Engineering topics
Publications and source records attributed to Tavassoli, A. A..
The need for further development and reevaluation of current space-vehicle materials (intended for a single mission) to meet the long-time requirements of a space shuttle is demonstrated. Leading metallic material candidates and their properties are tabulated for a delta-wing space shuttle configuration with a metallic thermal protection system.
Bend angles for columbium-base alloys, WC3015 and Cb752, at temperatures between -300 F and +500 F are reported. WC3015 exhibited a bend transition temperature well below -100 F, but was severely embrittled by silicide coatings. Cb 752 exhibited a bend transition temperature below -300 F, and the silicide coating application did not influence bend angle of the substrate. However, coating failure on both alloys was observed at less than 60 deg bend, even at 500 F. The effect of electron beam welding and gas tungsten-arc welding on the properties of WC3015 and Cb752 are also reported. Both techniques are shown to produce a marked reduction in the bend angle of WC3015. Unlike WC3015, ductility is restored in Cb752 after a suitable postweld anneal. Microstructural and hardness tests results for both alloys are reported and discussed.
Effect of changes in basic composition and additions of alloying elements on mechanical properties of niobium alloy WC3015
Niobium alloy use for space shuttle thermal protection, examining oxidation and mechanical properties
Study of bare and coated specimens of columbium alloys WC3015 and Cb752 cycled to 2400 F in vacuum. Tensile and bend tests on both alloys after 0, 5, and 20 exposure cycles were carried out. Substrate metal interaction of the alloys with VH112 and R512E coatings was considered with respect to mechanical properties. The most obvious difference between the alloys was the ductile-brittle transition temperature.