Spectrum Manager

AFGROW Spectrum Manager is a user-friendly Windows based software application that uses a visual approach to develop and modify structural loading spectra for damage tolerance analysis.


The primary capabilities and features of Spectrum Manager are:
  • Visual spectrum design
  • Spectrum level reordering
  • Sub-spectra may be 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 available at a glance
  • Exceedance curve plotting
  • Stress ratio plotting (R-plots)
  • Synchronized data/spectrum plot views
  • Spectrum level tagging for environmental effects
  • Spectrum level damage tagging to track damage accumulation
  • Spectra normalization/de-normalization
  • Clipping/Truncation capability
  • Import data from "old" AFGROW text-based sub-spectrum files
  • Context-Sensitive Help
  • Undo/Redo capability

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 cycle-counted 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, creates spectrum stress ratio (R) and exceedance plots.

Spectrum Manager also provides several new capabilities for spectrum development. Until now, AFGROW has been limited to single channel spectrum data. This means that axial, bending, and bearing loading fractions are assumed to be constant for all load 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

We have additional information in AFGROW User Workshop proceedings .

Spectrum Manager - Main layout
Spectrum Manager - layout

The standard spectrum 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.

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 in terms of percentage of total crack growth for each damage tag.