The need for protecting thin gage Rene 41 from oxidation when heated above approximately 1550 F for extended periods is discussed. An evaluation of cladding as a means of protection is presented. It was found that oxidation protection for times up to 100 hr at 1800 F, or 10 hr at 2000 F, can be provided with cladding thickness of 0.001 in. However, interalloy diffusion and alloy depletion from the Rene 41 were problems with each of the potential clad alloys investigated.
The morphology of salt water stress corrosion cracks in 8A1-1Mo-1V titanium alloy has been determined. In the interior of the specimens the cracks are brittle in nature and far more extensive than indicated by cracks visible at the specimen surface. The direction of propagation of the internal cracks is away from the plane of the specimen starter crack. These crack characteristics are explained in terms of internal stress state and presence of contaminants containing chlorides.
The concept of fail-safe structure has introduced requirements for evaluation of new types of material properties and new sets of conditions for the design of pressure cabins of high altitude aircraft. A brief review is given of the fracture toughness properties of candidate materials for the SST environment. The results of recent tests on residual strength and rate of crack growth in stiffened and unstiffened panels and cylinders made from titanium and steel are presented. The results of a titanium full-scale fuselage panel tested under heat (550–650 F) and cyclic pressure are discussed in light of SST design requirements.
Abstract The basic thinking leading to the selection of the double-delta wing planform as optimum for the United States supersonic transport is outlined in terms of aerodynamic efficiency, propulsive efficiency, weight, sonic boom, and airport noise considerations. The fundamental matching of a large, lightly loaded wing to high acceleration and cruise altitudes for minimum sonic boom, while at the same time attaining maximum lift-drag ratio, and the low take-off and landing power requirements for noise abatement is explained. The unique low-speed aerodynamic characteristics inherent in this wing approach and the method by which they contribute directly to low-speed handling qualities and safety of operation surpassing the levels of current subsonic transports is described. Lack of an abrupt stall introduces a new dimension in operating safety and offers flexibility in operation.