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At least 73 records · Page 4

All sources NASA NTRS DOE OSTI

NASA NTRS1978

Effects of fabrication and joining processes on compressive strength of boron/aluminum and borsic/aluminum structural panels

Processes for forming and joining boron/aluminum and borsic/aluminum to themselves and to titanium alloys were studied. Composite skin and titanium skin panels were joined to composite stringers by high strength bolts, by spotwelding, by diffusion bonding, by adhesive bonding, or by brazing. The effects of the fabrication and joining processes on panel compressive strengths were discussed. Predicted buckling loads were compared with experimental data.

Royster, D. M.↗

NASA NTRS1984

Joined-wing research airplane feasibility study

The joined wing is a new type of aircraft configuration which employs tandem wings arranged to form diamond shapes in plan view and front view. Wind-tunnel tests and finite-element structural analyses have shown that the joined wing provides the following advantages over a comparable wing-plus-tail system; lighter weight and higher stiffness, higher span-efficiency factor, higher trimmed maximum lift coefficient, lower wave drag, plus built-in direct lift and direct sideforce control capability. To verify these advantages at full scale a manned research airplane is required. A study has therefore been performed of the feasibility of constructing such an airplane, using the fuselage and engines of the existing NAA AD-1 oblique-wing airplane. Cost and schedule constraints favored converting the AD-1 rather than constructing a totally new airframe. By removing the outboard wing panels the configuration can simulate wings joined at 60, 80, or 100 percent of span. For maximum versatility the aircraft has alternative control surfaces (such as ailerons and elevators on the front and/or rear wings), and a removeable canard to explore canard/joined-wing interactions at high-lift conditions. Design, performance, and flying qualities are discussed.

Wolkovitch, J.↗

NASA NTRS1987

Joining of ceramics for high temperature applications

Summarized is a literature survey of the methods for joining ceramics to ceramics or ceramics to metals for high temperature applications. Also mechanical properties and potential applications of the joints are considered. The joining of ceramics is usually carried out by brazing or diffusion bonding. Especially the latter has been found useful, increasing the application of bonded ceramics. The possibility of using electron beam and laser beam welding for joining ceramics has also recently been investigated. The bonding of ceramics has found numerous applications typical for high operating temperatures, i.e., sensors and thermocouples.

Vilpas, Martti↗

NASA NTRS1991

Permanent wire splicing by an explosive joining process

The invention is an apparatus and method for wire splicing using an explosive joining process. The apparatus consists of a prebent, U-shaped strap of metal that slides over prepositioned wires. A standoff means separates the wires from the strap before joining. An adhesive means holds two ribbon explosives in position centered over the U-shaped strap. A detonating means connects to the ribbon explosives. The process involves spreading strands of each wire to be joined into a flat plane. The process then requires alternating each strand in alignment to form a mesh-like arrangement with an overlapped area. The strap slides over the strands of the wires, and the standoff means is positioned between the two surfaces. The detonating means then initiates the ribbon explosives that drive the strap to accomplish a high velocity, angular collision between the mating surfaces. This collision creates surface melts and collision bonding results in electron sharing linkups.

Bement, Laurence J.↗

NASA NTRS1991

Alleviation of whirl-flutter on a joined-wing tilt-rotor aircraft configuration using active controls

The feasibility of using active controls to delay the onset of whirl-flutter on a joined-wing tilt rotor aircraft was investigated. The CAMRAD/JA code was used to obtain a set of linear differential equations which describe the motion of the joined-wing tilt-rotor aircraft. The hub motions due to wing/body motion is a standard input to CAMRAD/JA and were obtained from a structural dynamics model of a representative joined-wing tilt-rotor aircraft. The CAMRAD/JA output, consisting of the open-loop system matrices, and the airframe free vibration motion were input to a separate program which performed the closed-loop, active control calculations. An eigenvalue analysis was performed to determine the flutter stability of both open- and closed-loop systems. Sensor models, based upon the feedback of pure state variables and based upon hub-mounted sensors, providing physically measurable accelerations, were evaluated. It was shown that the onset of tilt-rotor whirl-flutter could be delayed from 240 to above 270 knots by feeding back vertical and span-wise accelerations, measured at the rotor hub, to the longitudinal cyclic pitch. Time response calculations at a 270-knot cruise condition showed an active cyclic pitch control level of 0.009 deg, which equates to a very acceptable 9 pound active-control force applied at the rotor hub.

Vanaken, Johannes M.↗

NASA NTRS1997

Explosive Spot Joining of Metals

The invention is an apparatus and method for wire splicing using an explosive joining process. The apparatus consists of a prebend, U-shaped strap of metal that slides over prepositioned wires. A standoff means separates the wires from the strap before joining. An adhesive means holds two ribbon explosives in position centered over the U-shaped strap. A detonating means connects to the ribbon explosives. The process involves spreading strands of each wire to be joined into a flat plane. The process then requires alternating each strand in alignment to form a mesh-like arrangement with an overlapped area. The strap slides over the strands of the wires. and the standoff means is positioned between the two surfaces. The detonating means then initiates the ribbon explosives that drive the strap to accomplish a high velocity. angular collision between the mating surfaces. This collision creates surface melts and collision bonding resulting in electron-sharing linkups.

Bement, Laurence J.↗

NASA NTRS1998

A New Approach to Joining of Silicon Carbide-Based Materials for High Temperature Applications

Ceramic joining is recognized as one of the enabling technologies for the application of silicon carbide-based materials in a number of high temperature applications. An affordable, robust technique for the joining of silicon carbide-based ceramics has been developed. This technique is capable of producing joints with tailorable thickness and composition. Microstructure and mechanical properties of reaction formed joints in a reaction bonded silicon carbide have been reported. These joints maintain their mechanical strengths at high temperatures (up to 1350 C) in air. This technique is capable of joining large and complex shaped ceramic components.

Singh, Mrityunjay↗

NASA NTRS1997

Joining of Silicon Carbide-Based Ceramic Materials for High Temperature Applications

Joining of high temperature silicon carbide-based ceramics has been a critical issue for their successful application. An affordable, robust technique for joining silicon carbide-based ceramics has been developed and is capable of producing joints that can be tailored for thickness and composition. These joints maintain their mechanical strength up to 1350 C (2462 F) in air. This technique is suitable for the joining of large and complex shaped ceramic components and can be extended to the repair of these materials.

Singh, Mrityunjay↗

NASA NTRS2002

Thermally Activated Joining Apparatus

A thermally activated joining apparatus is provided for reversibly joining piping components of a fluid management system. The joining apparatus includes a thermally activated sealant layers for securing the components together in a leakage free manner. A thermal conductor includes a ring shaped contact portion disposed between the layers for transferring heat from one or more heating elements to the sealant layers. After the seal in place, the components can later be disconnected by supplying heat from the heating element or elements through the thermal conductor to the sealant layers to cause breaking of the seal and thereby enable separation of components.

Melvin A Bryant, III↗

NASA NTRS2004

Robust Joining Technology for Solid Oxide Fuel Cells Applications

Recently there has been a great deal of interest in research development and commercialization of solid oxide fuel cells (SOFCs). Joining and sealing are critical issues that will need to be addressed before SOFCs can truly perform as expected. Ceramics and metals can be difficult to join together, especially when the joint must withstand up to 900 C operating temperature of the SOFCs. The goal of the present study is to find the most suitable braze material for joining of yttria stabilized zirconia (YSZ) to stainless steel. A number of commercially available braze materials TiCuSil, TiCuNi, Copper-ABA, Gold-ABA and Gold-ABA-V have been evaluated. The oxidation behavior of the braze materials and steel substrates in air was also examined through thermogravimetric analysis. The microstructure and composition of the brazed regions have been examined by optical and scanning electron microscopy and eDS analysis. Effect of braze composition and processing conditions on the interfacial microstructure and composition of the joint regions will be presented.

Shpargel, Tarah P.↗

NASA NTRS2006

Experimental Observations for Determining the Maximum Torque Values to Apply to Composite Components Mechanically Joined With Fasteners (MSFC Center Director's Discretionary Fund Final Report, Proj. 03-13}

Aerospace structures utilize innovative, lightweight composite materials for exploration activities. These structural components, due to various reasons including size limitations, manufacturing facilities, contractual obligations, or particular design requirements, will have to be joined. The common methodologies for joining composite components are the adhesively bonded and mechanically fastened joints and, in certain instances, both methods are simultaneously incorporated into the design. Guidelines and recommendations exist for engineers to develop design criteria and analyze and test composites. However, there are no guidelines or recommendations based on analysis or test data to specify a torque or torque range to apply to metallic mechanical fasteners used to join composite components. Utilizing the torque tension machine at NASA s Marshall Space Flight Center, an initial series of tests were conducted to determine the maximum torque that could be applied to a composite specimen. Acoustic emissions were used to nondestructively assess the specimens during the tests and thermographic imaging after the tests.

Thomas, F. P.↗

NASA NTRS2006

Preliminary Investigations of Joining Technologies for Attaching Refractory Metals to Ni-Based Superalloys

In this study, a range of joining technologies has been investigated for creating attachments between refractory metal and Ni-based superalloys. Refractory materials of interest include Mo-47%Re, T-111, and Ta-10%W. The Ni-based superalloys include Hastelloy X and MarM 247. During joining with conventional processes, these materials have potential for a range of solidification and intermetallic formation-related defects. For this study, three non-conventional joining technologies were evaluated. These included inertia welding, electro-spark deposition (ESD) welding, and magnetic pulse welding (MPW). The developed inertia welding practice closely paralleled that typically used for the refractory metals alloys. Metallographic investigations showed that forging during inertia welding occurred predominantly on the nickel base alloy side. It was also noted that at least some degree of forging on the refractory metal side of the joint was necessary to achieve consistent bonding. Both refractory metals were readily weldable to the Hastelloy X material. When bonding to the MarM 247, results were inconsistent. This was related to the higher forging temperatures of the MarM 247, and subsequent reduced deformation on that material during welding. ESD trials using a Hastelloy X filler were successful for all material combinations. ESD places down very thin (5- to 10- m) layers per pass, and interactions between the substrates and the fill were limited (at most) to that layer. For the refractory metals, the fill only appeared to wet the surface, with minimal dilution effects. Microstructures of the deposits showed high weld metal integrity with maximum porosity on the order of a few percent. Some limited success was also obtained with MPW. In these trials, only the T-111 tubes were used. Joints were possible for the T-111 tube to the Hastelloy X bar stock, but the stiffness of the tube (resisting collapse) necessitated the use of very high power levels. These power levels resulted in damage to the equipment (concentrator) during welding. It is of note that the joint made showed the typical wavy bond microstructure associated with magnetic pulse/explosion bond joints. Joints were not possible between the T-111 tube and the MarM 247 bar stock. In this case, the MarM 247 shattered before sufficient impact forces could be developed for bonding.

Gould, Jerry E.↗

NASA NTRS1987

Universal connectors for joining stringers

This invention is a lightweight, universal connector that joins stringers at various angles. The connectors 10 are fabricated from fiber-epoxy resin strips that wrap around stringers 30 and have ends, tabs 16 and 18, which extend in one general direction. The inside surface of the first tab 16 lies on a plane defined by the stringers being joined, and the second tab 18 is separated from the first tab 16 by a distance equal to their thickness. Stringers 30 of different shapes and sizes are joined by alternately bonding the first tab 16 of one connector between the first 16 and second 18 tabs of another connector. Tee-joints are formed by using web elements 41 and 42 which each partially wrap around a stringer 3010 and have tabs 411 and 421 which are offset, and are bonded between tabs 16 and 18 of universal connectors 109 and 1010 bonded to another stringer 309. Sharp corners are trimmed from the tabs so that a gusset area remains between the stringers for support. Acute angle through obtuse angle joints are formed by trimming those edges of the tabs which lie against the stringers. A specific application of the invention is a Walker 60, utilized by handicapped individuals, fabricated from composite materials that is 40% lighter than similar metallic structures.

Harrison, Jr., Ernest↗

NASA NTRS2010

Method of joining metallic and composite components

A method is provided for joining a metallic member to a structure made of a composite matrix material. One or more surfaces of a portion of the metallic member that is to be joined to the composite matrix structure is provided with a plurality of outwardly projecting studs. The surface including the studs is brought into engagement with a portion of an uncured composite matrix material so that fibers of the composite matrix material intertwine with the studs, and the metallic member and composite structure form an assembly. The assembly is then companion cured so as to join the metallic member to the composite matrix material structure.

Semmes, Edmund B.↗

NASA NTRS2011

Advances in Solid State Joining of High Temperature Alloys

Many of the metals used in the oil and gas industry are difficult to fusion weld including Titanium and its alloys. Solid state joining processes are being pursued as an alternative process to produce robust structures more amenable to high pressure applications. Various solid state joining processes include friction stir welding (FSW) and a patented modification termed thermal stir welding (TSW). The configuration of TSWing utilizes an induction coil to preheat the material minimizing the burden on the weld tool extending its life. This provides the ability to precisely select and control the temperature to avoid detrimental changes to the microstructure. The work presented in this presentation investigates the feasibility of joining various titanium alloys using the solid state welding processes of FSW and TSW. Process descriptions and attributes of each weld process will be presented. Weld process set ]up and welding techniques will be discussed leading to the challenges experienced. Mechanical property data will also be presented.

Ding, Jeff↗

NASA NTRS2009

Joining and Integration of Silicon Nitride Ceramics for Aerospace and Energy Systems

Light-weight, creep-resistant silicon nitride ceramics possess excellent high-temperature strength and are projected to significantly raise engine efficiency and performance when used as turbine components in the next-generation turbo-shaft engines without the extensive cooling that is needed for metallic parts. One key aspect of Si3N4 utilization in such applications is its joining response to diverse materials. In an ongoing research program, the joining and integration of Si3N4 ceramics with metallic, ceramic, and composite materials using braze interlayers with the liquidus temperature in the range 750-1240C is being explored. In this paper, the self-joining behavior of Kyocera Si3N4 and St. Gobain Si3N4 using a ductile Cu-based active braze (Cu-ABA) containing Ti will be presented. Joint microstructure, composition, hardness, and strength as revealed by optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Knoop microhardness test, and offset compression shear test will be presented. Additionally, microstructure, composition, and joint strength of Si3N4/Inconel 625 joints made using Cu-ABA, will be presented. The results will be discussed with reference to the role of chemical reactions, wetting behavior, and residual stresses in joints.

Singh, M.↗

NASA NTRS2015

Thermoplastic Joining and Assembly of Bulk Metallic Glass Composites Through Capacitive Discharge

Systems and methods for joining BMG Composites are disclosed. Specifically, the joining of BMG Composites is implemented so as to preserve the amorphicity of their matrix phase and the microstructure of their particulate phase. Implementation of the joining method with respect to the construction of modular cellular structures that comprise BMG Composites is also discussed.

Hofmann, Douglas C.↗

NASA NTRS2017

Combustion Joining of Regolith Tiles for In-Situ Fabrication of Launch/Landing Pads on the Moon and Mars

To mitigate dust problems during launch-landing operations in lunar and Mars missions, it is desired to build solid pads on the surface. Recently, strong tiles have been fabricated from lunar regolith simulants using high-temperature sintering. The present work investigates combustion joining of these tiles through the use of exothermic intermetallic reactions. Specifically, nickel aluminum (1:1 mole ratio) mixture was placed in a gap between the tiles sintered from JSC-1A lunar regolith simulant. Upon ignition by a laser, a self-sustained propagation of the combustion front over the mixture occurred. Joining was improved with increasing the tile thickness from 6.3 mm to 12.7 mm. The temperatures sufficient for melting the glass phase of JSC-1A were recorded for 12.7-mm tiles, which explains the observed better joining.

Ferguson, Robert E.↗