DAMAGE TOLERANCE OF METALLIC STRUCTURES: ANALYSIS METHODS AND APPLICATIONS STP 842

DAMAGE TOLERANCE OF

METALLIC STRUCTURES:

ANALYSIS METHODS AND

APPLICATIONS

STP 842

In the late 1960s and early 1970s, a number of aircraft structural failures occurred both during testing and in-service. Some of these failures were attributed to flaws, defects, or discrepancies that were either inherent or introduced during the manufacturing and assembly of the structure. The presence of these flaws was not accounted for in design. The design was based on a "safe-life"
fatigue analysis. Mean life predictions were made that were based upon materials' unflawed fatigue test data and a conventional fatigue analysis. A scatter factor of four was used to account for initial quality, environment, variation in material properties, and so forth. However, this conventional fatigue (safe-life) analysis approach did not adequately account for the presence and the growth of
these flaws.
In order to ensure the safety of the aircraft structure, the U.S. Air Force adopted the damage tolerance design approach to replace the conventional fatigue design approach starting from the mid 1970s. In recent years, a number of different industries have also adopted the damage tolerance approach, only calling it fracture control. The ability of a structure to maintain adequate residual strength in a damaged condition is called damage tolerance. The damage tolerance (or fracture control) approach assumes that flaws are initially present in the structure. The structure must be designed such that these flaws do not grow to a critical size and cause catastrophic failure of the structure within a specified period of time. In order to accomplish this, an accurate damage tolerance analysis
must exist.
A Forum on Damage Tolerance Analysis sponsored by ASTM Task Group E24.06.01 on Application of Fracture Data to Life Predictions was held at the University of California, Los Angeles, CA, on 29 June 1981. The purpose of this Forum was to present the state-of-the-art capability for performing damage tolerance analysis. Damage tolerance design requirements, analysis procedures, and
applications were presented. The results of the Forum are presented in this volume.

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