Slide 1GUI Familiarity Level Required: Advanced
Estimated Time Required: 40 minutes
MSC.ADAMS 2005 r2
Generate a .mnf file from Nastran
Import a .cmd file into ADAMS
Replace rigid body with a flexible body in ADAMS
Animate modes in ADAMS
Create FEMDATA with peak.load for Nastran in ADAMS
Set output in ADAMS
Process stresses using Patran
View Results in Patran
You will need to download “FEMDATA_starting_files.zip“ to begin this tutorial
If you have any difficulties, import the “FEMDATA_shortcut_1_files_exported_from_Nastran_1.zip” file and proceed from pg 6
If you have any difficulties, import the “FEMDATA_shortcut_2_files_exported_from_ADAMS.zip” file and proceed from pg 16
If you have any difficulties, import the “FEMDATA_shortcut_3_files_exported_from_Nastran_2.zip” file and proceed from pg 17
If you have any difficulties, import the “FEMDATA_complete_files_exported_from_Patran.zip” file and proceed from pg 19
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Problem Statement
This example demonstrates the output peak loads from an MSC.ADAMS simulation for a flexible component using FEMDATA. The loads are output in MD.Nastran input file format and solved for stresses. These stresses are viewed in MSC.Patran and compared with the modal stresses in MSC.ADAMS for the same component and simulation.
The syntax for the FEMDATA and OUTPUT statements are:
FEMDATA/1, LOAD, FLEX_BODY=1, PEAK=FX:FY:FZ, FILE=peak.loads
OUTPUT/LOAD = NASTRAN
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Model Description
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Start MSC.Nastran
Click Open
The Msc.Nastran Command Information dialog box will open
Enter scr=yes in Optional keywords text field
(This removes the bulky .MASTER and .DBALL database files after MSC.Nastran run has completed)
Click Run
(This Nastran run may take 5-10 minutes, depending on your computer resources. Upon successful completion, the run will produce an MNF names left_lca_0.mnf. If this file is not created, scan the left_lca.f06 file for FATAL errors.)
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To Import the Model into ADAMS/View
NOTE: the ATV model requires a huge memory setting to simulate in ADAMS/Solver (FORTRAN). Before starting your ADAMS/View session, make sure that your memory setting is set to Huge.
Start ADAMS/View.
Click OK
In the File To Read text field, enter ATV_4poster
Click OK
(There is no need to search for the model file, ATV_4poster.cmd, because the model is used in an ADAMS/Durability tutorial, it is part of the MSC.ADAMS installation (…/durability/examples/ATV); ADAMS/View knows how to locate it and all the .shl files it references.)
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Replace the rigid LCA with a flexible LCA
Select Build menu Flexible Bodies Rigid to Flex
In the Alignment tab, select the rigid part you want to replace and the model neutral file as follows:
Current part = RB2_left_lca_59
MNF file = left_lca_0.mnf
Note that the flexible body defined in the MNF is already correctly positioned
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Select the Connections tab.
The table displayed compares the connection points on the flexible body with those on the rigid body. Note that there are four bushings connecting the part to the model at these markers:
BUSHING_1 MARKER_1000052
BUSHING_2 MARKER_1000017
BUSHING_9 MARKER_1000052
BUSHING_11 MARKER_1000069
These four locations will be used later to generate peak loads for MSC.Nastran.
In the Distance column, you will notice that
there is a small offset for the four bushing
connection points. Keep the bushings at the
points where they were originally defined in
the rigid model.
Select Preserve Location button
replaced the rigid part. The flexible body
is connected to the frame, knuckle, and
damper the same way the rigid body connected.
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Zoom in on the left LCA in the front suspension
Right click the flexible LCA, select Flewiblw_Body: RB2_left_lca_59_flex Modify
Enter 7 in the Mode Number text field
Click Animation tool
(You can animate any of the 40 modes calculated by MSC.Nastran and imported from the .mnf. The first mode of interest is mode number 7, since modes 1-6 are rigid body modes and are automatically disabled)
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Modify the damping ration of the flexible link
In the Flexible Body Modify dialog box, clear the default checkbox next to Damping Ration
Enter the following function for the Damping Ration text field
STEP(FXFREQ,1000,0.005,10000,1)
This means:
Modes with a frequency below 1,000 Hz will have a 0.5% damping ratio
The damping ration will increase for modes in the range 1,000 – 10,000 Hz according to their frequency based on the STEP function.
Modes with a frequency above 10,000 Hz will be critically damped (100%)
Note that default damping would use a 10% damping ratio for mode 7, which is too much damping for a component made of steel.
Click OK
Select Loads On Flew Body from Type pull down menu
Enter RB2_left_lca_59_flex in Flex Body text field
Turn on FX, FY, and FZ checkboxes for Peak Slice
Enter peak.loads in file text field
Select OK to close the Create FEMDATA dialog box
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In the Solver Settings dialog box set:
Save Files: Yes
Graphics File: No
Request File: No
Results File: No
Select Durability Files from Output Category pull down menu
Select NASTRAN from Component Loads pull down menu
Select Close to close the Solver Settings dialog box
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Enter SIM_SCRIPT in Simulation Script Name text field
Turn on the Reset before and after checkbox
Turn off the Update graphics display checkbox
Click Play.
The simulation will take a few minutes to complete. Each post that the ATV is standing on will move up and down to simulate the vehicle running on rough terrain. You could have also done this using tire forces and a road profile.
A result of the FEMDATA definition is that a file named peak.loads is generated at the end of the simulation. This file contains the loads acting on the flexible LCA for each output step when each load reached a peak (maximum or minimum value -2 instances). These loads are defined using MSC.Nastran load cards, and each step that is output becomes a load case in MSC.Nastran. Because you specified 3 load components (FX, FY and FZ). And the flexible LCA has 4 load points, a total of 24(2*3*4) load cases are output. Confirm this be examining the load file in a text editor.
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Source: Objects
Filter: force
Object: BUSHING_9
Characteristic: Element_force
Component: Mag
Click Add Curves
Note that this is the force of the bushing connecting the LCA at MARKER_1000052 to the spring damper. Check the peak.loads file for consistency.
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Start MSC.Nastran
Click Open
In the MSC.NASTRAN Command Information dialog box, enter scr=yes in Optional keywords text field
Click Run
This Nastran run should take a few minutes depending on your computer resources. The run will create a file named left_lca_load.xdb. This file contains the displacements and stresses for each load case, and will be imported into MSC.Patran for postprocessing.
Note: You should scan left_lca_load.f06 for FATAL or WARN messages. You must resolve any issues before continuing.
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Start MSC.Patran
Create a new MSC.Patran database (.db file) by selecting File menu New
Enter WTSC_atv.db in File name text field
Click OK
Click Analysis main icon
Select Both from Method pull down menu
Click Select Results File button
Select File dialog box will appear
Browse directory, select left_lca_load.xdb file
Click OK
Click Apply
View Results in Patran
Click Results main icon
MSC.Patran displays a lit of 24 subcase that represents a time frame from MSC.ADAMS
Highlight all 24 subcase to see entire animation
(you can choose 1 subcase if you would like to see a select frame in time)
Click Stress Tensor from Select Fringe Result
Click Displacement, Translational from Select Deformation Result
Click Apply
Generate a .mnf file from Nastran
Import a .cmd file into ADAMS
Replace rigid body with a flexible body in ADAMS
Animate modes in ADAMS
Create FEMDATA with peak.load for Nastran in ADAMS
Set output in ADAMS
Process stresses using Patran
View Results in Patran
Check f06 files for warnings or errors.
Verify that when flexible body is imported it has the right orientation and location.
Verify all variables are set correctly.
Verify FEMDATA is created correctly.
Verify Nastran as output.
Make sure that the results are correctly set.
Verify that results are consistent.