Geometry in LMS Test.Lab
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:
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.
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:
Users should be able to work through the minor-worksheets from left to right to create a geometry.
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.
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).
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.
It is also possible to move a component relative to a global coordinate system by using the X, Y, Z, XY, XZ, YZ fields.
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.
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.
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.
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.
Once all the desired lines are added, press “Accept Table” to save your changes.
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.
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.
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.
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.
Here is what the geometry looks like after using the first five 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.
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.
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.
The shape specified above will look as follows:
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.
To display a geometry, grab the entire geometry from the Navigator tree, and drop it into a geometry display.
Animating data on a geometry can make understanding the behavior much easier.
Questions? Contact us.