Manufacturing & Prototyping

Submarine Design Certified on FEA and Sensor Testing

The American Bureau of Shipping certified a submarine solely on the basis of finite element analysis (FEA) and strain sensor testing. Submarine design typically follows American Bureau of Shipping (ABS) code, which establishes properties such as hull thickness, frame stiffness, and porthole and hatch design. During certification, ABS evaluates whether a design follows the relevant codes and then certifies it or not on that basis. The design of a deep-diving submarine was so unique that some ABS rules could not be adhered to.

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Attaching Thermocouples by Peening or Crimping

These techniques are simple, effective, and minimally invasive. Two simple, effective techniques for attaching thermocouples to metal substrates have been devised for high- temperature applications in which attachment by such conventional means as welding, screws, epoxy, or tape would not be effective. The techniques have been used successfully to attach 0.005-in. (0.127-mm)-diameter type-S thermocouples to substrates of niobium alloy C-103 and stainless steel 416 for measuring temperatures up to 2,600 °F (1,427 °C). The techniques are equally applicable to other thermocouple and substrate materials.

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Heat Treatment of Friction-Stir-Welded 7050 Aluminum Plates

Strength, ductility, and resistance to stress corrosion cracking are increased. A method of heat treatment has been developed to reverse some of the deleterious effects of friction stir welding of plates of aluminum alloy 7050. This alloy is considered unweldable by arc and high-energy-density beam fusion welding processes. The alloy can be friction stir welded, but as-welded workpieces exhibit low ductility, low tensile and yield strengths, and low resistance to stress corrosion cracking. Heat treatment according to the present method increases tensile and yield strengths, and minimizes or eliminates stress corrosion cracking. It also increases ductility.

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Manufacturing Precise, Lightweight Paraboloidal Mirrors

Success depends on the proper selection of materials and process conditions. A process for fabricating a precise, diffraction- limited, ultralightweight, composite-material (matrix/fiber) paraboloidal telescope mirror has been devised. Unlike the traditional process of fabrication of heavier glass-based mirrors, this process involves a minimum of manual steps and subjective judgment. Instead, this process involves objectively controllable, repeatable steps; hence, this process is better suited for mass production.

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Automated Solvent Seaming of Large Polyimide Membranes

Success depends on precise control of all relevant process details. A solvent-based welding process enables the joining of precise, cast polyimide membranes at their edges to form larger precise membranes. The process creates a homogeneous, optical - quality seam between abutting membranes, with no overlap and with only a very localized area of figure disturbance. The seam retains 90 percent of the strength of the parent material. The process was developed for original use in the fabrication of wide - aperture membrane optics, with areal densities densities of less than 1 kg/m2, for lightweight telescopes, solar concentrators, antennas, and the like to be deployed in outer space. The process is just as well applicable to the fabrication of large precise polyimide membranes for flat or inflatable solar concentrators and antenna reflectors for terrestrial applications.

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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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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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