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Geometry in LMS Test.Lab

Siemens Experimenter Siemens Experimenter
Siemens Experimenter

Geometry in LMS Test.Labcar.png

 

It is often desired to animate data onto a geometry. The geometry worksheet in LMS Test.Lab is designed to build a geometric definition of a test structure that can be used to visualize results.

 

Examples of commonly animated data include:

  • Operational deflection shapes
  • Mode shapes
  • Torsional vibration data
  • Acoustic modes

To create a geometry in LMS Test.Lab, load in the Geometry Add-in by going to Tools -> Add-ins -> Geometry. The Geometry worksheet is 16 tokens.

 

1.pngFigure 1: Turn on the Geometry add-in.

This article will describe creating a geometry from scratch. Note that it is possible to import a CAD model into the geometry worksheet.

 

The geometry worksheet consists of many minor-worksheets which are listed at the top of the geometry worksheet.

The minor-worksheets include:

  • Components
  • Nodes
  • Lines
  • Surfaces
  • Slaves
  • Mesh area
  • Torsional node

Users should be able to work through the minor-worksheets from left to right to create a geometry.


2.pngFigure 2: The minor-worksheets always appear at the top of the Geometry worksheet.

 

COMPONENTS

 

For this example, a modal analysis is performed on a body in white (the welded sheet metal components of an automobile body). The data is collected on a physical automobile body and the information must be mapped to a geometry in Test.Lab so that the mode shapes can be animated later. Thus, a geometry of the body in white must be created.

 

Start in the Components tab. For each component of the geometry, type in a name. Using multiple components in the geometry aids with visualization as well as organization.

 

The created components include the REAR, FLOOR, FRONT, RAIL, ROOF, and more. The components of the car are listed in the component table (Figure 3).

 

The color of a component is changed by clicking on the box in the color column and selecting a color. The color controls the node, line, and surface color on the geometry.

 

After any changes are made to the geometry, the “Accept Table” button (in the upper right of the worksheet) must be pressed to save changes. Many button will be inactive until “Accept Table” is selected.

 

3.pngFigure 3: Adding components to the geometry.

Once all the desired components are added, nodes for each component can be defined. The nodes represent physical locations on the component.

 

For each component, a coordinate system can be defined: either Cartesian, cylindrical, or spherical. The chosen coordinate system will specify whether node locations are determined using X/Y/X, r/theta/Z, or r/theta/phi respectively (see Figure 4 below).

4.pngFigure 4: Three different coordinate systems: Cartesian, cylindrical, and spherical.

For some products, it is useful to define components using multiple coordinate systems. For example, in Figure 5 below, it would be useful to define the green and blue components with cylindrical coordinates and the purple and yellow components with Cartesian coordinates. 

5.pngFigure 5: Cartesian, cylindrical, and spherical coordinate system examples.

 

It is also possible to move a component relative to a global coordinate system by using the X, Y, Z, XY, XZ, YZ fields.

 

NODES

 

In the Nodes tab, it is possible to add nodes component-by-component. To add nodes to a particular component, select that component in the tree on the left side of the screen.

 

6.pngFigure 6: The node worksheet. Select the component to add nodes to.

Fill in the “Name column”. Notice that the “full name” structure for each node is “Parent Component : Name”.

 

Fill in the X, Y, and Z coordinates for each node. This will place the nodes in space. You can chose to fill out with local or global coordinates (change this option under “Table Options”). It is also possible to rotate nodes about an axis using the XY, XZ, and YZ columns.  

 

7.pngFigure 7: Adding nodes to a geometry.

As always, press “Accept Table” when done adding nodes. This will cause the nodes to appear in the geometry preview window at the bottom of the screen.

 

Repeat this process until nodes have been added to all the desired components.

 

LINES

 

Now move to the Lines minor-worksheet.

 

To add lines, click between to nodes. You can continue clicking between nodes to create a continuous line. When done creating a line, double click on the last node.

 

8.pngFigure 8: Create a line by clicking node to node. When done creating the line, double click on the last node that the line should connect to.

Once all the desired lines are added, press “Accept Table” to save your changes. 

 

9.pngFigure 9: All created lines will be listed in the Lines table.

 

SURFACES

 

It is possible to add both triangle and quadrangle surfaces to the geometry. First, choose which surface type will be created using the radio buttons at the top of the surfaces minor-worksheet.

 

Next, click between either three or four nodes (depending on whether triangles or quadrangle is selected) to create the surface. The software will allow the user to continue creating surfaces until a node is double-clicked. Double click on a node to exit the surface-making mode.

 

10.pngFigure 10: Add surfaces by clicking between nodes. Double click on a node to exit the surface-making mode.

NOTE: Both lines and surfaces are purely tools for visualization and will not affect the data that is displayed on the geometry.  The movement of the nodes is purely dictated by the measurements, not by the connections in the geometry visualization.

 

NOTE: In both the Lines and Surfaces minor-worksheets, the “Add Surfaces [Lines] in Display” checkbox is on by default. If this box is unchecked, it allows editing the table manually. This can be useful as information can be copied between tables in different projects or information can be copied to/from Excel.

 11.pngFigure 11: It is possible to copy/paste to/from the table if the “Add surfaces in display” box is unchecked.

SLAVES

 

Typically, when doing an animation on a geometry, the only nodes that will animate are nodes which correspond to a physical measurement location. Sometimes, additional nodes are desired to be animated to make the mode shape look more complete. Slave can be used for this purpose.

 

Slave nodes are always linked to one or more master nodes. The slave node will animate as an average of the master node.

 

To create a Slave node, click on an existing node in the Geometry Display. The slave node will turn blue.

Next, click up to four master nodes. The master nodes will turn red.

 

You can chose to slave nodes in any combination of X, Y, and Z directions.

 

12.pngFigure 12: Selecting the slave node (blue) and master nodes (red).

When slaving a node, the software takes into consideration how the master nodes are moving. The resultant movement of the slave node is a weighted average of how the master nodes are moving. The weighting factor for each master node is determined by how close (spatially) the master node is to the slave node. The master node that is closest to the slave node will most heavily influence how the slave node moves.

 

Once the slave node is created by pressing “Accept”, the slave node, the directions, and its master nodes will be listed in the table and all color will return to normal.

 

13.pngFigure 13: The slave nodes will be listed in the table.

 

Here is what the geometry looks like after using the first five minor-worksheets.  

14.pngFigure 14: Geometry result after the first 5 minor-worksheets.

 

Additional geometry tips:

 

1. Mesh generator: Test.Lab includes a tool that can create nodes for simple geometry shapes.

 

In the main Test.Lab menu, under “Tools” there is a Mesh Generator tool.

 

 15.pngFigure 15: The Mesh Generator is located under “Tools” in the main Test.Lab menu.

The Mesh Generator will insert the specified shape into the Components minor-worksheet of the Geometry worksheet of the open project.

 

Open a Geometry worksheet in a project and then open the Mesh Generator tool.

 

Select a shape type to generate.

 

16.pngFigure 16: Select the type of shape.

NOTE: The Help button in the upper right will open a Mesh Generator help document with examples for creating each of the shape types.

 

Next, fill in the shape parameters.

 

Perimeter grid represents how many nodes will make up the smallest perimeter. Radius indicates the radius of the cylinder. Radius grid indicates how many nodes will make up the radius. Height indicates the height of the cylinder. Height grid indicates how many nodes will make up the height.

 

17.pngFigure 17: Parameters of creating a cylinder in the Mesh Generator.

The shape specified above will look as follows:

18.pngFigure 18: Shape generated with the Mesh Generator.

2. Geometry display

 

There are two default geometry displays in the navigator. The first is a single geometry display. The second is a quad-geometry display in which 4 view of the geometry are shown.

 

19.pngFigure 19: Zoomed in view of the geometry icons. The single geometry icon is on the left, the quad geometry icon is on the right.

 

To display a geometry, grab the entire geometry from the Navigator tree, and drop it into a geometry display.

 

20.pngFigure 20: Drag and drop the geometry into the display. This will bring in all the components of the geometry.

Animating data on a geometry can make understanding the behavior much easier.

 

Questions? Contact us. 

 

Related Links:

Comments
Creator
Creator

Hi friends!

 

I created a model in LMS Test.Lab for a building store, and I wish to animate it and I'm using the slaves nodes' option, but i need also to define the contour conditions for the first floor, for example. So that those nodes need to be fixed at the ground, so how can I do that?

 

Thanks for the help.

Alvaro

Siemens Phenom Siemens Phenom
Siemens Phenom

Hello Alvaro,

 

Your local support team can help more since I am not really clear what you are asking.  If your first floor has no movement and you don't want those points to move then make the geometry to include that floor and don't measure any data at those locations.  By default, if there are no measurements at those points they will not move - which is what I assume you want.

 

Kevin

Creator
Creator

Thanks Kevin.

 

Well, that is exactly my question.

 

But when I used automatic geometrical or topological option to animate the structure completely (at a specific mode identificated), extends the movement througth all nodes and the first floor movement too, in my building model.

 

Alvaro

Siemens Phenom Siemens Phenom
Siemens Phenom

Alvaro,

 

If you are using the automatic expansion, and you don't want those points to move then I suggest the following "trick":

 

  • Making a copy of some data and assign it to those Point ID's and Directions for the first floor by Editing the Properties of the FRF data.
  • Multiply that data by zero so it has zero amplitude.
  • Recalculate the modes using the original data and this data thus having mode shapes with an amplitude of zero at these locations.  You can verify that the mode shape properties show these nodes have zero aplitude.
  • Use the mode shape expansion as before.  Since we have some modal values with zero amplitude those will not move.

An example mode with the modal information having zero amplitude:

 

4-16-2018 1-33-35 PM.jpg

 

 

Creator
Creator

Hi Kevin.

 

Thanks for the help, but can you explain a more detailed the steps for do that?

 

Id' like to know how make a copy and assign some data to the points ID's and edite the Crosspower Data (Is operational test).

 

And how and where (in the LMS Test.Lab) to multiplicate by zero the data.

 

Thanks for the help

Alvaro

 

Siemens Phenom Siemens Phenom
Siemens Phenom

Hello Alvaro,

 

Tp multiply by zero:

1)  Use the Data Calculator and multiply by 0.  i.e. formula would be F1*0 or 

2) Display the data on the Navigator in a Picture, select it (Select All Curves for example) and then use the Conditioning toolbar to multiple (*) by 0.  The results will be stored in a Conditioning folder and the display will be updated by default.

 

To edit the properties, right click on the data and select Edit Properties... make the change to the Point ID and\or Reference Point ID and their directions as needed.

 

If you need assistance you can call your local support team and they can explain over the phone or do a screenshare with you.

 

Kevin

Experimenter
Experimenter

Hi guys,

             I need to do modal analysis of the tyre and animate it for a project. I am having trouble building the nodes. Can anyone help me with the materialfor geometry and on euler angle. An example would be great. And how to change from cartesian to cylinderical coordinates?

Siemens Legend Siemens Legend
Siemens Legend

First, there are two posts that may help:

Here are some separate instructions that may help.

 

In the LMS Test.Lab Geometry worksheet, type the component name “tyre”.  Select the Co-ordinate system to be “Cylindrical”.

geometry.png

 

After entering the component, press “Accept Table” in the upper right.

accept_table.png

 

Then select “Nodes”.  Let’s say you want to create a geometry of a tyre with 10 points around the outside.  Enter the co-ordinates as shown in picture:

coordinates.png

 

The co-ordinates get entered as r, theta, and Z:

  • R = Radius of tyre
  • Theta = angular position around circumference
  • Z = Depth of tiretire.png

     

In this case, there are 10 points spread around the circumference 36 degrees apart. Press “Accept Table” in the upper right to see the geometry.

 

nodes.png

 

Click on “Lines” at the top to add connections between points. Hover the mouse over the nodes.  When the name appears, click once on the node, move to another node, and when the name appears click to add a line connection. To stop adding nodes, click on the node again to stop adding.

 

It is not necessary to press “Accept Table” to save the line connections.  

lines.png

 

In the geometry display, the node names and local co-ordinates can be viewed. Right click in the display and choose “Model -> Node -> Names” and “Model -> Node -> Euler Angles”.  Notice that the co-ordinates X, Y, Z correspond to R, Theta, Z.

euler.png

 

In the Channel Setup worksheet, when doing the measurement, the point direction will still be specified as +X, -X, +Y, -Y, +Z, or –Z.  The X, Y, and Z corresponds to R, Theta, and Z.

Experimenter
Experimenter

Thank you so much PJS. Really appreciate your help. This will help me get all the data. 

Can you recomend any books or article which will help me build(Find) the transfer function from yhe obtained bode plot. I have come up with my equation. Just wanted to know if you have any idea.

Siemens Phenom Siemens Phenom
Siemens Phenom

Hello Hrushikesh,  

 

If you look at the Theory Documents (under Documentation, Theory documents PDF) you will find the Functions.pdf file which has the Frequency Response Function (FRF) explained.  You can measure the FRFs in Impact Testing, Spectral Testing or MIMO FRF Testing to list a few applications.

 

6-12-2018 1-24-28 PM.jpg

Experimenter
Experimenter

Okay. Anyway what i was asking is different. I have ploted the lms data and my equation data. They seem pretty close.

But i had another doubt: 

I have collected impact testing data. But my interest is to find Modal stiffness[K], DAMPING COEFFICIENT [c],MODAL MASS [m] (kg). How do i get these valuse.

I want to use this data for further use. 

Siemens Phenom Siemens Phenom
Siemens Phenom

To calculate damping, you can add the calculation to a single X cursor in the display.  See https://community.plm.automation.siemens.com/t5/Testing-Knowledge-Base/How-to-calculate-damping-from...

 

For the other modal parameters, if you have geometry and FRF's the next step is to calculate mode shapes.  To scale the mode shape properly and get modal mass and stiffness then you need to have a driving point measurement and it needs to be named properly so that we know it is a driving point.  For example, if you impacted at tyre:1 in the Z direction then the Point ID and Reference Point ID need to be tyre:1:+-Z.    If they are not named properly (never call the point ID of reference location hammer!) then we do not know it is a driving point and we cannot calculate modal mass and stiffness.

 

Once modes are calculated, right click on the mode(s) to get their properties and under details you see the information you want.  NOTE:  Modal mass and stiffness will changed based on the scaling method, so on modal validation scale the modes to the scaling method you want:  unity modal, unity stiffness, unity component, unity length, unity modal A, unity maximum component and residue vector are the available scaling methods.

 

Unity mass scaling:

6-13-2018 8-45-15 AM.jpg

 

Unity length scaling:

 

6-13-2018 8-56-27 AM.jpg

 

 

 

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