using adams/durability - md adams 2010

1Welcome to Adams/Durability

Welcome to Adams/Durability

Adams/DurabilityIntroduction to Adams/Durability

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Introduction to Adams/DurabilityAdams/Durability, part of the MD Adams 2010® suite of software, extends the traditional test-based durability design process into the virtual world. With Adams/Durability, you can simulate a durability duty cycle and write out component load histories in or formats and drive a durability test rig using output data in RPC III Format or DAC Format. You can visualize stress or detect hot spots in flexible or rigid components, and you can improve component design by interfacing with fatigue life prediction programs.

Some of the features of Adams/Durability are available as a demand-loaded library (DLL), while the rest are available as a plugin to the various Adams interface or vertical products, such as Adams/View, Adams/PostProcessor, and Adams/Car.

How You Benefit from Using Adams/DurabilityAdams/Durability enables you to work faster and smarter, letting you easily interface with durability test machines using the RPC III Format, and with fatigue life calculation programs using DAC Format, or with an FEA program for stress recovery.

You benefit from using Adams/Durability in the following ways:

• Shortens your development cycle, reducing costly durability testing.

• Reduces disk space requirements and improves performance by providing direct file input and output in RPC III and DAC formats. For example, when you perform a 25-second Adams simulation with 300 channels of data, sampled at a rate of 409.6 points per second, to capture a durability event, the Adams Request files are approximately 48 MB, whereas the RPC III file is only 6 MB.

• Provides access to the system-level simulation capabilities of Adams/View, or vertical products, such as Adams/Car.

• Provides access to dynamic stress recovery methods using NASTRAN or ANSYS.

• Performs modal stress recovery of flexible bodies.

• Provides access to component life prediction using MSC.Fatigue or FE-Fatigue.

Using Adams/Durability On DemandThe Adams/Durability installation includes a library that is compatible with most of the Adams products, including Adams/View, Adams/PostProcessor, Adams/Solver, and the vertical product solvers such as Adams/Car Solver. This library provides the DAC and RPC III file capabilities of Adams/Durability. It is demand-loaded automatically by the various products when you use a feature of Adams/Durability that requires this library; therefore, you do not need to know how to access this library.

With the Adams/Durability demand-loaded library, you can simulate a durability duty cycle in Adams and write out component load histories in RPC III and DAC formats. For example, you can simulate a virtual test rig where actuator inputs like spindle loads are taken from field measurements and stored in

3Welcome to Adams/DurabilityIntroduction to Adams/Durability

the RPC III format. Then, you can write out component load histories in DAC format for subsequent component durability testing or fatigue life prediction.

You can perform the following with DAC or RPC III files:

• Browse the files for header information, such as number of time steps, sample rate, number of channels, channel names, channel maximums, and channel minimums.

• Plot the time history data.

• Filter, integrate, or transform the sampled data.

• Drive or excite Adams models with the data.

• Interpolate the channel data by cubic splines.

Loading the Adams/Durability PluginThe Adams/Durability plugin gives you access to the various stress recovery techniques in Adams, and interfaces to NASTRAN, ANSYS, FE-Fatigue, and MSC.Fatigue. This plugin is available in most of the Adams interface or vertical products, such as Adams/View, Adams/PostProcessor, Adams/Car, and Adams/Driveline.

To load the Adams/Durability plugin:

1. Start one of the Adams interface or vertical products.

2. From the Tools menu, select Plugin Manager.

3. Select the Load checkbox next to Adams/Durability.

4. Select OK.

This creates the Durability menu, adds various stress and strain Plot Type menu options for the Contours tab in Adams/PostProcessor, and adds several functions to the Misc. Functions category in the Adams/View Function Builder, such as LIFE, MAX_STRESS, HOT_SPOTS, and TOP_SPOTS.

To unload the Adams/Durability plugin:

1. From the Tools menu, select Plugin Manager.

2. Clear the Load checkbox next to Adams/Durability.

3. Select OK.

Adams/DurabilityIntroduction to Adams/Durability

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1Performing Stress Recovery

Performing Stress Recovery

Adams/DurabilityStress Recovery in Adams/Durability

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Stress Recovery in Adams/DurabilityWith Adams/Durability you can recover stresses on flexible or rigid bodies. Recovering stresses on flexible bodies is called Modal Stress Recovery (MSR). You can perform MSR inside Adams or, in the case of NASTRAN, outside of Adams.

Recovering stresses on rigid bodies is based on the loading time history of the component and its geometry and mass. If a finite-element mesh is available for the rigid component, the forces from an Adams simulation can be exported and applied to the component’s mesh. A finite element program like NASTRAN can then be employed to recover the static stress resulting from the foce application at each Adams output step. This method of stress recovery is sometimes referred to as quasi-static stress recovery.

Note that user functions are available for modal stress recovery to determine hot spot regions and maximum stress. Learn more about User Functions.

3Performing Stress RecoveryModal Stress Recovery

Modal Stress Recovery The benefit of this process is being able to recover any type of output that is available in MSC.Nastran (also MD Nastran) such as element stresses or strains, nodal forces, and so on. Due to limitations of the MNF, only grid point stresses or strains can be post-processed in Adams. Also, MSC.Nastran does not allow grid point stress or strain on composite shell elements or beams, so it is not possible to post-process strain or stress for these type of elements in Adams. In addition, plates or shells have more than one layer, but the MNF allows only one layer of stress or strain to be stored in the file. These limitations are avoided by exporting data for MSC.Nastran.

MSC.Nastran has the function to recover stresses and strains in the version 2006 (MDR1) and later, and a special DMAP is not required. For modal stress recovery, a restart run is used thus MSC.Nastran database (.MASTER and .DBALL) have to be kept in the primary run to build the flexible body for Adams, and to do that the command option "scratch=no" should be applied. Modal transient response analysis (SOL 112) and modal frequency response analysis (SOL 111) should be applied for time dependent data and frequency dependent data respectively with ADMPOST parameter.

Learn Exporting Data for NASTRAN.

Restarting NASTRANA restart MSC.Nastran for modal stress recovery needs to be specified at the top of the MSC.Nastran input deck in the file management section:

ASSIGN <logical name>='<database name>'RESTART LOGICAL=<logical name>

where <logical name> is the logical name of the database to be assigned and <database name> is MASTER file name of the primary run. Note that the logical name is arbitrary characters within 8 letters and first one should be alphabet.

Reading Modal Deformations File (MDF)Modal deformations to be read have to be in binary (OUTPUT2) format, and the following statement needs to be specified near the top of the MSC.Nastran input deck in the file management section:

ASSIGN INPUTT2='<MDFilename>' UNIT=<load ID> [FORM=<binary format>]

where <MDFilename> is the name of the modal deformations file from Adams. For directions on how to create this file, see the FEMDATA or OUTPUT Adams/Solver statement. And <load ID> indicates an ID number of DLOAD statements in the case control section. The option FORM may be requested when the binary format of MDF is not applicable to the platform of MSC.Nastran (see the MSC.Nastran quick reference guide for more information).

Note: AUTOQSET cannot be used for the primary run due to the limitation of MSC.Nastran restart capability

Adams/DurabilityModal Stress Recovery

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Results PostprocessingDynamic stress/strain output can be either in F06, PUNCH OUT, XDB or OUTPUT2 according to standard MSC.Nastran functionality, and the output files can be postprocessed in Patran or SimXpert Structures.

If displacements, stresses, and/or strains are to be available for postprocessing, one or more of the following statements must appear in the case control section of the MSC.Nastran input file:

DLOAD = <load id>DISP(PLOT) = <set id>STRAIN(FIBER,PLOT) = <set id>STRESS(PLOT) = <set id>

where <load id> is a ID number indicated by ASSIGN statement in the executive control section, and <set id> is a ID number defined in SET statement.

PARAM, ADMPOST

Request modal stress recovery (see the MSC.Nastran quick reference guide for more information):

• 0: Modal stress recovery is not activated (default)

• 1: Request modal stress recovery without rigid body motion

• 2: Request modal stress recovery with rigid body motion

This parameter is used to activate modal stress recovery and control the addition of rigid body motion with modal deformations. Rigid body motions from an Adams simulation are included in the modal deformations file (MDF), but they are not applied unless this parameter is set to 2. Including rigid body motion affects the display or animation of the flexible component, but it has no effect on dynamic stresses.

PARAM, POST

Request stress/strain/displacement output for postprocessing (see the MSC.Nastran quick reference guide for more information):

• <= 0: Yes

• > 0: No

Example of Input FileAn example MSC.Nastran input file for modal stress recovery run compared to a typical input file for building flex body is shown below. These examples are located in the following installation files:

• <Adams installation directory>/durability/NASTRAN/plate.dat

• <Adams installation directory>/durability/NASTRAN/plate_msr.dat

• <Adams installation directory>/durability/NASTRAN/plate.cmd

5Performing Stress RecoveryModal Stress Recovery

Note that "plate.cmd" is the command file to create the example model with the flex body (MNF) by "plate.dat" and run the dynamic simulation.

For building flex body (plate.dat) For modal stress recovery (plate_msr.dat)

ASSIGN PRIMARY='plate.MASTER'

RESTART LOGICAL=PRIMARY Restart setting

ASSIGN INPUTT2='plate.mdf' UNIT= 31 Read MDF

SOL 103 SOL 112 Modal transient analysis

CEND CEND

$ GLOBAL CASE $ GLOBAL CASE

METHOD = 1 METHOD = 1

ADAMSMNF FLEXBODY=YES

DLOAD = 31

DISP(PLOT) = ALL

STRESS(PLOT) = ALL

Output data setting

BEGIN BULK BEGIN BULK

PARAM, ADMPOST, 2

PARAM, POST, -1 Parameter setting

DTI, UNITS, 1, KG, N, M, S

ASET1, 123, 1, 11, 78, 88

SPOINT, 10001, THRU, 10030

QSET1, 0, 10001, THRU, 10030

EIGRL, 1, , , 30

$

GRID, 1, , 0.0, 0.75, 0.0

GRID, 1, , 0.1, 0.75, 0.0

…

Geometry data is not needed

ENDDATA ENDDATA

Adams/DurabilityStress on Flexible Bodies

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Stress on Flexible Bodies

Recovering Stresses on Flexible BodiesIn order for Adams/Durability to compute stresses on a flexible body, the flexible body in your model must contain FEA stress mode information in its modal neutral file (MNF). For more information on including stress mode shapes during MNF generation, see the Adams/Flex online help.

You can also compute strains on a flexible body if its MNF contains strain mode information from FEA.

Computing Stresses or StrainsYou can use Adams/Durability to calculate nodal stress or strain values. These values can be used to generate x-y plot displays. When you compute nodal plots, the directions x, y, and z are with respect to the flexible bodies' local-body-reference-frame (the FEA package's global coordinate system).

To compute stresses or strains:

1. From the Durability menu, select Nodal Plots.

The Compute Nodal Plot dialog box appears.

2. In the Analysis text box, enter the name of a previously run analysis. Tips on Entering Object Names in Text Boxes.

3. In the Flexible Body text box, enter the name of the flexible body.

4. In the Node to Add to List text box, enter one or more nodes on which to calculate stresses.

You can right-click in the text box, and select Pick Flexbody Node. Then, select a node by clicking on a position in the model. As you pick the nodes individually, the Selected Nodes List text box accumulates a list of all selected nodes.

5. Select stress or strain.

6. Select the values desired, as necessary.

7. Select OK.

8. Adams/Durability stores the stress or strain components in a flexible body result set for the specified analysis. It adds the following field to the Adams/View database for the flexible body being analyzed:

FBname_STRESS.NodeID_Value (for stress components)FBname_STRAIN.NodeID_Value (for strain components)

where:

FBname is the name of your flexible body

NodeID is the node whose stress or strain you are calculating

_Value is the value of stress or strain you're calculating

You can also print these values to a text file.

../adams_flex/master.htm

7Performing Stress RecoveryStress on Flexible Bodies

Displaying Stress or Strain ContoursYou can use Adams/PostProcessor to display stress or strain as a color contour map on the flexible body. Adams/Durability automatically computes a value at each node of the flexible body.

To display stress or strain contours:

1. Load your animation in the current Adams/PostProcessor window.

2. Select the Contours tab.

3. Specify a stress or strain value in the Plot Type menu.

Adams/PostProcessor computes the stress or strain information. This may take a while depending on the size of your flexible body and simulation. Once completed, Adams/PostProcessor displays a contour legend.

4. Select the Play tool.

Adams/PostProcessor displays the contours according to the color map on the legend.

Plotting Stresses or Strains

To plot the results of your nodal stress or strain computation:

1. Open Adams/PostProcessor.

2. Load your plot.

3. Set Source to Results set.

4. From the Simulation list, select the analysis run that you entered in Computing Stresses or Strains.

5. Select the FBname_STRESS or FBname_STRAIN result set.

6. From the Component text box, select the node and value you previously identified.

7. Select Add Curves or Surf.

Adams/Postprocessor plots the nodal stresses or strains.

Visualizing Hot SpotsHot spots are locations of high stress or strain on a flexible body or rigid stress object. You can easily locate and view hot-spot information during animation displays in the Adams/PostProcessor. When the Adams/Durability plugin is loaded, a Hot Spots tab is available on the Adams/PostProcessor dashboard for Animation displays. This tab allows you to define the hot spots and control their display.

Hot-spot information is derived from the data that is generated and cached for a flexible body (or rigid stress object) during contour animations. This allows the display and control of hot-spot information to be completely interactive.

Hot spot visualization is currently supported for durability-type contours, such as stress, strain, or fatigue. Deformations are not supported.

Adams/DurabilityStress on Flexible Bodies

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To display hot spots:

1. Load your animation in the Adams/PostProcessor window.

2. Load the Adams/Durability plugin if it is not already loaded.

3. Select the Contours tab.

4. Specify a stress or strain value in the Plot Type menu.

Adams/PostProcessor computes the stress or strain information. This may take a while depending on the size of your flexible body and simulation. Once completed, Adams/PostProcessor displays a contour legend.

5. Select the Hot Spots tab, and then select Display Hotspots.

6. Make other selections as described in Animation Dashboard - Hot Spots.

7. Select the Play tool.

Adams/PostProcessor displays the animation with a cross hair and option label at the location of each hot spot.

9Performing Stress RecoveryStress on Rigid Bodies

Stress on Rigid Bodies

Recovering Stresses on Rigid BodiesStresses can be predicted on components of Adams models using loads that the component experiences from an Adams simulation. Both external and internal loads must be considered:

• External loads are a result of applied and constraining forces acting on the component.

• Internal loads are a result of motion, such as linear and angular acceleration and rotational velocity of the part's local reference frame (LPRF).

When all loads acting on the component are considered, the rigid component is in dynamic equilibrium at each output step, and a static finite-element analysis can be performed. This process of recovering stresses based on loads is sometimes referred to as quasi-static stress analysis. The process of recovering stress on rigid bodies can be broken down into the following steps:

1. Create a finite-element model (FEM) of your rigid body. This requires the definition of material properties for the part and a mesh for the part geometry.

2. Apply loads from an Adams simulation to the FEM.

3. Solve for deformations in the FEM due to the applied loads using finite-element analysis (FEA).

4. Recover stresses due to the FEA deformations.

Using Adams/Durability, you can perform this process easily and efficiently by exporting applied loads on the rigid body to a finite element program like NASTRAN where they can be easily applied to a component model to compute the stresses.

Adams/DurabilityStress on Rigid Bodies

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1Exporting Data

Exporting Data

Adams/DurabilityExporting Data Using Adams/Durability

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Exporting Data Using Adams/DurabilityUsing Adams/Durability, you can export data from an Adams simulation to compare simulation results to a physical test, input data to durability analysis programs, or provide input to test equipment. You can store the exported data in either RPC III Format or DAC Format.

With Adams/Durability, one of the first steps you take is to export data to validate your model against actual test data. You perform model validation by simulating the same system, load, and time interval, and then compare plots of physical test results to simulated results. Once you’re satisfied that your model and loads adequately match physical test results, you’ll want to output simulation results of What-If scenarios for input to durability analysis programs and durability test machines.

3Exporting DataExporting Data for ANSYS

Exporting Data for ANSYSUsing Adams/Durability, you can generate displacement mode shapes (in ASCII or binary format) that you can use to recreate mode substep results within ANSYS (when you need an ANSYS modal superposition, but don’t have the results file).

You can also directly apply the displacement time histories on the modal nodes (rather than use modal superposition) when you need finite-element (FE) stress recovery for an analysis with few time steps. You can generate an input file for the subsequent ANSYS analyses that consist of time domain impositions of flexible body node displacements.

To export data for ANSYS:

1. From the Durability menu, point to FE Modal Export, and then select ANSYS.

2. Complete the dialog box as described in ANSYS Modal Export Dialog Box.

3. Select OK.

Adams/DurabilityExporting Data for MSC.Fatigue

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Exporting Data for MSC.FatigueWith MSC.Fatigue, you can predict the life or damage of your flexible components using service loads from an Adams simulation. Adams/Durability provides a convenient interface to transfer results between MSC.Fatigue and Adams for flexible bodies. Note that the modal neutral file (MNF) of the flexible body does not have to contain stress modes to use the MSC.Fatigue interface. You can import modal stresses from MSC.Nastran into MSC.Fatigue using MSC.Patran. These stresses or strains can come from the MSC.Nastran .out or .xdb file. These can also be grid- or element-based stresses or strains.

The MSC.Fatigue interface in Adams/Durability relies on:

• MSC.Nastran to provide the finite/super-element model of the flexible component.

• MSC.Patran to import the model and stress or strain from MSC.Nastran for MSC.Fatigue.

To export data for MSC.Fatigue:

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

2. Complete the dialog box as described in MSC.Fatigue Export Dialog Box.

3. Select OK.

Running MSC.Fatigue from Adams/Durability

MSC.Fatigue with MSC.Patran can process MSC.Nastran .xdb .op2 files that contain element or grid-point modal stresses.

To complete the loading information in MSC.Fatigue from Adams/Durability:

1. In MSC.Patran, use the Group Modify menu to modify the default group of all grids and elements created in the MSC.Patran database.

2. Remove the members that are MPC-type (grids connected to RBE elements).

Modal stresses are not available for those members.

3. In the MSC.Fatigue Loading Information window, select Time History Manager to create a PTIME database of the DAC files.

4. Load all of the DAC files with the Job Name prefix that was specified in theMSC.Fatigue Export Dialog Box.

5. In the PTIME - Load Time History window, set Load Type to Scalar.

6. Set Units to none.

7. Set Results Type to Static.

8. In the Number of Static Load Cases text box, enter the number of modes for the flexible body.

9. Set Fill Down to ON to complete the Load Case ID, Time History, and Load Magnitude columns in this window.

The loading information section is now complete. You will also need to complete the material properties section before you can submit your MSC.Fatigue job.

5Exporting DataExporting Data for NASTRAN

Exporting Data for NASTRANMSC.Nastran (also MD Nastran) Stress Recovery is the process of exporting the modal deformations of a flexible body from an Adams simulation to MSC.Nastran. A MSC.Nastran restart analysis is then performed to recover dynamic stresses or strains on the finite-element model of the flexible body. This process assumes that the flexible body originated from a finite-element model in MSC.Nastran (that is, a MSC.Nastran analysis was performed, the MNF of the flexible body was created using ADAMSMNF statement and the database which includes .MASTER and DBALL is kept).

The FEMDATA and OUTPUT statements can also be used to export modal deformations to a NASTRAN formatted file for stress or strain recovery. MSC.Nastran format, OUTPUT2 is only supported.

By definition, the modal deformations (coordinates) are unitless quantities, so the modal stresses (or strains) will be recovered correctly in MSC.Nastran regardless of the unit settings in the Adams and MSC.Nastran models. Rigid body motion of the flexible body is also included in the modal deformation file. In addition, the unit of length in the Adams model must be consistent with that in the MSC.Nastran model for the overall displacement of the component to be recovered correctly.

To export data for MSC.Nastran:

1. From the Durability menu, point to FE Modal Export, and then select NASTRAN.

2. Complete the dialog box as described in NASTRAN Modal Export Dialog Box.

3. Select OK.

Adams/DurabilityExporting for nCode

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Exporting for nCodeYou can generate a partial FES file (nCode FE-Fatigue file format) suitable for fatigue life prediction (FLP) analysis when stress or strain blocks are present in the MNF. You can also export modal coordinates for subsequent FE-Fatigue damage analysis or FE modal superposition. When exporting modal coordinates, Adams/Durability also creates an nCode load association file (LAF).

To export data for nCode:

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

2. Complete the dialog box as described in FE-Fatigue Export Dialog Box.

3. Select OK.

Note: The online help will not discuss the entire functionality of nCode, only those features that specifically apply to exporting data. For more detailed information on nCode, refer to your nCode documentation on FE-Fatigue.

7Exporting DataExporting to RPC III or DAC

Exporting to RPC III or DACYou can export either RPC III Format or DAC Format request files from Adams/View after a simulation completes. This technique does not require you to set up requests before running the simulation.

By definition, results output to an RPC III or DAC file must have constant time steps. If the results data being output includes non-constant time steps, Adams/View provides a warning and the time axis of the data will be warped so that the time interval is constant.

To export a result set to DAC files:

1. From the File menu, select Export to display the File Export dialog box.

2. Set File Type to DAC File.

3. Enter the name of the DAC file in the File Name text box.

4. Right-click the Result Data text box to display the shortcut menu. Point to Result_Set_Component, and then select Browse to display the Database Navigator.

5. Select the result set from the Database Navigator, and then select OK.

Result set components can come from results sets, Measures, or Requests. You can only have one result set per DAC file.

6. Select OK in the File Export dialog box.

To export a result sets to an RPC III file:

1. From the File menu, select Export to display the File Export dialog box.

2. Set File Type to RPC3 File.

3. Enter the name of the RPC III file in the File Name text box.

4. Right-click the Result Data text box to display the shortcut menu. Point to Result_Set_Component, and then select Browse to display the Database Navigator.

5. Select one or more result sets from the Database Navigator using Shift+click or Ctrl+click techniques.

6. Once you’ve selected all the result sets, select OK.

7. Select OK in the File Export dialog box.

Note: Result set components can come from result sets, measures, or requests.

Adams/DurabilitySetting Up Requests

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Setting Up RequestsYou can create Requests to output RPC III Format or DAC Format files. You do this before you execute the simulation.

To set up a request:

1. Define desired requests.

2. From the Settings menu, point to Solver, and then select Output to display the Solver Settings dialog box.

3. Set Save Files to Yes.

4. Set Graphics File, Request File, and Results File to No if these files are not needed.

5. In the File Prefix text box, enter the name of the model or some other meaningful name.

6. Select More.

7. Set Output Category to Durability files.

8. Set either of the following to On:

• DAC Files

• RPC File(s)

9. Select Close in the Solver Settings dialog box.

After the simulation finishes, Adams/View creates the RPC III or DAC files for all defined requests. If you’re running an interactive simulation, you need to reset the model before the files are created.

Learn more about Requests.

9Exporting DataSimulating the Model

Simulating the ModelUsing Adams/Durability you can access test data in two formats: RPC III Format or DAC Format. First you must validate your model, then you can perform what-if simulations.

Performing Model Validation

When simulating your model to compare it to physical test data, you need to follow the general steps listed below.

To validate a model:

1. Input the forces or motions using spline data (see Referencing Test Data). Make sure you use the INTERP function for the RPC III or DAC files (see Applying Test Data).

2. Set up requests that correspond to the physical data channels (learn how).

3. Set up Adams/View to output the results in the format you prefer (learn how).

4. When you’re ready to simulate the model, make sure the End Time and number of Steps in the Simulation container correspond to the physical test data that you are using for model validation.

5. When the simulation completes, make sure you reset the model.

6. Import the virtual and physical test data (see Importing Test Data).

7. Use Adams/PostProcessor to compare the virtual data to the physical test data (see Plotting Data).

8. Modify your model and repeat these steps as necessary until you’re satisfied that the virtual test data correlates well with the physical test data.

Performing Durability What-If Simulations

Once you’ve validated your model, you’re ready to make modifications to determine their impact on system response or component durability. To obtain data that lets you determine system sensitivity to various design changes, you should follow the general steps listed below.

To perform durability what-if simulations:

1. Make simple model modifications, so that you can easily determine model sensitivity to each change.

2. Use the same input forces or motions that you used in the initial model validation.

3. Use the same requests that correspond to the physical data channels (learn how).

4. Set up Adams/View to output the results in the format that you prefer (learn how).

5. When you’re ready to simulate the model, make sure the End Time and number of Steps in the Simulation container correspond to the physical test data that you used for model validation.

6. When the simulation completes, make sure you reset the model.

7. Import the new virtual and physical test data (see Importing Test Data).

Adams/DurabilitySimulating the Model

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8. Use Adams/PostProcessor to compare the virtual data to the physical test data (see Plotting Data). If system response looks better, you can input these data to durability analysis programs and compare them to the results you obtained from the physical test data. Otherwise, make further model modifications and simulate again.

1Using Adams/Durability with Adams/Solver

Using Adams/Durability with Adams/Solver

Adams/DurabilityUsing Adams/Durability with Adams/Solver

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Using Adams/Durability with Adams/SolverAlthough we recommend that you use Adams/View to access Adams/Durability functionality, you can perform these functions directly within Adams/Solver. This topic provides specific statement syntax that you can use to implement Adams/Durability functionality in Adams/Solver. For complete details on any statements in this topic, see the Adams/Solver online help.

Setting Up a Motion or ForceAdams/Solver includes the INTERP function as part of Adams/Durability support. When defining a motion or force with data from an RPC III Format or DAC Format file, you must define a spline with the data file as input, and use the INTERP function in the MOTION, GFORCE, SFORCE, or VFORCE statement. For example, you could define a translational motion as follows:

MOTION/Motion Id, TRANSLATIONAL, JOINT=id, FUNCTION=INTERP(time, 3, spline id)

where:

• Motion id is a sequential number that represents the current motion number.

• TRANSLATIONAL is the motion type.

• Joint id specifies the joint marker that is moving.

• spline id is the identifier of the spline that specifies the RPC III or DAC file input.

Setting Up a SplineWith Adams/Durability, the SPLINE statement includes arguments that let you input RPC III Format or DAC Format time history data files. These data files provide one dependent variable and one independent variable, TIME, as a fixed-time interval. Because RPC III files support multiple channels of data in a single file, you must specify a channel for this type of file. DAC time history files only have a single channel of data in a file.

The SPLINE statement, as it appears for durability analysis, looks like:

SPLINE/id, FILE=path [, CHANNEL=n]

Where:

• id is the identifier of the spline.

• path is the absolute or relative path to the RPC III or DAC file. These files may have any file extension. Adams/Solver reads the file header to determine the file type.

• n is the channel number. This parameter is required for RPC III files, even if the file only has a single channel. This parameter should not appear for DAC files.

../adams_solver/master.htm

3Using Adams/Durability with Adams/SolverUsing Adams/Durability with Adams/Solver

Setting Up and Outputting FEM DataYou use the FEMDATA statement to indicate the set of data you want Adams/Solver to write for subsequent finite-element (FE) or durability analyses. You can specify loads on a component, modal coordinates or nodal deformations, or stresses or strains of a flexible body.

As part of Adams/Durability, the OUTPUT statement indicates output options for each type of FEMDATA. You use the OUTPUT statement to specify the format of each type.

The following output formats may be available, depending on the type of data you are using:

• DAC

• Generic

• ANSYS

• ABAQUS

• NASTRAN

• RPC III

Setting Up and Outputting RequestsYou use the REQUEST statement to indicate the set of data you want Adams/Solver to write. Adams/Durability supports any existing form of the REQUEST statement. You can specify functions, forces, displacements, velocities, acceleration, and user requests.

As part of Adams/Durability, the OUTPUT statement includes two additional output types, RPCSAVE and DACSAVE. When you specify an OUTPUT statement with one of these types, Adams/Solver writes the request to a file with a .rsp or .dac extension, respectively.

For RPC files, Adams/Solver writes all of the requests to a single file. Because DAC files can only have a single channel per file, Adams/Solver writes a separate file for each component of each request. Therefore, every request results in six output files.

The statement for RPC III output is:

OUTPUT/ RPCSAVE

The statement for DAC output is:

OUTPUT/ DACSAVE

Adams/DurabilityUsing Adams/Durability with Adams/Solver

4

1About User Functions

About User Functions

Adams/DurabilityUser Functions

2

User FunctionsYou can use functions in Adams/Durability to interrogate a flexible or rigid body for useful stress, strain, or life data. The user functions are:

• HOT_SPOTS

• LIFE

• MAX_STRESS

• TOP_SPOTS

These functions facilitate the definition of a design objective or variable that can be used in a design of experiments (DOE) or optimization study. When Adams/Durability is loaded, you can find these functions in the Misc. Functions category of the Adams/View Function Builder.

3About User FunctionsHOT_SPOTS

HOT_SPOTSReturns all of the spots on the body that exceed the specified threshold. The spots returned are sorted from hottest to lowest. This function is useful for obtaining information on all hot spots on a body. A hot spot is defined as a point where the stress exceeds a certain defined limit (threshold). The Assist dialog box for the HOT_SPOTS (see Array HOT_SPOTS (Name array, Integer array, Real array)) function is available in the Adams/View Function Builder.

Radius defines the distance between spots (that is, the spherical region that is considered one spot) on the body. A value of zero (0) considers all points (nodes) of the body as a unique spot.

The figure below shows a close up of the hottest region of stress on a flexible body. This illustrates how the radius can affect the definition of a hot spot region. In this figure, the top seven hottest nodes (those with the largest stress) are listed. If seven hot spots or a threshold of 100 is specified with no (zero) radius, all of these nodes would be returned by the user function. If a radius of 0.5 mm is specified, only node four from this region would be returned, and the remaining hot spots would come from nodes with the highest stress from other regions.

A 6-by-N array is returned, where N is the number of hot spots. The X, Y, Z, Time, Value, and Node are the columns in the array. Coordinate data is returned in the local part reference frame (LPRF) of the body.

Adams/DurabilityHOT_SPOTS

4

Value is the maximum value of the hot spot for the analysis. Time is the actual time of the analysis that the maximum value occurred. The number of spots found is defined as the number of rows in the array.

If no value exceeding the threshold is found for the body, HOT_SPOTS returns an array with one row of the hottest spot. If the body or analysis does not exist, or the type of data does not exist for the specified body, HOT_SPOTS issues an error message and returns an array with one row filled with zeros.

Example

Suppose you want to locate hot spots in a part called shaft, where the maximum von Mises stress is higher than 700 MPa for the analysis named engine_stall. And, you only want to consider points that are 25 millimeters apart from the other hot spots. After creating a rigid stress object for the part, you can use the following Adams/View command:

VAR SET VAR=hotspots REAL=(EVAL(HOT_SPOTS({shaft,engine_stall}, {0,1}, {700.0,25.0})))

Note that it is not necessary to define all elements in each array argument explicitly. For example, if engine_stall was the default analysis run, and because the default setting for stress is 1, you could simplify the above command to:

VAR SET VAR=hotspots REAL=(EVAL(HOT_SPOTS(shaft, 0, {700,25})));

5About User FunctionsLIFE

LIFEReturns the minimum life of a flexible body for the specified analysis. Results from FE-Fatigue or MSC.Fatigue for the flexible body need to be imported before using this function. If no fatigue data are available, the function returns 0 (zero). The analysis argument is optional. The default analysis is used if one is not given. The Assist dialog box for the LIFE function (see Real LIFE (FlexBody [, Analysis])) is available in the Adams/View Function Builder.

../adams_view_fn/master.htm

Adams/DurabilityMAX_STRESS

6

MAX_STRESSReturns the maximum value of stress for the body for the default analysis. The last-run analysis is the default analysis. If the body does not exist or does not contain stress data, or there is no default analysis, MAX_STRESS issues an error message and returns a zero. The Assist dialog box for the MAX_STRESS function (see Real MAX_STRESS (Body, Criterion)) is available in the Adams/View Function Builder.

Example

The following Adams/View command (see Adams/View command file) will set the maximum principal stress of the flexible body named link in the current model for the last-run analysis to the variable maxstress. Because units of stress are equivalent to pressure, maxstress will also have the correct units associated with the variable.

VAR SET VAR=maxstress REAL=(EVAL(MAX_STRESS(link, 7))) UNITS=PRESSURE;


7About User FunctionsTOP_SPOTS

TOP_SPOTSReturns a fixed number of the hottest spots in the body. The Assist dialog box for the TOP_SPOTS function (see Array TOP_SPOTS (Name array, Integer array, Real array)) is available in the Adams/View Function Builder.

Count is the number of hot spots to locate. If Count is zero, TOP_SPOTS uses Percent to determine the number of hot spots to return based on the total number of points nodes in the body. If both Count and Percent are zero, then TOP_SPOTS issues an error message and returns an array with one row filled with zeros.

Radius defines the distance between spots (that is, the spherical region that is considered one spot) on the body. A value of zero (0) considers all nodes of the body as a unique hot spot.

The figure below shows a close up of the hottest region of stress on a flexible body. This illustrates how the radius can affect the definition of a hot spot region. In this figure, the top seven hottest nodes (those with the largest stress) are listed. If seven hot spots or a threshold of 100 is specified with no (zero) radius, all of these nodes would be returned by the user function. If a radius of 0.5 mm is specified, only node four from this region would be returned, and the remaining hot spots would come from nodes with the highest stress from other regions.



Adams/DurabilityTOP_SPOTS

8

TOP_SPOTS returns a 6xN array. X, Y, Z, Time, Value, and Node occupy the columns in the array. Coordinate data is returned in the local part reference frams (LPRF) of the body. The number of spots TOP_SPOTS found is the number of rows in the array.

If the body or analysis does not exist, or no data of the specified type is available for the body, TOP_SPOTS issues an error message and returns an array with one row filled with zeros.

Examples

Use the following Adams/View commands (see Adams/View command file) to return the maximum principal stress in the link, as well as the node and time that the peak stress occurred:

VAR SET VAR=topspot REAL=(EVAL(TOP_SPOTS(link,{7,1},{0,0.0},1)));VAR SET VAR=maxstress REAL=(topspot.real_value[5]) UNITS=PRESSURE; VAR SET VAR=maxnode INT=(topspot.real_value[6]); VAR SET VAR=maxtime REAL=(topspot.real_value[4]) UNITS=TIME;

Similarly, the location of maximum stress could also be extracted from the returned array as real values 1, 2, and 3

1Stress Recovery Theory

Stress Recovery Theory

Adams/DurabilityCoordinate Reference Transformation

2

Coordinate Reference TransformationSince stress and strain are second order tensors, the following equation will be used to transform these quantities to a reference coordinate system:

where:

• is the skew-rotation matrix from the flexible body’s LPRF (FE origin) to the marker’s

coordinate reference

• is the symmetric stress or strain tensor:

S ' AR T S AR =

AR

S

S

Sxx Sxy Sxz

Syx Syy Syz

Szx Szy Szz

= where Sij Sji=

3Stress Recovery TheoryStress Recovery Analysis

Stress Recovery AnalysisThere are many ways to calculate the flexibility effect of complex machine members. Adams uses a modal synthesis method. This approach is very effective because it allows you to drastically reduce the total number of degrees of freedom (DOFs) of a typical FE component used for detailed stress analysis, while preserving its local deformations with high level of accuracy (assuming that the modal component synthesis procedure is performed correctly). Flexible structural component motion with N DOF and defined boundaries is described by a combination of P normal modes (normal constrained modes) and S constraint modes (static correction modes).

The system DOFs are partitioned between internal and boundary DOFs, so the flexible body motion equation becomes:

(1)

with I internal DOFs (equal to R = N – S) and B boundary ones (equal to S).

From a static equilibrium analysis, assuming that interior forces are set to zero, equation (1) becomes:

(2)

and led to extract the constrain modes matrix as :

(3)

Moreover, from an eigenvalue analysis, you have:

(4)

yielding the normal modes matrix :

(5)

From equation (5), a subset of the N normal modes is considered, and the physical coordinates are calculated as a linear combination of the mode shapes.

(6)

where:

• {x} is the vector of physical displacements

mBB 0

0 mII

xB

xI kBB kBI

kIB kII

xB

xI

+fB

fI

=

kBB kBI

kIB kII

xB

xI fB

fI

=

C

C kII l– kIB –=

2 mII – kII + I

N

N I 1 ..., I P =

x xB

xI I 0

C N

qB

qI

q = = =

Adams/DurabilityStress Recovery Analysis

4

• {q} is the vector of modal coordinates

• [ ]=[{ }I,...,{ }P+S] is the modal matrix that includes both P normal and S constraint modes

Now, equation (1) can be rewritten as:

(7)

An ortho-normalization of the reduced system described by equation (7) is performed while translating from each FE output file into the Adams modal neutral file (MNF). The effect is to obtain a diagonal model and to associate a frequency content to the static correction modes as well.

FEM structural analysis obtains the modal and static information needed to perform modal reduction, in a sequence of static load cases with varying boundary conditions, as described in equation (1).

Adams assembles and solves fully inertially coupled equation of motion of the mechanical system including the flexible part(s). It also adds the generalized modal coordinates as unknowns. Adams/Solver manages the full set of equations giving the parts rigid body coordinates and modal coordinates as a result. Adams/Solver also computes the reaction forces acting on the flexible component through algebraic constraint or external forces.

Once Adams/Solver has computed the set of modal coordinates, it is possible to recover stress in the FE code using equation (6) and pass the physical displacements to the FE code. Strains and stresses would

then be recovered in the FE code from the solution of by:

(8)

(9)

where:

• is the strain vector

• is the stress vector

• is a function matrix of the FE geometry relating strains to displacements

• is the stress-strain relationship (constitutive equation based on the material properties)

Note that this can be a very inefficient solution for large meshes and when a large number of time steps are involved. In addition, this method is dependent on the Adams solution and, therefore, not conducive to system studies, such as DOE or optimization.

M q· K q + mBB mBN

mNB mNN

q· B

q· I kBB 0

0 kNN

qB

qI

+f·B

f·I

f· = = =

X

B x =

E =

B

E

5Stress Recovery TheoryModal Stress Recovery

Modal Stress RecoveryModal stress recovery (MSR) is an analysis-independent alternative to stress recovery analysis. During the modal basis generation phase, the FE code can also pre-compute additional information for lately combining the modal coordinates to the FE stresses in Adams.

Substituting in equation (6) and combining equations (8) and (9) yields:

(10)

where:

(11)

and:

(12)

Here, is the ortho-normalized modal stress matrix that identifies the stress component associated

with each orthogonalized mode shape.

Therefore, assuming that the reduction of the full set of mode shapes of the flexible body to a subset is correct and comprehensive of all the required effects, the stress distribution related to the body deformation can be calculated in a similar way to the one used for physical displacements (equation (6)).

If the modal stress matrix has been computed by the FE code and stored in the MNF for the flexible body, it is possible to perform MSR in Adams. It is also possible to perform MSR in the FE code or in the fatigue code, such as MSC.Fatigue, with the modal coordinates from Adams and the modal stress matrix from the FE code's database.

By combining the modal stress matrix with the modal coordinates as in equation (10), it is possible to calculate stress components with very good accuracy and a computational time much shorter than a full dynamic analysis in the FE code.

Likewise, for strains we have:

and

where:

• is the strain vector for the flexible body

• is the ortho-normalized modal strain matrix identifying the strain component associated

with each orthogonalized mode shape

q =

E B =

1 ..., P S+ =

q =

B =

Adams/DurabilityRecovering Stress on Preloaded Flexible Bodies

6

Recovering Stress on Preloaded Flexible BodiesFor a preloaded flexible body, equation (10) becomes:

where:

is the prestress state due to preload. This vector also needs to be computed by the FE code and

stored in the MNF for the flexible component to perform MSR on proloaded flexible bodies in Adams. Note that this vector could represent a nonlinear stress state of the flexible component since the preload could have taken on a nonlinear load path.

Similarly, recovering strain on a preloaded flexible body becomes:

where:

is the prestrain state of the flexible body due to preload.

Note that when exporting modal coordinates to a fatigue program, such as MSC.Fatigue, Adams/Durability outputs one more DAC file or RPC file channel than the number of modes for a preloaded flexible body. This additional file or load channel equals a constant value of one (1.0), representing the DC component or static offset of the pre-stress or pre-strain. This file or channel should be mapped to the result set of the preload case from the FE code.

' 0 q +=

0

' 0 e q +=

0

7Stress Recovery TheoryMesh Refinement for Stress Recovery

Mesh Refinement for Stress RecoveryThe FEM is an approximate method, employing a mesh with elements of finite length. This means that there will be some error in the results related to the mesh size or discretization. The convergence rate of the mesh discretization error can be expressed in the L2-Norm.

For displacements, the error is:

For stress or strain, it is:

where:

• c is a constant independent of h and u.

• u is the phenomenon being approximated (x for displacements or for stresses)

• h is the mesh parameter characterizing the refinement of the mesh (0<h<1)

The mesh parameter, h, can also be thought of as the inverse of n, the number of elements in the mesh (1/n). In the limit, as h -> 0, the error also goes to zero. However, the convergence rate of error for displacements is better than that for stress or strain. The dynamics of a flexible component depend on the ability of its mesh to capture deformations or displacements. Therefore, a mesh suitable for dynamics may not necessarily be suitable for stress recovery.

Therefore, you should consider mesh refinement if you are interested in recovering stress for the component. In the case of MSR, this means that you must perform the mesh-refinement stage before the initial modal analysis in the FE code. There is no assurance that the modal coordinates computed by Adams for a given mesh density can be suitably applied to another mesh density of the same component or geometry. In fact, the opposite has been observed and you should only combine modal coordinates with modal stresses or strains from the same FE run that produced the mode shapes.

e 0 ch2 u 2

e 1 ch u 2

Adams/DurabilityComponent Mode Synthesis

8

Component Mode Synthesis

BackgroundComponent mode synthesis is an effective method of evaluating stress. The following topics show how the results of a finite-element (FE) analysis are comparable to theoretical ones

An important issue in machine design is ensuring that the strength of a part’s material exceeds the stress of the loads imposed on it.

The basic stress equation formulas assume that no geometrical irregularities occur in the member under consideration. This is not always true in the practical design of real machines, when changes to the cross-sections of the members are permitted.

Such geometric variations in a machine part modify the stress distribution in the neighborhood of the discontinuities, so that the elementary stress equation no longer describes the correct stress distribution. For example, if you consider the latter on a rectangular plate with a hole in the center, you would find that the stress is highest at the edge of the hole, and that the stress concentration effect is highly dependent on the vicinity of the hole’s edge.

A theoretical stress concentration factor (Kt) is used to relate the maximum stress at the discontinuity to

the nominal stress; the factor is defined by the equations.

where Kt is used for normal stress and Kts is used for shear stress.

The nominal stress is usually calculated by the basic stress equations. Meanwhile, the maximum stress (which depends on the geometry of the part or the type of irregularity considered) can be calculated by numerical methods (finite-element analysis (FEA)) or by experimental tests.

Stress Concentration EvaluationA study on stress and stress concentration evaluation was performed using modern numerical tools. The multi-body approach to the study of flexible parts has been compared to the well-known finite-element model (FEM) method, giving important results about the accuracy of the component mode synthesis method used by multi-body software Adams.

Example: Rectangular Filleted Bar in BendingThis example shows how stress on a reference model is calculated (using the CMS approach), comparing the MB CMS results with finite-element model (FEM) results and analytical ones.

It validates stress recovery from a multi-body analysis in the presence of stress concentration, considering a rectangular plane filleted bar under bending load.

Kt

max

0----------- Kt

max

0----------= =

9Stress Recovery TheoryComponent Mode Synthesis

The following figure shows the stress concentration factor (Kt) for the normal stress, plotted against the

geometric dimensions of the part. The main test case properties are shown in table below the figure.

In this example, Kt= 2.225, so the maximum nominal stress can be analytically evaluated as:

and the maximum normal stress due to the stress concentration is:

The same problem was studied in a finite-element program (ANSYS 5.4) and a multi-body software (Adams 9.2).

A planar FE model was realized using shell43 elements (7194 elements and 7369 nodes). Then, the model was exported in Adams, creating an MNF with 26 modes (20 normal and 6 static correction modes).

MaterialYoung Modulus

(N/m2) D (m) d (m) r (m) s (m) M (N m)

Steel 2.1E11 5.0E-2 3.85E-2 2E-3 1.0E-2 1

nMW----- M

J----- d

2--- 6 M

s d2------------ 6 1

0.01 3.85E 22–----------------------------------------- 4.0479E 05N m+= = = = =

max Kt n 9.0065E 05N m+= =


10

Both FE and MB models were loaded with the same conditions as in the analytical case. The modal coordinateresulting from the MB analysis and the modal stress matrix were used to calculate the nodal stresses.

The results of the comparisons between FEM and MB analysis are shown below:

Stress comparisons (N/m2)

Kt

ANSYS Node 408 -8.7086E+05 -4.0686E+04 0.0 1.4512E+05 0.0 0.0 8.8758E+05 2.1922

ANSYS Node 4040 -4.0492E+05 -0.0094E+04 0.0 -0.00678E+05 0.0 0.0 4.0487E+05

Adams Node 408 -8.5691E+05 -3.9986E+04 0.0 1.4284E+05 0.0 0.0 8.7340E+05 2.1640

Adams Node 4040 -4.0375E+05 -0.0302E+04 0.0 -0.00346E+05 0.0 0.0 4.0360E+05

x y z xy yz xz vonmises

11Stress Recovery TheoryComponent Mode Synthesis


12

1About Test Data

About Test Data

Adams/DurabilityPlotting Test Data

2

Plotting Test Data

Plotting DataOnce you've imported test data (whether physical or virtual), the source files appear in the Adams/PostProcessor source list. Use the Source pull-down menu to select either RPC III Format or DAC Format files to appear in the list. You can then plot data from a selected source file in the list.

If the source file is an RPC III file, Adams/PostProcessor displays a Channel list. If the source file is a DAC file, Adams/PostProcessor displays a File Data list.

To plot test data after importing it, you can do one of the following:

1. Select the Surf check box and select data in the Channel or File Data list to see what the curve looks like.

2. Clear the Surf check box.

3. Select Clear Plot to remove any curves in the plot area.

4. Select data in the Channel or File Data list, and then select Add Curves to display the curve.

Comparing Data

To graphically compare data:

1. Clear the Surf check box.

2. Select Clear Plot to remove any curves in the plot area.

3. Set Source to either RPC III or DAC format files.

4. Select the file from the source list.

5. Make a selection in the File Data list, and then select Add Curves to display the curve.

6. Repeat Steps 3 through 5 to add more curves to the plot.

Importing Test DataTest data can appear in RPC III Format or DAC Format. The steps involved in importing the data are essentially the same regardless of the file format; however, it is important to remember that RPC III format supports multiple channels per file while DAC format only has one channel per file.

To import test data:

1. In the Adams/PostProcessor window, from the File menu, point to Import, and then select either DAC Files or RPC File as appropriate to display the File to Import dialog box.

2. Right-click the File to Read text box, and then select Browse to display the Select File dialog box.

3. Select one or more files and select OK.

3About Test DataPlotting Test Data

With DAC files, you may want to select multiple files because each file has only one result set. You can use Shift+click or Ctrl+click multiple selection techniques.

4. Select OK in the File Import dialog box.

Adams/PostProcessor creates a DAC_FILE or RPC_FILE object below Root in the database after you successfully import these files. Adams/PostProcessor only stores information about the imported file from the file header. It does not store time history data in the database. Adams/PostProcessor creates Result_Set_Component place holders below the file object for each RPC III data channel or DAC file.

Adams/DurabilityUsing Test Data

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Using Test Data

Applying Test DataOnce you reference test data using a spline, you use the INTERP function to apply the spline as a force (torque) or motion.

Using an INTERP Function in a Force or Torque

To apply a spline to a force in a dynamic model, you modify the force and specify a function expression that includes an INTERP function that references the spline. For example, to modify a single-component force (SFORCE) to use test data that is scaled by -1000, follow the steps below.

To modify an SFORCE:

1. In your model, right-click the Force icon, point to Force:force_name or Torque:torque_name, and then select Modify.

The Modify a Force dialog box appears.

2. In the F(time,...)= text box, enter the following function: where:

• -1000 is the scale you need to apply to the spline data.

• 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.

• spline_name is the name of the referenced spline.

3. Select OK.

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

Tip: You can specify any expression of time in the first argument of the INTERP function. For example, you can have a spline that references test track data with a 110-second duration, but only simulate the last 30 seconds of this data. The INTERP function in this case would be:

INTERP(time+80, 3, spline_name)

In addition, you would set the simulation time from 0 to 30 seconds.

5About Test DataUsing Test Data

Using an INTERP Function in a Motion

To apply a spline in any motion, you modify the motion and specify an INTERP function that references the spline. For rotational motion, test data in DAC and RPC III files may be acquired in degrees, so you would add a conversion from degrees to radians (DTOR) in your function expression because Adams/Solver expects rotational motion in radians.

To modify a joint motion:

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

The impose Joint Motion dialog box appears.

2. In the F(time,...)= text box, enter one of the following functions:

• For rotational motion: INTERP(time, 3, spline_name)*DTOR

• For translational motion: INTERP(time, 3, spline_name), 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.

• spline_name is the name of the referenced spline.

• DTOR is the degrees to radians conversion function.

3. Select OK.

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

Browsing RPC III or DAC DataTo assist you in defining a spline using RPC III or DAC file input, you can use the Database Navigator to view file header or detailed data.

To view RPC III or DAC file headers:

1. Import the RPC III or DAC file. Learn how.

2. In Adams/View, from the Tools menu, select Database Navigator.

3. In the Filter area of the Database Navigator dialog box, use the pull-down menu to select All.

4. If necessary, widen the Database Navigator dialog box so that you can see the column that specifies the type of object.

5. Select the object RPC_FILE or DAC_FILE.

6. Select OK to open an Information window.

7. If you haven’t selected it previously, select the Verbose check box, and then select Apply.

Tip: You must select the Clear button to erase the data in the Information dialog box. Closing the dialog box leaves the data in the dialog box the next time you open it.


6

8. When you’re done, select the Close button.

To view RPC III or DAC file data:

1. If necessary, follow Steps 1 through 4 in the procedure above.

2. To expand the object to show the data in the file, double-click the object RPC_FILE or DAC_FILE.

3. Select the desired data channel (note that DAC files only have a single data channel), and select OK to open an Information window. This displays a summary of the data from the header. If you want to see the actual data values continue with Step 4.

Warning: The entire channel of data appears in the dialog box. If the data has millions of data points this could take a significant amount of time to load and display.

4. If you haven’t selected it previously, select the Verbose check box, and then select Apply.

Creating a SplineYou use a spline to reference time history test data in RPC III Format or DAC Format. Each spline that you define uses one independent variable (time) and one dependent variable (or channel) from the DAC or RPC III file. By definition, DAC files only contain one channel of data, while RPC III files can contain multiple channels identified by an integer channel number.

This procedure provides a brief overview on how to create splines for use with Adams/Durability. Learn more about data element Splines.

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 the name you want to use for your spline.

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

The Select File dialog box appears.

4. Select the DAC or RPC III file.

Because these files can have any file extension, Adams/View opens the file and reads the file header to determine the file type during the verification stage of the simulation. If the file type is RPC III, you must enter a valid channel number in the Channel text box. If no channel or an invalid number is specified for RPC III spline data, Adams/View reports an error and stops the simulation.

5. In the Channel text box, enter the channel number you want this spline to use.

6. Select OK.

Note: The range of valid numbers is from 1 to the number of channels in the file.

7About Test DataUsing Test Data

Adams/View creates a spline that references the physical test data from the channel in the file.

Filtering Test DataThere are two ways to filter your test data stored in RPC III or DAC files:

• Use the Curve Edit Toolbar in Adams/PostProcessor to modify the data once the file has been imported and plotted in Adams/PostProcessor. For more information, see the Adams/PostProcessor online help.

• Use the standalone utility, durfilter, that is available from the Adams/Durability Toolkit.

Referencing Test DataHere, you'll find information on the types of test data that you can input to Adams/Durability, and the method for applying that data to an Adams model. When you input physical data to Adams/Durability, you create a Spline data element and define the output channel used to record the data of interest.

Using Adams/Durability you can access test data in two formats:

• RPC III Format

• DAC Format

Note: • Adams/View ignores the Linear Extrapolate text box for splines that reference DAC or RPC III files because Adams/Durability only allows constant extrapolation of test data. In constant extrapolation, Adams/Durability uses the last recorded value in the test file if the simulation extends beyond the duration of the test in the file.

• Adams/View ignores the Block Name text box for splines that reference DAC or RPC III files.

../adams_ppt/master.htm


8

1Using the Adams/Durability Toolkit

Using the Adams/Durability Toolkit

Adams/DurabilityAdams/Durability Toolkit

2

Adams/Durability ToolkitThe Adams/Durability toolkit has three utilities for processing data or converting data from one format to another. They are:

• Durfilter - Filtering test data

• MNF2FES - Creating FES files from MNF

• RES2DUR - Processing Results files for Durability

To run the Adams/Durability toolkit from the program menu, enter mdadams2010 –c durtk on UNIX systems or mdadams2010 durtk on Windows systems.

Creating FES Files from MNFUsing the MNF2FES tool in the Adams/Durability toolkit, you can create an nCode partial FES file that can be used in an FE-Fatigue analysis from a Modal Neutral File (MNF). The MNF must contain either stress or strain modes for a partial FES file to be created. The difference between a partial and full FES file is that the full FES file contains material and loading information, while the partial FES only contains stress or strain information that is independent of the loading history.

MNF2FES Format

Following is the format of the mfn2fes command under durtk:

mnf2fes MNFname [-b] [-e] [-n nodefile] [-o FESname] [-u units]

Arguments

Following are the arguments for the mnf2fes statement.

Argument: Description:

MNFname Specifies the name of the MNF to process.

-b Specifies the binary FES file (.fes) switch.

Default: ASCII (.asc) format

-e Specifies whether or not to create an FES file of strain data.

Default: Create a stress data FES file.

Note: A stress FES file can be used in an E-N or S-N fatigue analysis, while an FES file containing strains can only be used in an EN analysis.

3Using the Adams/Durability ToolkitAdams/Durability Toolkit

-n nodefile Specifies the file name with a list of nodes to process. Only those nodes listed in this file will have their stress or strain stored in the FES and therefore, processed by FE-Fatigue.

Default: All nodes in the MNF will be processed.

-o FESfile Specifies name of the FES file to be created.

Default: Derive name of FES file from MNFname.

-u units Specifies units of stresses to be stored in the FES (not needed with the -e option).

FES-supported units: MPA, PA, PSI, KSI, KGPA

Default: MPA


Adams/DurabilityFiltering Test Data

4

Filtering Test Data

ArgumentsFollowing are the arguments that can be used in your durfilter statement.


inputfile Specifies the name of the RPC III Format or DAC Format file to process, or the prefix (job name) of a group of DAC files to process.

-b f1 f2 Specifies a band-pass filter. It takes two frequency values, f1 and f2, which are specified in Hertz. Only frequencies between f1 and f2 are passed using this filter option. Range: 0 < f1 < f2 <= Nyquist, where Nyquist is half the sampling frequency of the data.

-c channels Specifies the channels in an RPC III file to filter, or a group of DAC files to filter. It takes one or more integer values separated by commas (,) or a colon (:). These integer values represent specific channel IDs or a range of channel IDs to process. This option is used in combination with the inputfile argument to specify a set of DAC files to filter.

-d factor Specifies the decimation factor to be applied to the test data. It takes one integer value as the decimation factor. Decimation reduces the sampled rate of the data by this factor. For example, a factor of 2 halves the number of data points. A factor of 1 results in no change in the sample rate and this is the default.

Range: factor > 0

-h freq Specifies a high-pass filter. It takes one frequency value, freq, specified in Hertz. Only frequencies above this cutoff frequency are passed.

Range: 0 < freq <= Nyquist, where Nyquist is half the sampling frequency of the data.

-l freq Specifies a low-pass filter. It takes one frequency value, freq, specified in Hertz. Only frequencies below this cutoff frequency are passed.

Range:0 < freq <= Nyquist, where Nyquist is half the sampling frequency of the data.

-n order Specifies the order of the filter to apply. It takes one integer value as the filter order.

Default: order = 6. Range: order > 0.

5Using the Adams/Durability ToolkitFiltering Test Data

Channel SelectionTypically, a group of DAC Format files acquired from one experiment or test are named with a common prefix representing the job name and a two- or three-digit suffix representing the channel ID before the extension (.dac). To apply the same filter to all or a set of DAC files from the same test, you specify the prefix or job name only in the inputfile argument and the channel IDs or range of channel IDs using the -c channels option. These arguments will then be used to compose the input file names for durfilter to process as <inputfile><channel_ID>.dac where channel_ID is one of the channel IDs specified.

For RPC III data, only the channels specified in the -c option will be filtered and written out if they exist.

Data DecimationDecimation or downsampling can be an effective way of saving disk space or reducing the amount of data that Adams/Solver needs to interpolate if the given set of data has been oversampled. It can also result in aliasing, however, a form of corruption in digital data. To ensure that aliasing does not occur, the maximum frequency in the data should be less than half the decimated data sample rate.

Decimation is performed after filtering (if both are specified) to ensure more effective downsampling of the test data.

Data FilteringYou can only specify one filter option in the durfilter argument list. The transfer function coefficient form of the MATLAB Butter function is used in each filter option. Also, a forward and backward pass is always performed to ensure no phase shift is introduced in the data.

For example, to perform a 6th-order high pass Butterworth filter with a cutoff frequency of 13 Hz and zero-phase shift on data sampled at 200 Hz, the following MATLAB syntax (or its equivalent) is used:

[b,a] = butter(6, 13/100, ‘high’);

y = filtfilt(b, a, x);

where:

-o outputfile Specifies the file name for storing the filtered and/or decimated data. A default output file name composed of inputfile and the filtered/decimated specification will be given if you do not specify this option.

-s f1 f2 Specifies a band-stop filter. It takes two frequency values, f1 and f2, which are specified in Hertz. Only frequencies before f1 and beyond f2 are passed using this filter option.

Range: 0 < f1 < f2 <= Nyquist, where Nyquist is half the sampling frequency of the data.



6

• b is the vector of numerator filter design coefficients and a is the vector of denominator coefficients of the transfer function.

• x is the vector of test data

• y is the vector of filtered data

• 6 is the specified filter order

• 13 is the specified cutoff frequency

• 100 is the computed Nyquist frequency (1/2 sampled rate)

In the transfer function coefficient form of the Butterworth filter, numerical problems can arise for filter orders as low as 15. Filter orders between 6 and 8 should be sufficient for most applications.

Default Naming Convention of Filtered FilesIf you do not specify the -o outputfile option, durfilter creates output file(s) of the filtered data with names composed of the inputfile prefix and filter specifications as follows.

For high or low pass filters:

<inputfile><h|l><order>_<freq>_<d><factor>_<channel_id>.dac

For band pass or stop filters:

<inputfile><b|s><order>_<f1>_<f2>_<d><factor>_<channel_id>.dac

For RPC III Format data, the _<channel_id> is left off the default output file name and the extension is .rsp.

ExamplesHere are three examples of how to use durfilter.

• Example 1

• Example 2

• Example 3

Example 1durfilter /disk/test/block.rpc –b 1 60 –n 8

All frequencies between 1 and 60 Hz are passed with an 8th-order filter on the data of each channel found in the RPC III file /disk/test/block.rpc. Because no outputfile specification is provided, the filtered data will be stored in file /disk/test/block_b8_1_60.rpc.

Example 2durfilter rawdata –c 7:12 –l 120 –d2 –o filterdata

7Using the Adams/Durability ToolkitFiltering Test Data

A 6th-order low-pass filter is performed on the input DAC files in column 1 of the table shown below. The filtered data is decimated by a factor of 2 and stored in the DAC files in column two of this table.

Example 3durfilter beltest_ –c 101,102,103,201,202,203 –h 10 –n 8

An eighth-order high-pass filter is performed on the input DAC files in column one of the table shown below. Because no outputfile specification is provided, the filtered data is stored in DAC files with names composed of the given filter specifications as shown in column two of this table.

Filtering Test Data (Durfilter)You use the durfilter tool of the Adams/Durability toolkit to filtering test data stored in RPC III files or in one or more DAC files. The durfilter tool is only accessible from the durtk selection code in the Adams Program Menu. We recommend you filter your experimental data to remove unwanted frequencies before input to Adams/Solver. durfilter uses the transfer coefficient function form of the Butterworth digital filter from MATLAB. Four filter options are available:

• band-pass

• high-pass

• low-pass

• band-stop (or notch)

Input filename: Output filename:

rawdata07.dac filterdata07.dac






Input filename: Output filename:

beltest_101.dac beltest_h8_10_101.dac







8

A two-pass filter operation is performed to ensure zero-phase shift of the test data. Decimation of the test data is also available in durfilter.

FormatFollowing is the format of the filtering command using durfilter:

durfilter inputfile[ -b f1 f2 | -h freq | -l freq | -s f1 f2 ][ -c channels ][ -d factor ][ -n order ][ -o outputfile ]

9Using the Adams/Durability ToolkitProcessing Results File for Durability

Processing Results File for DurabilityWhen FEMDATA statements, DACSAVE, or RPCSAVE OUTPUT options have been specified in the .adm file, a results file is produced. This file contains only the results of the simulation that are necessary to process the FEMDATA statements and/or DAC or RPC files. The format of the results file is Adams XRF (XML Result File). This file is named after the Adams results file (run.res), and is not deleted at the end of the simulation. Note that this results file format is platform independent.

When this results file is processed, a temporary file with the extension .rcf (Results Cache File) is produced. This file maps the data contained in the results on disk, instead of in memory. This temporary file is platform dependent. The name of the file is run_os.rcf, where run is the name of the results file and os is the name of the operating system (irix32 for SGI IRIX, hpux11 for HP/UX, and so on). You can safely delete this temporary file; however, note that it takes a considerable amount of time to regenerate it from the results file. As long as it exists, any subsequent processing of the results file is faster.

A standalone module called res2dur is available in the Adams/Durability toolkit for processing the temporary results file.

RES2DUR Format

This utility is useful if you encounter a problem when processing the Durability output files (FEMDATA, DAC, or RPC); for example, if an Adams/Durability license is not available at the end of a simulation.

To run this utility, execute the following at the command line in the Durability toolkit:

res2dur modelfile [resultsfile]

Arguments

Following are the arguments for res2dur:



modelfile Specify the name of Adams/Solver model file (.adm file).

resultsfile Specify the name of results file from the Adams/Solver run.

Default: Derive name from model file name.

Note: • The model file provides the output specifications for the FEMDATA and REQUEST statements, as well as the OUTPUT options. The results file name argument is optional. By default, the model file name is used.

• Once the Durability output files have been successfully produced, you can safely delete the temporary results files (.res and .rcf).

Adams/DurabilityProcessing Results File for Durability

10

1Examples

Examples

Adams/DurabilityTutorials and Examples

2

Tutorials and ExamplesThe following Adams/Durability examples are available:

• Getting Started Using Adams/Durability

• Examples of Adams/Durability features

• Durfilter examples

• Example of Bending Rectangular Filleted Bar

../getting_started_durability/master.htm

http://support.adams.com/kb/faq.asp?ID=kb10504.html

1Dialog Box - F1 Help

Dialog Box - F1 Help

Adams/DurabilityANSYS Modal Export Dialog Box

2

ANSYS Modal Export Dialog Box

Durability -> FE Modal Export -> ANSYS

Generates files you can use as input to a Modal Stress Recovery (MSR) analysis in ANSYS. A customized version of ANSYS (ANSCUST) containing macros must be built to perform this MSR analysis in ANSYS. The MSR macros and source code are found in the Adams release directory install_dir/durability/ANSYS (where install_dir is the directory where Adams/Durability is installed). Consult your ANSYS documentation for more information on building an ANSCUST executable.

Learn more about Exporting Data for ANSYS.

For the option: Do the following:

Tips on Entering Object Names in Text Boxes.

Tips on Entering File Names in Text Boxes.

Flexible Body Enter the name of the flexible body you want to analyze.

Output File Enter the name of the output file you want to create.

Note: The file extension must be .out.

(Export Option) Select if you want to export modal coordinates or mode shapes.

If you select Modal Coordinates, Adams/Durability displays the following options:

Analysis Enter the name of a previously run analysis.

Output Time Start/End Specify the starting and ending time of the analysis you want to export. If you do not specify a range, Adams/Durability exports the entire analysis.

Basis Specify Orthonormalized or Unorthonormalized. If you don’t know the basis, select Unknown.

Note: It is important for modal superposition that the modal coordinates are in the same basis as the stress or strain modes. Which Basis Option Should I Use?

Format Specify the type of output file you want to create:

• DAC: Adams/Durability creates multiple output files.

• RPC III: Adams/Durability creates one file

Include Modal Velocities

Select to include modal velocities along with modal deformations in the .MDF file. If not selected, only the modal deformations are included in the .MDF file.

3Dialog Box - F1 HelpANSYS Modal Export Dialog Box

If you select Mode Shapes, Adams/Durability displays the following options:

Select Nodes Select one of the following:

• All: Exports the complete set of nodes.

• From File: Exports a partial set based on a file. If selected, displays the Node List File text box where you can specify the name of the file that contains a list of specific nodes.

• From List: Exports a partial set based on individual nodes. If selected, displays the following additional text boxes:

• Node to Add to List: Enter the node you want to add.

• Node List: Displays the list of nodes as they are added.

• Write to File: If you want to write this information to a file, select this checkbox and then specify the name of the file to which you want the information saved.


Adams/DurabilityCompute Nodal Plot

4

Compute Nodal Plot

Durability -> Nodal Plots

Calculates nodal stress or strain values. These values can be used to generate X-Y plot displays of nodal stress or strain time histories.

Learn more about Computing Stresses or Strains.




Flexible Body Enter the name of the flexible body.

Select Node List Displays the list of nodes as they are selected.

Node to Add to List Enter one or more nodes on which to calculate stresses.

You can right-click the text box, and select Pick Flexbody Node. Then, select a node by clicking on a position in the model.

As you pick the nodes individually, the Selected Nodes List text box accumulates a list of all selected nodes.

Type Options Select Stress or Strain.

Value Select the value of stress or strain you want to calculate.

Reference Marker Enter a coordinate reference marker in the model that will be used to transform the stress or strain components. If not specified, stress or strain values are plotted in the basic FEA coordinate system of the flexible body (LPRF).

This option can be useful when correlating strain gauge data from a physical test. If the orientation of the strain gauge does not match the FEA coordinate system, you can reference a marker whose orientation does match. The reference marker does not have to belong to the flexible body and can be any marker in the model.

All six components of stress or strain (Sxx, Syy, Szz, Sxy, Syz, Szx) can be affected by this coordinate transformation. Since values, such as von mises, maximum principal or shear, are strain/stress invariants, these values will not be affected by the coordinate transformation.

5Dialog Box - F1 HelpFE-Fatigue Export Dialog Box

FE-Fatigue Export Dialog BoxDurability -> FE-Fatigue -> Export

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

Learn more about Exporting for nCode.





Job Name Enter the name of the job you want to create. All files created in this procedure will have this entry as the prefix.

Modal Coordinates Select if you want to export modal coordinates




Basis Specify Orthonormalized or Unorthonormalized. If you don’t know the basis, select Unknown.

Note: It is important for modal superposition that the modal coordinates are in the same basis as the stress or strain modes. Which Basis Option Should I Use?

Format Specify the type of output file you want to create:

• DAC: Adams/Durability creates multiple output files.

• RPC III: Adams/Durability creates one file

Include Modal Velocities Select to include modal velocities along with modal deformations in the .MDF file. If not selected, only the modal deformations are included in the .MDF file.

FES File Select if you want to export to an nCode FES file.

Note: When creating an FES file, the stresses are outputted in units corresponding to the current modeling set of units for Force and Length, providing they are supported by FES. List of FES-Supported Units.

If you select FES File, Adams/Durability displays the following options:

Adams/DurabilityFE-Fatigue Export Dialog Box

6

Format Specify the format of the file you want to export:

• ASCII: ASCII FES files can be easily viewed and edited, and are portable between Windows and UNIX platforms.

• Binary: Binary FES files are smaller, but are not portable across platforms.

Note: Adams/Durability will attempt to comply with nCode’s requirements for a file name when creating the FES file. The prefix of the FES file name will be the job name specified earlier. The extension will be based on the Format option, .fes for Binary and .asc for ASCII.

Stress/Strain Specify whether you want to export stress or strain.

Select Nodes Select one of the following:

• All: Exports the complete set of nodes.

• From File: Exports a partial set based on a file. If selected, displays the Node List File text box where you can specify the name of the file that contains a list of specific nodes.

• From List: Exports a partial set based on individual nodes. If selected, displays the following additional text boxes:

• Node to Add to List: Enter the node you want to add.

• Node List: Displays the list of nodes as they are added.

• Write to File: If you want to write this information to a file, select this checkbox and then specify the name of the file to which you want the information saved.


7Dialog Box - F1 HelpFE-Fatigue Import Results File Dialog Box

FE-Fatigue Import Results File Dialog BoxDurability ->MSC.Fatigue -> Import

Imports MSC.Fatigue results for a flexible body into Adams. Results from an MSC.Fatigue analysis are stored in a file called jobname.fef. Once imported, Adams/Durability can process these results and postprocess them in Adams/PostProcessor. You can use the LIFE function to search the MSC.Fatigue results and return the minimum life of the flexible body.

Fatigue Result




Fatigue Results Enter the name of the fatigue results file (.fef) that you want to import.

Flexible Body Enter the name of the flexible body to which you want the results associated.

Analysis Enter the name of a previously run analysis to which you want the fatigue results associated. This text box is optional. If the analysis is not specified, the fatigue results will be associated only with the flexible body and the results will be available for all analyses.

This is useful for a duty-cycle fatigue analysis where more than one Adams analysis set was used.

Note: Once you have successfully imported MSC.Fatigue results (by completing this dialog box), Adams/Durability adds additional options in the Plot Type menu of the Contours tab (in Adams/PostProcessor). This allows you to specify the fatigue result to contour.

Adams/DurabilityFE-Fatigue Import Universal Results File Dialog Box

8

FE-Fatigue Import Universal Results File Dialog BoxDurability ->FE-Fatigue -> Import

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




File Name Enter the name of the results (.unv) file you want to import.

Flexible Body Enter the name of the flexible body to which you want to associate the results.

Analysis Optionally, enter the name of a previously run analysis to which you want the FE-Fatigue results associated. If you don't specify an analysis, Adams/Durability associates the FE-Fatigue results to the flexible body, and makes it available for the postprocessing of any Adams run.

Note: Once you have successfully imported FE-Fatigue results (by completing this dialog box), Adams/Durability adds additional options in the Plot Type menu of the Contours tab (in Adams/PostProcessor). This allows you to specify the fatigue result to contour.

9Dialog Box - F1 HelpHot Spots Information Dialog Box

Hot Spots Information Dialog BoxDurability -> Hot Spots Table

Provides a convenient method of generating a hot spot report on a body. It uses the HOT_SPOTS or TOP_SPOTS user function depending on the option selected.

Learn more about Visualizing Hot Spots.




Body Enter the name of a flexible or rigid body.

Analysis Enter the name of the analysis.

Type Specify the value to be computed at each hot spot, and then select stress (for bodies with a rigid stress object) or strain.

Radius Enter the distance between hot spots. All nodes that fall within this radius are candidates for the same hot spot. A value of 0.0 considers all nodes to be potential hot spots.

Threshold/Count Specify one of the following:

• Threshold - Enter a threshold for hot spots. All spots that meet or exceed this value are considered a hot spot.

• Count - Enter the number of hottest spots to return.

Sort Order Specify one of the following sorting options:

• Absolute - The sign of the value is ignored when sorting hot spots. You would use this option when only the magnitude is important, not the sign or direction (in the case of stress or strain).

• Maximum - Hot spots are ranked from maximum to minimum.

• Minimum - Hot spots are ranked from minimum to maximum.

File Format Specify one of the following:

• HTML - Saves information to an HTML file viewable in a Web browser. The information is displayed in the dialog box in HTML format.

• Tab Delimited text - Saves information to a text file, with data separated by tab characters. This format is convenient for importing the data into a spreadsheet program.

Adams/DurabilityHot Spots Information Dialog Box

10

File Name Optionally, enter the name of the file to which you want to save the information. If no extension is given for the name, a default extension is used depending on the File Format setting (.txt for tab-delimited text and .htm for HTML). Both file formats can be displayed in Adams/PostProcessor (from the File menu, point to Import, and then select Report).

Start Optionally, enter the time in the analysis to begin checking for hot spots. The default is the beginning of the analysis.

End Optionally, enter the time in the analysis to stop checking for hot spots. The default is the end of the analysis.

Base Font Size Enter the font size of the information that is displayed in the report section of the dialog box. You can change the font size before or after the data is displayed.

Report Select to generate a report with hot spots information.


11Dialog Box - F1 HelpINTERP

INTERPThe INTERP function returns the iord derivative of the interpolated value of SPLINE/id at time=x. The INTERP function supports time-series splines, which are splines that include a FILE argument that specifies a time history file of type DAC or RPC III.

FormatINTERP (x, method, id [,iord])

Arguments

Extended Definition

The INTERP function uses linear or cubic interpolation to create a function across a set of data points. The data points are defined in a SPLINE statement in the Adams/Solver data deck. The SPLINE statement with the FILE argument that you define in the Adams/Solver dataset must reference a time series file of type DAC or RPC III. For more information on these file types, see Introduction to Adams/Durability.

In general, the INTERP function with linear interpolation will not be a smooth function because, in almost all cases, the function will be discontinuous in the first derivative. Therefore, the estimate of the first derivative may be erroneous even though, by definition, the data points of a DAC or RPC time history file are evenly spaced. In all cases, the second derivative of the function being approximated is unreliable with linear interpolation.

id An integer variable that specifies the identifier of a SPLINE statement that you define in the Adams/Solver dataset. The SPLINE id must reference time series data from a DAC or RPC III file.

iord An integer variable specifying the order of the derivative that Adams/Solver takes at the interpolated point, and then returns through

INTERP.

Default: 0 (take no derivative)

Range: 0 < iord < 2

method An integer variable that specifies the method of interpolation, either linear or cubic interpolation.

Range: method = 1 (linear interpolation)

method = 3 (cubic interpolation)

x A real variable that specifies the value of time, the independent variable along the x-axis of the time series spline that is being interpolated.

Adams/DurabilityINTERP

12

On the other hand, with cubic interpolation, the INTERP function will be continuous to the second derivative. Therefore, we recommend that you use cubic interpolation, especially if first or second derivatives of the function will be evaluated.

ExamplesSPLINE/101,FILE=test_data.rsp,CHANNEL=9SFORCE/1, I=409, J=109, TRANSLATION,FUNCTION=INTERP(TIME,3,101)

The SFORCE statement defines a translational force that acts between Markers 409 and 109. The SPLINE statement specifies that the discrete data used to interpolate the value of the SFORCE comes from CHANNEL 9 of the RPC III file test_data.rsp.

The INTERP function references this spline, defines the independent variable to be simply, TIME, and selects cubic as the method of interpolation.

13Dialog Box - F1 HelpMSC.Fatigue Export Dialog Box

MSC.Fatigue Export Dialog Box

Durability -> MSC.Fatigue -> Export

Exports Adams results as DAC time history files and/or launches MSC.Fatigue. Currently, only the modal coordinates of flexible bodies are supported. You can combine these modal coordinate time histories in MSC.Fatigue with the modal stresses from MSC.Nastran to compute stress time histories, and ultimately, the life or damage of the flexible body.

Learn more about Exporting Data for MSC.Fatigue.





Job Name Enter the name of the job you want to create. All DAC files will be named with this prefix.

Modal Coordinates Select if you want to export modal coordinates.

If you select Modal Coordinates, Adams/Durability displays the following text boxes:


Output Time Start/End Specify the starting and ending time of the portion of the analysis you want to export. If you do not specify a range, Adams/Durability exports the entire analysis.

Run MSC.Fatigue Select if you want to launch the MSC.Fatigue program.

If you select Run MSC.Fatigue, Adams/Durability displays the following text boxes:

Run Command Enter the command on your system that starts MSC.Fatigue.

Note: Currently, only MSC.Fatigue with MSC.Patran is supported; therefore, enter the command that actually runs MSC.Patran.

New/Old/XDB (Patran DB) Select one of the following:

• New - Creates a new MSC.Patran database using an MSC.Nastran BDF and OP2.

• XDB - Creates a new MSC.Patran database using an XDB file.

• Old - Opens an existing MSC.Patran database of the finite-element model (FEM) of the flexible body.

Patran DB Enter the name of the MSC.Patran database you want to create or open.

If you select New, Adams/Durability displays the following text boxes:

Adams/DurabilityMSC.Fatigue Export Dialog Box

14

Nastran BDF Specify the file that contains the MSC.Nastran Bulk Data File that was used to generate the Modal Neutral File (MNF) of the flexible body.

Nastran OP2 Specify the MSC.Nastran OP2 file that contains the modal stress or strain data for the flexible body. This should be the .out file that was used to generate the MNF of the flexible body or created in the same run as the MNF using the ADMOUT option on the Nastran AdamsMNF command.

If you select XDB, Adams/Durability displays the following text boxes:

Nastran XDB Specify the MSC.Nastran XDB file that contains the MSC.Nastran model and modal stress or strain data for the flexible body. This should be the .xdb file that was created in the same Nastran run as the MNF with the "PARAM,POST,0" Nastran card. For more information, see Computing MSC.Nastran Stress/Strain Modes.


15Dialog Box - F1 HelpNASTRAN Modal Export Dialog Box

NASTRAN Modal Export Dialog Box

Durability -> FE Modal Export -> NASTRAN

Creates an .mdf file that can be referenced in a NASTRAN DMAP to recover dynamic stresses of the flexible component in NASTRAN.

Learn about Exporting Data for NASTRAN.





Output File Enter the name of the output file you want to create.

Note: The file extension must be .out.

File Format Select one of the following:

• Output2: Saves the file as a binary file. This file can only be used on a platform identical to that on which the file was created.

• Punch: Saves as an ASCII file. This file is platform independent.

(Export Option) Select one of the following:

• Modal Coordinates: The modal coordinates are the modal response of the flexible part per time step.

• Unit Matrix: The Unit Matrix contains just the normalized unit deformations of the mode shapes. This option allows you to apply the normalized unit deformations of the mode shapes to your NASTRAN bulk data file, run a stress analysis in NASTRAN, and then view the stress modes of the flexible part in Patran. This is a good debugging exercise to ensure that your stress modes make physical sense.




Skip Enter the number of steps you want to skip.

Adams/DurabilityNASTRAN Modal Export Dialog Box

16

Remove 1G deformation Select if you want to subtract static deformation from the transient results. If selected, Adams/Durability removes the static component from the dynamic stresses recovered in Nastran.

Include Modal Velocities Select to include modal velocities along with modal deformations in the .MDF file. If not selected, only the modal deformations are included in the .MDF file.


Appendix

Adams/DurabilityAbout Load Association Files (LAF)

2

About Load Association Files (LAF)When exporting modal coordinates, Adams/Durability also creates an nCode load association file (LAF). This file is named jobname.laf, where jobname is the job name specified in the FE-Fatigue Export dialog box. The LAF is an ASCII file containing a list of the time history DAC files mapped to the modal stress cases. This file is used by FE-Fatigue to automatically complete the Loading Input form for an FE-Fatigue job.

3AppendixElement Order

Element OrderWhen specifying the element order in the Create Rigid Stress dialog box, enter one of the following:

• Linear - Sets linear element order for first-order elements.

• Parabolic - Sets parabolic for second-order elements.

The following table identifies the effects of selecting different element types and orders:

Element order:

Number of nodes:

DOF per node: Limitations: Element examples:

Linear 4 3 Generally stiffer elements that do not represent bending or stresses very accurately

Only translational forces can be applied directly at the nodes. Rotational forces must be distributed along three or more non-colinear nodes.

Parabolic 10 3 Only translational forces can be applied directly at the nodes. Rotational forces must be distributed along three or more non-colinear nodes.

Tip: We recommend parabolic elements for stress recovery. Linear versions of these elements are able to predict only a constant stress state in their element domain, therefore, requiring much finer meshes than their parabolic counterparts.

Adams/DurabilityEntering File Names in Text Boxes

4

Entering File Names in Text Boxes

To enter file names in text boxes, you can do either of the following:

• Enter the file name directly in the text box.

• Clear the text box and then double-click to open a selection window.

• Right-click to either:

• Search a database

• Browse a database

5AppendixEntering Object Names in Text Boxes

Entering Object Names in Text Boxes

To enter object names in text boxes, you can do either of the following:

• Enter the object name directly in the text box.

• Clear the text box and then double-click to open the Database Navigator.

• Right-click to either:

• Pick an object shown on the screen.

• Browse a complete list of available objects.

• Choose from a product-generated list of guesses.

Adams/DurabilityFES-Supported Units

6

FES-Supported UnitsIf the current unit settings of force and length do not match one of the rows in the table, a warning will be issued and stresses will be written out to the FES file in the default units of MPa.

Force Length Stress

Newton millimeter Mpa

Newton meter Pascal

Pound inch PSI

Kilopound inch KSI

Kilogram meter kg/m2

7AppendixMSC.NASTRAN Input Deck

MSC.NASTRAN Input DeckThe following figure provides an example input data deck of type 1 stress recovery and how it compares to the initial CMS input deck.

Adams/DurabilityMSC.NASTRAN Input Deck Example

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MSC.NASTRAN Input Deck ExampleThe example shown below demonstrates strain recovery type 1 by referencing the Output2 file (rod1.out) from the initial modal analysis. The modal deformations file from Adams (rod1_bin.mdf) is in binary (Output2) format. Only element strains and nodal displacements due to modal deformation are being recovered. The chosen postprocessor to display the results is I-DEAS.

9AppendixWhich Basis Option Should I Use?

Which Basis Option Should I Use?It depends on the answers to the following series of questions:

1. What program created the FES file?

If Adams was used to create the FES file, the basis of the modal coordinates should be orthonormalized. By definition, all modal information contained in the MNF is orthonormalized, so modal stress strain data in an FES file created from Adams will always be orthonormal. Thus, when choosing to create an FES file while exporting modal coordinates, the only valid option for basis is orthonormalized.

If a program other than Adams was used to create the FES file, the modal stress data in the FES file may not be orthonormalized, and the following question needs to be considered.

2. Did the FE program perform orthonormalization when the MNF was created?

If the answer to this question is yes, then the correct basis to use is still orthonormalized. If the orthonormalization was not performed by the FE program (for example, the ANSYS MNF interface does not support it), then specify the basis as unorthonormalized. If you don’t know the answer to this question, specify unknown for the basis and Adams/Durability will output the modal coordinates to the basis that is compatible with the stresses from the FE program based on the information contained in the MNF.

Note: If you select to export to an FES file later in this procedure, the Basis text ox will automatically change to Orthonormalized.

Adams/DurabilityWhich Basis Option Should I Use?

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using adams/durability - md adams 2010

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