8:309:15 
Basics of StressCheck + AFGROW Application Development: An Engineering Perspective
Brent Lancaster, Anil Mehta  ESRD
StressCheck’s flexible COM API and superior fracture mechanics capability make it well suited to be paired with LexTech’s AFGROW for life prediction calculations. Therefore, a partnership has been forged between LexTech, Inc. and ESRD, Inc. to explore AFGROW plugin tools which use StressCheck FEA as a solver engine. The interoperability between AFGROW and StressCheck allows computation of 2D and 3D elasticity solutions when closedform or empirical relationships do not exist. This presentation will cover the basic fundamentals of designing and developing a StressCheck plugin tool for AFGROW, with the target audience being experienced StressCheck users who wish to develop engineering applications driven by AFGROW.

10:1512:00 
Recent Developments in AFGROW COM and PlugIn Applications
Alex Litvinov, James Harter, Thomas Latta  LexTech, Inc
The COM abilities of AFGROW allow users to automate manual tasks, incorporate AFGROW services into proprietary software, and enable the reuse of code that has been prebuilt and tested.
AFGROW PlugIn technology allows the creation of Proprietary, ClosedForm, Tabular / Interpolative / Extrapolative, and ExternalK (if available) UserDefined custom solutions.
This presentation will include practical examples of the PlugIn and COM capabilities of AFGROW, and describe lessons learn during application development.
Future changes and additions to COM and Plugin interfaces will be presented and discussed.

1:15 – 1:30 
Next Generation Crack Growth Predictions  Coupled Finite Element Modeling and Crack Growth Analysis
Joshua Hodges  USAF AFMC OOALC/GHMEJ, Kaylon Anderson  USAF AFMC OOALC/GHAEJ
Traditionally, stress intensity solution development and crack growth predictions are developed independently. For standard geometries and loading, this typically works quite well. However, for complex geometry and/or loading, varying crack aspect ratios, multiple cracking scenarios, etc., this classic approach doesn’t always fit. Synergies between the factors that affect the overall crack shape and growth are not necessarily captured, and thus can have a significant influence on the crack growth life.
The T38 and A10 analysis groups have developed a generic AFGROW plugin that couples stress intensity development via StressCheck with AFGROW’s crack growth analysis capability. This new capability allows AFGROW to open, update, solve, and extract solutions from parameterized StressCheck models automatically. Solutions are imported into AFGROW, crack growth is calculated, and the new crack geometry is sent back to StressCheck. This process is repeated automatically until a defined failure or stop criteria is reached. This seamless integration allows for more accurate crack growth predictions in complex situations and eliminates many of the assumptions that are required with the traditional approach.
This paper describes the development of the code, keys to building a proper StressCheck model, limitations of the plugin, as well as future applications and directions of this capability. It also presents comparisons to Classic and Advanced AFGROW solutions. Finally, test data will be presented to help focus the experimental validation process.

1:30 – 2:00 
Influence of Secondary Crack Growth in Continuing Damage Cases
Luke Hanks  USAF AFMC OOALC/GHMEJ
Continuing Damage models involve the addition of a secondary, 0.005inch crack
at a hole, directly opposite the primary crack under consideration. These
models are currently analyzed by assuming the influence of one crack on the
other to be negligible; thus, a 3phase approach is used with Phase 1 for the
primary crack, Phase 2 for the secondary crack, and Phase 3 for the continuing
damage crack growth. In order to investigate the effects of multiple flaws on
crack growth and how this will impact the current continuing damage approach,
several models were developed in StressCheck, including both cracks
simultaneously, for two Fatigue Critical Locations (FCLs). The beta factors
were calculated and compared to show the effects that are currently neglected
in the continuing damage models. Two optional methods for modeling these cases
are outlined and performed, and the resulting crack growth curves are compared
for the two FCLs under consideration.
