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Title: "Non-Contact Ultrasonic Treatment of Metals in a Magnetic Field"

Abstract

A concept has been originated for non-contact ultrasonic treatment of metals based on the use of an induction coil located in a high-field superconducting magnet. An advantage of using a high magnetic field environment (> 9 T) is that this allows the induced surface current in the sample to be decreased proportionately. As a result, the incidental induction heating associated with the use of the EMAT (Electromagnetic Acoustical Transducer) is greatly reduced, which improves the energy efficiency of the EMAT approach. The method can be coupled with high-field magnetic processing, but can also be used where only ultrasonic treatment is beneficial. In the proof-of-principle experiments, a high-field EMAT was used for non-contact ultrasonic processing of aluminum samples during solidification. The magnetic field for the EMAT was supplied by a high-field (20 Tesla) resistive magnet, and the current was provided by an induction coil. This resulted in a highly efficient EMAT that delivered 0.5 MPa (~5 atmospheres) of acoustic drive to the surface of the sample while coupling less than 100 watts of incidental induction heating. The exceptionally high energy efficiency of the electromagnetic transducer is due to the use of the high magnetic field, which reduces the current needed tomore » achieve the same acoustic pressure. In these initial experiments, aluminum samples of A356 alloy were heated to the liquid state and allowed to solidify at a controlled cooling rate while subjected to the non-contact ultrasonic stimulation (0.5 MPa @ 165 kHz) provided by an induction coil located within the 200 mm (~8-inch) bore of a 20-T Bitter resistive magnet.« less

Authors:
 [1];  [1];  [1];  [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
963903
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: ASM Heat Treating Society Conference, Detroit, MI, USA, 20070917, 20070919
Country of Publication:
United States
Language:
English
Subject:
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; ALUMINIUM ALLOYS; MELTING; SOLIDIFICATION; SUPERCONDUCTING MAGNETS; ULTRASONIC WAVES; ORE PROCESSING; HEATING; INDUCTION; ENERGY EFFICIENCY

Citation Formats

Ludtka, Gerard Michael, Wilgen, John B, Kisner, Roger A, Jaramillo, Roger A, and Ludtka, Gail Mackiewicz-. "Non-Contact Ultrasonic Treatment of Metals in a Magnetic Field". United States: N. p., 2007. Web.
Ludtka, Gerard Michael, Wilgen, John B, Kisner, Roger A, Jaramillo, Roger A, & Ludtka, Gail Mackiewicz-. "Non-Contact Ultrasonic Treatment of Metals in a Magnetic Field". United States.
Ludtka, Gerard Michael, Wilgen, John B, Kisner, Roger A, Jaramillo, Roger A, and Ludtka, Gail Mackiewicz-. Mon . ""Non-Contact Ultrasonic Treatment of Metals in a Magnetic Field"". United States. doi:.
@article{osti_963903,
title = {"Non-Contact Ultrasonic Treatment of Metals in a Magnetic Field"},
author = {Ludtka, Gerard Michael and Wilgen, John B and Kisner, Roger A and Jaramillo, Roger A and Ludtka, Gail Mackiewicz-},
abstractNote = {A concept has been originated for non-contact ultrasonic treatment of metals based on the use of an induction coil located in a high-field superconducting magnet. An advantage of using a high magnetic field environment (> 9 T) is that this allows the induced surface current in the sample to be decreased proportionately. As a result, the incidental induction heating associated with the use of the EMAT (Electromagnetic Acoustical Transducer) is greatly reduced, which improves the energy efficiency of the EMAT approach. The method can be coupled with high-field magnetic processing, but can also be used where only ultrasonic treatment is beneficial. In the proof-of-principle experiments, a high-field EMAT was used for non-contact ultrasonic processing of aluminum samples during solidification. The magnetic field for the EMAT was supplied by a high-field (20 Tesla) resistive magnet, and the current was provided by an induction coil. This resulted in a highly efficient EMAT that delivered 0.5 MPa (~5 atmospheres) of acoustic drive to the surface of the sample while coupling less than 100 watts of incidental induction heating. The exceptionally high energy efficiency of the electromagnetic transducer is due to the use of the high magnetic field, which reduces the current needed to achieve the same acoustic pressure. In these initial experiments, aluminum samples of A356 alloy were heated to the liquid state and allowed to solidify at a controlled cooling rate while subjected to the non-contact ultrasonic stimulation (0.5 MPa @ 165 kHz) provided by an induction coil located within the 200 mm (~8-inch) bore of a 20-T Bitter resistive magnet.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Conference:
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  • A high-field EMAT (Electromagnetic Acoustical Transducer) has been used for non-contact ultrasonic processing of aluminum samples during solidification. The magnetic field for the EMAT is supplied by a high-field (20 Tesla) resistive magnet, and the current is provided by an induction coil. This resulted in a highly efficient EMAT that delivered 0.5 MPa of acoustic drive to the surface of the sample while coupling less than 100 watts of incidental induction heating. The exceptionally high energy efficiency of the electromagnetic transducer is due to the use of high magnetic field, which reduces the current needed to achieve the same acousticmore » pressure. In the initial experiments, aluminum samples of A356 alloy were heated to the liquid state and allowed to solidify at a controlled cooling rate while subjected to the non-contact ultrasonic stimulation (0.5 MPa @ 165 kHz) provided by an induction coil located within the bore of a 20-T resistive magnet« less
  • We have developed an ultrasonic spectroscopy method for measuring the elastic constants of solids in hostile environments and over a broad temperature regime. The sample is cut as a rectangular parallelepiped, approximately 1 mm{sup 3} in volume. One or two of the sample surfaces are coated with a thin film of a magnetostrictive material such as nickel. The sample is placed coaxially with two solenoids. One solenoid is used to generate an AC magnetic field of small amplitude which stretches the films. By sweeping the frequency of this field, the sample is excited successively into its various mechanical resonance modes.more » The second solenoid detects the mechanical resonances. The elastic constants are then deduced from the spectrum of mechanical resonances measured at constant temperature. The internal friction is deduced from the width of the resonance peaks. Because the technique is strictly non-contact (the sample may be encapsulated in a fused silica tube), it is deal for measuring elastic constants in hostile environments or under controlled atmospheres. In its present version the system allows us to measure the elastic constants and ultrasonic attenuation of a given sample between 80 and 100 K. The operation of the system is exemplified by measurements on amorphous Ni{sub 80}P{sub 20} and crystalline Ti{sub 60}Cr{sub 40}. 17 refs., 6 figs.« less
  • The Applied Physics group at the Pacific The Applied Physics group at the Pacific Northwest National Laboratory (PNNL) in Richland, WA has evaluated a method for waterless/liquidless coupling of ultrasonic energy from planar ultrasonic contact transducers to irregular test surfaces for ultrasonic non-destructive evaluation applications. Dry couplant material placed between a planar transducer face and a curved or uneven steel or plastic surface allows for effective sound energy coupling and preserves the integrity of the planar transducer sound field by serving as an acoustic impedance matching layer, providing good surface area contact between geometrically dissimilar surfaces and conforming to roughmore » and unsmooth surfaces. Sound fields radiating from planar ultrasonic contact transducers coupled to curved and uneven surfaces using the dry coupling method were scanned and mapped using a Pinducer receiver connected to a raster scanner. Transducer sound field coverage at several ultrasonic frequencies and several distances from the transducer contact locations were found to be in good agreement with theoretical beam divergence and sound field coverage predictions for planar transducers coupled to simple, planar surfaces. This method is valuable for applications that do not allow for the use of traditional liquid-based ultrasonic couplants due to the sensitivity of the test materials to liquids and for applications that might otherwise require curved transducers or custom coupling wedges. The selection of dry coupling material is reported along with the results of theoretical sound field predictions, the laboratory testing apparatus and the empirical sound field data.« less
  • Thermal contact conductance is an important consideration in such applications as thermally induced stress in supersonic and hypersonic flight vehicles, nuclear reactor cooling, electronics packaging, spacecraft thermal control, and gas turbine and internal combustion engine cooling. In many instances, the highest possible thermal contact conductance is desired. For this reason, soft, high conductivity, metallic coatings are sometimes applied to contacting surfaces (often metallic) to increase thermal contact conductance. Two previously developed theoretical models for thermal contact conductance of metallic coated metals have been proven accurate for flat, rough surfaces. However, these two theories often substantially over-predict the conductance of non-flat,more » rough, metallic coated metals. In this investigation, a previously developed semi-empirical conductance model for flat and non-flat, rough, uncoated metals is employed in predicting the conductance of flat and non-flat, rough, metallic coated metals. The more commonly cited of the previous theoretical models for flat surfaces and the semi-empirical model are compared to experimental thermal contact conductance results from a number of investigations in the literature. Results for a number of metallic coating/substrate combinations on surfaces with widely varying flatness and roughness were analyzed. Both models agree well with experimental results for flat, rough, metallic coated metals. However, the semi-empirical model is substantially more accurate and more conservative than the theoretical model compared to the majority of experimental results for non-flat, rough, metallic coated metals.« less
  • Contact and friction problems are of great importance in many engineering applications, for example in ball bearings, bolted joints, metal forming and also car crashes. In these problems the behavior on the contact surface has a great influence on the overall behavior of the structure. Often problems such as wear and initiation of cracks occur on the contact surface. Contact problems are often described using complementarity conditions, w {>=} 0, p {>=} 0, w{sup T}p = 0, which for example represents the following behavior: (i) two bodies can not penetrate each other, i.e. the gap must be greater than ormore » equal to zero, (ii) the contact pressure is positive and different from zero only if the two bodies are in contact with each other. Here it is shown that by using the theory of non-linear complementarity problems the unilateral behavior of the problem can be treated in a straightforward way. It is shown how solution methods for discretized frictionless contact problem can be formulated. By formulating the problem either as a generalized equation or as a B-differentiable function, it is pointed out how Newton`s method may be extended to contact problems. Also an algorithm for tracing the equilibrium path of frictionless contact problems is described. It is shown that, in addition to the {open_quotes}classical{close_quotes} bifurcation and limit points, there can be points where the equilibrium path has reached an end point or points where bifurcation is possible even if the stiffness matrix is non-singular.« less