Unique Features and Capabilities
There are a number of unique features and capabilities that set AFGROW apart from other fatigue crack growth life prediction software. Brief descriptions of these capabilities are given below for your consideration:
The beta correction capability may be used to obtain an unknown K-solution for a unique and/or specific geometry by modifying a similar, known stress intensity factor solution for a given geometry (or loading case) that is available in AFGROW. This is implemented through a modification to the non-dimensional geometry correction factor (β).
The correction is calculated based on a Gaussian integration of the ratio of the normalized unflawed stress distribution ratios of the unknown/known geometries. An example of the input required for a through cracked case is shown below:
The spectrum filtering capability allows tension and compression values to be adjusted independently to account for external or internal effects which may behave differently under tensile and compressive loading.
The spectrum filtering capability is a function of the crack length in the c-direction, and may be entered in tabular format or by using AFGROW’s new embedded java script engine.
Stress Intensity Filters
Stress intensity (K) solutions are typically provided in terms of the geometry correction factor (β), where:
β=K/(σ √(πx )) , where x is the crack length of interest
The K-filtering capability permits the beta values to be adjusted independently for tensile and compressive loading for all load cases (axial, bending, and bearing). This allows for independent beta values to be applied for tension and compression spectrum stresses.
One example of the application of this capability is the classic lug geometry.
The beta values for this case should be zero for compressive spectrum loads.
In addition to operating as a stand-alone, interactive life analysis tool, AFGROW can also be executed from any Windows© application using COM technology. This feature allows users to pass information to AFGROW and execute nearly all of its capability via another application. One of the most common applications is the use of MS Excel. AFGROW input parameters for any number of life calculations may be passed to AFGROW from Excel using the VBA for applications option. This also allows a user to write code to control how AFGROW uses this data in an automated environment.
Information on the use of AFGROWs COM capability (including sample applications) is available in the Component Object Model manual.
Plug-In Stress Intensity Factor Modules
Users can develop addition stress intensity solutions to add to the existing AFGROW. These solutions may be shared with other users, or kept as proprietary models as desired. AFGROW has built-in drawing tools to allow these modules to be animated during execution as is done for all of the native AFGROW solutions. The modules must be compiled as Dynamic Link Libraries (DLLs).
This capability, along with the AFGROWs COM capability was used to demonstrate the use of an external stress intensity solver to solve very complex problems in an interactive manner. Geometric data was sent to a 3rd party finite element code (i.e. StressCheck), and stress intensity data was passed back to AFGROW on an incremental basis during the life prediction process.
Information and step-by-step instructions on the development and use of AFGROWs Plug-In capability (including a sample plug-in module) is available in the Building AFGROW Plug-Ins presentation in the document download section
Advanced Multiple Crack Analysis Capability
AFGROW has the ability to perform crack growth analyses for multiple cracks. Each crack tip in AFGROW is treated as a separate object so that all life prediction operations may be performed independently for each object. This capability has been utilized in AFGROWs Advanced Model interface to for two, independent cracks in a plate (including holes).
Detailed information on the multiple crack solutions (corner and through-the-thickness cracks) is available in the references provided in the document download section. The User’s Manual includes the capabilities and limitations of the currently available solutions.