Publications

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The purpose of this paper is to investigate the structural behavior of aluminum alloys used in the aerospace industry when exposed to conditions similar to those of an accident scenario, such as a fuel fire. This study focuses on the role that the aluminum oxide layer plays in the deformation and the strength of the alloy above melting temperature. To replicate some of the thermal and atmospheric conditions that the alloys might experience in an accident scenario, aluminum rod specimens were subjected to temperatures near to or above their melting temperature in air, nitrogen, and vacuum environments. The characteristics of their deformation, such as geometry and rate of deformation, were observed. Tests were conducted by suspending aluminum rods vertically from an enclosure. This type of experiment was performed in two different environments: air and nitrogen. The change in environments allowed the effects of the oxide layer on the material strength to be analyzed by inhibiting the growth of the oxide layer. Observations were reported from imaging taken during the experiment showing creep behavior of aluminum alloys at elevated temperatures and time to failure. In addition, an example of tensile load-displacement data obtained in air and vacuum was reported to understand the effect of oxide layer on aluminum deformation and strength.

Aluminum is commonly used for structural applications in the aerospace industry because of its high strength in relation to its weight. It is necessary to understand the mechanical response of aluminum structures at elevated temperatures such as those experienced in a fire. Aluminum alloys exhibit many complicated behaviors that require further research and understanding, such as aluminum combustion, oxide skin formation and creep behavior. This paper discusses the effect of grain orientation on aluminum deformation subjected to heating at incipient melt conditions. Experiments were conducted by applying a vertical compressive force to aluminum alloy 7075 block test specimens. Compression testing was done on test specimens with the applied load on the long transverse and short transverse orientations. Results showed that the grain orientation significantly influences aluminum's strength and mode of failure.

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Solid rocket propellant plume temperatures have been measured using spectroscopic methods as part of an ongoing effort to specify the thermal-chemical-physical environment in and around a burning fragment of an exploded solid rocket at atmospheric pressures. Such specification is needed for launch safety studies where hazardous payloads become involved with large fragments of burning propellant. The propellant burns in an off-design condition producing a hot gas flame loaded with burning metal droplets. Each component of the flame (soot, droplets and gas) has a characteristic temperature, and it is only through the use of spectroscopy that their temperature can be independently identified.

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Accidents involving solid propellants containing aluminum can be difficult to model due to the additional heat transfer from molten aluminum or aluminum combustion and impingement/deposition of oxide on target objects. A series of tests has been carried out using a commercially available oxy-acetylene torch and powder feeder to investigate the effects of molten/oxidized aluminum on stainless steel 304 substrates. SEM and EDS have been used to determine diffusion/interaction of aluminum with the stainless steel and characterize the constituents of the resulting interfacial layers. These techniques indicated that at the test conditions, aluminum was undetectably oxidized before it deposited on the substrate surface. However, temperature data from thermocouples attached to backside of each substrate detected an increased heat flux to the substrate when aluminum is introduced into the flame spray. Results also indicate that the boundary layers of the aluminum and stainless steel were well defined implying that little diffusion or solution of the aluminum with the stainless steel occurred. Copyright © 2012 by ASME.

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This paper discusses testing and modeling efforts to experimentally determine, and numerically model the behavior of aluminum at incipient melt conditions. More particularly, the role of the oxide layer which develops on the surface of aluminum which is heating in an oxidizing environment has been found to influence deformation. Several configurations where tested composed of aluminum rods at different orientations with regard to standard gravity, and video images were taken to record movement. Modeling with comparable materials shows similar behavior and encourages additional work where some numerical comparisons could be researched further. © 2011 INTERNATIONAL ASSOCIATION FOR FIRE SAFETY SCIENCE.

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