normal vectors for each node of my gearbox' housing. If it's not possible in HV or HM. How can I extract normal vector's coordinates for each node ?

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Did you check vector option in HyperView for your case.

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Yes I checked. But it plot vectors in function of its global system (see "My_housing.jpg"). I would like something like my first picture called "Normal.jpg".

BR

Karl

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On 2/1/2018 at 10:01 AM, karl landet said:

ok, but how can I make 170 000 different local coordinate systems, 1 per node, where one of three axis is the local normal vector ? I need to extract values along normal vectors for each node of my gearbox' housing. If it's not possible in HV or HM. How can I extract normal vector's coordinates for each node ?

One local system for each node? Wow !!!

How you can build the "local normal vector"? normal to what? You're speaking about NODES, not ELEMENTS.

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Yes I know that I'm speaking about nodes... and a node it's not a surface ... but values are define at nodes ...

Normal to what ? As I said in my first message " their local surfaces ", It's not possible ? I don't know ... maybe it's possible to use the nearest element normal vector ? Or a mean of nearest element normal vector? To do my computation I need each value along its nearest normal vector...

So, there is a mean to extract values along normal vector of local surfaces ?

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I will check internally if it is possible to export eigen values of nodes along normal direction of their local surfaces in HyperView. I also want to know the end objective of this requirement.Please do let us know about same.

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To get a projection of Displacement to a face normal create the following expression:

Dot(BCElemToNode(ElementAxisVector("0.0 0.0 1.0","LC0F1.Elements","LC0F1.Coordinates","Bisect"),"avg","LC0F1.Elements"),"Displacement")

For crash models:

Dot(BCElemToNode(ElementAxisVector("0.0 0.0 1.0","LC0F1.Elements","LC0F1.Coordinates","Bisect"),"avg","LC0F1.Elements"),("Coordinates"-"LC0F1.Coordinates"))

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I work on the acoustic optimization of gearboxes. I will do some measure in few months. I need to determine an optimal placement of my sensors to see my modal shapes. My sensors are 1D accelerometers (normal direction).  To compute a good placement of my sensors I need a matrix (lines: modal basis; columns: my nodes) and the values in this matrix are the Eigen value along normal direction (because I have 1D accelerometers). With this matrix I can do a QR decomposition or a Monte Carlo method (where I select the smaller conditioning of the computed sub-matrix) to determine a good placement.

Also I need these Eigen values to do a spectral iterative computation to get the dynamic response of my gearbox where I take account the non-linearity of my excitatory effort, transmission error, etc.

On 09/02/2018 at 7:07 PM, Rahul R said:

To get a projection of Displacement to a face normal create the following expression:

Dot(BCElemToNode(ElementAxisVector("0.0 0.0 1.0","LC0F1.Elements","LC0F1.Coordinates","Bisect"),"avg","LC0F1.Elements"),"Displacement")

For crash models:

Dot(BCElemToNode(ElementAxisVector("0.0 0.0 1.0","LC0F1.Elements","LC0F1.Coordinates","Bisect"),"avg","LC0F1.Elements"),("Coordinates"-"LC0F1.Coordinates"))

Ok thank you I will try this week

BR

Karl

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On 09/02/2018 at 7:07 PM, Rahul R said:

To get a projection of Displacement to a face normal create the following expression:

Dot(BCElemToNode(ElementAxisVector("0.0 0.0 1.0","LC0F1.Elements","LC0F1.Coordinates","Bisect"),"avg","LC0F1.Elements"),"Displacement")

For crash models:

Dot(BCElemToNode(ElementAxisVector("0.0 0.0 1.0","LC0F1.Elements","LC0F1.Coordinates","Bisect"),"avg","LC0F1.Elements"),("Coordinates"-"LC0F1.Coordinates"))

Thank you for your help. But your expression doesn't work. I take time to understand how work the builder expression (from "Derived Results") and I did some corrections :

Dot(BCElemToNode(ElementAxisVector("0.0 0.0 1.0","LC0F1.Elements","R1.LC0F1.V1","Bisect"),"avg","LC0F1.Elements"),"R1.V2")

R1.LC0F1.V1 : Coordinates

R1.V2 : Eigen mode

BR

Karl

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Thanks for the update.

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