Simcenter Testing Solutions Simcenter Testlab Geometry

Direct YouTube link: https://youtu.be/TC3IrO3icyc

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

Examples of data viewed with a geometric representation include:

• Operational deflection shapes
• Mode shapes
• Torsional vibration data
• Sound intensity

This article contains the following sections:
1. Getting Started
2.  Simcenter Testlab Geometry Worksheet
    2.1 Components
    2.2 Co-ordinate Systems
    2.3 Nodes
    2.4 Lines
    2.5 Surfaces
3.  Additional Features
    3.1 Mesh Generator
    3.2 Geometry Displays
    3.3 Mode Shape Expansion
 

1. Getting Started

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

Figure 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.

2.  Simcenter Testlab 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.

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

2.1 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 Simcenter Testlab 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.

Figure 3: Adding components to 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.

2.2 Co-ordinate Systems

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).

Figure 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.

Figure 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.

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

2.3 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.

Figure 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.

Figure 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.

2.4 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.

Figure 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.

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

2.5 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.

Figure 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.

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

Here is what the geometry looks like after using the minor-worksheets (Figure 12).

Figure 12: Geometry result after the minor-worksheets.

A typical geometry consists of components (in different colors), nodes, lines connecting the nodes, and surfaces.

3.  Additional Features

There are several other features available in Simcenter Testlab Geometry:

3.1 Mesh Generator

Simcenter Testlab includes a tool that can create nodes for simple geometry shapes.

In the main Simcenter Testlab menu, under “Tools” there is a Mesh Generator tool (Figure 13).

Figure 13: The Mesh Generator is located under “Tools” in the main Testlab 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 (Figure 14).

Figure 14: Select the type of shape.

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 (Figure 15).

Figure 15: Parameters of creating a cylinder in the Mesh Generator.

The shape specified above will look as follows (Figure 16):

Figure 16: Shape generated with the Mesh Generator.

In addition to the separate mesh generator tool, there is a special "acoustic" mesh generator which is useful for sound intensity measurements.  See the article: "Simcenter Testlab: Measuring Sound Intensity" for more information.

3.2 Geometry Displays

There are two default geometry displays (Figure 17) 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.

Figure 17: 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 (Figure 18).

Figure 18: 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.

The knowledge article "Simcenter Testlab: Geometry Displays" contains more information on using the geometry displays.

3.3 Mode Shape Expansion

It is also possible to import Computer Aided Drafting (CAD) models to use as the basis for animation in Simcenter Testlab as shown in Figure 19.

Figure 19: A CAD model used to animate test mode shapes.

To accomplish this, a stereolithography file (*.stl) is exported from a CAD system and imported into Simcenter Testlab.  The test mode shapes, which typically have fewer nodes than the CAD model, can be projected and animated on the full CAD model.  See the following articles:

• Import CAD Geometry into Simcenter Testlab Geometry
• Animate CAD Geometry: Simcenter Testlab Modal Analysis

Hope this article was helpful!

Questions? Email charles.rice@siemens.com or post a reply!

 

Modal Data Acquisition Links:

• Index of Testing Knowledge Articles
• History of Modal Analysis
• Modal Testing: A Guide
• Simcenter Testlab Impact Testing
• Modal Impact Testing: User Defined Impact Sequence
• What modal impact hammer tip should I use?
• Modal Tips: Roving hammer versus roving accelerometer
• Attach Modal Shaker at Stiff or Flexible Area of Stucture?
• Using Pseudo-Random for high quality FRF measurements
• Multi Input Multi Output MIMO Testing
• Ground Vibration Testing and Flutter
• Modal Testing Seminar

Modal Analysis and Operational Deflection Shapes Analysis Links:

• Natural Frequency and Resonance
• What is Frequency Response Function (FRF)?
• How to calculate damping from a FRF?
• Getting Started with Modal Curvefitting
• Modal Assurance Criterion
• Simcenter Testlab Modal Analysis: Modification Prediction
• Import CAD into Simcenter Testlab
• Animate CAD Geometry
• Alias Table: Mapping Test Data to Geometry
• Geometry in Simcenter Testlab
• Maximum Likelihood estimation of a Modal Model (MLMM)
• Difference Between Residues and Residuals?
• What is an Operational Deflection Shape (ODS)?
• What is an Operational Modal Analysis (OMA)?
• Simcenter Testlab: Geometry Displays
• Making a Video of a Time Animation
• Modal Analysis and FEA-Test Correlation Seminar
• Modal Analysis YouTube Playlist