Spectrum Manager

Spectrum Manager is now available for use by AFGROW, Version 5.3 Users who have been issued a permanent user license and current with user maintenance.

For most applications, structural loading is random and can be represented as a series of loading events that change over time. To be able to use these data for fatigue crack growth analysis, the sequence must be converted to a cycle-counted format. Spectrum Manager allows users to define a usage spectrum based on structural loading information. The spectrum is compiled as a combination of sub-spectra with one or more stress (or load) levels. This allows the use of multiple sub-spectra with different combinations of loading conditions. The spectra can also be time dependent. The user defines a sequence of these sub-spectra in the order desired to build the spectrum. Once the spectrum is defined, Spectrum Manager calculates the statistics, R plot, and exceedance plot for that spectrum.

We have additional information in AFGROW User Workshop proceedings .

The capabilities and primary features of Spectrum Manager are:

  • Visual spectrum design
  • Spectrum level reordering
  • Sub-spectra organized in any user-defined sequence
  • Sub-spectra may be placed in the sequence more than once
  • Sub-spectra may be re-ordered in the sequence
  • Spectrum statistics at a glance
  • Exceedance curve plotting
  • R-plots
  • Sub-spectra tagging for future analysis
  • Synchronized data views
  • Spectrum level damage tagging
  • Spectra normalization/de-normalization
  • Clipping/Truncation capability
  • Import data from “old” text sub files
  • Context-Sensitive Help
Spectrum Manager - Main layout
Spectrum Manager - layout

Spectrum Manager provides several new capabilities for spectrum development and analysis in a user-friendly, visual design interface. Until now, AFGROW has been limited to single channel spectrum data. This has meant that axial, bending, and bearing loading fractions were constant for all loading cases represented in the spectrum. While this new tool works with single channel data, it also has the ability to handle three, independent load channels for axial, bending, and bearing data.

The standard format for Spectrum Manager is an XML format that has been used for AFGROW input and output files for several years. Spectrum Manager will also work with the existing AFGROW text base spectrum format for single channel spectra. The XML format allows the user to include additional information (e.g., altitude, temperature, etc.) for each stress level or sub-spectra.

Another useful feature incorporated in the new format is the ability to add environmental and damage tags to the spectrum. Environmental tags allow AFGROW to use different crack growth rate data for different loading cycles in the input spectrum. This can be useful if some portion of the loading spectrum is applied under different environmental conditions (e.g. high altitude with low temperature and humidity). Damage tags may be used to label loading cycles to track the amount of crack growth for each tagged spectrum level. The resulting damage information is printed in the AFGROW output file.