Unit Manufacturing Processes Issues and Opportunities in Research (1995) / Chapter Skim
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7 Consolidation Processes
7 Consolidation Processes
Pages 93-110
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From page 93... ...
Other consolidation processes produce composites, with either polymer, graphite, metal, or ceramic matrices. Welding and joining processes, a unique group of consolidation processes, are used to combine subcomponents, often of dissimilar materials, into pennanent assemblies.
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From page 94... ...
Powder-based components are often selected for their low costs, but there are recognized advantages in improved quality, homogeneity, and performance properties. A few examples illustrate the established diversity of products: lamp filaments, dental restorations, oil-less bearings, spark plugs, aircraft brakes, connecting rods, timing gears, lightweight armor, electrical contacts, nuclear fuel elements, orthopedic implants, business machine parts, high-temperature filters, sporting equipment, horseshoes, and jet-engine disks.
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From page 95... ...
Fundamental research is performed at universities, with some recent, successful industry-university partnerships in atomization, spray forming, powder injection molding, and advanced ceramics. The transfer of this technology to industry has been effective through industrial hiring of the university graduates.
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From page 96... ...
Such materials are useful in forming lightweight soundproofing. Powder Production The advent of total quality programs in the powder processing industry has resulted in considerable evidence that subtle variations in the powder production process reflect changes in powder characteristics.
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From page 97... ...
Considerable research is needed to develop processing technologies to fabricate larger components, with greater shape complexity and closer precision. The fabrication of high-performance materials, such as titanium and silicon nitride, by powder injection molding is widely discussed, but improved processing control to move them into commercial reality is lacking.
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From page 98... ...
Fundamental research is needed to bring together a unified view of densification that includes consideration of stress state, strain rate, powder characteristics, temperature, and time to allow rational analysis of complex geometries. Instrumentation and Control The powder processing industries require research to develop, integrate, and adapt modern tools to improve production processes.
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From page 99... ...
For example, vision systems need to be developed for both die compaction presses and powder injection molding machines. Such systems would allow automated inspection of the tooling after each cycle to identify damage from an improperly ejected compact and excessive tooling wear.
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From page 100... ...
These include flexibility in part geometry, high fiber content, excellent fiber wet-out, and better control of fiber volume fraction distribution. Because of these advantages, prepreg processing is filmily entrenched in high-value products, such as aerospace applications, in spite of its high cost.
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From page 101... ...
, while cycle times for resin transfer molding range from 10 to 100 minutes. The resin transfer molding process can accommodate a higher fiber content than S-RIM with concomitant higher mechanical properties.
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From page 102... ...
In addition, this process, unlike resin transfer molding, requires high pressures, which call for expensive tooling. Low-cost tooling concepts for this process need to be developed to bring unit cost down, especially for the low production volumes inherent in many composite products.
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From page 103... ...
The result is an increased number of joint failures in spite of improving joining technologies aIld quality control processes. A number of new materials and processes are emerging, though what can be considered "emerging" depends on the industry as well as the type of material being considered.
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From page 104... ...
Fifty years ago, designers selected from available materials such as wood, canvas, and aluminum. Today, design engineers dream of a hypersonic passenger airplane (known as the Orient Express)
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From page 105... ...
. Thus, some of the challenges in joining emerging materials include faster new product development cycles; fabrication of smaller components, especially in the electronics industry; and more dissimilar material combinations.
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From page 106... ...
· Powder injection molding has enormous potential. Research is needed on sensors and analysis techniques to isolate defect sources and institute defect detection schemes within the molding operation.
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From page 107... ...
The construction of accurate fiber preforms is essential to the production of high-quality parts by resin transfer modeling or S-RIM techniques. Innovative equipment design is needed for automated handling of dry fiber and creating preforms with the required local fiber orientations and fiber distribution densities.
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From page 108... ...
· Innovative processes that have great potential for achieving superior joints in advanced materials include high-energy density processes (e.g., laser and electron beam) , solid-state joining processes (e.g., diffusion bonding and Fiction welding)
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From page 109... ...
Consolidation Processes 109 · Most welding processes are extremely complex from the viewpoint of conventional control theory. The process physics must be understood, and control algorithms developed that can handle the nonlinear behavior of welding systems.
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From page 110... ...
1990. Challenges in joining emerging materials.
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