james a. harter alexander v. litvinov - afgrow · 2019. 1. 11. · version 5.3.3 (bug fixes): •...

James A. Harter

Alexander V. Litvinov

LexTech, Inc.

8285 Rhine Way

Centerville, OH 45458

11/26/2018 © Copyright 2019, LexTech, Inc

Class Agenda

AFGROW Fundamentals & New Capabilities

Jim Harter, Consultant, LexTech, Inc.

Break

AFGROW COM Automation

Alex Litvinov, LexTech, Inc.

Example Problems

Jim Harter & Alex Litvinov

1:00 – 3:00

3:10 – 3:30

3:30 – 5:00

3:00 – 3:10


AFGROW, Version 5.3Fundamentals and New Capabilities

Topics

Changes in Version 5.3.1 – 5.3.3

Basic LEFM Assumptions in AFGROW

AFGROW User Interface Features

Crack Growth Rate Modeling

Spectrum Generation/Management

Beta Correction Process

Residual Stress Analysis Capability


Recent Changes to AFGROWVersion 5.3.1:

• 64 bit application

• Ability to use different growth rate data in two orthogonal directions

• Ability to use different growth rate data as a function of spectrum level

• Corrosion effects (exfoliation, intergranular, pitting)

• New XML spectrum format

• Ability to open read-only material data from a network or local folder

• More flexibility in out-of-plane bending solution for through cracks

• New K-solution for a corner crack at the base of a countersink

• Bearing and bending solutions for advanced through crack models

• New user-defined solution for two, interdependent cracks

• New edge crack solution for a finite height plate

• Global “Constrained” in-plane bending property for advanced models88

New Spectrum Management Software Tool


Recent Changes to AFGROWVersion 5.3.2 (Bug Fixes):

• The “Constrained” option for a classic edge crack could not be set using COM

• Under certain conditions, a corner crack at the base of a C/S (knee) model

could go into an endless loop

• Spectrum title was missing in the *.pl2 file

• The H/W value was not being calculated/reported correctly in the Notification

frame for a "single edge crack in a finite height plate" model

Version 5.3.3 (Enhancements):

• Added the ability to use residual stresses for advanced models with crack(s) at

a hole

• Made significant improvements to the residual stress Gaussian integration

routine

• Added the ability for AFGROW to provide COM interface information at runtime


Recent Changes to AFGROWVersion 5.3.3 (Bug Fixes):

• Resolved a crack Initiation issue for high cycle fatigue (interpolation error)

• Ultimate Strength value for Tabular Lookup model may not be set through the COM

interface

• Resolved an issue where AFGROW sometimes used the wrong NASGRO K* value

for Advanced and Plugin models

• Added a block size variable to ConstAmplitudeSpectrum COM method

• Delta K threshold and Yield Strength for the tabular lookup material model are no

displayed in the Tree Status view

• Resolved an issue where the K* parameter for the NASGRO equation was not

recalculated correctly when any model without a hole was selected through the COM

interface

• Resolved an issue with sub-spectra plotting in the spectrum view

• AFGROW now displays the spectrum pass count on the status bar

• Resolved an issue reading a saved Forman material model file

• Resolved an issue with the 2-D Beta correction table becoming 1-D after through

crack transition

• Resolved an issue where the option to output after each beta calculation was not

being saved in the input file

• The filled, unloaded hole correction is now applied to the a-direction for part-through

cracks


LEFM Fundamentals

and

Version 5.3 New Features


Fracture Energy

A.A. Griffith

Irwin/Orowan


Crack Length/Grain Size Effects


Griffith Energy BalanceStable Crack Growth Implies That There is a Balance Between the

Potential Energy Loss and the Energy Required to Create New

Crack Surfaces as a Crack Extends

E – Total Energy

A – Crack Area

P – Potential Energy

Ws – Energy Required to Create New Crack Surfaces


Strain Energy Releasefor

Perfectly Elastic Materials Under Plane Stress Conditions

Un-cracked Plate: 𝑈𝑣 = න𝜎 𝑑𝜖 =𝐸 𝜖2

2=

𝜎2

2 𝐸

Energy Released in an Edge Cracked

Plate:

𝑈𝑡 = −𝜎2

2 𝐸𝜋 𝑎2

(unit volume)

(unit thickness)


Failure Criteria (Energy Based)Consider a Crack of Length 2a in an Infinite Plate Under Remote Tension

Griffith/Irwin:

At Failure:

Note: Gc is a material constant – Therefore, the Critical Values of

Stress and Crack Length are Interrelated

Plane Stress: E* = E

Plane Strain: E* = E (1 – u2)


Cracking Modes


Failure Criteria (K Based)Consider a Crack of Length 2a in an Infinite Plate Under Remote Tension

Note: Because of Similitude, KIC is a Constant – Therefore, the

Critical Values of Stress and Crack Length are Interrelated

At Failure:

(for a given stress state)


Crack Tip Stress

Looking at it Another Way …….


Assumption of Similitude

Similitude: Fracture Toughness (or Critical Strain Energy

release Rate (Gc)) is INDEPENDENT* of the

size and geometry of the cracked body

(As Applied to Failure Criteria)

* Assuming a given stress state


Crack Growth Under Cyclic LoadingPaul Paris (1950s) Noted That Crack Growth Per Load Cycle

(da/dN) May Be Represented as Follows:

Crack Growth Life, In Terms of Cycles (Time), May Be Calculated By

Numerical Integration:

(Straight line in log-log scale)


Crack Growth Rate Data

da/dN – Crack Extension Per Load Cycle (smax – smin)

DK – Stress Intensity Range for a Given Load Cycle (smax – smin)11/26/2018 © Copyright 2019, LexTech, Inc

Assumption of Similitude

Similitude: Crack growth rate data for a given material are

INDEPENDENT of the size and geometry of the

cracked body

(As Applied to Growth Rate Data)

For a given material, this is a critical assumption that allows us to predict the

crack growth life of any structure

There is a unique relationship between growth rate, Kmax, & Kmin



Short Crack

Ridiculous Crack

Ludicrous Crack


Material Properties and LEFM

Linear Elastic Fracture Mechanics Principles Are Generally

Applicable for Isotropic and Linearly Elastic Materials

Additional Requirements/Assumptions:

Plastic deformation is small relative to the crack length

Crack length is large relative to the material grain structure

Similitude must be demonstrated

Crack Growth is continuous wrt applied cyclic loading


AFGROW User Interface Features

James A. Harter


LexTech, Inc.

8285 Rhine Way



AFGROW Layout

Menu/Toolbars

Animation Frame

Main Frame

Status Bar

Output Frame


Resizing the Layout

• Analogous to the ‘Split Screen’ in Excel ®


Main Frame

Views Include:

• Status

• Crack Length vs. Cycles

• Crack Growth Rate Data

• Initiation Plots


Status View


Crack Length vs. Cycles


Bonded Repair Plot


Crack Initiation Plots


Animation Frame

Classic or Weight

Function

Geometries

Advanced

Geometries


Resizing the Animation View

• Drag a window on the animation frame

• Use the Magnifying tools

– Zoom Out

– Zoom In

– No Zoom


Refresh

• Resets the animation frame to initial crack length


Model Identification

• Title of Model Geometry being Analyzed

• Coordinate System


Dimensions

• Allows you to toggle the dimensioning on/off within the animation frame

• Found in the View Menu


Running a Prediction

• Pause

• Start

• Stop

• Also found in the Predict Menu


Output Frame


Notification List


Menu and Toolbars


Status Bar


Units

• On the Status Bar – bottom right hand side of screen

• Choices

– English

– Metric

• Conversions are done “On The Fly”


Units

• English – Stress (ksi)– Length (inch)– Force (Kip)– Temperature (Degrees Fahrenheit)

• Metric– Stress (MPa)– Length (meter)– Force (MNewton)– Temperature (Degrees Kelvin)


File Menu

• Open

• Close

• Save

• Save As

• Mail

• Recent File

• Exit


Toggling Toolbars or Views


Copy / Paste / Freeze / Erase All

• Copy

• Copy Data

• Copy Image

• Paste

• Paste Data

• Freeze

• Erase All


Window Tools

• Window Menu

– Tile

– Cascade


Docking Windows

AFGROW Windows may be moved as desired

The configuration is stored in the registry


Help Menu

Accessed Through:

• F1

• Arrow/Question Mark Hot Key

Slightly Less Comprehensive Than the Printable Manual

Searchable

Context Sensitive and Organized in an HTML Format

Use this to open help for any item on the

tool bar


Getting Help… in General

Read the Manual

• F1 (On-Line Help)

• Downloadable / Paper / Adobe Version

AFGROW Blog (web site)

Other Documentation (web site)

Support Option (Email in the File Menu)


About AFGROW

• Version Information/Compile Date

• Credits

• Contributors

• Available through the Help Menu or Question Mark Icon


Demonstration


Crack Growth Rate Modeling

James A. Harter


LexTech, Inc.

8285 Rhine Way



AFGROW Crack Growth Rate Input


Growth Rate Models

• Forman Equation

• Harter T-Method

• NASGRO Equation (Version 3)

• Tabular Look-up

• Walker Equation


Growth Rate Model TerminologyDKThreshold

KIC

KC

RHI (+)

RLO (-)

da/dNHI

da/dNLO

SIF range (at R=0) below which no crack growth is assumed

Plane strain fracture toughness

Plane stress fracture toughness

Stress Ratio (SMIN/SMAX) above which no data shift occurs (DK)

Stress Ratio (SMIN/SMAX) below which no data shift occurs (KMAX)

Upper Limit on Growth Rate

Lower Limit on Growth Rate


Forman Equation


Harter T-Method

When, R1 & R2 > 0*

The m-value [0 – 1] controls the

amount of data shifting. As ‘m’

increases, the shifting decreases

(Applies the Walker Equation on a Point-by-Point Basis)

* If Ri < 0, Kmax is used instead of DK, and the exponent is reversed (1-m) to maintain the proper shifting trend

For a given crack growth rate:


Harter T-MethodCalculating m-values

−

−

D

D+=

)1(

)1(log/log1

1

210

2

110

R

R

K

Km

( )( )( )

−−

D+= 2110

2

1max

10 11log/log1 RRK

Km

−

−

−=

)1(

)1(log/log1

1

210

2max

1max

10R

R

K

Km

if R1 and R2 ≥ 0

if R1 < 0 and R2 ≥ 0

if R1 and R2 < 0


Harter T-Method, ExampleSample Data


NASGRO Equation, Version 3


Tabular Look-UpSeveral Improvements in Version 5.3

May use crack direction dependent growth rate data and/or

multiple data sets for different environmental conditions11/26/2018 © Copyright 2019, LexTech, Inc

Tabular Look-UpExample for Two Growth Directions


Tabular Look-UpExample for Different Temperatures


Tabular Look-Up Curve Fits Now Available On-Line


Walker Equation


Walker Equation, Example

Discontinuities May Occur, Depending on User Parameters


Tabular Look-Up Demonstration


Spectrum Management

James A. Harter


LexTech, Inc.

8285 Rhine Way



Spectrum Manager

New for Version 5.311/26/2018 © Copyright 2019, LexTech, Inc

Definition: Stress or Load Cycle

A cycle is defined as a stress (or load) excursion which starts at

a certain level, and returns to the same level over time. A cycle

may be characterized by it’s maximum and minimum value.


Definition: Stress Ratio (R)

R = smin/smax

A stress cycle is defined by it’s minimum and maximum value, but the

resulting crack growth rate is determined by the stress intensity range

(DK) and the stress ratio (R).


Definition: Spectrum

A spectrum is a sequence of cycles as they are applied over time.


Spectrum Dialog :

Or


Stress Multiplication Factor (SMF)

Each Maximum and Minimum Value for All Cycles in the Input Spectrum is

Multiplied by the SMF.

This Provides the Capability to Scale an Input Spectrum to Determine the

Effect of Various Operating Stress (or Load) Levels on Crack Growth Life


Residual Strength Requirement (Pxx)

This is the Stress (or Load) Value Which a Structure Must be Able to Bear

for All Crack Lengths During the Life Prediction.

It is Useful for Cases in Which the Time of Occurrence of the Maximum

Stress (or Load) is Unknown, and It is Desirable to Test this Condition for

any Crack Length. Using Zero for Pxx Simply Turns the Option Off, and

Failure is Based on the Current Applied Spectrum Stress (or Load).


Stress Preload (SPL)

This is the Stress (or Load) Which is Assumed to Exist in a Component in

Addition to any Applied Spectrum Loading.

This is Useful for Cases Where There Are Loads on a Component as a

Result of Some Type of Structural Constraint. Examples Include:

• Part Mismatch

• Independent Mechanical Loading

• Thermal Expansion Effects


Stress or Load?

When a model requiring a stress

spectrum has been selected, the

spectrum dialog will appear with

a stress icon.

When a model requiring a load

spectrum has been selected, the

spectrum dialog will appear with

a load icon.


Spectrum Terminology

Level

Sub-Spectrum

BLOCKED

Spectrum

CYCLExCYCLE

Spectrum

Pass

A line in the spectrum containing maximum, minimum, and

number of cycles

Subset of the input spectrum, and must be less than 4MB so

it may be read into system memory. The complete spectrum

consists of one or more Sub-Spectra.

Spectrum in which one or more levels consists of multiple

cycles for a given max, min.

Spectrum in which each level consists of a single cycle

The crack growth analysis for the entire input spectrum.

Once completed, the spectrum is repeated from the

beginning.


Standard Spectrum Text File Format

Two or more files are required to determine the input spectrum

for AFGROW.

The first file is the spectrum information file, containing the basic

information required to define the spectrum (i.e. title, sub-

spectrum label.., and number of files containing the actual

spectrum data)

The subsequent files contain the spectrum data


Standard (Cyclic) Spectrum Text Format

Spectrum Information Filename : [name].sp3

Spectrum Information File Format :

[Title]

[Sub-Spectrum Label] (i.e. Flight, Block, Hour, etc)

[Type of Spectrum] (Either BLOCKED or CYCLExCYCLE)

[Number of Files to Follow] (1-99)

Spectrum Data Filename : [nameXX].sub (must be 2 digits, i.e. 01, 02 ….)

Spectrum Data File Format :

[Sequential Sub-Spectrum Number] [Number of Levels]

[Maximum] [Minimum] [Number of Cycles]

The Above Pattern Repeats for the Number of Levels and Number of Sub-

Spectra in a given Data File.

X - Text Characters, X - Integer Value X - Floating Point Value


AFGROW Spectrum Input Options

• Create a New Spectrum File

• Open a Spectrum File

• Constant Amplitude Loading


Create a New Spectrum File

Version 5.2 includes a “Wizard” to create a new spectrum file, but this wizard is

being phased out in favor of the new Spectrum Management Tool.


Open a Spectrum File

Sample spectra are available in the Documents\AFGROW\Spectra

folder.11/26/2018 © Copyright 2019, LexTech, Inc

Constant Amplitude Loading

Note: The Constant Amplitude Loading Option Simply Creates a

Sequence of Constant Amplitude Cycles Based on the Specified

Block Size and R-Value. The Values Are Scaled Using the SMF11/26/2018 © Copyright 2019, LexTech, Inc

Time Dependence

The time dependent analysis capability in AFGROW is taken in addition to the cyclic

crack growth calculations. Additional time dependent material data must be input by

the user (see the tools menu).

100 Segments


Spectrum Manager Demonstration


Beta Correction Capability

James A. Harter


LexTech, Inc.

8285 Rhine Way



Beta Factors

What is beta? b

Beta is a geometry factor used to determine Stress Intensity (K) as

a function of crack size and applied loading.

Where, x is the crack length of interest


Classic Solutions

Plates

Plates w/Holes

Plates w/Notch

Lugs

Pipes

Rods

WOL/CT Specimen


Reference Stress for Classic Models


Reference Stress, Kt, & Beta Factor(as the crack length → 0)

Through-the-Thickness Cracks

• Internal Crack: b = 1.0 (no Kt)

• Edge Crack: b = 1.12 * Kt

Part-Through Cracks

• Internal Crack: b = 2/p (no Kt)

• Corner/Surface Crack at a Hole or

Notch: b = 1.12 * 2/p * Kt

• Corner/Surface Crack: b = 1.12 * 2/p


Beta Correction Dialog Box


Beta Correction

That solution is close to what I’m looking for!

Two Options

– Table of Normalized Stress Distribution Ratios

• 1D (through-the-thickness cracks)

• 2D (part-through cracks)

– Input Beta Correction Factors Manually


Gaussian Integration Method

2-D Gaussian Integration Method Uses a Point Load Stress Intensity Solution from Tada, Paris, and Irwin

AFGROW uses integration points

for each crack growth direction at

user-defined radial distances from

the crack origin. The residual K

value for each crack is determined

using the linear interpolation

between points.

This can be an additional source

for error if the crack shape is not

relatively close to circular, but it is

not practical to anticipate crack

shape changes in advance.


Beta Correction Calculation

Unknown Solution Known Solution



Unknown Solution Known Solution Stress Distribution Ratio

Normalize the Stress Distribution Ratio at the Crack Origin



Normalized

Beta

Correction

Normalization Factor is Incorporated in the Spectrum SMF

Stress Distribution Ratio

1 1

Unit Stress


Beta Correction ExampleSingle thru-crack at a fastener hole growing toward a nut plate attachment hole


Beta Correction Example, continued

𝜷𝒅𝒆𝒔𝒊𝒓𝒆𝒅 = 𝜷𝒌𝒏𝒐𝒘𝒏* 𝜷𝒄𝒐𝒓𝒓𝒆𝒄𝒕𝒊𝒐𝒏

𝜷𝒌𝒏𝒐𝒘𝒏 = 𝜷𝒔𝒊𝒏𝒈𝒍𝒆 𝒕𝒉𝒓𝒖 𝒄𝒓𝒂𝒄𝒌 𝒂𝒕 𝒂 𝒉𝒐𝒍𝒆

𝜷𝒄𝒐𝒓𝒓𝒆𝒄𝒕𝒊𝒐𝒏 is estimated from the ratio of the unflawed stress

distributions (desired/known) at a number of discrete distances from

the assumed crack origin. AFGROW uses a Gaussian integration

method to determine a beta correction value at each integration point

using a table of normalized* stress distribution values. AFGROW

interpolates the appropriate beta correction value from this table to

modify the known solution.

* The stress distribution ratio at the crack origin is used as the normalization factor, and the SMF

value for the analysis is multiplied by this value to retain the magnitude of the local stress at the crack

origin11/26/2018 © Copyright 2019, LexTech, Inc


1.0

1.5

2.0

2.5

3.0

3.5

0.0 0.1 0.2 0.3 0.4

Stre

ss

Distance From Fasterner Hole Edge

Stress Distribution

Nut Plate

Open Hole



0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0.0 0.1 0.1 0.2 0.2 0.3 0.3 0.4

Stre

ss D

istr

ibu

tio

n R

atio

Distance From Fasterner Hole Edge

Stress Distribution Ratio r Sn/So Normalized

0.000 1.004 1.000

0.015 1.008 1.004

0.035 1.023 1.018

0.050 1.026 1.022

0.065 1.028 1.024

0.085 1.038 1.034

0.100 1.038 1.034

0.149 1.060 1.056

0.200 1.104 1.100

0.222 1.144 1.139

0.252 1.260 1.255

0.274 1.460 1.454

0.300 2.164 2.155

0.308 2.696 2.685

0.310 2.874 2.863



• The accuracy diverges as the crack

length increases

• It is important to use a reference

model that is as close to the

desired model as possible

• The integration points are not

required to evenly spaced, but

should represent the curve well for

linear interpolation

• Use two integration points beyond

the longest crack length expected

• For best results, the change in

slope between any two points

should be < abs(600)

• For 2-D cases, enter a value of 1.0

for the a-direction for r-values >

plate thickness*.

* Transition points may be required to avoid

problems caused by large slope changes

between points


Beta Correction Example, continuedC Stress Beta Correction

0.0150000 1.0040 0.994752

0.0350000 1.0180 1.006129

0.0500000 1.0220 1.010551

0.0650000 1.0240 1.009895

0.0850000 1.0340 1.018735

0.1000000 1.0340 1.019253

0.1490000 1.0560 1.036639

0.2000000 1.1000 1.067747

0.2220000 1.1390 1.087303

0.2520000 1.2550 1.170824

0.2740000 1.4540 1.298666

0.3000000 2.1550 1.364330

0.3080000 2.6850 1.574385

0.3100000 2.8630 1.62399011/26/2018 © Copyright 2019, LexTech, Inc


0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 5000 10000 15000 20000 25000 30000 35000 40000

Cra

ck L

engt

h

Cycles

No BetaCorrection

BetaCorrection


Residual Stresses

James A. Harter


LexTech, Inc.

8285 Rhine Way



Residual Stress Input

Input Residual Stresses and Calculate Residual Ks

• 1D Weight Function

• 2D Gaussian Integration

Similar to the beta correction method,

but in this case, the un-flawed residual

stress distribution (not the ratio of two

distributions) is used to calculate K

directly.

Note: Since K is not defined for compression, this

approach should be considered to be an engineering

approximation for compressive residual stresses.11/26/2018 © Copyright 2019, LexTech, Inc

New in Version 5.3.3

The residual stress capability is now available for cracks at holes in our Advanced Model Interface


Issue

The Gaussian integration method is somewhat sensitive to the

change in slope between integration points

Reasonable results have been obtained with the Gaussian

method for:𝑑𝑆𝑙𝑜𝑝𝑒

𝑑𝑟≤ 600


Issue

A Newton polynomial interpolation method is used as part of the

Gaussian integration process for each integration point.

It is highly recommended that two integration points be included

beyond the longest expected crack length.


Gaussian Integration Approach

Changes in Version 5.3

A bug was found and fixed in the Newton interpolation method

For Part Through Cracks:

• A part-through correction was added to the integration results

• Integration is performed twice

• Once for the 2-D stress distribution

• Second, for the C-direction (distribution in the A-direction is set to 0)


Other Options


Weight Function

The Weight Function Method Allows for Stress Gradients in One-Dimension

May Only Be Used With Applicable Weight Function Geometries


Input Residual K Directly


Example Problem for a Cold-Worked

Hole• Plate Width = 4 in

• Thickness = 0.25 in

• Hole Diameter = 0.25 in

• Initial Crack Size:

• a = 0.05 in c = 0.05 in


2-D Residual Stress Distribution

C Direction A Direction

r Residual Stress (r,0) Residual Stress (0,r)

0.000 -41.20 -43.00

0.020 -43.00 -50.00

0.040 -39.00 -55.00

0.100 -27.75 -57.00

0.150 -17.00 -55.00

0.200 -5.25 -51.00

0.225 -1.00 -49.25

0.250 1.85 -48.00

0.300 6.00 0.00

0.350 7.36 0.00

0.500 6.50 0.00

0.750 5.10 0.00

1.000 4.75 0.00

1.500 4.44 0.00

1.740 4.00 0.00

1.750 4.00 0.00

-50.00

-40.00

-30.00

-20.00

-10.00

0.00

10.00

0.000 0.500 1.000 1.500 2.000

C Direction

-60.00

-50.00

-40.00

-30.00

-20.00

-10.00

0.00

0.000 0.500 1.000 1.500 2.000

A Direction


Model Dimensions


Residual Stress Input


Residual K Results

-15.000

-10.000

-5.000

0.000

5.000

10.000

0.000 0.500 1.000 1.500 2.000

Kc Residual

-30.000

-25.000

-20.000

-15.000

-10.000

-5.000

0.000

0.000 0.050 0.100 0.150 0.200 0.250 0.300

Ka Residual


Conclusions

• Keep slope changes between integration points below |600|

• It is generally helpful to include multiple points for uniform stress distributions to decrease potential interpolation errors in the resulting stress intensities.

• It is important to add two additional integration points beyond the maximum expected crack length


AFGROW Automation

James A. Harter


LexTech, Inc.

8285 Rhine Way



COM Automation

COM (Component Object Model) - Service Of Microsoft Windows

Automation is an industry-standard technology that applications

use to expose their objects to development tools, macro

languages, and other applications that support Automation.

Object is an a combination of code and data that can be treated

as a unit, for example, AFGROW initiation data, AFGROW

material, AFGROW residual stresses data, AFGROW retardation.

•Software Language Independence

•No Cost (Comes With Windows Operating System)

•Highly Supported in Software Industry

•Familiar to the Software Development and Engineering

Community

•Easy to Use


Property, Method and Event

• Property: A named attribute of an object which defines object

characteristics such as width or stress ratio, or state of an

object such as enabled or disabled.

• Method: A function that acts on an objects. For example: start

crack growth analysis in AFGROW or create new crack

configuration model.

• Event: An event is an action recognized by an object, such as a

crack fracture or transition, and for which user can write code

to respond. Events can occur as a result of a user action or

program code, or they can be triggered by the system.


Easy Terminology

Object – Has Properties

Method – Actions

Event – Reaction

Forms – Have a visual representation (Controls, Text Boxes, etc.)

Modules - Have no visual representation, but provide a link between the

spreadsheet and a user-defined form


AFGROW Automation (required files)

afgrow.exe - Application executable file (application

and interface implementation)

afgrow.tlb - Object library (interface description).

Object browser can be used to examine the context of

the library.


AFGROW Interface description

Application

Harter-T Material

Forman Material

NASGRO Material

Tabular-Lookup Material

Walker Material

Output Information

Crack Initiation

Predict Properties

Residual Stresses

Retardation

User Defined Beta

Application Events

Global Parameters

Beta Correction

Advanced Models

Specimen Draw

Predict Manage

Beta Plugin

Spectrum Filtering

K-Solution Filtering11/26/2018 © Copyright 2019, LexTech, Inc

What can be done with AFGROW

• Start AFGROW or Connect to Running Application

• Run AFGROW Visibly or Invisibly (as a Process)

• Change any Properties Currently Available Through the GUI interface (Material, Model Configuration, Load, Predict Preferences ...)

• Execute Crack Growth Analysis

• Obtain Complete Output Information From AFGROW During the Analysis as Well as Transition and Fracture Notification

• Shutdown AFGROW on Demand From a Client Application

• Ability to Shutdown “Invisible” AFGROW Manually

AFGROW COM server will add an icon that appears in the Windows

taskbar tray When the server is running, the AFGROW icon will appear in

the tray. The server may be controlled by right clicking on the AFGROW

icon.


What Kind of Development Tool Can be Used to Automate AFGROW

• Any Windows Application which incorporates Visual Basic for Application (VBA) Including: Excel, PowerPoint, AutoCAD, MS Office..

• C++, C# and VB.NET

• Matlab

• Web Server Through ASPX or PHP pages

• Any Scripting Language for Windows Including Perl, Windows Script Host and Python (not always easy)

• Any computer language written for MS Windows (not always easy)


First steps to start AFGROW automation

• Excel menu: “File”, “Options”

• Select “Customize Ribbon”, check “Developer” check box


AFGROW Object

• VBA Environment menu: “Tools”,

“References”

• Check AFGROW Check Box

• VBA Environment menu “View”, “Object

Browser”


Object Browser Explained

AFGROW Object

Interfaces

Enumerated groups

Properties

Functions

Events


Properties

• A COM object property is a value that defines the visible, functional, and other characteristics of a COM object

• Property can be always used to get value, and very often to set value


Methods

• A COM object method is a specialized function associated with a COM object that performs an action on the COM object or alters the behavior of the COM object. COM object methods may or may not return a value and may or may not require parameters. Com methods parameters can be passed by value or by reference.

• Method with no return value and optional parameters


Methods (Continued)

• Method with the return value and parameters

• Method with the return value and parameters passed by reference


Events

An event is typically a user-initiated action that takes place in a server application, which often requires a reaction from the client. For example, clicking the mouse at a particular location in a server interface window might require the client to respond. When an event is fired, the server communicates this occurrence to the client. If the client is listening for this particular type of event, it responds by executing a routine called an event handler.

• Only AFGROW.Application interface can raise events

• Use WithEvents keyword to specifies that variable that refer to an instance of a AFGROW.Application object can raise events.


Events (Continued)

Variable that can

raise events

List of all available

eventsEvent function implementation


Interfaces

Interfaces exists to allow us to interact with objects based on what they do, not how they do it.

All AFGROW interfaces are accessible through the main Afgrow.Application interface as read only properties.


Coding Practices

Use Option Explicit at the start of your VBA code

Make AFGROW visible to help with debugging

Always know what your units are

Do not forget to release the object

Always set a model number first, before setting any other model

properties11/26/2018 © Copyright 2019, LexTech, Inc

VBA Code ExampleDeclaration

Instantiatio

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Setting up

Parameters


Matlab Code Example

Instantiatio

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Event

Handler

Setting up

Parameters


Resources

• Excel VBA Reference: https://msdn.microsoft.com/en-us/library/office/ee861528.aspx• Download AFGROW COM Manual and Examples (login required): http://www.afgrow.net/userarea/


https://msdn.microsoft.com/en-us/library/office/ee861528.aspx

http://www.afgrow.net/userarea/

Resources (Continued)

• AFGROW YouTube page: https://www.youtube.com/user/AFGROW

Email questions: [email protected], [email protected]


https://www.youtube.com/user/AFGROW

mailto:[email protected]

mailto:[email protected]

How AFGROW automation can be used

• Use COM to control AFGROW and perform repetitive tasks

• Create a new stress intensity factor solution/continued damage model using COM API

• Incorporate AFGROW in different software solutions, and create a different GUI interface for AFGROW

• Solve optimization problems (find a result by adjusting an input value)
