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Four coating processes have been scaled up to coat components of aerospace vehicles: (1) slurry, (2) atmospheric-pressure pack cementa tion, (3) vacuum pack cementation, and (4) fluidized bed. The principal advantage of the slurry process is its ability to coat limited access areas such as the interior channels of built-up corrugated panels. This makes the process ideal for coating spot-welded corrugated panels after they have been welded. The other three coating processes, which are vapor-deposi tion processes, are not so suitable for coating limited-access areas. When they are used for parts such as built-up corrugated panels, the individual parts (including rivets) are coated, then riveted together, and then the entire assembly is recoated. This shortcoming is off set by the fact that the coatings applied by the vapor-deposition processes are more protective at higher temperatures than are the slurry coatings.
To aid in quick identification and easy location of specific technical data and information in the various reports and memoranda which have been prepared and distributed by the Defense Metals Information Center, as well as by DMIC's forerunner, the Titanium Metallurgical Laboratory, a classification by major subject matter was prepared. The classification covers reports through DMIC Report 193 and memoranda through DMIC Memorandum 183. (Author).
The primary purpose of this memorandum was to make the results of Neuber's stress analysis more readily usable by those engaged in evaluating the crack sensitivity of materials. While the more intense effect of a crack dies out rapidly near the crack tip, a measurable effect does persist over a great enough area that strain gages could be used to determine the extent to which Neuber's analysis can be applied to granular materials like metals and alloys. The results indicate that, except in the immediate vicinity of the crack tip, the stress field is quite insensitive to crack geometry. (Author).
Three types of ferrous materials that deserve to be considered as future hull materials are discussed. The present state of knowledge can be summarized this way: quenched and tempered steels with 0.20% carbon and yield strengths of about 170,000 psi can probably be developed into a useful hull material in less time than either of the other two classes. Maraging steels have great potential if it is possible to improve their toughness. This may be resolved within a few months and surely within a year. The stable austenitic steels appear to offer the greatest potential, but less is known about these than about the other two classes of materials. (Author).
Metallic fibers in the form of whiskers, chopped fine wire, or wool have been incorporated into metallic matrices by two principal methods: classical powder-metallurgical methods, and infiltration of the fibers with molten matrix metal. Ceramic fibers, notably alpha-A1203, have been used as whiskers or wool for reinforcing metallic matrices, the methods of preparation of the composite being the same as with metallic fibers. When metallic fibers are used to reinforce ceramics, the ceramic is either slip cast into the fiber mat and dried, or a mixture of the fiber and ceramic is hot pressed. Plastics and elastomers are combined with fibers by several methods, for example, dipping a sintered skeleton of the fibers into liquid Teflon. Several programs have resulted in combinations which show that reinforcement of metals by either metallic or alpha-A1203 fibers is possible. Both the room-temperature and elevatedtemperature tensile properties of the composite seem to increase linearly with the volume fraction of the fiber phase. (Author).