A thermal hydraulic model of melt-lubrication in railgun armatures

Kothmann, R.E.; Stefani, F.

doi:10.1109/20.911797

Cited by 35 publications

(5 citation statements)

References 12 publications

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“…This paper revealed the presence of relatively larger amounts of noise on the earlier pulses followed by a substantial reduction on the subsequent pulses potentially highlighting a change in the behavior related to transition from start up to running. Specifically, this new and interesting result could be attributed to the positional effects or an improving electrical contact due to the thermal effects consistent with a melt-layer hypothesis [11] or brush seating. Fig.…”

Section: Muzzle Voltage Waveforms and Noisementioning

confidence: 63%

A Railgun Test Bench and Standardized Methodology for Muzzle Voltage Noise Analysis

Rada

Engel

2015

IEEE Trans. Plasma Sci.

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This paper presents the design, development, and initial testing results of a small-bore railgun and test bench for the study of muzzle voltage traces. An analysis of the noise observed on voltage traces taken from the muzzle during motional and locked-armature operations is presented and discussed. The average velocities for a 3.38-g projectile were 50 m/s over a series of 21 tests. The railgun is powered by a sequentially fired pulse-forming network consisting of six electrolytic capacitor banks. Typical current and voltage characteristics are approximately 20-kA peak current at 275 V for a 6-ms pulse train length. Noise root-mean-square voltage and noise margins are extracted from the muzzle voltage waveforms and discussed. This investigation also develops a quantitative method to analyze muzzle voltage noise, which can be applied to any electromagnetic launcher. The technique reveals a new and interesting result that shows noise levels were greatest during early pulses of the firing sequence and generally decreased with subsequent pulses. This demonstrates that the technique has the potential to provide insight into the nature of the armature-rail sliding contact. Index Terms-Contact, muzzle voltage, railgun. Nicholas M. Rada (S'04) received the B.S. degree in electrical engineering and the M.S. degree in electrical engineering from the University of Missouri, Columbia, MO, USA, in 2008 and 2010, respectively, where he is currently pursuing the Ph.D. degree in electrical and computer engineering with the

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Section: Muzzle Voltage Waveforms and Noisementioning

confidence: 63%

A Railgun Test Bench and Standardized Methodology for Muzzle Voltage Noise Analysis

Rada

Engel

2015

IEEE Trans. Plasma Sci.

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“…11 the effects of turbulence on the melt film viscosity are investigated. It was suggested by Kothmann and Stefani [23] and further investigated by Merrill and Stefani [22] that a higher effective viscosity, which includes a laminar viscosity term and a turbulent viscosity term, is necessary for better agreement between experimental data and melt lubrication theory. For this investigation the effective viscosity term is defined as follows…”

Section: Melt Lubrication Theorymentioning

confidence: 99%

Wear at high sliding speeds and high contact pressures

Siopis

Neu

2015

Wear

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Metal on metal wear at high sliding speeds and high contact pressures results in the melting of one or both of the sliding solid bodies due to heat generated at the contact interface. Understanding the influence of sliding speeds and contact pressures on normalized wear rates is important in developing predictive models for designing more efficient and effective engineering system components. Typical engineering applications subjected to extreme sliding conditions include ultrahigh speed machining, rocket sleds, large caliber cannon, and electromagnetic launchers. Sliding speeds on the order of 1,000 m/s and contact pressures in excess of 100 MPa are common in these applications and difficult to replicate in a laboratory environment. A unique electromagnetic tribometer based on a minor caliber electromagnetic launcher has been designed and implemented to characterize wear deposition of a 6061-T6 aluminum pin (slider) on a UNS C11000-H2 copper flat (guider) at sliding speeds from 0-1,200 m/s and contact pressures from 100-225 MPa. Optical microscopy and 3D profilometry were used to investigate and quantify slider wear. Three distinct wear regions were observed. Test results provided evidence that the aluminum slider contact interface was molten and experimental wear data showed a dependence on both pressure and velocity. Comparisons between melt lubrication theory and experimental data provide insight into the nature of the contact interface under the sliding conditions tested.

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“…At the region of the ARI, the physical phenomenons are very complex which involve electrical, mechanical, thermal field, etc., and these fields interact with each other. A lot of research findings have been achieved from different aspects by far, such as the contact resistance [7,8], the velocity skin effect in the contact surface Layer [9], the thermal analysis of the interface [10], and the contact pressure in the starting stage [11,12], etc. However, to completely understand these phenomenons and their mutual effect still is a long-term hard work.…”

Section: Introductionmentioning

confidence: 99%

Experiment and computation on the initial contact force of the rails and C-shaped solid armature interface

Yan

Yuan

et al. 2010

2010 IEEE International Power Modulator and High Voltage Conference

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The contact condition of the armature-rail interface (ARI) is analyzed by building a two-dimensional (2-D) model and a three-dimensional (3-D) model, and a small experimental electromagnetic launcher (EML) and a C-shaped solid armature are designed and used to verify the simulation results. Simulated by the finite element software ANSYS, the distributions of the contact pressure, contact area (or contact length) and the von mises stress (VMS) are shown in the 2-D and 3-D models, and the simulation results of two models are analyzed by processing the data. The simulation and experimental results are carefully compared by observing the distribution of the melted object remaining on the surface of rails at the initial position after launch, and the variation of contact condition with the sliding of the armature can also be found. The results show that the contact pressure and contact area distributions of the ARI are not only non-uniform along the armature arm length, but also nonuniform along the thickness, and it is nearly impossible to make the armature arm completely contact with the rail. The results also tell us that the satisfactory contact force and contact area can be gotten by properly designing the armature structure.

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A thermal hydraulic model of melt-lubrication in railgun armatures

Cited by 35 publications

References 12 publications

A Railgun Test Bench and Standardized Methodology for Muzzle Voltage Noise Analysis

A Railgun Test Bench and Standardized Methodology for Muzzle Voltage Noise Analysis

Wear at high sliding speeds and high contact pressures

Experiment and computation on the initial contact force of the rails and C-shaped solid armature interface

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