Modal Stress Recovery Tutorial - Kxcad.net

Modal Stress Recovery Tutorial
Modal Stress Recovery Tutorial
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Overview
In this tutorial, you’ll learn to compute stresses on a crankshaft model.
The model contains one rigid body of the piston and two flexible bodies with modal stress shape
information from a NASTRAN analysis. A simulation will be performed of only the inertia effects of the
crankshaft starting at rest and ramping up to about 5000 RPM in 0.1 seconds. The goal is to determine
the maximum von Mises stress in the arm.
Stresses or strains can only be animated on flexible bodies that reference an MNF containing stress or
strain modes. For more information, see the Adams/Flex online help.
The tutorial includes the following sections:
• Importing the Model and Loading the Plugin
• Running an Analysis
• Viewing Flexible Body Stresses
• Plotting Nodal Stress
This tutorial takes about one hour to complete.

Importing the Model and Loading the Plugin
Here, you will import the crankshaft model and load the Adams/Durability plugin.
Modal Stress Recovery Tutorial
Note: On Windows, you may need to set the permissions to Full Control to modify the tutorial
files.
To import the model:
1. Copy the files from install_dir/durability/examples/engine to your working directory.
install_dir is the directory where your MD Adams software is installed. If you cannot locate this
directory, contact your system administrator.
2. Start Adams/View.
3. From the Welcome dialog box, select Import a file.
4. Select the Find Directory tool next to the Start in text box. Navigate to your working
directory, and then select OK.
5. In the File Import dialog box, set File Type to Adams/View Command File (*.cmd).
6. Right-click the File To Read text box, and then select Browse.
The Select File dialog box appears.
7. Select the file crankshaft.cmd.
8. In the Select File dialog box, select OK.
9. In the File Import dialog box, select OK.
The crankshaft model appears in the Adams/View main window.
To load Adams/Durability:
1. From the Tools menu, point to Plugin Manager.
2. In the Load column, select the Yes check box next to Adams/Durability.
3. Select OK.
This creates the Durability menu and adds various stress and strain Plot Type menu
options for Contours in Adams/PostProcessor. You will use these commands later in this
tutorial.
Note: To automatically load Adams/Durability each time Adams/View starts up, select the Load
at Startup checkbox.
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Running an Analysis
Here you will run an analysis on the crankshaft model. Note that in this tutorial, the shaft and arm (biele)
are defined as flexible bodies, and the piston as a rigid body.
Piston
To run an analysis:
1. Select the Simulation tool .
Shaft
2. Set up a simulation with an end time of 0.1 second and a step size of 0.001.
3. Select the Simulation Start tool .
The model simulates, and then remains in simulate mode.
Arm (biele)
4. To return to the initial model configuration, select the Reset tool .

Viewing Flexible Body Stresses
Here, you will view the stresses on the crankshaft.
To view the stresses on the crankshaft:
1. Open Adams/Postprocessor.
2. Switch to Animation mode.
3. Right-click in the blank animation window, and select Load Animation.
Adams/Postprocessor displays the model to be animated.
4. Select the Contour Plots tab.
5. From the Contour Plot Type pull-down menu, select Von Mises Stress.
Modal Stress Recovery Tutorial
Notice that a legend appears in the window, mapping contour colors to stress values. The default
maximum and minimum values of the legend correspond to those for the model displayed for the
time frames currently defined in the Animation tab. You can alter the appearance of the legend
using the parameters in the bottom of the window.
Because both the shaft and biele components contain stress, they are shaded blue indicating zero
stress state for the current (initial) frame.
6. To start the animation, select the Play tool.
The colors on the model map to the colors in the legend, indicating the level of stress at the
various points on the model. Note that during the animation, the arm and most of the shaft remain
blue due to highly localized stresses in the shaft. The default legend scale is not useful in this case.
7. Pause the animation by selecting the Pause tool.
8. Change the Maximum Value from about 545 to 200 MPa.
9. Play the animation again.
Adams/Postprocessor performs the animation, with stress appearing on both the shaft and biele.
Note that the color on the biele and shaft is adjusted (from the previous animation) so that the
scale is consistent on all parts in the display.
10. Reset your animation.
Now you will animate one component of your model.
To isolate the stresses on the arm (biele):
1. Select the Animation tab.
2. In the Component text box, specify the biele flexible body.
3. In the treeview, select the biele component.
4. In the property editor for the biele, in the Flex Props tab, set the (deformation) Scale to 200.
5. Restart the animation.
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Notice that the arm no longer animates in the system. Instead, the display isolates the arm. Also
note that the stress contours exhibit mostly a bending stress state in the arm: blue representing zero
stress in the middle of the arm and red representing high stress along its edges. This is consistent
with the arm’s deformation. Typically, a piston arm inside an engine primarily undergoes axial
(compression) stress due to combustion forces. But these forces are not simulated in this model.
Only the effects of inertia are being simulated.
6. Stop the animation.

Plotting Nodal Stress
Here you will generate a plot of the stress at a particular node over time.
To plot nodal stress:
1. In Adams/Durability, from the Durability menu, select Nodal Plots.
2. Set Analysis to Last_Run.
3. Set Flexible Body to Biele.
4. In the Select Node List text box, enter 768.
5. Select OK to close the Compute Nodal Plot Components window.
Modal Stress Recovery Tutorial
A new result set named biele_STRESS will be generated for the nodal stress component.
6. Open the Adams/PostProcessor window.
7. Right-click the Page Layout tool and select the Page Layout:2 Views, over & Under tool
.
This splits the Adams/PostProcessor window into two.
8. Right-click in the blank animation window, and then select Load Plot.
9. Set Source to Results Sets.
10. Set Result Set to biele_STRESS.
11. Select the node_768_VON_MISES component.
12. Select Add Curves.
An X-Y plot of nodal stress is displayed. Note that a maximum value of approximately 91 MPa
occurs at time 0.094 seconds.
Note: If you plan to go on to the next tutorial, save the results (database) from this tutorial, or
remain in Adams/View (don’t exit).
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