cares 8.1 user guide a - ceramic reliability 8.1 user guide connecticut reserve technologies, inc....

Copyright © Connecticut Reserve Technologies, Inc. September 13, 2007

CARES User Guide

CERAMICS ANALYSIS AND RELIABILITY EVALUATION OF STRUCTURES

CARES 8.1 User Guide Connecticut Reserve Technologies, Inc.

Table of Contents Page Introduction 3 Features 3 Specifications 3 Installation 4 Execution 4 Licensing 5 Component Reliability Analysis – General Steps 6 Finite Element Modeling 7 ANSYS Elements ANSCARES Surface Macro 8 ANSYS Post Processing Risk of Rupture Intensities 10 Parameter Estimation 11 Program Use

Menus 12 File Estimate View Help

Pages 14 Project FEM Material Parameters Material Reliability Load Output

Example 1 – 4-Point Bend Bar 25 Example 2 – Surface Option for the Bend Bar 28 Example 3 – Integrating CARES with ANSYS/PDS 31 Override CMP File 33 Glossary 35


Introduction The Ceramics Analysis and Reliability Evaluation of Structures (CARES) program calculates component reliability of structures fabricated of brittle materials. The calculation is performed on finite element models of the components utilizing the temperature dependent integration point stresses. Features

• Reliability Analysis – Fast Fracture, Time Dependent

• Finite Element Model – Results files from FEA are translated into CARES neutral files that include multiple load step information for volumes and surfaces of models of up to 1,000,000 elements.

• Material Parameters – Parameters may be input directly for each material or may be linked to a CARES Material Parameter (CMP) file. The CMP files may contain parameter sets from multiple temperatures.

• Material Reliability – Fracture criteria included: Principle of independent action (PIA), Weibull normal, maximum tensile stress, Batdorf coplanar strain energy release rate, and Batdorf Shetty. Crack geometry included: Griffith, Griffith notch, penny, and semicircular. Not all combinations of fracture and crack criteria are available, they are element (volume or surface) dependent.

• Load Control – User may select a range of the available load steps including all or a single step. When a single step is selected the user may override the finite element information with either static fatigue or dynamic fatigue. For multiple load steps the user may also choose to repeat the load scheme.

• Output Options – Post processing files may be generated for display in the finite element program. Printing mode and depth options may be used to control the quantity and detail of the results.

• Programs – The various modules of CARES are FORTRAN based executables controlled by the GUI. Each runs without user interaction and sends either success or error messages back to the GUI. These programs have not been designed to run standalone.

Specifications CARES, a 32-bit Windows program, has been tested under the following Windows versions: XP, 2000, and NT. The program has additionally been updated for the German and Italian versions of Windows XP. The program, supporting files, documentation, and example files require 11 MB of hard disk space. The zipped setup program is 6 MB and the unzipped Setup program is 6 MB.


Installation The Downloaded Zip File:

• Use Windows Explorer to create a temporary folder. • Place the zip file in this folder. • Unzip the file (use PKZIP or WinZip). • Double-click on SETUP.EXE • Continue with the Setup instructions below. • Once setup is complete, archive the zip file, and delete the temporary folder.

SETUP Program:

1. The Setup program will prompt the user through the installation process.

2. The recommended program folder: C:\Program Files\CRT Inc\CARES 8.1\

If CARES already exists in this folder, all program files, supporting files, and example files will be overwritten with copies from the SETUP program.

Execution

• The CARES Program may be initiated from the CARES 8.1 icon on the desktop or from the CARES 8.1 icon under [Start | Programs | CARES 8.1].

• The CARES Guides may be initiated from within the CARES program using the [Help …] menu or from the icons under [Start | Programs | CARES 8.1].


Licensing CARES requires a valid license. When a valid license does not exist some of the program functions are limited. The license will allow program use on a single computer for any local (non-network) user of that computer. Once the program has been installed follow the steps below to license the program:

_________________________________________________________________________

L I C E N S I N G

>>>>>> NOTE: CARES is licensed for SINGLE computer use. <<<<<< _________________________________________________________________________

N E W I N S T A L L -- New License Required

_________________________________________________________________________

1. Initiate the Licensing process: a) Start the CARES Program b) From the HELP menu select "License --> Get Client Information"

The following file will be created and displayed:

C:\Program Files\CRT Inc\CARES 8.1\license\CARESClientInfo.txt

2. Email "CARESClientInfo.txt" to <[email protected]>

3. Upon validation, the License File "CARESLicense.txt" will be emailed to you. Place the license file in the following location:

C:\Program Files\CRT Inc\CARES 8.1\license\CARESLicense.txt _________________________________________________________________________

U P G R A D E -- Existing License

_________________________________________________________________________

1. Copy the file "CARESLicense.txt" from your previous CARES installation.

2. Paste the license file into the following location: C:\Program Files\CRT Inc\CARES 8.1\license\CARESLicense.txt

NOTES:

• Except when otherwise noted, your existing License will work with each program upgrade.

• The version header within the license file will not require modification. _________________________________________________________________________


Component Reliability Analysis GENERAL STEPS

1. Finite Element Analysis:

a. Create the model

b. Execute the NUMCMP,ALL command (ANSYS)

c. Optional: Run the SURF macro (ANSYS)

d. SOLVE the model

2. Create a new project in CARES

3. Convert the stress results file into a CARES neutral file

4. Select a Material Reliability criterion

5. Assign Material Parameters

6. Set the Load controls

7. Set the Output options

8. Evaluate the Reliability of the Component

9. Post Process the Risk of Rupture Intensities


Finite Element Modeling Standard finite element modeling techniques should be utilized when modeling a ceramic or brittle material component. After the model has been created, meshed, the boundary conditions have been applied, and the stress analysis has been solved, the CARES interface program will translate the results into a CARES neutral file. ANSYS Users: It is necessary to execute NUMCMP,ALL before using CARES. Finite Element Interface Codes

FE Program Interface CARES version # of Elements Element Types

ABAQUS 6.7-6.6 ABACARES 8.1 1,000,000 Vol, Sur ANSYS 10.0 ANSCARES 8.1 1,000,000 Vol, Sur* ANSYS 9.0 ANSCARES 8.1 & 7.3 1,000,000 Vol, Sur* ANSYS 8.1-7.0 ANSCARES 8.0 & 7.3 1,000,000 Vol, Sur* COMSOL 3.2b COMCARES 8.1 1,000,000 Vol MARC 2005r3 MARCARES 8.1 1,000,000 Vol, Sur COSMOS CSMCARES 5.2 50,000 Vol, Sur NASTRAN NASCARES 5.2 50,000 Vol, Sur * CARES Surface elements may be generated from shell elements or from the ANSCARES surface macro. See the following section for more information. NOTE: This guide includes information regarding the ANSYS interfaces codes. Consult the individual User Guides for the interface programs listed above. ANSYS Interface ANSCARES: The following ANSYS elements are currently available for use with CARES:

PLANE42 2D or Axisymmetric PLANE82 2D or Axisymmetric SHELL41 Shell SHELL63 Shell SHELL93 Shell SOLID92 Tetra SOLID187 Tetra SOLID45 Brick SOLID95 Brick VISCO107 Brick

Contact the authors if elements that you commonly use are not listed above.


ANSCARES Surface Macro The ANSCARES Surface Macro (for use in ANSYS) provides the user with a method to calculate surface reliability in CARES when the finite element model consists of volume or axisymmetric elements. The macro is located here: ..\CARES 8.1\interface\ansys\AnsCares81.lib MACRO USE:

1. Preliminaries: a. Mesh the model b. Compress all numbers:

NUMCMP,ALL

2. Create a component in ANSYS ASEL,s,,,1,4 ß Select the appropriate areas CM,surface1,area ß The Component name is ‘surface1’

3. Call the macro *ULIB,AnsCares81,lib ß Must reside local to the project or include the full path *USE,SURF81 ß Called without parameters, interactive prompts

Alternative call:

*USE,SURF81,1,’surface1’ ß Called with parameters for automatic use.

The alternative call must include the number of surfaces to be processed followed by a list of the Component names. Each Component name must be 8 characters or less and listed in single quotes. An example with 3 surfaces:

*USE,SURF81,3,’surf_all’,’surf_top’,’surf_bot’

4. SOLVE the model

5. Create the Neutral file (CARES GUI) PROCEDURE DETAILS:

1. Preliminaries: After meshing, the NUMCMP,ALL command must be executed in ANSYS. This ensures that the *.SUR and *.RST files will both be in sync in regards to nodal and element numbering during the CARES neutral file generation.

2. The user identifies the surface of interest by creating an Area Component for use with solid elements, a Line Component for use with axisymmetric components, or a Nodal Component when the solid geometry is not available. The Component names must consist of 8 characters or less and not include any spaces. Please consult the ANSYS user guide for more information about identifying Components in ANSYS.


3. Either AnsCares81.lib must reside in the project folder or the complete path to the ..\CARES 8.1\interface\ansys folder must be utilized in the *ULIB call. Please consult the ANSYS help files for more information. The CARES Surface macro is called with or without parameters. Without parameters the user is prompted for the number of surfaces to process and the name of each Component. Alternatively, the macro may be called with parameters including the number of surfaces to be processed and the name of each Component. The macro then creates the *.SUR file. This file contains the element faces that coincide with the identified surface. The face number, element number, and node numbers are listed for each face.

4. The model is solved. The nodes and elements should not be modified between the generation of the *.SUR file and the generation of the *.RST file.

5. ANSCARES Neutral file creation: When the *.SUR file exists, it is automatically included. Stresses, temperatures and areas for the faces of the elements are extracted or calculated from the *.RST file for each load step.

NOTES:

• The SURF81 macro works for the following elements:

PLANE42, PLANE82 – when used as axisymmetric elements SOLID92, SOLID187, SOLID45, SOLID95, VISCO107

Elements not listed above are skipped. The presence of Contact and Target elements will not affect the CARES Surface macro generation of the *.SUR file.

• The *.SUR file is a list of the faces of the elements; therefore, the file does not need to be created for every load step in a multiple load step analysis. It is sufficient to create the file once as long as the mesh is not significantly changing between load steps.

• A material number is automatically assigned to each surface. The value is 100 + the component index. For example the first surface would be 101, the second surface would be 102, etc.

• The SURF81 macro checks to see if the face is free (exterior of the model); therefore, no faces interior to the model are included.

• The *.SUR file may contain reduced mode faces (the point or edge of a TET). These faces will be skipped by ANSCARES during Neutral File generation.

• The curvature of QUAD faces is no longer checked by ANSCARES (orthogonality check). The user must take responsibility for the validity of the elements in their model.

• The variables in the SURF81 macro each end in “_ac” so they will hopefully not interfere with other variable names in the model.


ANSYS Post Processing Risk of Rupture Intensities

1. On the Output tab of the CARES user interface select 'ANSYS' as the post processor. This selection will cause CARES to create an *.RR8 file for the active project. This file contains element risk of rupture intensities. The jobname of the *.RR8 file will match the jobname of the neutral file *.CN8. These will not necessarily match the project jobname.

2. Return to ANSYS and execute the RRI macro from the AnsCares81.lib library.

a. *ULIB,AnsCares81,lib

b. *USE,RRI81

Either AnsCares81.lib must reside in the project folder or the complete path to the ..\CARES 8.1\interface\ansys folder must be utilized in step 2a. Please consult the ANSYS help files for more information.

3. Run Mode: The RRI macro may be run for either a single CARES material ID or for the entire set of CARES material ID’s. The user will be prompted for one of the following:

a. Load All (1) – The risk of rupture intensities will be assigned to the applicable elements through a single ANSYS element table, “CARES”.

b. by CARES MATID (2) – When selecting this option, the user will be prompted for the CARES MatID and the Element Table Name. The risk of rupture intensities will be assigned only for those elements that match the CARES MatID. When executing the macro for each CARES MatID, the user should assign unique Element Table Names for each CARES MatID.

Note: For both of the above options, elements will accumulate risk of rupture intensities (additive) for the cases when the element number is listed more than once within the *.RR8 file. This situation occurs when a volume element has been used as a CARES generated surface element via the AnsCARES SURF macro. This situation also arises when multiple faces of the same volume element have been selected for this CARES generated surface.

4. Upon completion the RRI macro will plot the risk of rupture intensities. Subsequent executions of the RRI macro will either replace the entries in the ETABLE or add to the ETABLE when option (2) outlined in 3b above is utilized and different Element Table Names are used. The user may switch views with the following plot ETABLE command:

pletab,CARES,1

Where CARES may be replaced by the ETABLE name. The third parameter averages the element items at common nodes.


Parameter Estimation Weibull material parameters are required for fast fracture life prediction of brittle components. Both Weibull material parameters and fatigue material parameters are required for time dependent and cycle dependent life prediction of brittle components. Material parameters are emphasized as parameters that are independent of the specimen geometry from which they were calculated. In the case of the fast fracture Weibull parameters, the Weibull slope parameter, m, and the Weibull characteristic strength parameter, σθ, are readily calculated from the raw data of a specimen fracture test. These two parameters along with the specimen geometry are then utilized to calculate the Weibull material characteristic strength or scale parameter, σ0. Note the difference in subscripts. The same procedure is applied to the fatigue parameters in that CARES requires the material specific N and B parameters instead of the specimen specific N and D parameters. Material parameters are applied to each material through either direct input on the Material Parameters page, or through a link to a CARES Material Parameter (CMP) file. Example CMP file: DBlock, Vol1, Fast , Tensile , , c WMeth TMeth Temp Slope Scale W_MLE2U, , 2.10000E+01 , 8.51587E+00 , 1.18245E+03 W_MLE2B, , 2.10000E+01 , 9.68208E+00 , 1.08326E+03 W_LIN2B, , 2.10000E+01 , 7.30115E+00 , 1.34352E+03 W_User , , 2.10000E+01 , 1.00000E+01 , 1.00000E+03 ENDDBlock DBlock, Vol1 , SCG , Tensile c WMeth TMeth Temp M SP (unused) N B Static W_MLE2U, T_LIN2, 2.100E+01, 8.51587E+00, 1.18245E+03, 0, 9.83111E+01, 2.93624E+00 W_MLE2B, T_LIN2, 2.100E+01, 9.68208E+00, 1.08326E+03, 0, 9.83111E+01, 1.83243E+00 W_LIN2B, T_LIN2, 2.100E+01, 7.30115E+00, 1.34352E+03, 0, 9.83111E+01, 2.95742E+00 W_User , T_USer, 2.100E+01, 1.00000E+01, 1.00000E+03, 0, 9.00000E+01, 3.00000E+00 ENDDBlock This hypothetical CMP file demonstrates how a variety of solution techniques reside within the same file. The CARES GUI will allow the user to pan through the available sets and apply one set. Temperature dependent parameter sets are included when the temperature in the third column above is varied. Parameter Estimation Software WeibPar, a Weibull parameter estimation program, has been developed separately by Connecticut Reserve Technologies, Inc. This program has been adapted to output CMP files with parameter estimation results ready for direct use within CARES. WeibPar is available at www.WeibPar.com.


Program Use This section describes the program functions available through the Menu system and through the various Pages of the program. For more information about reliability analysis please review the CARES Theory Guide. Menus Shortcut key combinations exist for common menu operations. For example [Ctrl+N] is the shortcut key combination to create a New Project. Note the shortcut key combination listed to the right of each applicable menu item. File Menu

New – Creates a New Project. If the Project already exists it is overwritten. Open – Opens an existing Project. The user is prompted if the current Project

has been modified, but not saved. Save – Saves the current Project.

Save As – Saves the current Project under a different Jobname. If the new

Jobname already exists it is overwritten. JobNames – The 8 most recent Projects are listed for easy access. When switching

Projects the user is prompted if the current project has been modified, but not saved.

Exit – Exits the CARES program. The user is prompted if the current project

has been modified, but not saved. Estimate Menu


Material Parameters – Opens the designated parameter estimation program. Reliability – Executes the CARES reliability prediction calculation given the user

selected options. The input options are scanned for inconsistencies before the reliability prediction is performed. This function is also available on the Output page as the Calculate Reliability button.

View Menu

Refresh – Scans the user-selected options for validity. Project files that have been updated outside of the CARES program are verified. Some user-selected options are modified based on the results of the scan.

Clear Results – Clears the accumulated results from the Output page. This includes the

list of past runs and the contents of the output file display. See also the Output Page.

Show Results – Displays the contents of the output file in the output display area. Large

output files are suppressed, only showing the first and last section of the file. See also the Output Page.

Open Results – Opens the output file in the Notepad Editor.

Help Menu

User Guide – Opens the User Guide PDF. Theory Guide – Opens the Theory Guide PDF. About – Displays the About screen.


Pages Many of the options displayed on each of the pages are dependent on previously chosen options. When an item is not available (grayed out) it is not applicable to the current analysis. Project Page

Project File – The current Project with its complete path. Use the New or Open icons (or the File menu) to modify the current Project.

Project Title – Enter a descriptive Title for this Project. Reliability Analysis – Select the appropriate Reliability Analysis for this Project. Modifying

the Reliability Analysis will affect the availability of other options.


FEM Page

Convert Automatically – Monitors the Finite Element Results File and automatically keeps the

CARES neutral file current. If this option is not checked the user will be prompted when the Neutral file is out of date.

Service Load page – This page contains the options for the Service Load Neutral File. Results From – Select the Finite Element Analysis Program. Results File – Set the Finite Element Results file. The Results File JobName need not

be the same as the Project JobName. Materials – Set the range of materials to be included in the Neutral File. Load Steps – Set the range of load steps to be included in the Neutral File.


Convert to CARES Neutral File – Executes the interface code that will translate the Results File into a CARES Neutral File. Upon successful translation the information fields will be populated with details about the model.

Stress Space – Controls which stress tensor is used in the calculations. Symmetry Segments – Set the number of Symmetry Segments. For example for ¼ symmetry

the number of Symmetry Segments would be 4.0.


Materials Page – Reliability, Direct Input

Material – Each button represents the materials found in the finite element model. Each material is identified by a material ID number and the type (Volume, Surface, or Edge elements). Selecting a material button will display the material’s reliability and parameters settings. Each material has its own settings.

Reliability – Each material is assigned its own fracture criterion. Fracture Criteria – Principle of independent action (PIA), Weibull normal, maximum tensile

stress, Batdorf coplanar strain energy release rate, and Batdorf Shetty. Crack Geometry – Griffith, Griffith notch, penny, and semicircular (when applicable) Poisson – Poisson’s ratio (when applicable) C-Shear – Shetty’s constant (when applicable)


Not all combinations of fracture and crack criteria are available, they are element (volume or surface) dependent. The GUI will display only the applicable options.

Material Parameters – The Direct Input option is shown selected above. For Fast Fracture

only M and σ0 are available as shown above. Input boxes for the additional parameters are available for time dependent analysis.


Material Parameters Page – CMP File Input

Material Parameters – The CARES Material Parameter (CMP) file option is shown selected above. Once a valid CMP file is set the user may pan through the available parameter sets using the arrows on the right. The top set of arrows pans through the type of specimens while the bottom set of arrows pan through the parameter estimation techniques. The Active Parameter Set displays the selected parameters. When applicable this display will show multiple temperature parameter sets.


Material Parameters Page – Override Option

Override – The Override option is used when external programs such as ANSYS/PDS or

WeibPar will be utilized to control the input of the material parameters for this material.


Load Page

Service Load – Loading options for the Service Load

Load Factor – Multiplying factor overriding the finite element stresses. Used in linear elastic analysis to easily raise and lower the stresses without having to rerun the model.

Load Range – Select the range of load steps for analysis. The ending time of each step

is listed in the drop down boxes, while the step number is listed to the right.

Load Control – When applicable the user may override the finite element model load step

information. This option is dependent on whether a single step or multiple steps are selected in the Load Range, and on which Reliability Analysis was selected on the Project page.

Repeat Load – Allows the user to repeat the loading scheme designated in the previous

sections. The Exact method cycles through the load steps Multiplier


times. The Approximate method cycles through the load steps one time and uses a multiplier function to extrapolate the result Multiplier times. The Improved Approximate method allows the user to apply both methods simultaneously.


Output Page

Print Mode – Output: Displays the Title, the Analysis, and the results only (shown above). Input: Displays all Input parameters and does not perform an analysis. Both: Displays all Input parameters and the results.

Print Depth – Component: Displays material and component results only. Material:

Displays material level detailed results for the selected range of material IDs. Elements: Displays element level detailed results for the selected range of elements. SubElements: Displays subelement level detailed


results for the selected range of subelements. Load Steps: Displays load step level detailed results for the selected range of load steps.

Note: Leaving the first field blank or entering a zero is interpreted as

selecting the entire available range for that depth field. Post – Set the Post processor option to generate a risk of rupture intensity file for

subsequent display in the finite element program. Component Reliability – Executes the CARES reliability prediction calculation given the user

selected options. The input options are scanned for inconsistencies before the reliability prediction is performed. This function is also available as Reliability on the Estimate menu.

Results Table – The overall Component Probability of Failure, the Component Reliability,

and the Maximum Effective Stress results for each subsequent prediction along with the Run number are listed in this table. The most current run is added to the top of the table.

Results Display – Upon successful execution, the CARES reliability calculation output text

file is displayed in this area. Large output files are suppressed, only showing the first and last section of the file. When a large file is suppressed use Open Results on the View menu to display the entire output file in the Notepad editor.

See also Clear Results, Show Results, and Open Results on the View menu.


EXAMPLE 1 – 4-Point Bend Bar (3D ¼ symmetry with 10 step loading)

1. Open ANSYS (any version from 7.0 to 10.0)

2. Create the new project “bendbar” in the ..\examples\ansys\bendbar folder.

3. Run the provided <bendbar.mac> macro.

/input,bendbar,mac This macro creates a 4-point bend bar model (¼ symmetry) and applies an increasing pressure for 5 steps and then decreases the pressure for 5 steps. The desired output from this step is the ANSYS results file *.rst.

Alternatively, if you would like to skip steps 1 through 4, the following files are provided in the folder: ..\examples\ansys\bendbar\verify

bendbar.rst – stress solution (converted by CARES interface code) bendbar_animate.avi – animation of the 10 load step bending of the bar bendbar_results.jpg – the principle stress results for load step 5 (shown below)

Load Step 5 – Principle Stress Results


4. Close ANSYS.

5. Open CARES 8.1. Project Page

6. Create a new project [File | New] in the ..\examples\ansys\bendbar folder. The project name does not need to be the same project name as the FEA.

7. Enter a Title for the project.

8. Select Time Dependent as the type of Reliability Analysis for this Project.

FEM Page – Service Load

9. Set the Program to ANSYS.

10. Set the Results file to the *.rst created in step 3 (or the alternative step).

11. Click the Convert to CARES Neutral File. The Neutral file header information is displayed.

12. Set the Stress Space to Principle Stresses.

13. Set the number of Symmetry Segments – in this case 4.0. Materials Page

14. Select the Material, in this case the only material is “1 – Volume”.

15. Set the Fracture Criteria to PIA.

16. Select Direct Input.

17. Enter the following Volume Material parameters: M = 10 σ0 = 130 N = 20 B = 750

If the N and B edit boxes are not available return to the Project page and select Time Dependent for the Reliability Analysis. Load Page – Service Load

18. Set the Load Factor = 1.0

19. Set the Service Load Range to All.


20. Set the Load Control to Use the FEM Load Step.

21. Set the Repeat Load Block Method to Exact.

22. Set the Repeat Load Block Multiplier to 1.

Output Page

23. Set the Print Mode to Both.

24. Set the Print Depth to Component.

25. Set the Post Mode to None.

26. Click Component Reliability. The results are displayed in the Output window (pan to the bottom to view the reliability details). Alternatively, the user may select Open Results from the View menu to display the results in the Notepad Editor. Try different Load schemes, reliability methods, and material parameters. A summary of each run will accumulate in the table on the Output Page. NOTE: The results presented within this example are for a hypothetical component with hypothetical material parameters. The results and the material parameters should not be used for anything except program demonstration purposes.


EXAMPLE 2 – Surface Option for the Bend Bar The bend bar generated in the previous example consists entirely of SOLID95 volume elements. CARES has the capability of identifying the free surfaces on these volume elements and generating pseudo-surface elements. The generation of these elements allows a surface reliability analysis to subsequently be performed. Since the model was designed with ¼ symmetry in mind, the areas that will be included in the CARES surface generation routine are the free end (upper right), the top, the bottom, and the far side of the bar. The beam.mac file includes the commands to generate an area component, surf_all, that identifies these areas.

Selected Areas applied to CARES surface generation Surface Generation and Analysis

27. Repeat steps 1 through 3 from the previous bend bar example.

28. At the ANSYS command line type

*ULIB,AnsCares81,lib and then *USE,SURF81

A local copy (within the project folder) of the AnsCares81.lib macro file is necessary for this procedure. Alternatively the full path should be listed to the location of the library.


29. Answer the dialog questions in the following manner:

a. Number of Surfaces = 1 b. Name of the Surface = surf_all

The *.SUR file is generated.

ALTERNATE CALL: *USE,SURF81,1,’surf_all’ ß Include the answers to the prompts

30. Close ANSYS and open CARES 8.1.

Project Page

31. Open the Project file created in the previous example [File | Open] (it may already be open as the program automatically opens the most recently used project).

FEM Page

32. Click Convert to CARES Neutral File. This will translate the *.RST into a *.CN8 with the addition of the *.SUR file information. The *.CN8 file display will now include one Volume material and one Surface material.

33. Reset the Symmetry Segments to 4.0.

Materials Page

34. Select “1 – Volume” in the Material drop down box.



37. Enter the following Volume Material Parameters: M = 10 σ0 = 130 N = 20 B = 750

38. Select “101 – Surface” in the Material drop down box.



41. Enter the following Surface Material Parameters:

M = 12 σ0 = 150 N = 25 B = 1000


Load Page

42. Set the Service Load Range to All. Output Page

43. Click Calculate Reliability. The results (pan to the bottom of output text) now list the reliability of each material and the total reliability of the component. NOTE: The results presented within this example are for a hypothetical component with hypothetical material parameters. The results and the material parameters should not be used for anything except program demonstration purposes.


EXAMPLE 3 – Integrating CARES with ANSYS/PDS This example demonstrates integrating CARES with the ANSYS Probabilistic Design System (ANSYS/PDS). This methodology accounts for stochastic variables such as loading, component geometry, material properties, and lifing parameters on component probability of survival over time.

1. This example works from the following folder: ..\Cares 8.1\examples\ansys\PDS\

2. Open bendbar.mac in a text editor such as Notepad.

3. Find the system calls near the bottom of the file that specify the path to CARES. Verify the accuracy of the folder path to the CARES bin folder. Note that the quotes are required.

/sys, “C:\Program Files\CRT Inc\Cares 8.1\bin\ac10\AnsCares10081” bendbar /sys, “C:\Program Files\CRT Inc\Cares 8.1\bin\Life81” bendbar

4. Close bendbar.mac (saving if changes were made). ANSYS

5. Open ANSYS setting the current path to

..\Cares 8.1\examples\ansys\PDS\

and the jobname to

bendbar

6. At the ANSYS command line Enter:

/input,bendbar,mac

7. It is expected that you may get an error on the VREAD command. If the error occurs:

Click Proceed. Click Yes (to stop processing)

CARES

8. Open CARES

9. Open the example file: ..\Cares 8.1\examples\ansys\PDS\bendbar.icl

10. FEM Page a. Choose ANSYS 10.0 as the program and set the results file to ‘bendbar.rst’ b. Set the Symmetry Segments to 4.0


11. Materials Page a. Set the Fracture Criteria to PIA b. Set the Parameter Options to Override

12. [ File | Save ]

13. Close CARES

ANSYS 14. Return to ANSYS and Enter:

/quit /clear Yes /input,bendbar,mac

15. This time you should get a successful solution and the final line in the ANSYS Command Output Window should be

Pfail = 0.1166434202E-01

16. To run the PDS function on this model, Enter: /input,bendbar_PDS,mac

17. In the “bendbar_report” folder open the file “bendbar_report.html” to view the results. We find that given the distributions assigned to the varying parameters in this example (Height, Width, Weibull Slope, and Weibull Scale) the Probability of Failure is significantly dependent on the Weibull parameters while the effect on Probability of Failure of the changes in Height and Width were insignificant.


ANSYS/PDS – OVERRIDE.CMP File The handoff of the Weibull Parameters from ANSYS/PDS to CARES occurs through the use of the override.cmp file. The user’s input file must create and write this file. CARES deletes the override file during processing to ensure the file is reset for each subsequent PDS run. The top part of the CARES section in bendbar.mac provides an example of how the override.cmp file is created and how the material information and parameters are written: Temp1=25. Weib_Slope1=10. Weib_Scale1=200. *CFOPEN,override,cmp ! OPEN - CARES Material Parameter File *vwrite, TEMP1, Weib_Slope1, Weib_Scale1 ('Vol 1 ', 3(E13.5)) *CFCLOS ! CLOSE - CMP File Here the first part of the format line of the VWRITE command indicates a Volume material, Vol, followed by a space and the Material ID. The temperature and Weibull parameters are passed as parameters. Override Multiple Temperatures If multiple temperature Weibull parameters exist for this model they may be included as follows: Temp1=25. Weib_Slope1=10. Weib_Scale1=200. Temp2=1000. Weib_Slope2=10. Weib_Scale2=150. *CFOPEN,override,cmp ! OPEN - CARES Material Parameter File *vwrite, TEMP1, Weib_Slope1, Weib_Scale1 ('Vol 1 ', 3(E13.5)) *vwrite, TEMP2, Weib_Slope2, Weib_Scale2 ('Vol 1 ', 3(E13.5)) *CFCLOS ! CLOSE - CMP File Note that Vol 1 is the same in each VWRITE since the parameters are being applied to the same material.


Override Multiple Materials If the Weibull parameters are to be assigned to multiple materials they may be included as follows: Temp1=25. Weib_Slope1=10. Weib_Scale1=200. Weib_Slope2=15. Weib_Scale2=140. *CFOPEN,override,cmp ! OPEN - CARES Material Parameter File *vwrite, TEMP1, Weib_Slope1, Weib_Scale1 ('Vol 1 ', 3(E13.5)) *vwrite, TEMP1, Weib_Slope2, Weib_Scale2 ('Sur 101 ', 3(E13.5)) *vwrite, TEMP1, Weib_Slope2, Weib_Scale2 ('Sur 102 ', 3(E13.5)) *vwrite, TEMP1, Weib_Slope2, Weib_Scale2 ('Sur 103 ', 3(E13.5)) *CFCLOS ! CLOSE - CMP File Here one set of Weibull parameters applies to the Volume material while another set applies to the Surface materials 101, 102, and 103.


Glossary CARES – Ceramics Analysis and Reliability Evaluation of Structures FEA – Finite Element Analysis FEM – Finite Element Model File Extensions:

ICL – Input to CARES/Life OCL – Output from CARES/Life RST – ANSYS results file translated by ANSCARES to the CN8 or CP8. CN8 – CARES 8 Neutral file (service load) CP8 – CARES 8 Neutral file (proof test load) SUR – CARES Surface file generated by the ANSCARES surf macro. The SUR and the

RST file are translated by ANSCARES to create the CN8 (CP8). RR8 – CARES 8 Risk of Rupture file. Output by CARES for application within ANSYS to

the FEM. Jobname – The root word of each Project filename. The Jobname used within the finite

element program need not match the Jobname used within CARES. Load Step – In finite element analysis a component may be subjected to varying loads for

varying durations. Each increment in load is a single load step. Neutral file – The CN8 (CP8) file contains the subelement stress results at each load step for a

component. This file is generated by a CARES interface code that translates a finite element results file into the CARES formatted Neutral file. The CARES program then directly reads the Neutral file during reliability analysis.

Project – A collection of interrelated files that share a common Jobname. Subelements – The integration points of the elements. The finite element stress results are

listed within the results file (and subsequently in the CN8 file) at the subelement or integration point level. Consequently, CARES performs reliability analysis on the load steps of each subelement.

Transient analysis – A reliability analysis preformed on a component subjected to multiple load

steps. Although fast fracture reliability boils down to the load step of maximum stress, this is not true for time dependent reliability across multiple load steps. For time dependent reliability all load steps must be considered through recursive iteration.

Weibull Distribution – Parameter estimation of the fast fracture of brittle components follows the

Weibull distribution. In turn fast fracture component reliability is based on these Weibull parameters.

cares 8.1 user guide a - ceramic reliability 8.1 user guide connecticut reserve technologies, inc....

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