Manufacturing & Prototyping

Progress in Fabrication of Rocket Combustion Chambers by VPS

Several documents in a collection describe aspects of the development of advanced materials and fabrication processes intended to enable the manufacture of advanced rocket combustion chambers and nozzles at relatively low cost. One concept discussed in most of the documents is the fabrication of combustion-chamber liners by vacuum plasma spraying (VPS) of an alloy of 88Cu/8Cr/4Nb (numbers indicate atomic percentages)—a concept that was reported in "Improved Alloy for Fabrication of Combustion Chambers by VPS" (MFS-26546), NASA Tech Briefs, Vol. 23, No.1 (January 1999), page 50. Another concept is the deposition of graded-composition wall and liner structures by VPS in order to make liners integral parts of wall structures and to make oxidation-and thermal- protection layers integral parts of liners: The VPS process is started at 100 percent of a first alloy, then the proportion of a second alloy is increased gradually from zero as deposition continues, ending at 100 percent of the second alloy. Yet another concept discussed in one of the documents is the VPS of oxidation-protection coats in the forms of nickel-and-chromium-containing refractory alloys on VPS-deposited 88Cu/8Cr/4Nb liners.

Posted in: Manufacturing & Prototyping, Briefs

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Controlling Force and Depth in Friction Stir Welding

The proportionality between penetration force and penetration depth is exploited. Feedback control of the penetration force applied to a pin tool in friction stir welding has been found to be a robust and reliable means for controlling the depth of penetration of the tool. This discovery has made it possible to simplify depth control and to weld with greater repeatability, even on workpieces with long weld joints.

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Two Heat-Transfer Improvements for Gas Liquefiers

Medical oxygen liquefiers could operate more efficiently. Two improvements in heat-transfer design have been investigated with a view toward increasing the efficiency of refrigerators used to liquefy gases. The improvements could contribute to the development of relatively inexpensive, portable oxygen liquefiers for medical use.

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Modifications of Fabrication of Vibratory Microgyroscopes

The goal is to increase production yields. A micromachining process for the fabrication of vibratory microgyroscopes from silicon wafers, and aspects of the microgyroscope design that are inextricably linked with the fabrication process, have been modified in an effort to increase production yields from perspectives of both quantity and quality. Prior to the modifications, the effective production yield of working microgyroscopes was limited to one or less per wafer. The modifications are part of a continuing effort to improve the design and increase production yields to more than 30 working microgyroscopes per wafer.

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Vehicle Maintenance Shelters Meet Structural Requirements Through FEA Analysis

Anchor Industries supplies tents and fabric products to the outdoor amusement and entertainment industries, and municipalities. With their experience in producing portable structures, Anchor re-entered the military market of vehicle maintenance shelters (VMS). The first Anchor VMS, designed several years ago to compete with another company’s lightweight maintenance enclosure (LME), was overpriced compared to similar products in the U.S. and Europe, so the company sought to create a more competitive and efficient shelter.

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Treatments To Produce Stabilized Aluminum Mirrors for Cryogenic Uses

Selected heat treatments are performed between and after fabrication steps.Five metallurgical treatments have been tested as means of stabilizing mirrors that are made of aluminum alloy 6061 and are intended for use in cryogenic applications. Aluminum alloy 6061 is favored as a mirror material by many scientists and engineers. Like other alloys, it shrinks upon cool-down from room temperature to cryogenic temperature. This shrinkage degrades the optical quality of the mirror surfaces. Hence, the metallurgical treatments were tested to determine which one could be most effective in minimizing the adverse optical effects of cooldown to cryogenic temperatures. Each of the five metallurgical treatments comprises a multistep process, the steps of which are interspersed with the steps of the mirror- fabrication process. The five metallurgical- treatment/fabrication–process combinations were compared with each other and with a benchmark fabrication process, in which a mirror is made from an alloy blank by (1) symmetrical rough machining, (2) finish machining to within 0.006 in. (˜ 0.15 mm) of final dimensions, and finally (3) diamond turning to a mirror finish. Two specimens ? a flat mirror and a spherical mirror ? were fabricated in each case. The blanks for all the specimens were cut from the same plate of aluminum alloy 6061-T651. (The suffix “T651” denotes a stress-relieving treatment that involves reducing residual stresses by mechanical stretching of the previously untreated alloy.) Of the five metallurgical-treatment/fabricationprocess combinations tested, the one found to exert the greatest stabilizing effect comprises the following ten steps:

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Portable Electron-Beam Free-Form Fabrication System

The electron beam in this system will be of relatively low voltage. A portable electron-beam free-form fabrication (EB F3) system, now undergoing development, is intended to afford a capability for manufacturing metal parts in nearly net sizes and shapes.

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