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DTD Handbook

Handbook for Damage Tolerant Design

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    • Sections
      • 1. Introduction
      • 2. Fundamentals of Damage Tolerance
      • 3. Damage Size Characterizations
      • 4. Residual Strength
      • 5. Analysis Of Damage Growth
      • 6. Examples of Damage Tolerant Analyses
      • 7. Damage Tolerance Testing
      • 8. Force Management and Sustainment Engineering
      • 9. Structural Repairs
        • 0. Structural Repairs
        • 1. Required Analysis
        • 3. Spectrum Analysis for Repair
          • 0. Spectrum Analysis for Repair
          • 1. Definition of Stress Histories
          • 2. Spectra Descriptions
            • 0. Spectra Descriptions
            • 1. Exceedance Curve Descriptions
            • 2. RMS Descriptions
          • 3. Crack Growth Analysis
        • 4. Life Sensitivity for Stress Effects
        • 5. Life Sensitivity Analysis for Hole Repair
        • 6. Blend-Out Repairs
        • 7. Residual Strength Parametric Analysis
        • 8. References
      • 10. Guidelines for Damage Tolerance Design and Fracture Control Planning
      • 11. Summary of Stress Intensity Factor Information
    • Examples

Section 9.3.2.0. Spectra Descriptions

The stress history uniquely defines the sequence and magnitude of the individual stress events applied at a specific location.  While this information is essential for conducting a cycle-by-cycle crack growth analysis that accounts for load interaction, it is both difficult to use and interpret without computer programs that perform such analyses.  One of the side benefits associated with describing flight-by-flight crack growth rates as a function of a characteristic stress-intensity factor is that one is forced into presenting stress history information simply.  This subsection addresses two such schemes – the exceedance curve and an RMS characterization.