AFGROW
Encyclopedia
AFGROW is the Air Force Growth (AFGROW) crack life prediction software tool that allows users to analyze crack initiation, fatigue crack growth, fracture, and assess the life of metallic structures. AFGROW is one of the fastest, most efficient, and user-friendly crack life prediction tools available today. AFGROW is mainly used for aerospace
applications; however it can be applied to any type of metallic structure that experiences fatigue cracking.
AFGROW implements five different material models (Forman Equation, Walker Equation, Tabular lookup, Harter-T Method and NASGRO Equation) to determine crack growth per applied cyclic loading. Other AFGROW user options include five load interaction (retardation) models (Closure, FASTRAN, Hsu, Wheeler, and Generalized Willenborg), a strain-life based fatigue crack initiation model, and the ability to perform a crack growth analysis with the effect of the bonded repair. AFGROW also includes useful tools such as: user-defined stress intensity solutions, user-defined beta modification factors (ability to estimate stress intensity factors for cases, which may not be an exact match for one of the stress intensity solutions in the AFGROW library), a residual stress analysis capability, cycle counting, and the ability to automatically transfer output data to Microsoft Excel.
AFGROW provides COM (Component Object Model)
Automation interfaces that allow users to build scripts in other Windows applications to perform repetitive tasks or control AFGROW from their applications.
AFGROW also has new plug-in crack geometry interface that allows AFGROW to interface with any structural analysis program capable of calculating stress intensity factors (K) in the Windows environment. Users may create their own stress intensity solutions by writing and compiling dynamic link libraries (DLLs) using relatively simple codes. This includes the ability to animate the crack growth as is done in all other native AFGROW solutions. This interface also makes it possible for FE analysis software (for example, StressCheck
) to feed AFGROW three-dimensional based stress intensity information throughout the crack life prediction process, allowing for a tremendous amount of analytical flexibility.
for IBM-PCs by Mr. Ed Davidson at ASD/ENSF in the early-mid-1980s. In 1985, ASDGRO was used as the basis for crack growth analysis for the Sikorsky H-53 Helicopter under contract to Warner-Robins ALC. The program was modified to utilize very large load spectra, approximate stress intensity solutions for cracks in arbitrary stress fields, and use a tabular crack growth rate relationship based on the Walker equation on a point-by-point basis (Harter T-Method). The point loaded crack solution from the Tada, Paris, and Irwin Stress Intensity Factor Handbook was originally used to determine K (for arbitrary stress fields) by integration over the crack length using the unflawed stress distribution independently for each crack dimension. After discussions with Dr. Jack Lincoln (ASD/ENSF), a new method was developed by Mr. Frank Grimsley (AFWAL/FIBEC) to determine stress intensity, which used a 2-D Gaussian integration scheme with Richardson Extrapolation which was optimized by Dr. George Sendeckyj (AFWAL/FIBEC). The resulting program was named MODGRO since it was a modified version of ASDGRO.
to Turbo Pascal
and C
. Numerous small changes/repairs were made based on errors that were discovered. During this time period, NASA/Dryden implemented MODGRO in the analysis for the flight test program for the X-29
.
language for UNIX
to provide performance and portability to several UNIX Workstations.
In 1994, the results of the Navy project were presented to the Navy sponsor and MODGRO was renamed AFGROW, Version 3.X.
Since 1996, the Windows based version of AFGROW has replaced the UNIX
version since the demand for the UNIX
version did not justify the cost to maintain it. There was also an experiment to port AFGROW to the Mac OS
. The Mac
version had the same problem (lack of demand) as the UNIX
version. An automated capability was added to AFGROW in the form of a Microsoft Component Object Model (COM)
interface. The AFGROW COM
interface allows users to use AFGROW as the crack growth analysis engine for any Windows based software.
. Drawing tools have been included in AFGROW to allow the user-defined solution to be animated during the analysis. Interactive stress intensity solutions have been demonstrated using AFGROW to perform life predictions while sending geometric data to an external FEM code, which returns updated stress intensity solutions back to AFGROW.
Verification testing is a continuing process to improve AFGROW and expand the available database. There are plans to continue to add new technology and improvements to AFGROW. A Consortium has been started with users in Government and Industry to combine the best fracture mechanics
methods available.
Aerospace
Aerospace comprises the atmosphere of Earth and surrounding space. Typically the term is used to refer to the industry that researches, designs, manufactures, operates, and maintains vehicles moving through air and space...
applications; however it can be applied to any type of metallic structure that experiences fatigue cracking.
Software architecture
The stress intensity factor library provides models for over 30 different crack geometries (including tension, bending and bearing loading for many cases). In addition, an advanced, multiple crack capability allows AFGROW to analyze two independent cracks in a plate (including hole effects), non-symmetric corner cracked. Finite Element (FE) based solutions are available for two, non-symmetric through cracks at holes as well as cracks growing toward holes. This capability allows AFGROW to handle cases with more than one crack growing from a row of fastener holes.AFGROW implements five different material models (Forman Equation, Walker Equation, Tabular lookup, Harter-T Method and NASGRO Equation) to determine crack growth per applied cyclic loading. Other AFGROW user options include five load interaction (retardation) models (Closure, FASTRAN, Hsu, Wheeler, and Generalized Willenborg), a strain-life based fatigue crack initiation model, and the ability to perform a crack growth analysis with the effect of the bonded repair. AFGROW also includes useful tools such as: user-defined stress intensity solutions, user-defined beta modification factors (ability to estimate stress intensity factors for cases, which may not be an exact match for one of the stress intensity solutions in the AFGROW library), a residual stress analysis capability, cycle counting, and the ability to automatically transfer output data to Microsoft Excel.
AFGROW provides COM (Component Object Model)
Component Object Model
Component Object Model is a binary-interface standard for software componentry introduced by Microsoft in 1993. It is used to enable interprocess communication and dynamic object creation in a large range of programming languages...
Automation interfaces that allow users to build scripts in other Windows applications to perform repetitive tasks or control AFGROW from their applications.
AFGROW also has new plug-in crack geometry interface that allows AFGROW to interface with any structural analysis program capable of calculating stress intensity factors (K) in the Windows environment. Users may create their own stress intensity solutions by writing and compiling dynamic link libraries (DLLs) using relatively simple codes. This includes the ability to animate the crack growth as is done in all other native AFGROW solutions. This interface also makes it possible for FE analysis software (for example, StressCheck
StressCheck
StressCheck is a finite element analysis software product developed and supported by ESRD, Inc. of St. Louis, Missouri. It is one of the first commercially available FEA products to utilize the p-version of the finite element method.-History:...
) to feed AFGROW three-dimensional based stress intensity information throughout the crack life prediction process, allowing for a tremendous amount of analytical flexibility.
History
AFGROW's history traces back to a crack growth life prediction program (ASDGRO) which was written in BASICBASIC
BASIC is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use - the name is an acronym from Beginner's All-purpose Symbolic Instruction Code....
for IBM-PCs by Mr. Ed Davidson at ASD/ENSF in the early-mid-1980s. In 1985, ASDGRO was used as the basis for crack growth analysis for the Sikorsky H-53 Helicopter under contract to Warner-Robins ALC. The program was modified to utilize very large load spectra, approximate stress intensity solutions for cracks in arbitrary stress fields, and use a tabular crack growth rate relationship based on the Walker equation on a point-by-point basis (Harter T-Method). The point loaded crack solution from the Tada, Paris, and Irwin Stress Intensity Factor Handbook was originally used to determine K (for arbitrary stress fields) by integration over the crack length using the unflawed stress distribution independently for each crack dimension. After discussions with Dr. Jack Lincoln (ASD/ENSF), a new method was developed by Mr. Frank Grimsley (AFWAL/FIBEC) to determine stress intensity, which used a 2-D Gaussian integration scheme with Richardson Extrapolation which was optimized by Dr. George Sendeckyj (AFWAL/FIBEC). The resulting program was named MODGRO since it was a modified version of ASDGRO.
Early years
Many upgrades were made during the late 1980s and early 1990s. The primary improvement was modifying the coding language from BASICBASIC
BASIC is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use - the name is an acronym from Beginner's All-purpose Symbolic Instruction Code....
to Turbo Pascal
Turbo Pascal
Turbo Pascal is a software development system that includes a compiler and an integrated development environment for the Pascal programming language running on CP/M, CP/M-86, and DOS, developed by Borland under Philippe Kahn's leadership...
and C
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
. Numerous small changes/repairs were made based on errors that were discovered. During this time period, NASA/Dryden implemented MODGRO in the analysis for the flight test program for the X-29
Grumman X-29
|-See also:-References:NotesBibliography* Thruelsen, Richard. The Grumman Story. New York: Praeger Publishers, Inc., 1976. ISBN 0-275-54260-2....
.
Recent times
In 1993, the Navy was interested in using MODGRO to assist in a program to assess the effect of certain (classified) environments on the damage tolerance of aircraft. Work began at that time to convert the MODGRO, Version 3.X to the CC (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
language for UNIX
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
to provide performance and portability to several UNIX Workstations.
In 1994, the results of the Navy project were presented to the Navy sponsor and MODGRO was renamed AFGROW, Version 3.X.
Since 1996, the Windows based version of AFGROW has replaced the UNIX
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
version since the demand for the UNIX
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
version did not justify the cost to maintain it. There was also an experiment to port AFGROW to the Mac OS
Mac OS
Mac OS is a series of graphical user interface-based operating systems developed by Apple Inc. for their Macintosh line of computer systems. The Macintosh user experience is credited with popularizing the graphical user interface...
. The Mac
Mac OS
Mac OS is a series of graphical user interface-based operating systems developed by Apple Inc. for their Macintosh line of computer systems. The Macintosh user experience is credited with popularizing the graphical user interface...
version had the same problem (lack of demand) as the UNIX
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
version. An automated capability was added to AFGROW in the form of a Microsoft Component Object Model (COM)
Component Object Model
Component Object Model is a binary-interface standard for software componentry introduced by Microsoft in 1993. It is used to enable interprocess communication and dynamic object creation in a large range of programming languages...
interface. The AFGROW COM
Component Object Model
Component Object Model is a binary-interface standard for software componentry introduced by Microsoft in 1993. It is used to enable interprocess communication and dynamic object creation in a large range of programming languages...
interface allows users to use AFGROW as the crack growth analysis engine for any Windows based software.
Present Day
An advanced model feature has been added to allow users to select cases with two, independent cracks (with and without holes). This feature continues to be improved and expanded to cover more combinations of corner and through-the-thickness cracks. A user-defined plug-in stress intensity model capability has also been added to AFGROW. This allows users to create their own stress intensity solutions in the form of a Windows DLL (dynamic link library)Dynamic-link library
Dynamic-link library , or DLL, is Microsoft's implementation of the shared library concept in the Microsoft Windows and OS/2 operating systems...
. Drawing tools have been included in AFGROW to allow the user-defined solution to be animated during the analysis. Interactive stress intensity solutions have been demonstrated using AFGROW to perform life predictions while sending geometric data to an external FEM code, which returns updated stress intensity solutions back to AFGROW.
Verification testing is a continuing process to improve AFGROW and expand the available database. There are plans to continue to add new technology and improvements to AFGROW. A Consortium has been started with users in Government and Industry to combine the best fracture mechanics
Fracture mechanics
Fracture mechanics is the field of mechanics concerned with the study of the propagation of cracks in materials. It uses methods of analytical solid mechanics to calculate the driving force on a crack and those of experimental solid mechanics to characterize the material's resistance to fracture.In...
methods available.