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DTD Handbook

Handbook for Damage Tolerant Design

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    • Sections
      • 1. Introduction
      • 2. Fundamentals of Damage Tolerance
        • 0. Fundamentals of Damage Tolerance
        • 1. Introduction to Damage Concepts and Behavior
        • 2. Fracture Mechanics Fundamentals
        • 3. Residual Strength Methodology
        • 4. Life Prediction Methodology
        • 5. Deterministic Versus Proabilistic Approaches
        • 6. Computer Codes
          • 0. Computer Codes
          • 1. Structural Analysis
          • 2. Life Prediction
            • 0. Life Prediction
            • 1. NASGRO Fracture Analysis Software
            • 2. AFGROW Fracture Analysis Software
            • 3. Cracks2000 Structural Integrity Software
          • 3. PRobability Of Fracture (PROF)
        • 7. Achieving Confidence in Life Prediction Methodology
        • 8. References
      • 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
      • 10. Guidelines for Damage Tolerance Design and Fracture Control Planning
      • 11. Summary of Stress Intensity Factor Information
    • Examples

Section 11.5.1. NASGRO Fracture Analysis Software

NASGRO was originally developed at NASA Johnson Space Center to perform fracture control analysis on NASA space systems. Later, after the NASA/FAA/USAF Aging Aircraft Program was formed and began supporting the development effort, NASGRO was developed further for use in damage tolerance analysis of aircraft, including that required for FAA certification.

The software is comprised of the following three modules:

·        NASFLA - Life Assessment 

·        NASBEM - 2-D Boundary Element 

·        NASMAT - Database of da/dN & fracture test results

NASFLA is part of the NASGRO 3.0 suite of programs Stress Intensity Factor -These are computed for the crack geometry and loading chosen from the NASFLA library of models, and displayed in tabular or graphical form.

NASBEM is part of the NASGRO 3.0 suite of programs.  It is a two-dimensional boundary element program used to perform the following analyses:

·        Stress Intensity Factors - These can be calculated for any geometry and loading. Tables of stress intensity factors and corresponding crack lengths can be generated for use by the NASFLA module in performing life assessments.

·        Stress Fields - These can be calculated for any collection of points in the two-dimensional uncracked object being modeled including its boundary.

NASMAT is used to store, retrieve and curve fit crack growth and fracture toughness data. It has a database containing over 9000 sets of data. This includes over 3000 sets of fatigue crack growth data and over 6000 fracture toughness data points. These data can be searched, plotted, and fitted to either the NASGRO crack growth rate equation or a user specified growth rate equation, or they can be entered into a growth rate table.