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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
        • 0. Residual Strength
        • 1. Introduction
        • 2. Failure Criteria
        • 3. Residual Strength Capability
        • 4. Single Load Path Structure
        • 5. Built-Up Structures
          • 0. Built-Up Structures
          • 1. Edge Stiffened Panel with a Central Crack
          • 2. Centrally and Edge Stiffened Panel with a Central Crack
          • 3. Analytical Methods
          • 4. Stiffener Failure
          • 5. Fastener Failure
          • 6. Methodology Basis for Stiffened Panel Example Problem
          • 7. Tearing Failure Analysis
          • 8. Summary
        • 6. References
      • 5. Analysis Of Damage Growth
      • 6. Examples of Damage Tolerant Analyses
      • 7. Damage Tolerance Testing
      • 8. Force Management and Sustainment Engineering
      • 9. Structural Repairs
      • 10. Guidelines for Damage Tolerance Design and Fracture Control Planning
      • 11. Summary of Stress Intensity Factor Information
    • Examples

Section 4.5.8. Summary

The most important factor to consider in residual strength prediction of a cracked built-up structure is to decide whether the structure is skin or stiffener critical.  Normally, a short crack length is likely to be a skin critical case and a long crack length a stiffener critical case.  However, there is no clear cut demarcation between the two cases.  Factors such as percentage stiffening, spacing of stringers, lands in the structure, and other structural details will influence the type of failure.  Hence, a good technique is to determine the residual strength of a given structure based on both skin critical and stiffener critical cases.  The minimum fracture stress of the two will then represent the residual strength of the structure and should be considered to be the governing case.