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21Welcome to Adams/Durability

Welcome to Adams/Durability


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Adams/DurabilityIntroduction to Adams/Durability

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Introduction to Adams/Durability

Adams/Durability, part of the Adams 2014

suite of software, extends the traditional test-baseddurability 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 Formator 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/Durability

Adams/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 Demand

The 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 Adamsand 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
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23Welcome 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 Plugin

The 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 Toolsmenu, select Plugin Manager.

3. Select the Loadcheckbox 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 Toolsmenu, select Plugin Manager.

2. Clear the Loadcheckbox next to Adams/Durability.

3. Select OK.


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Performing Stress Recovery


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Adams/DurabilityStress Recovery in Adams/Durability

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Stress Recovery in Adams/Durability

With 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 components 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.


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27Performing 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.Nastrandatabase (.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 NASTRAN

A 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 =''RESTART LOGICAL=

where is the logical name of the database to be assigned and 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='' UNIT= [FORM=]

where is the name of the modal deformations file from Adams. For directions on how

to create this file, see the FEMDATAor OUTPUTAdams/Solver statement. And indicatesan ID number of DLOAD statements in the case control section. The option FORMmay be requestedwhen 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
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Results Postprocessing

Dynamic 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 SimXpertStructures.

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 = DISP(PLOT) = STRAIN(FIBER,PLOT) =

STRESS(PLOT) =

where is a ID number indicated by ASSIGN statement in the executive control section, andis 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: No

Example of Input File

An 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:

/durability/NASTRAN/plate.dat

/durability/NASTRAN/plate_msr.dat

/durability/NASTRAN/plate.cmd


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29Performing 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=PRIMARYRestart setting

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

SOL 103 SOL 112 Modal transient analysisCEND 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, -1Parameter 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


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Adams/DurabilityStress on Flexible Bodies

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Stress on Flexible Bodies

Recovering Stresses on Flexible Bodies

In 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 Strains

You 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 Durabilitymenu, select Nodal Plots.The Compute Nodal Plotdialog box appears.

2. In the Analysistext box, enter the name of a previously run analysis. Tips on Entering Object

Names in Text Boxes.

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

4. In the Node to Add to Listtext 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 stressor 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 bodybeing analyzed:

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

where:

FBnameis the name of your flexible body

NodeIDis the node whose stress or strain you are calculating

_Valueis the value of stress or strain you're calculating

You can also print these values to a text file.
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31Performing Stress RecoveryStress on Flexible Bodies

Displaying Stress or Strain Contours

You 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 Contourstab.

3. Specify a stress or strain value in the Plot Typemenu.

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

a contour legend.

4. Select the Playtool.

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 Sourceto Results set.

4. From the Simulationlist, select the analysis run that you entered in Computing Stresses or

Strains.5. Select the FBname_STRESSor FBname_STRAIN result set.

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

7. Select Add Curvesor 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.

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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 Contourstab.

4. Specify a stress or strain value in the Plot Typemenu.

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 Spotstab, and then select Display Hotspots.

6. Make other selections as described inAnimation Dashboard - Hot Spots.

7. Select the Playtool.

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

each hot spot.

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33Performing Stress RecoveryStress on Rigid Bodies

Stress on Rigid Bodies

Recovering Stresses on Rigid Bodies

Stresses 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.

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Exporting Data

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yExporting Data Using Adams/Durability

Exporting Data Using Adams/Durability

Using 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 canstore the exported data in either RPC III Formator 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 youre satisfied that your model

and loads adequately match physical test results, youll want to output simulation results of What-If

scenarios for input to durability analysis programs and durability test machines.

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Exporting Data for ANSYS

Exporting Data for ANSYS

Using 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 modalsuperposition, but dont 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 Durabilitymenu, point to FE Modal Export, and then select ANSYS.

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

3. Select OK.

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Exporting Data for MSC.Fatigue

Exporting Data for MSC.Fatigue

With 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 betweenMSC.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 Durabilitymenu, 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 Modifymenu 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 Informationwindow, select Time History Managerto 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 Historywindow, set Load Typeto Scalar.

6. Set Unitsto none.

7. Set Results Typeto Static.

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

9. Set Fill Downto ONto 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.

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Exporting Data for NASTRAN

Exporting Data for NASTRAN

MSC.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 thenperformed 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 FEMDATAand OUTPUTstatements 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 Durabilitymenu, 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 nCode

Exporting for nCode

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. You can also export modalcoordinates 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 Durabilitymenu, 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.

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Exporting to RPC III or DAC

Exporting to RPC III or DAC

You can export either RPC III Formator DAC Formatrequest 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 Filemenu, select Exportto display the File Exportdialog box.

2. Set File Typeto DAC File.

3. Enter the name of the DAC file in the File Nametext box.

4. Right-click the Result Datatext box to display the shortcut menu. Point to

Result_Set_Component, and then select Browseto 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 OKin the File Exportdialog box.

To export a result sets to an RPC III file:

1. From the Filemenu, select Exportto display the File Exportdialog box.

2. Set File Typeto RPC3 File.

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

4. Right-click the Result Datatext box to display the shortcut menu. Point to

Result_Set_Component, and then select Browseto display the Database Navigator.

5. Select one or more result sets from the Database Navigatorusing Shift+click or Ctrl+click

techniques.

6. Once youve selected all the result sets, select OK.

7. Select OKin the File Exportdialog box.

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

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Setting Up Requests

You can create Requeststo output RPC III Formator DAC Formatfiles. You do this before you execute

the simulation.

To set up a request:

1. Define desired requests.

2. From the Settingsmenu, point to Solver, and then select Outputto display the Solver Settings

dialog box.

3. Set Save Filesto Yes.

4. Set Graphics File, Request File, and Results Fileto Noif these files are not needed.

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

6. Select More.

7. Set Output Categoryto Durability files.

8. Set either of the following to On:

DAC Files

RPC File(s)

9. Select Closein the Solver Settingsdialog box.

After the simulation finishes, Adams/View creates the RPC III or DAC files for all defined

requests. If youre running an interactive simulation, you need to reset the model before the files

are created.

Learn more about Requests.

55Exporting DataSimulating the Model
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Simulating the Model

Using Adams/Durability you can access test data in two formats: RPC III Formator 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 theINTERPfunction for the RPC III or DAC files (seeApplying 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 youre ready to simulate the model, make sure the End Timeand number of Stepsin the

Simulationcontainer 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 youre satisfied that the virtual test

data correlates well with the physical test data.

Performing Durability What-If Simulations

Once youve validated your model, youre ready to make modifications to determine their impact onsystem 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 youre ready to simulate the model, make sure the End Timeand number of Stepsin the

Simulationcontainer 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.

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Using Adams/Durability with

Adams/Solver

Adams/DurabilityUsing Adams/Durability with Adams/Solver

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Using Adams/Durability with Adams/Solver

Although 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 thatyou can use to implement Adams/Durability functionality in Adams/Solver. For complete details on any

statements in this topic, see theAdams/Solver online help.

Setting Up a Motion or Force

Adams/Solver includes the INTERPfunction as part of Adams/Durability support. When defining a

motion or force with data from an RPC III Formator DAC Formatfile, you must define a spline with thedata 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 idis a sequential number that represents the current motion number.

TRANSLATIONALis the motion type.

Joint idspecifies the joint marker that is moving.

spline idis the identifier of the spline that specifies the RPC III or DAC file input.

Setting Up a Spline

With Adams/Durability, the SPLINEstatement includes arguments that let you input RPC III FormatorDAC Formattime 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:

idis the identifier of the spline.

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

nis the channel number. This parameter is required for RPC III files, even if the file only has asingle channel. This parameter should not appear for DAC files.

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Setting Up and Outputting FEM Data

You use the FEMDATAstatement 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, modalcoordinates or nodal deformations, or stresses or strains of a flexible body.

As part of Adams/Durability, the OUTPUTstatement 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 REQUESTstatement 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 OUTPUTstatement 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

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About User Functions

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User Functions

You 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 thesefunctions in the Misc. Functions category of the Adams/View Function Builder.

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HOT_SPOTS

Returns 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 spotis defined as a point where the stress exceeds a certain defined limit (threshold). The Assist dialog box

for the HOT_SPOTS (seeArray 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 (thosewith 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.

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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 ofthe 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})));

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LIFE

Returns 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 areavailable, 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 theAdams/View Function Builder.

Adams/DurabilityMAX_STRESS

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MAX_STRESS

Returns 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 theAdams/View Function Builder.

Example

The following Adams/View command (seeAdams/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 unitsassociated with the variable.

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

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TOP_SPOTS

Returns a fixed number of the hottest spots in the body. The Assist dialog box for the TOP_SPOTS

function (seeArray TOP_SPOTS (Name array, Integer array, Real array)) is available in theAdams/ViewFunction 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

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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 (seeAdams/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

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Adams/DurabilityCoordinate Reference Transformation

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Coordinate Reference Transformation

Since 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 bodys LPRF (FE origin) to the markers

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=

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Stress Recovery Analysis

There 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 thetotal 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 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{ }= = =

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{q} is the vector of modal coordinates

[ ]=[{ },...,{ }] 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 translatingfrom 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 aresult. 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.

1 P S+

M[ ] q{ } K[ ] q{ }+ mBB mBN

mNB mNN

qB

qI kBB 0

0 kNN

qB

qI

+fB

fI

f

{ }= = =

X{ }

{ } B[ ] x{ }=

{ } E[ ] { }=

{ }

{ }

B[ ]

E[ ]

39Stress Recovery TheoryModal Stress Recovery

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Modal Stress Recovery

Modal 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 latelycombining 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[ ] [ ]=

{ }

[ ]

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Recovering Stress on Preloaded Flexible Bodies

For 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

{ }

41Stress Recovery TheoryMesh Refinement for Stress Recovery

Mesh Refinement for Stress Recovery


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Mesh Refinement for Stress Recovery

The 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 ofthe mesh discretization error can be expressed in the L2-Norm.

For displacements, the error is:

For stress or strain, it is:

where:

cis a constant independent of h and u.

uis the phenomenon being approximated (xfor displacements or for stresses)

his the mesh parameter characterizing the refinement of the mesh (0


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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 parts 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 holes edge.

A theoretical stress concentration factor (Kt) is used to relate the maximum stress at the discontinuity tothe nominal stress; the factor is defined by the equations.

where Ktis used for normal stress and Ktsis 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 Evaluation

A 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-elementmodel (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 Bending

This 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.

Ktmax

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

max

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

43Stress Recovery TheoryComponent Mode Synthesis

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


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g g ( t) , p g

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

nM

W-----

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+= =

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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 2.1640Adams 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

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69About Test Data

About Test Data


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About Test Data

Adams/DurabilityPlotting Test Data

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Plotting Test Data


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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 FormatorDAC

Formatfiles 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 Surfcheck box and select data in the Channelor File Datalist to see what the curve

looks like.

2. Clear the Surfcheck box.

3. Select Clear Plotto remove any curves in the plot area.

4. Select data in the Channelor File Datalist, and then select Add Curvesto display the curve.

Comparing Data

To graphically compare data:

1. Clear the Surfcheck box.

2. Select Clear Plotto remove any curves in the plot area.

3. Set Sourceto either RPC IIIor DACformat files.

4. Select the file from the source list.

5. Make a selection in the File Datalist, and then select Add Curvesto display the curve.

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

Importing Test Data

Test data can appear in RPC III Formator DAC Format. The steps involved in importing the data areessentially 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 Filemenu, point to Import, and then select either

DAC Filesor RPC Fileas appropriate to display the File to Importdialog box.

2. Right-click the File to Readtext box, and then select Browseto display the Select File dialog box.3. Select one or more files and select OK.

71About Test DataPlotting Test Data

With DAC files, you may want to select multiple files because each file has only one result set.

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You can use Shift+click or Ctrl+click multiple selection techniques.

4. Select OKin 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.

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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 INTERPfunction 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 Forceicon, point to Force:force_nameor 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:

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

timeis the independent variable that specifies what you are interpolating.

3is the method of interpolation, which indicates cubic interpolation between data points. 1,

which indicates linear interpolation, is also a valid entry.

spline_nameis 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.

73About 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
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To apply a spline in any motion, you modify the motion and specify an INTERPfunction 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 becauseAdams/Solver expects rotational motion in radians.

To modify a joint motion:

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

Modify.

The impose Joint Motiondialog 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:

timeis the independent variable that specifies what you are interpolating.

3is the method of interpolation, which indicates cubic interpolation between data points. 1,

which indicates linear interpolation, is also a valid entry.

spline_nameis the name of the referenced spline. DTORis 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 Toolsmenu, select Database Navigator.

3. In the Filterarea 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_FILEor DAC_FILE.

6. Select OKto open an Information window.

7. If you havent selected it previously, select the Verbosecheck box, and then select Apply.

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


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8. When youre done, select the Closebutton.
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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_FILEor

DAC_FILE.

3. Select the desired data channel (note that DAC files only have a single data channel), and select

OKto 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 havent selected it previously, select the Verbosecheck box, and then select Apply.

Creating a Spline

You use a spline to reference time history test data in RPC III Formator 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 containmultiple 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 Buildmenu, point to Data Elements, point to Spline, and then select General.

The Data Element Create Splinedialog box appears.

2. In the Spline Nametext box, enter the name you want to use for your spline.

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

The Select File dialog box appears.

4. Select the DACor RPC IIIfile.

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 isRPC 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 Channeltext 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.

75About Test DataUsing Test Data

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

There 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 theAdams/Durability Toolkit.

Referencing Test Data

Here, 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.


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77Using the Adams/Durability Toolkit

Using the Adams/Durability Toolkit


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Adams/DurabilityAdams/Durability Toolkit

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Adams/Durability Toolkit

The Adams/Durability toolkit has three utilities for processing data or converting data from one format


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The 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 adams2014 c durtkon Linux

systems or adams2014 durtkon Windows systems.

Creating FES Files from MNF

Using 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 anFES file containing strains can only be used in an EN analysis.

79Using 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



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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

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Filtering Test Data


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


inputfile Specifies the name of the RPC III Formator DAC Formatfile 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 arespecified in Hertz. Only frequencies between f1 and f2 are passed using this

filter option. Range: 0 < f1 < f2 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


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Channel Selection

Typically, a group of DAC Formatfiles 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 .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 Decimation

Decimation 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, themaximum 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 Filtering

You can only specify one filter option in the durfilter argument list. The transfer function coefficient formof 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:

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


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yis the vector of filtered data

6is the specified filter order

13is the specified cutoff frequency

100is 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 Files

If 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:

___.dac

For band pass or stop filters:

____.dac

For RPC III Formatdata, the _ 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 2

durfilter rawdata c 7:12 l 120 d2 o filterdata

83Using 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.

I t fil O t t fil


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Example 3

durfilter 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






Adams/DurabilityFiltering Test Data

84

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.


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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 ]

85Using the Adams/Durability ToolkitProcessing Results File for Durability

Processing Results File for Durability

When 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


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.adm file, a results file is produced. This file contains only the results of the simulation that are necessary

to process the FEMDATAstatements and/or DAC or RPC files. The format of the results file is AdamsXRF (XML Result File). This file is named after the Adams results file (run.res), and is not deletedat 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 resultsfile and osis 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 toregenerate 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 FEMDATAand

REQUESTstatements, 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

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87Examples

Examples


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Adams/DurabilityTutorials and Examples

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Tutorials and Examples

The following Adams/Durability examples are available:
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Getting Started Using Adams/

durability 2014

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