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# Mechanical Event Simulation of a Snap-Fit Clip Assembly

In this brief tutorial, we show you an example of performing a Mechanical Event Simulation (MES) using Autodesk® Simulation Mechanical 360 and reviewing the analysis results. For a plastic snap-fit clip assembly, we will determine and graph the stress as a function of time throughout the analysis event as the two parts are pushed together. The model is a quarter-symmetry representation of the assembly, since the clip is symmetrical about two planes.

Before you begin, please watch this short video that demonstrates the steps of the tutorial:

Note: If the video does not load, click "F5" to refresh the screen.

To start, download the model archive (Clip-Quarter-Simple.ach) by clicking here. Save this file to a folder on your computer, and unzip the contents.

## Open the Model

1. Locate the file Clip-Quarter-Simple.ach using your Windows file browser and double-click the file to launch the Simulation Mechanical 360 software.
• You will be prompted to select the folder where you want the extracted model files to be located. The default location is the folder where the archive file resides.
• Click OK. The model appears in the FEA Editor environment and appears as shown in the following image.

The model has already been meshed and set up with the following material, constraints, contact pairs, and analysis parameters:

• Mesh size: 0.04 inch
• Material: Plastic - Polycarbonate (Molded), both parts
• Constraints:
• Prescribed displacement of 1.225 inches in the X-direction on Part 1 (indicated by purple arrows)
• Constrained against translation in the X-direction at flat rectangular surface on Part 2 (corresponds to location of prescribed displacement on Part 1)
• Y-symmetry constraints on surfaces lying along the XZ plane
• Z-symmetry constraints on surfaces lying along the XY plane
• General surface-to-surface contact: Defined between appropriate pairs of contact surfaces
• Event Duration: 1 second
• Number of time steps: 25

## Analyze the Model

We are now ready to analyze the model.
1. Click Analysis Analysis Run Simulation.
• The analysis will run and the model will be displayed within the Results environment while the solution is progressing. The analysis will likely take approximately 5 or 6 minutes to solve, plus the time to transmit the model to the cloud and the results from the cloud to your computer. Thus, the total time is dependent upon the speed on your Internet connection.
• You will be sent an email message notifying you that the analysis has completed (assuming you completed the instructions under Cloud Notification Setup on the Introduction page. This feature is useful for large or complex analyses that may complete while you are not at the analysis workstation.

## Reviewing the Results

As you can see, the displacement magnitude values appear by default in the Results environment. We will display the von Mises stress results and animate them. We will also graph the maximum von Mises stress versus time for the full simulation event.

1. Click Results Contours Stress von Mises.
2. Click Results Contours Load Case Options Load CaseMiddle to see the stresses at the middle of the event time. The model appears as pictured below.

NoteYou can also use the Next and Previous commands to progress through the various time steps.
3. Click Results Contours Captures Start. The results well be animated continuously until you stop it. By default, the legend range is automatically adjusted to the range of stresses that exist in the model for each individual time step. Therefore, nearly every frame will show a full range of colors, from blue to red.
• Click Results Contours Captures Stop to stop the animation.
4. Click Selection Select All to select all of the surface nodes in the model. Note that this command is within the pull-out section of the Select panel.
5. Right-click in the display area and choose the Edit New Graph command from the context menu.
• In the Edit Curve dialog box, choose the Maximum option from the Multiple Nodes drop-down box. Each data point on the resultant graph now indicates the maximum stress level at each time step. Therefore, different data points may represent different locations on the model.
• Click the red X () in the upper right corner of the Edit Curve dialog box to close it. The graph appears as pictured below.

## Next Steps

This completes the Snap-Fit Clip Assembly Quick-Start Tutorial! To explore the complete process of setting up and running an MES, we recommend that you start with the Piston CAD Model tutorial on the Autodesk Simulation Mechanical 2013 Wiki Help.

To go to Simulation TV to see more examples of Autodesk® Simulation products in action, click here.

To connect with other Autodesk® Simulation Mechanical users and experts in our Discussion Groups, click here.