Contact transition in metal armatures (railguns)

Barber, J.P.; Challita, A.; Maas, B.L.; Thurmond, L.

doi:10.1109/20.101031

Cited by 37 publications

(12 citation statements)

References 13 publications

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“…T h s mechanism is the basis for currendmelt wave models, in which an erosion front moves forward along the armature surface until it reaches the leading edge and culminates in changing the solid contact mode into the plasma mode. As a result, a dramatic increase of the contact surface erosion begins and the effectiveness of For these reasons, melting of the armature (and rail) and the appearance of the liquid phase is usually considered as an unwanted process [ 11, [2]. Perhaps, the only work, which mentions a possible positive influence of the melt owing to its lubricative properties, is [3] in which, for some rather intensive regimes, a non-monotonic velocity increase of a hollow cylindric armature was noted.…”

Section: Calculating the Liquid Film Effect On Solid Armature Rail-gumentioning

confidence: 99%

Calculating the liquid film effect on solid armature rail-gun launching

1999

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Absrrmt -In existing EM launchers with solid electroconductive armatures the achievement of high velocities is limited by the velocity skin-effect (VSE) and wearing of contact surfaces due to inhomogeneities of the electric current, and frictional tearing and heating. Inevitably, a liquid phase appears that is considered usually to be undesirable.We believe the deliberate injection of electroconductive liquid in the gaps between the armature and rails is capable of significantly decreasing friction between these surfaces and the resulting wear, of improving electric contact and reducing armature overheating in zones of electric current concentration caused by inperfectness of surface manufacturing or by the VSE.We present the calculation of temperature fields in the armaturehail interface with due account of VSE, energy release, and heat transfer in a continuous liquid film that completely covers the contacting surfaces. The motion of viscous liquid in the gap is considered with due regard to Ampere forces and inertial forces caused by acceleration of the armature. We have found that the rate of the armature heating, which ultimately leads to melting in a region at the trailing edge, depends essentially on thickness and material of the film. By optimizing these parameters it is possible to delay the crisis phenomena associated with melting of the armature material and subsequent transition of the armature/rails contact into the plasma mode of operation.

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Section: Calculating the Liquid Film Effect On Solid Armature Rail-gumentioning

confidence: 99%

Calculating the liquid film effect on solid armature rail-gun launching

1999

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“…7nR-m) for use as a metal armature contact. Also, armature contacts have been observed toobey the same physics as pinon-disk experiments [2]. The plating of rails also needs to be exploited.…”

Section: Introductionmentioning

confidence: 98%

Plated armature contacts for solid armature electromagnetic railgun launchers

Aalto

Yee

1995

IEEE Trans. Magn.

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Solid armature firing tests have shown that, under electromagnetic railgun firing conditions, the armature contact areas wear excessively and, after transitioning, loses contact with the rail surfaces. It is desirable to maintain rail contact as long as possible. Previous work, regarding the engineering design of metal armature contacts has shown that copper, plated on aluminum armatures, as a contact material in rail guns, may be over twice as good as aluminum. It was stated, also, that the armature contacts obey the same physics as pinon-disk contact experiments have shown. Recent work has led to the development of a process for the copper plating of aluminum 7075-T6 armature contact surfaces. This paper reports on the armature fabrication process, the copper plating, and the associated testing required to assure that the copper adheres to the aluminum armature substrate material. The armatures were test fired at ARL. and the results of these tests and observations are presented.

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“…Hsieh [11] used a simple model for the contact resistance and the Joule heating for the simulation of the armature-rail interface. Barber [2] used the analog of thermal and electrical resistances for the description of a current transfer function. A micromechanically motivated model for electrical contacts is given by [4].…”

Section: Introductionmentioning

confidence: 99%

Numerical modeling of electrical contacts

Weißenfels

Wriggers

2009

Comput Mech

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The focus of this work is the investigation of the behavior in electrical contacts, where electrical, thermal and mechanical fields are coupled. Specifically, theoretical constitutive models for the electrical conductance and electrical wear phenomena are developed and implemented in a three dimensional finite element setting. Also a new relation for wear is proposed, where the amount of wear is coupled to the dissipation arising at the contact interface. Additionally, the numerical results of the new theoretical formulations are validated by means of experimental data.

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Contact transition in metal armatures (railguns)

Cited by 37 publications

References 13 publications

Calculating the liquid film effect on solid armature rail-gun launching

Calculating the liquid film effect on solid armature rail-gun launching

Plated armature contacts for solid armature electromagnetic railgun launchers

Numerical modeling of electrical contacts

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