SEARCH · Search NASA
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Stress corrosion of titanium and its alloys at elevated temperatures is minimized by replacing trichloroethylene with methanol or methyl ethyl ketone as a degreasing agent. Wearing cotton gloves reduces stress corrosion from perspiration before the metal components are processed.
Stress corrosion testing method to separate corrosion and stress effects applied to Al and Ti alloys
Study was initiated to determine methods or test specimens for evaluating stress corrosion cracking characteristics of common structural materials. It was found that the methods of externally loading and corrosion testing were reliable in yielding reproducible results for stress corrosion evaluation.
Corrosion and stress effects separation in stress corrosion of Al-Zn-Mg-Cu alloy, considering machined surface finishing role
The problems encountered and the methods used to prevent corrosion and stress corrosion cracking on current space vehicles and aircraft are discussed. Preventing these problems on the Space Shuttle, in particular, by properly using materials that are highly resistant to this phenomenon, is examined in detail.
External loading procedures for stress corrosion tests of aluminum alloys, and ferrous and nickel alloys
Stress corrosion of high strength aluminum alloy in NaCl solution, separating corrosion and stress effects
Mechanical and electrochemical factors involved in stress corrosion of aluminum alloys
Candidate alloys for the Shuttle Solid Rocket Booster (SRB) case were tested under simulated service conditions to define subcritical flaw growth behavior under both sustained and cyclic loading conditions. The materials evaluated were D6AC and 18 Ni maraging steel, both heat treated to a nominal yield strength of 1380 MN/sq m (200 ksi). The sustained load tests were conducted by exposing precracked, stressed specimens of both alloys to alternate immersion in synthetic sea water. It was found that the corrosion and stress corrosion resistance of the 18 Ni maraging steel were superior to that of the D6AC steel under these test conditions. It was also found that austenitizing temperature had little influence on the threshold stress intensity of the D6AC. The cyclic tests were conducted by subjecting precracked surface-flawed specimens of both alloys to repeated load/thermal/environmental profiles which were selected to simulate the SRB missions. It was found that linear removal operations that involve heating to 589 K (600 F) cause a decrease in cyclic life of D6AC steel relative to those tests conducted with no thermal cycling.
Salt stress corrosion of residually stressed titanium-aluminum-molybdenum-vanadium alloy sheet after high temperature exposure
The corrosion and stress corrosion cracking (SCC) characteristics of annealed and hardened 440C stainless steel were evaluated in high humidity and 3.5-percent NaCl solution. Corrosion testing consisted of an evaluation of flat plates, with and without grease, in high humidity, as well as electrochemical testing in 3.5-percent NaCl. Stress corrosion testing consisted of conventional, constant strain, smooth bar testing in high humidity in addition to two relatively new techniques under evaluation at MSFC. These techniques involve either incremental or constant rate increases in the load applied to a precracked SE(B) specimen, monitoring the crack-opening-displacement response for indications of crack growth. The electrochemical corrosion testing demonstrated an order of magnitude greater general corrosion rate in the annealed 440C. All techniques for stress corrosion testing showed substantially better SCC resistance in the annealed material. The efficacy of the new techniques for stress corrosion testing was demonstrated both by the savings in time and the ability to better quantify SCC data.
Stress corrosion tests on aluminum alloys with respect to statistical nature of distribution of failure times
Salt stress corrosion cracking of residually stressed titanium alloy brake formed sheet for supersonic transport
Stress-corrosion cracking has been the most common cause of structural-material failures in the Apollo Program. The frequency of stress-corrosion cracking has been high and the magnitude of the problem, in terms of hardware lost and time and money expended, has been significant. In this report, the significant Apollo Program experiences with stress-corrosion cracking are discussed. The causes of stress-corrosion cracking and the corrective actions are discussed, in terminology familiar to design engineers and management personnel, to show how stress-corrosion cracking can be prevented.
The cold working process of stress coining is used to provide fatigue improvement of fastener holes in aircraft structures. The cold working produces a radial flow of the metal. The residual stresses resulting from stress coining provide protection against fatigue damage by opposing the applied tensile stresses in service at the edge of the fastener hole. However, it is shown in this paper that in addition to the compressive stresses surrounding the stress coined hole, there are tensile stresses that result from the coining operation and that these residual tensile stresses can have a deleterious effect on the stress corrosion susceptibility of the postcoined structure.
Electrochemistry of freshly generated titanium surfaces and stress corrosion cracking in aqueous solutions and in molten salts
Stress corrosion resistance is increased by distorting surface grain-boundary structure and by interrupting the corrosion and stress corrosion. The first is accomplished by machining or shot peening and the second by removal from and later reexposure to the corrosive environment.
A family of high performance aerospace fasteners made from corrosion resistant alloys for use in applications where corrosion and stress-corrosion cracking are of major concern are discussed. The materials discussed are mainly A-286, Inconel 718, MP35N and MP159. Most of the fasteners utilize cold worked and aged materials to achieve the desired properties. The fasteners are unique in that they provide a combination of high strength and immunity to stress corrosion cracking not previously attainable. A discussion of fastener stress corrosion failures is presented including a review of the history and a description of the mechanism. Case histories are presented to illustrate the problems which can arise when material selection is made without proper regard for the environmental conditions. Mechanical properties and chemical compositions are included for the fasteners discussed. Several aspects of the application of high performance corrosion resistant fasteners are discussed including galvanic compatibility and torque-tension relationships.