fsae flex body tutorial (msc adams)

MSC Software Confidential

FSAE Flex Body TutorialReplacing a Solid Upright with a Flexible Upright

Presented By: Reed Sullivan

April 8, 2023

MSC Software Confidential 2

• We will simulate the stress in an upright during a braking event using the Formula SAE demo car shown below (view slideshow to watch animation).

What We Will Simulate

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• We will use ViewFlex in Adams/View to generate a Modal Neutral File (MNF) and import it to our subassembly in Adams/Car.– Open Adams/View.– Select New Model.– Name the model flexible_upright.– Select File -> Import.– Fill out the box as shown. (your upright parasolid file may be in a different

location)– Select OK.– Rename the upright part from

PART_2 to upright.

Creating the Flexible Body

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• We now need to create all of the attachment points as joints in order for ViewFlex to generate an MNF.– Change your working grid to the XZ plane by selecting Settings ->

Working Grid… and setting the orientation to the Global XZ plane.– Create fixed joints between upright and ground at:

• 0,0,0• 0,0,115• 0,0,-115• 85,0,-72.6

*MUST BE IN THAT ORDER FOR FUTURE STEPS– To input joints at specified locations, right click anywhere on the screen

and the following dialog box will appear.


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• Now we must make the upright geometry flexible.– Right click on the upright and select Part:upright -> Make Flexible.– Select Create New.– Change the material to aluminum by right clicking the box and selecting

Materials -> Guesses -> Aluminum.– Check the advanced

settings box.– Fill in the box as shown

below and select

Mesh preview:


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• We must now determine how we will distribute loads from each of the attachment points.– Select the Attachments button.– Now select Find Attachments.– For Coordinate Reference 1:

• Make Selection Type = Closest Nodes• Make Attachment Method = Compliant(RBE3)• Make Number of nodes = 40• Select Transfer IDs


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– For Coordinate Reference 2:• Make Selection Type = Cylindrical• Make Attachment Method = Rigid(RBE2)• Make Radius = 5mm• Make End Location = 0,0,90• Select Symmetric• Select Transfer IDs

– For Coordinate Reference 3:• Make Selection Type = Cylindrical• Make Attachment Method = Rigid(RBE2)• Make Radius = 5mm• Make End Location = 0,0,-90• Select Symmetric• Select Transfer IDs


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– For Coordinate Reference 4:• Make Selection Type = Cylindrical• Make Attachment Method = Rigid(RBE2)• Make Radius = 5mm• Make End Location = 96.26,0,-74.93• Select Symmetric• Select Transfer IDs

• Select Flexbody preview to make

sure everything looks as expected.

• If everything looks as it does on the

right, select OK


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• In your working directory, there is now a file named upright_0.mnf.

• In this unique case where the upright part is symmetric (about its own mid-plane), we will use the same mnf file for the right and left side. Therefore, we need a copy.

• Copy and paste the mnf file into the same directory so you now have a upright_0 – Copy in your directory and rename it upright_0_2.mnf

Accessing the MNF File

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• Open Adams/Car

• If you do not have the FSAE database downloaded, please download it from this link.

• To be able to use the database, follow the directions to add your database to the session in the technical article linked above.

• Set the FSAE database as your default writable database by selecting Tools -> Database Management -> Select Default Writable… and select the FSAE database.

Loading the FSAE Database

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• Please copy and paste the templates _fsae_frontsusp_flex.tpl and _fsae_frontsusp_noflex.tpl to the templates.tbl folder in the FSAE database.

• Please copy and paste the subsystems fsae_front_susp_flex.sub and fsae_front_susp_noflex.sub to the subsystems.tbl folder in the FSAE database.

• These files have been created to adapt the FSAE front suspension to accommodate the upright design.

Importing the Tutorial Files

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• Open the subsystem fsae_front_susp_flex.sub.

• After making sure all of the icons are showing, right click near the left hub and select General Part: gel_upright -> Modify.

• In the dialog box, select Rigid to Flex.

• Fill out the box as shown:

Using the MNF File

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• Now select Launch Precision Move Panel.

• Fill the box out as follows to bring the part from 0,0,0 to the bearing center hardpoint:

• Select OK on the open dialog boxes and your upright should be in place.

Using the MNF File

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• Now do the same for the right upright but using the upright_0_2.mnf file and making C2=700.

Using the MNF File

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• We now need to create two suspension assemblies, one with the flexible uprights and one without the flexible uprights.

• Select File -> New -> Full-Vehicle Assembly… and create the following assemblies:

Comparing Flex vs. No Flex

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• We will now look at the effect of flexible uprights on a harsh braking event, where the driver will apply enough force for a 1.1g decel in .01 seconds.

• Select Simulate -> Full-Vehicle Analysis -> Straight-Line Events -> Braking… and run the two events shown below:


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• Switch to the Post-Processor by pressing F8.

• Highlight both simulations we performed and plot chassis_accelerations -> longitudinal.


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• Notice how the flexible-body simulation has a peak that does not exist in the simulation with a rigid body. This is due to a front wheel lock-up that only occurs in the flexible-body simulation. When the wheel re-gains traction, there is an acceleration spike. See below:

• Go through other results sets and see what else is different between the flexible upright simulation vs. the rigid upright simulation.


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• Select View -> Load Animation.

• Now select flex -> flex_brake.

• We need to load the Adams/Durability Plugin to analyze stress by selecting Tools -> Plugin Manager…

• Select Yes under Load for Adams/Durability and select OK.

Analyzing Stress in the Flexible Upright

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• Select the Camera tab.

• Right-click in the Follow Object box and select Flexible_Body -> Guesses -> ger_upright_flex.

• Press Shift+S to view the animation in wireframe view and zoom in on the right upright.

• Select the Contour Plots tab.

• Set Contour Plot Type to Von Mises Stress.

• You can now watch the stress plot as the model runs.

• You can see the animation in the flex_braking_event.avi file attached to the example page.


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• To plot stress of the node that sees the highest stress, go to the Hot Spots tab.

• Select Display Hotspots and Node ID.

• Notice that it says Node=22256 which is the node ID.

• Now select Durability -> Nodal Plots…

• Fill out the box as shown below:


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• To plot the stress in this node, select View -> Load Plot

• Select Source -> Result Sets and type *flex* in filter.

• Plot the option shown below:


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fsae flex body tutorial (msc adams)

Documents

msc software

fsae database

select file

body simulation

mnf file

flexible body

flexible uprights

attachment