Electroforming: (10.50 - 24.03.2011)
A variation of electroplating, electroforming actually is a metal-fabricating process. Metal is electrodeposited on a mandrel (also called a mold or a matrix), which is then removed; thus, the coating itself becomes the product. Both simple and cmplex shapes can be produced by electroforming, with wall thicknesses as small as 0.0025 mm. Parts may weigh from a few grams to as much as 270 kg. Production rates can be increased through the use of multiple mandrels.
Mandrels are made from a variety of materials: metallic (zinc or aluminum) or nonmetallic (which can be made electrically conductive with the proper coatings). Mandrels should be able to be removed physically without damaging the electroformed part. They also may be made of low-melting alloys, wax, or plastics, all of which can be melted away or dissolved with suitable chemicals.
The electroforming process is particularly suitable for low production quantities or intricate parts (such as molds, dies, waveguides, nozzles and bellows) made of nickel, copper, gold, and silver. The process is also suitable for aerospace, electronics, and electro-optics applications.
(Kalpakjian S. Schmid S.R.,Manufacturing Engineering and Technology Sixth Edition in SI Units, p. 986)
Eddy Current Testing: (11.06 - 24.03.2011)
Eddy-current testing uses electromagnetic induction to detect flaws in conductive materials. In a standart eddy current testing, a circular coil carrying current is placed proximity to the test specimen. The alternating current in the coil generates changing magnetic field which interact with the test specimen and generates eddy current. Variations in the phase and magnitude of these eddy currents can be monitored using a second "search" coil, or by measuring changes to the current flowing in the primary "excitation" coil. Variations in the electrical conductivity or magnetic permeability of the test object, or presence of any flaws, wiil cause a change in eddy current flow and a corresponding change in the phase and amplitude of the measured current.
Eddy-current testing can detect very small cracks in or near te surface of the material, the surfaces need minimal preparation, and physically copmlex geometries can be investigated. It is also useful for making electrical conductivity and coating thickness measurements.
(Effective Building Maintenance: Protection of Capital Assets, Herbert W. Stanford,Stanford III, Herbert W., p.74)
Laser Doppler Vibrometer: (11.46 - 24.03.2011)
The Laser Doppler Vibrometer (LDV) is commonly used instrument to measure velocity in structures in a non-contact fashion. The LDV works by splitting a laser, inside the system, and sending one part of split beam to receptive surface (reference beam), with the other part of the split laser sent to the structure in question. This second laser, or measurement, beam reflects back to the LDV unit after hitting the point of interest. The velocity of structure changes the frequency of the measurement beam. The velocity is calculated by comparing the frequency of the reference and reflected beams.
(Development and verification of a computer vision technique to measure the response of civil structures, Glen R. Wieger,University of South Carolina. Civil Engineering, p.3)
Electrochemical Deburring: (15:58 – 24.03.2011)
Electrochemical deburring is another modification electrochemical machining carrying out with smaller-scale ancillary and control equipment. It is used essentially to remove sharp corners,, points and other raised imperfections which have been left by mechanical machining. The projecting areas have a locally high positive potential and are selectively removed by the high prevailing anodic current density. Applications lie particularly in the manufacture of components for engineering and include the finishing of pistons, power steering shafts, connecting rods and fuel injector nozzles. It requires the design of only a simple cathode tool and generally the currents do not exceed a few hundred ampers.
A particular advantage of electrochemical machining is the highly selective nature of removal, which does not adversely affect other features such as thread forms.
(Industrial electrochemistry,2nd Edition, Derek Pletcher, Frank Walsh, p.467-468)
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