Research and application problems in fracture of materials and structures in the united states air force

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Abstract

This paper reviews current and projected Air Force R&D activities in the area of fracture mechanics for materials and structures and cites systems problems which have been essentially responsible for the recent flurry of activity in this area. The specific technology areas reviewed in this paper range from basic material property data generation to the improvement of fracture analysis procedures which account for the complex structural geometries, chemical and stress environment. The emphasis, direction and guidance for selecting specific topics of research has been assisted by recent past failure incidents, and knowledge of the technological deficiencies gained from current attempts to formulate and apply requirements to design, analyze and test for safe crack growth and residual strength. While the current R&D efforts are directed toward improving the material data base and analytical capability needed to effectively implement fracture control procedures, unknowns and areas of concern still exist. Examples of these include the accurate assessment of cost weight and performance impacts caused by the imposition of fracture requirements, the need for, and magnitude of safety or confidence factors for residual strength or safe crack growth analyses and the scope and magnitude of test and/or analysis required to prove conformance with specifications.Â