getting started using adams/durability - md adams 2010

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Getting Started Using Adams/Durability• Learning Adams/Durability Tutorial

• Modal Stress Recovery Tutorial

• nCode FE-FATIGUE Tutorial

• MSC.Fatigue Tutorial

Getting Started Using Adams/Durability2

Learning Adams/Durability Tutorial

3Learning Adams/Durability TutorialOverview

OverviewThis chapter guides you through a tutorial that teaches you how to use Adams/Durability with Adams/View.

We assume that you will work through this tutorial in sequential order. Therefore, we give you more guidance in the beginning and less as you proceed through the tutorial. If you choose not to work through the tutorial in sequential order, you may have to reference the beginning sections for some of the basic concepts.

This chapter contains the following sections:

• What You Will Create and Simulate

• Starting Adams/View and Creating a Database

• Applying a Rotational Joint Motion

• Applying a Translational Joint Motion

• Setting Up Requests

• Comparing Physical Test Data with Virtual Test Data

• Conclusion

This tutorial takes about one hour to complete.

Note: Before doing this tutorial you should be familiar with the basic features of the Adams/View interface. For information about the Adams/View interface, refer to the online help for Adams/View.

Getting Started Using Adams/DurabilityAbout Adams/Durability

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About Adams/DurabilityAdams/Durability extends the traditional test-based durability design process into the virtual world. Using Adams/Durability, you can read and write time history information of loads, forces, and accelerations in the following traditional formats:

• nCode’s DAC

• MTS Systems Corporation’s RPC® (Remote Parameter Control) III

Adams/Durability interfaces with measured load histories, such as vehicle spindle loads, and communicates with durability analysis programs such as nSoft, FE-Fatigue, and with durability test machines. With Adams/Durability, you can also examine stresses, strains, damage, or fatigue life on flexible components of your virtual system.

5Learning Adams/Durability TutorialWhat You Will Create and Simulate

What You Will Create and SimulateIn this tutorial, you validate an Adams kinematic model of an automotive quarter suspension against a physical model, to verify if the Adams model response to imported physical test data matches the physical model response to the same data.

You will use Adams/Durability to perform a load cycle on an Adams suspension model using physical test data in RPC III format. You will write out response time histories in DAC format and compare this response to output data from a test lab.

You will use an existing Adams model of a quarter vehicle suspension, which we developed using CAD data, and go through the steps shown next:

• First, you will define two joint motions that reference spline data and vary over time and cause displacement at the spindle.

• Next, you will instrument the model to monitor the resulting displacement.

• After that, you will simulate the model and output the data in DAC format.

• Finally, you will compare the virtual test data (in DAC format) with physical test data (in RPC III format), from a physical model. The physical test data represents 10 seconds of motion data sampled at a rate of 51.2 points per second in a test lab.

Figure 1 shows the suspension model.

Figure 1 Adams Model of Suspension

Upper_Arm

Strut_Top

Rack

Lower_Arm

Wheel

Knuckle

Tie_Rod

Body

Getting Started Using Adams/DurabilityStarting Adams/View and Creating a Database

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Starting Adams/View and Creating a DatabaseYou’ll start by running Adams/View and importing a model called suspension.

To start Adams and create your database:

1. Do either of the following depending on the platform on which you are running Adams/View:

• In UNIX, type the command to start the Adams Toolbar at the command prompt, and then press Enter. Select the Adams/View tool .

• In Windows, from the Start menu, point to Programs, point to MSC.Software, point to MD Adams 2010, point to AView, and then select Adams - View.

The Welcome dialog box appears in the Adams/View main window.

2. Select Import a file.

3. Select the Find Directory tool next to the Start in text box. This displays the Find Directory dialog box.

4. Navigate to a drive and directory that you want to use as your working directory. If you need to create a new directory, select the Create New Folder button, and enter a directory name.

5. Select the directory, and select OK.

This ensures that all your work gets stored in the working directory you selected.

6. Select OK.

The File Import dialog box appears.

7. Set File Type to Adams/View Command File (*.cmd).

8. Right-click the File To Read text box, and select Browse.

The Select File dialog box appears.

9. Navigate to the directory install_dir/durability/examples, and select the directory suspension.

install_dir is the directory where the Adams software is installed. If you cannot locate this directory, please contact your system administrator.

Note: On Windows, you may need to set the permissions to Full Control to modify the tutorial files.

Note: The Start in text box specifies the working directory that Adams/View uses as the default directory for reading and writing files.

Note: Navigating to a directory makes this new directory the default for file selection. Adams/View reads all files associated with the model from this new directory, but does not change the working directory for saving and writing files.

7Learning Adams/Durability TutorialStarting Adams/View and Creating a Database

10. Select the file suspension.cmd.

11. In the Select File dialog box, select Open.

12. In the File Import dialog box, select OK.

The suspension model appears in the Adams/View main window.

Getting Started Using Adams/DurabilityApplying a Rotational Joint Motion

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Applying a Rotational Joint MotionIn this section, you’ll apply a rotational joint motion to the Upper_Arm that references a spline function. You will apply the motion using the INTERP function. The INTERP function returns either a derivative of a test data curve or an interpolated value from a test data curve. You supply the test data curve using a SPLINE statement that references a RPC III file.

You will apply the motion as shown next:

• Creating a Spline

• Defining a Rotational Joint Motion

Creating a SplineIn this section, you’ll create a spline to reference the RPC III file and channel arguments from a test performed on a physical model in a test lab. You use the RPC III file physical_test.rsp, and reference data in channel 1.

To create a spline:

1. From the Build menu, point to Data Elements, point to Spline, and then select General.

9Learning Adams/Durability TutorialApplying a Rotational Joint Motion

The Data Element Create Spline dialog box appears, as shown next.

2. In the Spline Name text box, enter .suspension.jounce_data.

3. Right-click the File Name text box, and then select Browse.

The Select File dialog box appears with the current directory showing the files in the directory you last selected (install_dir/durability/examples/suspension).

4. Select the file physical_test.rsp.

This file contains physical test data from a test performed on a physical model in a test lab.

5. Select OK.

6. In the Channel text box, enter 1.

7. Select OK.

Adams/View creates a spline that references the physical test data from channel 1 of the RPC III file, physical_test.rsp.

Defining a Rotational Joint MotionNow you’ll apply a rotational joint motion to the Upper_Arm revolute joint, using the INTERP function to reference the spline you created in the previous section.

Getting Started Using Adams/DurabilityApplying a Rotational Joint Motion

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For more information on the INTERP function, refer to the Adams/Solver online help.

To define a rotational joint motion:

1. From the Motion tool stack in the Main Toolbox, select the Rotational Joint Motion tool .

2. Select Upper_REV as the rotational joint.

Adams/View creates a rotational joint motion. Next, you will rename the joint motion so that you can easily identify it.

To rename the rotational joint motion:

1. In your model, right-click the rotational joint motion icon, point to Motion:MOTION_2, and then select Rename.

The Rename Object dialog box appears.

2. In the New Name text box, enter jounce_input.

3. Select OK.

By default, Adams/View creates a constant-speed rotational joint motion. You want the rotational joint motion to vary over time, based on the referenced spline. Therefore, next, you will modify the rotational joint motion so that it varies over time.

To modify the rotational joint motion:

1. In your model, right-click the rotational joint motion icon, point to Motion:jounce_input, and then select Modify.

11Learning Adams/Durability TutorialApplying a Rotational Joint Motion

The Impose Joint Motion dialog box shown next appears.

2. In the Function (time) text box, enter the following function:

3. INTERP(time, 3, jounce_data)*DTOR

where:

• time is the independent variable that specifies what you are interpolating

• 3 is the method of interpolation, which indicates cubic interpolation between data points. 1, which indicates linear interpolation, is also a valid entry.

• jounce_data is the name of the referenced spline

• DTOR is the angle conversion factor from degrees to radians.

4. Select OK.

Note: If you enter the function incorrectly, you receive an error when you select OK. Check your function syntax carefully.

Getting Started Using Adams/DurabilityApplying a Translational Joint Motion

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Applying a Translational Joint MotionIn this section, you’ll apply a translational joint motion to the Rack translational joint. You will apply the motion using the INTERP function, as follows:

• Creating a Spline

• Defining a Translational Joint Motion

• Simulating Your Model

Creating a SplineIn this section, you’ll create a spline statement to reference the file and channel arguments from a test performed on a physical model in a test lab. You use the same RPC III file, physical_test.rsp, but you reference data in channel 2.

To create a spline:

1. From the Build menu, point to Data Elements, point to Spline, and then select General.

The Data Element Create Spline dialog box appears.

2. In the Spline Name text box, enter .suspension.steer_data.

3. Right-click the FIle Name text box, select Browse.


4. Select the file physical_test.rsp.

This file contains physical test data from a test performed on a physical model in a test lab.

5. In the Channel text box, enter 2.

6. Select OK.

Adams/View creates a spline that references the physical test data from channel 2 in the RPC III file, physical_test.rsp.

Defining a Translational Joint MotionNow you’ll apply a translational joint motion to the Rack translational joint, using the INTERP function to reference the spline you created in the previous section.

To define a translational joint motion:

1. From the Motion tool stack in the Main Toolbox, select the Translational Joint Motion tool .

2. Select Rack_Joint as the translational joint.

Adams/View creates a translational joint motion. Next, you will rename the joint motion so that you can easily identify it.

13Learning Adams/Durability TutorialApplying a Translational Joint Motion

To rename the translational joint motion:

1. In your model, right-click the translational joint motion icon, point to Motion:MOTION_3, and then select Rename.

The Rename Object dialog box appears.

2. In the New Name text box, enter steer_input.

3. Select OK.

By default, Adams/View creates a constant-speed translational joint motion. You want the translational joint motion to vary over time, based on the referenced spline. Therefore, the next step is to modify the translational joint motion so that it varies over time.

To modify the translational joint motion:

1. In your model, right-click the translational joint motion icon, point to Motion:steer_input, and then select Modify.

The Joint Motion dialog box appears.

2. In the Function (time) text box, select the Function Builder tool .

The Adams/View Function Builder displays.

3. Delete the existing expression.

4. From the pull-down list of expression types, select Spline.

5. Select Durability Interpolation.

6. Select Assist.

The Interpolation dialog box displays.

7. Enter the following:

• Independent variable: time

• Interpolation Method: Cubic (3)

• Spline Name: steer_data

8. From the Interpolation dialog box, select OK.

9. From the Function Builder, select OK.

10. From the Joint Motion dialog box, select OK.

Simulating Your ModelNow you will simulate the model to verify that it runs.

Note: If you enter the function incorrectly, you receive an error when you select OK. Check your function syntax carefully.

Getting Started Using Adams/DurabilityApplying a Translational Joint Motion

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To simulate your model:

1. Select the Simulation tool .

2. Set up a simulation with an end time of 5 second and 50 output steps.

3. Select the Simulation Start tool .

The model simulates and completes a jounce-rebound followed by a right-hand turn maneuver, and then remains in simulate mode.

4. To return to the initial model configuration, select the Reset tool .

Note: If your simulation fails, check your spline definitions and motion function expressions. For example, make sure that you are referencing channel 2, the spline definition for steer_data.

15Learning Adams/Durability TutorialSetting Up Requests

Setting Up RequestsIn this section, you will set up a virtual instrument to monitor the displacement at the spindle_center as follows:

• Creating a New Request

• Setting Up Adams Results in DAC Format

• Simulating the Model

Creating a New RequestYou’ll create a new request that behaves like an instrument to measure and output the displacement at the spindle_center.

To create a new request:

1. From the Build menu, point to Measure, point to REQUEST, and then select New.

Getting Started Using Adams/DurabilitySetting Up Requests

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The Create a Request dialog box shown next appears.

2. In the Request Name text box, enter instrument.

3. Set Output Type to displacement.

4. Right-click the I Marker Name text box, point to Triad, and then select Browse.

The Database Navigator appears.

5. Under Knuckle, select Spindle_Center, and then select OK.

6. Right-click the J Marker Name text box, point to Triad, and then select Browse.

The Database Navigator appears.

7. Under ground, select Spindle_Ref.


8. From the Database Navigator, select OK.

9. Select OK.

Setting Up Adams Results in DAC FormatBy default, when you simulate the model, Adams/View generates results in Adams format. However, you cannot use results in Adams format in physical testing machines. Therefore, you want the results of your simulation in standard RPC III or DAC format.

In this tutorial, you will set up Adams/Durability to generate results in DAC format. For information on generating results in RPC III format, refer to the Using Durability tab in the Adams/Durability online help.

To set up Adams results in DAC format:

1. From the Settings menu, point to Solver, and then select Output.

The Solver Settings dialog box appears.

2. Set Save Files to Yes.

3. In the File Prefix text box, enter suspension.

4. Set all of the file options to No.

5. Select More.

Additional text boxes appear.

6. Set Output Category to Durability Files.

The Durability Files container appears.

7. Set DAC Files to On.

8. Use the defaults for all other text boxes.

Getting Started Using Adams/DurabilitySetting Up Requests

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9. Your dialog box should look like the following:

10. Select Close to close the Solver Settings dialog box.

Simulating the ModelNow you will simulate the model to generate results in DAC format.

To simulate your model:

1. Set up and run a simulation with an end time of 10 seconds and 512 output steps.

This matches the sampled rate of the physical test data that you will use later in the tutorial to validate the results of this simulation.


As the simulation proceeds, Adams/Durability outputs requests in DAC format.

2. After the simulation completes, reset the model.

Adams/View can only store one channel of data in a DAC file. Therefore, in this simulation, Adams/View creates six DAC files, one per request component. The files are named according to the DAC file naming convention shown next:

prefix_request name_component label.dac where:

• prefix is the prefix you specified when you set up the Adams results in the Simulation Settings dialog box. In this case, it is suspension.

• request name is the request name you specified when you created a new request in the Create a Request dialog box. In this case, it is instrument.

• component label is the reserved label assigned to the six components of request data by Adams (one of X, Y, Z, R1, R2, R3).

Therefore, the files will be named: suspension_instrument_X.dac, suspension_instrument_Y.dac, and so on.

Note: You will receive several warning messages (spline out of range and required extrapolation). You can ignore these messages.

Note: If you don’t reset the model, then all the simulation results will not be entered into the DAC files. Adams/View stores DAC files in the current working directory.

Getting Started Using Adams/DurabilityComparing Physical Test Data with Virtual Test Data

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Comparing Physical Test Data with Virtual Test DataIn this section, you will compare physical test data from a physical model with the virtual test data you generated in this tutorial.

• Importing Physical Test Data

• Importing Virtual Test Data

• Plotting Data

Importing Physical Test DataThis section describes how to import physical test data from tests performed on a physical model in a test lab. The test data represents 10 seconds of motion data sampled at a rate of 51.2 points per second. This data is in RPC III format. There are the following five channels of data in the RPC III file:

• Upper control arm actuator drives data that controls jounce and rebound in the suspension.

• Rack and pinion actuator drives data that controls steer.

• Translational response of the spindle center measured in the global x-direction.

• Translational response of the spindle center measured in the global y-direction.

• Translational response of the spindle center measured in the global z-direction.

To import physical test data:

1. Open Adams/PostProcessor.

2. From the File menu, point to Import, and then select RPC File.


3. Right-click the File to Read text box, and then select Browse.


4. Select physical_test.rsp, and then select OK.

5. Select OK.

6. In the RPC III File list, select physical_test.

7. Select the Surf check box.

8. From the Channel list, select Measure_Spindle_1, Measure_Spindle_2, and Measure_Spindle_3, and look at the plots.

21Learning Adams/Durability TutorialComparing Physical Test Data with Virtual Test Data

Importing Virtual Test DataHere you import virtual test data from the simulation you performed in the previous section.

To import virtual test data:

1. In the Adams/PostProcessor File menu, point to Import, and then select DAC Files.


2. Right-click the Files to Read text box, and then select Browse.


3. Navigate to the working directory that you specified at the start of the tutorial (see Step 4 ).

4. Select suspension_instrument_x.dac, and then press the Shift key and select suspension_instrument_z.dac to select all three files.

5. Select Open.

Adams/PostProcessor enters the file names in the Files to Read text box.

6. In the DAC Object Name text box, enter instrument.

7. Select OK.

8. Set Source to DAC.

9. From the DAC list, select Instrument.

10. Select Surf.

11. From the File Data list, select REQUEST_1_X, REQUEST_1_Y, and REQUEST_1_Z, and look at the plots.

Plotting DataFinally, you will compare the virtual test data from your suspension model with physical test data from the physical model of a suspension.

To plot data:

1. Set Source to RPC III.

2. Clear selection of Surf.

3. Select Clear Plot.

Note: Virtual test data is stored in DAC or RPC III files and not in the modeling database. However, the DAC and the RPCIII file objects are stored in the database and they reference the virtual test data stored in the DAC and RPC III files.

Note: This becomes the default directory for any further file selections.

Getting Started Using Adams/DurabilityComparing Physical Test Data with Virtual Test Data

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4. From the RPC III File list, select physical_test.

5. From the Channel list, select Measure_Spindle_1.

6. Select Add Curves.

7. Set Source to DAC.

8. From the DAC list, select instrument.

9. From the File Data list, select REQUEST_1_X.


By default, Adams/PostProcessor gives a slightly different scale for the two vertical axes. You need to manually adjust one of them.

11. Select the right vertical axis.

12. Clear the selection of Auto Scale.

13. Change the limits to match the other (left) vertical axis (that is, -75 to 0).

14. Compare the two plots.

15. Similarly, compare:

• Measure_Spindle_2 (RPCIII source) with REQUEST_1_Y (DAC source)

• Measure_Spindle_3 (RPCIII source) with REQUEST_1_Z (DAC source)

The virtual test results and the physical test results should be almost exactly the same, indicating that there is no phase shift, and that the displacement peaks are captured. There is a minor amplitude shift, however, due to possible joint relaxation in the physical test.

Note: Since a vibration of about 10-20 Hz was not damped out in the physical test, you will notice noise in the physical test data plots. The noise is most prevalent on the Measure_Spindle_1 and Measure_Spindle_2 plots.

23Learning Adams/Durability TutorialConclusion

ConclusionThis tutorial shows that despite minor differences, there is a good correlation between the physical test data and the virtual test data from Adams/Durability. It also shows that the Adams model’s response to imported physical test data matches the physical model’s response to the same data, and that the virtual prototype is kinematically consistent with the physical prototype.

Getting Started Using Adams/DurabilityConclusion

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1Modal Stress Recovery Tutorial

Modal Stress Recovery Tutorial

Getting Started Using Adams/DurabilityOverview

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OverviewIn 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


3Modal Stress Recovery TutorialImporting the Model and Loading the Plugin

Importing the Model and Loading the PluginHere, you will import the crankshaft model and load the Adams/Durability plugin.

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 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.


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: On Windows, you may need to set the permissions to Full Control to modify the tutorial files.

Note: To automatically load Adams/Durability each time Adams/View starts up, select the Load at Startup checkbox.

Getting Started Using Adams/DurabilityRunning an Analysis

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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.

To run an analysis:

1. Select the Simulation tool .

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.

4. To return to the initial model configuration, select the Reset tool .

Arm (biele)

Shaft

Piston

5Modal Stress Recovery TutorialViewing Flexible Body Stresses

Viewing Flexible Body StressesHere, 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.

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.

Getting Started Using Adams/DurabilityViewing Flexible Body Stresses

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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.

7Modal Stress Recovery TutorialPlotting Nodal Stress

Plotting Nodal StressHere 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.

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.


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).

Getting Started Using Adams/DurabilityPlotting Nodal Stress

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1nCode FE-FATIGUE Tutorial

nCode FE-FATIGUE Tutorial


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OverviewIn this tutorial, you’ll learn about modal stress recovery for fatigue life prediction (FLP) in the nCode environment.

This chapter will not discuss the entire functionality of nCode, only those features that specifically apply to this tutorial. For more detailed information on nCode, refer to your nCode documentation.

The following sections are included:

• Getting Started

• Exporting for nCode

• Starting nCode and Setting the Working Directory

• Specifying the FE-Fatigue Options

• Viewing FatFE - Material Input

• Analyzing Current Job

• Viewing nCode FATIGUE Results in Adams


3nCode FE-FATIGUE TutorialGetting Started

Getting StartedBefore starting this tutorial, you must complete the procedures in Importing the Model and Loading the Plugin and Running an Analysis.

Getting Started Using Adams/DurabilityExporting for nCode

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Exporting for nCodeYou can generate a partial FES file (nCode file format) suitable for FLP analysis when stress or strain blocks are present in the MNF. You can also export modal coordinates for subsequent FE-Fatigue damage analysis using modal superposition.

To export for nCode:

1. From the Durability menu, point to FE-Fatigue, and then select Export.

The FE-Fatigue Export dialog box displays.

2. In the Flexible Body text box, enter shaft.

3. In the Job Name text box, enter shaft-skin.

4. Select Modal Coordinates and complete the following:

• Analysis: Last_Run

• Basis: Orthonormalized

• Format: DAC

5. Select FES File and complete the following:

• Set Format to Binary.

• Select Stress.

• Select All Nodes.

6. Select OK.

The following files are created and will be used as input for an FE-Fatigue analysis:

• shaft-skin.fes (binary partial FES file)

• shaft-skin.laf (loads association file)

• shaft-skin_n.dac (modal coordinate time history for mode n, where n goes from 1 to 28)

5nCode FE-FATIGUE TutorialStarting nCode and Setting the Working Directory

Starting nCode and Setting the Working DirectoryThe working directory for this tutorial cannot have any blank spaces in the path. For example, you can’t use c:\Program Files\Adams\working. You will encounter error messages later in this tutorial if your working directory path contains spaces. If your FES, DAC, and LAF files from the last tutorial are located in a path containing blanks, move them to a different location before you continue.

To start nCode and set your working directory:

1. Start nCode.

2. Select Set Directory.

3. Set your working directory to the one where the FES, DAC, and LAF files you generated in the previous section are located.

Your screen should now look like the following:.

Note: If you don’t have nCode but want to try displaying fatigue results, use the sample universal files Biele.unv and Shaft.unv provided in the directory, /install_dir/durability/examples/engine. Skip the following procedures and start in the section, Viewing nCode FATIGUE Results in Adams using these sample universal files.

Getting Started Using Adams/DurabilityStarting nCode and Setting the Working Directory

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7nCode FE-FATIGUE TutorialSpecifying the FE-Fatigue Options

Specifying the FE-Fatigue OptionsIn this section, you will be:

• Creating the FATFE-Fatigue Jobname Entry

• Setting the FatFE - Loadcase Input

Creating the FATFE-Fatigue Jobname Entry

To create the FatFE-Fatigue jobname entry:

1. From the nSoft Menu dialog box, select the FE-Fatigue tab.

2. Select the fatfe tool.

3. Enter shaft-skin as the input fatigue filename.

4. Select OK.

The FATFE - Partial to Full FES Completion dialog box appears.

5. Complete the dialog box as shown below:

6. Select OK.

Getting Started Using Adams/DurabilitySpecifying the FE-Fatigue Options

8

7. Complete the Advanced Options dialog box as shown below:

8. Select OK.

Next, nCode will search for a load association file for this job (shaft-skin.laf). It is an ASCII file relating to each unit load (stress) case in the FES file to a DAC file of the load time history.

If this Adams/Durability-generates file exists, the following message window appears:

9. Select Yes to continue.

The FATFE - Partial to Full FES Completion - Loading Input dialog box displays.

Setting the FatFE - Loadcase Input

To set the FatFe load case input:

1. In the FATFE - Partial to Full FES Completion - Loading Input dialog box, double-click on a load case.

The time history appears.

Note: If you encounter error messages here, you may need to check the path of your working directory. Refer to Starting nCode and Setting the Working Directory.

9nCode FE-FATIGUE TutorialSpecifying the FE-Fatigue Options

2. Select OK to return to the full list of load cases.

3. Select OK.

4. If you do not have a local materials database for FE-Fatigue, nCode warns you that a copy of the central database will be made to the local area. Select OK to continue.

The FATFE - Partial to Full FES Completion - Material Input dialog box appears.

Getting Started Using Adams/DurabilityViewing FatFE - Material Input

10

Viewing FatFE - Material Input

To view the FatFE material input:

1. In the FATFE - Partial to Full FES Completion - Material Input dialog box, double-click Group 1.

2. Complete the rest of the dialog box as shown below:

3. Select OK.

11nCode FE-FATIGUE TutorialViewing FatFE - Material Input

The Material Input dialog box appears as shown below:

4. Select OK.

A message window appears asking if you want to begin the analysis.

5. Select Yes.

The Analysis Form dialog box appears.

Getting Started Using Adams/DurabilityAnalyzing Current Job

12

Analyzing Current JobYou are now ready to perform a fatigue analysis.

Starting Analysis

To analyze the current job:

1. Complete the Analysis Form dialog box as shown below:

2. Select OK.

The Results Filename Entry dialog box appears.

13nCode FE-FATIGUE TutorialAnalyzing Current Job

3. Complete the Results Filename Entry dialog box as shown below:

4. Select OK.

As the analysis runs, a dialog box displays the progress.

Viewing Global Results After the Fatigue Analysis finishes, you can view the results showing the most damaged nodes.

• After reviewing the results, select OK.

Getting Started Using Adams/DurabilityViewing nCode FATIGUE Results in Adams

14

Viewing nCode FATIGUE Results in AdamsHere you will learn to import and view your FE-Fatigue results.

To import your FE-Fatigue results:

1. From the Durability menu, point to FE-Fatigue, and then select Import.

The FE-Fatigue Import Universal Results File dialog box appears.

2. Right-click the File Name text box, and then select Browse.

3. Select the name of the .unv file in which your nCode FE-Fatigue results were saved.

This will be SHAFT-SKIN.UNV if you ran your own FE-Fatigue analysis, or Shaft.unv if you are using the sample results file.

4. Select OK.

5. In the Flexible Body text box, select shaft.

6. In the Analysis text box, select Last_Run.

7. Select OK.

Once you’ve imported a universal file from FE-Fatigue, Adams/Durability adds more Plot Type options (under Contours) to Adams/PostProcessor. These options are used for postprocessing nCode results.

To view your FE-Fatigue results on the shaft:

1. Open Adams/Postprocessor.

2. Right-click in the Adams/Postprocessor window, and then select Load Animation.

The model to be animated is displayed in the window.

3. In the treeview, select the shaft component of the crankshaft model.

4. In the property editor, set Plot Type to Contour.


6. From the Contour Plot Type pull-down menu, select Damage.

Notice that a legend appears in the window.

7. Start the animation by selecting the Play tool.

8. Notice that the damage contours do not change during the animation. This is because FE-Fatigue computes the total result instead of providing intermediate results over time.

Note that the arm appears grey in this display. This is because no FE-Fatigue results are available for this flexible body.

The damage plot shows two highly damaged spots on the shaft. Damage is the inverse of life of a part. Zero (0) damage means infinite life.

9. Pause the animation by selecting the Pause tool.

10. From the Plot Type pull down menu in the Contours tab section, select Life Repeats.

15nCode FE-FATIGUE TutorialViewing nCode FATIGUE Results in Adams

11. Notice that the contours of the shaft and legend are updated with the life of the component.

Here, life is represented in number of repeats and 1x1020 is considered infinite life in FE-Fatigue. Infinite life is predicted for the component, except at the two damaged points on the shaft, and where the arm connects to the shaft.

Getting Started Using Adams/DurabilityViewing nCode FATIGUE Results in Adams

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1MSC.Fatigue Tutorial

MSC.Fatigue Tutorial


2

OverviewIn this tutorial, you will perform modal stress recovery and fatigue analysis using:

• MSC.Patran

• Adams

• MSC.Nastran

• MSC.Fatigue

This chapter will not discuss the entire functionality of these products, only those features that specifically apply to this tutorial. For more detailed information, refer to your specific product documentation.

The following sections are included:

• About the Model

• Part 1 - Mode-Shape Analysis

• Part 2 - System-Level Simulation

• Part 3 - Fatigue Life Calculation


3MSC.Fatigue TutorialAbout the Model

About the ModelThe model is an Adams system model of an all-terrain vehicle (ATV) mounted on a four-post test rig (see Figure 1 below). The model that is distributed in the Adams/Durability installation is made up of rigid bodies only. We also provide an MSC.Nastran model of the left lower control arm (LCA) for building a flexible body's modal neutral file (MNF). You will generate the MNF using MSC.Nastran and then replace the rigid part with a flexible one for the left LCA. After the Adams simulation, you will perform a fatigue analysis using MSC.Fatigue and MSC.Patran with component loads from Adams. These component loads are in the form of modal coordinates (responses), so the method of fatigue analysis will be based on modal susperposition.

Figure 1 ATV Model

Getting Started Using Adams/DurabilityPart 1 - Mode-Shape Analysis

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Part 1 - Mode-Shape AnalysisIn this section, you will run MSC.Nastran to obtain the reduced flexible modes in MNF format and the modal stresses in XDB (MSC.Nastran binary attachable) format.

You will perform the following steps:

• Running the MSC.Nastran Simulation

• Importing the Model in MSC.Patran

• Attaching Results in MSC.Patran

• Viewing Results in MSC.Patran

Running the MSC.Nastran Simulation

To run the MSC.Nastran simulation:

1. Copy the file left_lca.dat from the install_dir//durabilityexamples/ATV directory to your working directory.

2. Run MSC.Nastran using left_lca.dat as the input file.

Depending on your computer resources it could take 5-10 minutes to run the job. You can move on to the next step in the tutorial while the analysis is running. When the job has completed successfully, you will find two files that were created in the run directory: left_lca_0.mnf and left_lca.xdb. These files are important in completing the rest of the tutorial.

The MSC.Nastran input file we provided for this tutorial is set up for MNF generation using the ADAMSMNF statement:

ADAMSMNF FLEXBODY=YES,FLEXONLY=YES,MINVAR=PARTIAL,PSETID=2,OUTGSTRS=YES,OUTGSTRN=NOThe output of grid point stresses are requested with the OUTGSTRS option. No output of grid-point strains are requested with the OUTGSTRN option.

The geometry and stress data that will be stored in the resulting MNF is optimized with the PSETID option for the surface (skin) only. A partial mass invariant calculation is requested with the MINVAR option.

MSC.Nastran supports the output of ortho-normal modal stress or strain resulting from MNF generation in XDB format. This data can be efficiently combined with the modal coordinate results from Adams for subsequent fatigue evaluations in MSC.Patran and MSC.Fatigue. To take advantage of this feature, the following statement has been added to the MSC.Nastran input file:

PARAM POST 0

Note: On Windows, you may need to set the permissions to Full Control to edit the tutorial files.

Note: install_dir is the directory where Adams is installed.

5MSC.Fatigue TutorialPart 1 - Mode-Shape Analysis

Importing the Model in MSC.Patran

To import the model into MSC.Patran:

1. Start MSC.Patran and open a new database (from the File menu, select New).

2. From the Look in pull-down menu, select your working directory.

3. In the Filename text box, enter tutorial.

4. Select OK to close the New Database dialog box.

5. From the File menu, select Import, and then specify the following:

• Set Object to Model.

• Set Source to MSC.Nastran Input.

• Set File name to *.dat.

• Browse to left_lca.dat, select it, and then select Apply to import the model.

• The Nastran Input File Import Summary dialog box displays as shown in Figure 2.

• Select OK to close the dialog box.

Figure 2 Nastran Input File Import Summary Dialog Box

The following operation automatically separates shells from solids. This will be handy during the fatigue analysis process in Part 3 - Fatigue Life Calculation.

6. From the Group menu, select Create.

7. Set Method to Property Type.

8. Set Create to Multiple Groups.

Getting Started Using Adams/DurabilityPart 1 - Mode-Shape Analysis

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9. Select Apply.

MSC.Patran creates two new groups named Membrane and Solid. You will reference the Membrane group later in this tutorial.

Fatigue is a phenomena that normally originates on the surface. It is, therefore, a common practice to skin any solid model with a thin shell membrane. This allows you to obtain a true two-dimensional stress tensor (which should always be the case on free surfaces) and also avoids uninteresting computation on internal nodes.

Attaching Results in MSC.PatranYou will now attach the modal results from MSC.Nastran in MSC.Patran.

To attached results in MSC.Patran:

1. Select Analysis, and then specify the following:

• Action: Access Results

• Object: Attach XDB

• Method: Result Entities

2. Select Select Results File.

3. In the Select File dialog box, browse to the left_lca.xdb file, and then select OK.

4. Select Apply.

Viewing Results in MSC.Patran

To view the results in MSC.Patran:

1. Select Results.

A list of 40 mode cases in the result selection window appears. These represent the orthonormalized modes that were computed by MSC.Nastran and imported into Adams using the MNF.

2. Perform some simple plotting as follows:

• Set Action to Create.

• Set Object to Quick Plot.

• Highlight one mode case with a frequency higher than zero (that is, a nonrigid body mode). For example, highlight mode 7.

• Select Stress Tensor as the Fringe Result.

3. Select Apply, and then view the results.

The stresses you are viewing are not actual stress values sustained by the component, but modal stress shapes. Later in this tutorial, these stress shapes will be combined with results from Adams to obtain actual stress values. This process is called modal stress recovery (MSR).

7MSC.Fatigue TutorialPart 1 - Mode-Shape Analysis

4. Close the MSC.Patran session by closing the MSC.Patran window or by selecting File and then Quit.

By default, MSC.Patran saves all databases.

Getting Started Using Adams/DurabilityPart 2 - System-Level Simulation

8

Part 2 - System-Level SimulationIn this section, you will run a dynamic simulation of the vehicle to produce loads (modal coordinates) for the flexible lower control arm (LCA) in the left-front suspension. The modal coordinates will be exported to MSC.Fatigue and used for stress calculation.

In this session you will perform the following steps:

• Importing the Model into Adams/View

• Building the Flexible Suspension Arm

• Animating Modes of the Flexible LCA

• Modifying the Damping of the Flexible LCA

• Running the Adams Dynamic Simulation

• Viewing Adams Results

• Exporting Results to MSC.Fatigue

Importing the Model into Adams/View

To import the model into Adams/View:

1. Start Adams/View.

2. In the Welcome dialog box, select Import a file.

3. Select OK.

4. In the File to Read text box, enter ATV_4poster.

There is no need to browse for this file. By typing in the name, Adams/View locates the file in the Adams installation directory (in durability/examples/ATV).

5. Select OK.

This model contains the all-terrain vehicle standing on a four-poster rig. All parts are rigid.

Building the Flexible Suspension ArmNext you will replace the rigid LCA with a flexible one.

To build the flexible suspension arm:

1. Zoom in on the left LCA in the front suspension as shown in the figure below.

9MSC.Fatigue TutorialPart 2 - System-Level Simulation

Figure 3 Left LCA

• To rotate the view: Press r on the keyboard, and then rotate while pressing left mouse button.

• To translate: Press t.

• To zoom: Press w.

2. To replace the rigid LCA with a flexible LCA, from the Build menu, point to Flexible Bodies, and then select Rigid To Flex.

3. In the Alignment tab, select the rigid part you want to replace and the MNF as follows:

• Current Part: RB2_left_lca_59

• MNF File: left_lca_0.mnf

• To select the rigid body to be replaced, right-click the Current Part text box, point to Part, and then select Pick. Using your mouse, click on the lower left suspension arm.

To browse for the MNF, right-click the MNF File text box, and then select Browse.

The flexible body defined in the .mnf is already correctly positioned so this is all you need to do in the Alignment tab.

4. Select the Connections tab.

The table displayed compares the connection points on the flexible body with the connection points on the rigid body. In the Distance column, you will notice that there is a small offset for the four bushing connection points.

You want to keep the bushings at the point where they where originally defined in the rigid model.

5. Click on the first table row, and then select Preserve location.


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6. Repeat the previous step for rows 2 through 4 of the table.

The table should now look as shown in the figure below.

Figure 4 Connections Table

7. Select OK.

The rigid part is now replaced by the flexible body as defined in the .mnf. The flexible body is connected to the frame, knuckle, and damper in the same way as the rigid body.

To verify that the flexible LCA is correctly connected to the rest of the model:

1. From the Tools menu, select Database Navigator.

2. Select Topology By Parts.

3. Select the flexible LCA, .ATV_4poster.RB2_left_lca_59_flex.

It should be connected to the frame using two bushings, and to the damper (shock) and knuckle with one bushing each.

4. Close the Database Navigator.


Animating Modes of the Flexible LCA

To animate the modes of the flexible LCA:

1. Right-click the flexible LCA, and then select Modify.

2. Animate the modes by selecting a Mode Number (that is, 7) and then selecting the Animation tool .

You can animate each of the 40 modes calculated by MSC.Nastran and imported from the .mnf.

In the dynamic simulation results, expect to see 40 modal coordinates, one coordinate for each mode.

The first mode of interest is mode number 7. Modes 1 through 6 are rigid-body modes and are automatically disabled.

The first few modes are very similar to the free-free modes of the component. The high-frequency modes are usually unusual looking, but useful for describing local deformations around the attachment points.

Modifying the Damping of the Flexible LCAThe high-frequency modes are normally not very active in a dynamic simulation. There are two strategies to avoid them:

• Disable the modes. This may cause simulation difficulties if any of the disabled modes are necessary to describe, for example, a static position with local deformation around an attachment point.

• Modify damping so high-frequency modes are critically damped. The modes are enabled, but don’t participate in the dynamics because of the high damping applied to them.

Here, you will use the method of setting critical damping on the very high frequency modes. A STEP function will define the damping. The higher the frequency, the higher the damping.

To modify the damping of the flexible LCA:

1. If the Flexible Body Modify dialog box is not already displayed, right-click the flexible LCA, and then select Modify.

2. Clear the selection of default next to Damping Ratio.

3. Enter the following function for the Damping Ratio:

STEP(FXFREQ,1000,0.005,10000,1)

This means:

• Modes with a frequency below 1,000 Hz will have damping ratio of 0.5%.

• Modes with a frequency above 10,000 Hz will have damping ratio of 100%.

• Modes in the range of 1,000 - 10,000 Hz will be increasing with respect to their frequency based on the STEP function.


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Note that default damping is usually not useful, especially not in this case. If you used default damping here, you would get a 10% damping ratio for mode 7, which is too much considering the component is made of steel.

4. Select OK to save all modification and close the Flexible Body Modify dialog box.

Running the Adams Dynamic Simulation

To run the Adams dynamic simulation:

1. Change your Adams/Solver settings:

• From the Settings menu, point to Solver, and then select Executable.

• Set Choice to C++.

2. Modify Adams/Solver dynamics parameters:

• Set Category to Dynamics.

• Set Formulation to SI2 and Error to 0.01.

The Stabilized Index-2 formulation enables the integrator to monitor the integration error of velocity variables and, therefore, renders highly accurate simulations. A positive side effect of the SI2 formulation is that the Jacobian matrix remains stable at small step sizes, which increases the stability and robustness of the corrector at small step sizes. We use the SI2 formulation here because high accuracy of the inputs to the fatigue analysis is crucial.

3. Close the Solver Settings dialog box.

4. From the Simulate menu, select Interactive Controls.

5. Perform the following:

• Set End time to 10 seconds

• Change list2+ to Step Size

• Set Step size to 0.01 seconds

• Select Start at equilibrium position. If you do not start from equilibrium, your results will contain initial transient vibrations, which is not preferred.

• To avoid the screen being updated at every output time step taken by the solver (therefore speeding up the solve time), clear the selection of Update graphics display.

6. Select the Play tool to start the simulation.

Each post that the vehicle is standing on will move in the vertical direction to simulate the vehicle running in rough terrain. This could also have been done by defining tire forces and a road profile.

The simulation will take a few minutes.


Viewing Adams Results

To view the Adams results:

1. From the Review menu, select Postprocessing.

2. In the upper left corner of Adams/PostProcessor, use the pull-down menu to select Plotting.

3. In the dashboard (the lower section of the postprocessing window) select, for example, the following:

• Source: Objects

• Filter: force

• Object: BUSHING_9. This is the bushing connecting the LCA with the spring/damper

• Characteristic: Element_Force

• Component: Mag

4. Select Add Curves

The plot displays as shown next. This is the time history of force magnitude in the bushing between the flexible CLA and the shock.

Figure 5 Adams Results

Next, you will use Adams/Durability to view the stress data.

5. Load the Adams/Durability plugin using Tools Plugin Manager.

6. Load the animation, by right-clicking in the window, and then selecting Load Animation.

7. Before you start the animation:

• In the Contour Plots tab, set Contour Plot Type to Max Prin. Stress.


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• In the Camera tab, set Follow Object to RB1_frame_57 (the frame). Lock the rotations.

• Zoom in on the flexible LCA and orient the display so that you are looking at the bottom surface of the LCA.

8. Animate by pressing the Play button.

9. Reset the animation.

10. To create a table that lists the three most critical areas of the LCA, from the Durability menu, select Hot Spots Table, and then specify the following:

• Body: RB2_left_lca_59_flex (right-click in text box, point to body, and then select Pick or Browse)

• Analysis: Last_Run (right-click in the text box, point to Analysis, point to Guesses, and then select Last_Run)

• Type: Maximum Principal Stress

• Radius: 30.0

• Count: 3

11. Select Report.

When the calculation is complete, Adams/Durability displays the Hot Spots table as shown in the following figure. The hottest spot is located around node 2990, which is located on the bottom surface of the LCA, close to the cross-beam connection.

12. Close the Hot Spots Information dialog box.


Figure 6 Hot Spots Table

Exporting Results to MSC.FatigueWhen you export the results to MSC.Fatigue, it is actually not the stresses as calculated in Adams that we export, it is only the modal coordinates that are exported. The stress shapes are already calculated (Part 1 - Mode-Shape Analysis) and stored in the XDB file. The stress shapes in the XDB file will be combined with the modal coordinates from Adams in MSC.Fatigue.

To export results to MSC.Fatigue:

1. From the Durability menu, point to MSC.Fatigue, and then select Export. Specify the parameters as follows:

• Flexible Body: RB2_left_lca_59_flex

• Job Name: ATV_4poster

• Modal Coordinates (make sure this box is checked)

• Analysis: Last_Run

2. Clear the selection of Run MSC.Fatigue.

3. Select OK.

Modal coordinates for the flexible LCA are now exported in DAC format (40 files with prefix ATV_4poster) suitable for import to MSC.Fatigue. One file is produced for each modal coordinate.

Getting Started Using Adams/DurabilityPart 3 - Fatigue Life Calculation

16

Part 3 - Fatigue Life CalculationFor this portion of the tutorial, you will use MSC.Fatigue as a plugin to MSC.Patran. There is also a stand-alone version of MSC.Fatigue that is offered with a limited version of MSC.Patran.

In this section, you will predict fatigue life to failure and life factor of safety based on modal superposition and a standard S-N analysis (also known as Stress Life or Total Life).

You will perform the following steps:

• Setting up Stress-Life Analysis in MSC.Fatigue

• Importing and Combining Modal Coordinates in MSC.Fatigue

• Running S-N Fatigue and Factor of Safety (FOS) Analysis

• Importing and Reviewing Results in MSC.Patran

• Importing and Reviewing Results in Adams (Optional)

Setting up Stress-Life Analysis in MSC.Fatigue

To set up stress-life analysis in MSC.Fatigue:

1. Start MSC.Patran, and from the File menu, select Open to open the tutorial.db file that was created in Part 1 - Mode-Shape Analysis of this tutorial.

2. From the Tools menu, select MSC.Fatigue.

3. Select Main interface.

17MSC.Fatigue TutorialPart 3 - Fatigue Life Calculation

4. Complete the dialog box as shown next, being sure to set Analysis to S-N.

5. Enter fat_left_lca for the jobname for the fatigue jobs in MSC.Patran. All fatigue-related files will have this prefix.

The bottom section of the MSC.Fatigue dialog box contains the five steps to complete your fatigue job:

• Three inputs - Solution Parameters, Material, and Loading

• Job control - Used to submit and monitor fatigue jobs

• Results - Used to postprocess fatigue results


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6. Select Solution Params and complete the dialog box as shown next:

The Certainty of survival is set to 99%, indicating the highest conservatism in material properties scatter.

The design life is the number of repetitions this part is expected to withstand without failure. MSC.Fatigue will perform an additional analysis to assess the load scaling factor to reach a given target life. A design life of 60000 is derived from a simple assumption that under the given loading condition, the target life is around 10,000 km and that the 10-second repetition was performed at an average speed of 60 km/h.

7. Select OK to close the Solution Parameters dialog box.

8. Select Material Info.


MSC.Fatigue offers a built-in library with more than 200 predefined materials. You can select multiple materials for the same run and access advanced material options, such as temperature dependency.

9. Click in the first cell of the spreadsheet (Material) and scroll through the available material list below it. Select MANTEN_SN (carbon wrought steel).

10. Select No Finish and No Treatment.

11. Set Region to Membrane.

The region is the part of your model that will be analyzed. As mentioned previously, you are only interested in the surface element and you will use the previously created Membrane group as the target region.

12. Keep the defaults for all remaining fields, and then select OK.

Importing and Combining Modal Coordinates in MSC.FatigueThe Loading Information dialog box is the spreadsheet that displays the association between modal stresses (MSC.Nastran output) and modal coordinates (from Adams). This is the key in recreating the stress history at each node that will be used for rainflow cycle counting (central to fatigue analysis algorithm).


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Figure 7 Loading Information Dialog Box

To import and combine the modal coordinates:

1. Select Loading Info.

To access the modal variables, MSC.Fatigue needs to load the relative *.dac files (the output from Adams created in Part 2 - System-Level Simulation) into the local time database (ptime.tdb).

2. Select Time History Manager to open the local time database. Then, perform the following:

• Select Load files.

• Select OK.

3. In the PTIME – Load Time History dialog box, enter the following:

• Source and target Filename: ATV_4poster*

• Description 1: modal coordinates

• Load Type: Scalar


• Units: none

• Select OK.

• The 40 files start loading. Select More enough times to make sure all load channels are loaded.

4. Select End.

The PTIME dialog box shows that you have 40 .dac files.

5. Select exit, and then select OK to close the PTIME-Database Options dialog box.

6. In the Loading Information dialog box, perform the following:

• Set Number of Static Load Cases to 40. Be sure to select Enter on your keyborard after setting this value. Doing so will update the number of rows in the spreadsheet from 1 to 40.

• Select Fill Down OFF and the option changes to Fill Down ON.

• Select the first cell in the Load Case ID column.

• Select Get/Filter Results to open the Results Filter dialog box.

• To access all available results in the database in the Results Filter dialog box, select Select All Results Cases, and then select Apply.

7. Select the first available results loadcase (… Mode 1…) in the Select a Results Load Case list.

8. From the Select a Stress/Strain Tensor list, select 1.1 – Stress tensor.

9. Select Fill Cell to populate the Load Case ID column.

10. Make sure the first cell in the Time History column is selected to populate column 2.

11. Select ATV_4POSTER_01.DAC from the Select a Time History list.

Your spreadsheet should look similar to the image shown below.

12. Leave the remaining default values, and then select OK.

Figure 8 Spreadsheet for ATV_4POSTER_01.DAC:

Running S-N Fatigue and Factor of Safety (FOS) Analysis

To run the analysis:

1. From the MSC.Fatigue menu, select Job Control.

2. To start the analysis, select Apply.


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Wait a minute or two until the fat_left_lca fatigue job has been submitted.

You can check the status by accessing Job Control ActionMonitor Job, and then periodically selecting Apply.

When completed, the status window displays the following message:

Safety factor analysis completed successfully.

If you receive the message ERROR: cannot communicate with Queue Manager, MSC.Patran is trying to run MSC.Fatigue through the Analysis Manager without a defined environment. A workaround is to deactivate the Analysis Manager using the MSC.Patran command analysis_manager.disable(), and then resubmit the job.

Importing and Reviewing Results in MSC.Patran

To import and review the results in MSC.Patran:

1. Select the MSC.Fatigue tab near the bottom right corner of the MSC.Patran window.

2. Select Results.

3. Select Apply to read in the results.

MSC.Fatigue automatically accesses the results based on the current job name.

The results are now stored in the MSC.Patran database as the Total Life and Factor of Safety subcases for postprocessing.

4. To view a quick plot of the factor of safety in MSC.Patran, select Results on the main MSC.Patran form (not in MSC.Fatigue).

5. In the results window, scroll through the list of Result Cases, and then select Factor of Safety, fat_left….

6. Select Safety Factor as the fringe result, and then select Apply.

The smallest factor of safety is 2.70. You can create a damage plot to improve the visualization of the critical areas.

To see a damage plot:

1. Select Total Life from the Result Cases list.

2. Select Damage from the Fringe Result list.

3. Select Apply.

Note that the highest damage occurs at three critical regions of the LCA.

Importing and Reviewing Results in Adams (Optional)

To import and review the results in Adams:

1. From the Durability menu, point to MSC.Fatigue, and then select Import.


2. Browse to the fatigue results file (*.fef), for example, ...\fat_left_lca.fef.

3. Select RB2_left_lca_59_flx as the flex body, and then select OK.


5. Set Contour Plot Type to Life (Log Repeats).

The results are displayed in Adams/PostProcessor, as shown below.

Because the results represent the total results for the simulation, you do not need to animate the results.

Figure 9 RB2_left_lca_59_flx Contour Plot


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getting started using adams/durability - md adams 2010

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