Friction and ablation measurements in a round bore railgun

Aigner, Sandra; Igenbergs, E.

doi:10.1109/20.22500

Cited by 40 publications

(12 citation statements)

References 2 publications

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“…Kinetic friction force also must be concerned in the experiment. Reference [12] suggested a equation about the solid friction in a railgun. The friction coefficient could be written as:…”

Section: A Design Of the Experimentsmentioning

confidence: 99%

Effect of geometry change on solid C shaped armature

Zhang

Ruan

Liao³

et al. 2012

2012 16th International Symposium on Electromagnetic Launch Technology

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Armature takes an important role in the electromagnetic launch process. High current densities in the armature can result in high local temperature and consequent loss of strength and even melting and erosion. Conventional C-shaped armature is widely used which experiences high current densities in three areas: the leading edge, the trailing edge, and the throat. It is argued that if the armature shape is modified to better align with the magnetic field, the current density distribution could be more uniform.This paper tries to analyze the effect of the geometry change on C-shaped armature at low velocity. The geometry of the armature was changed to improve the current density and temperature distribution and reduce the erosion. Four variants of C-shaped armatures were designed to study the specific features, including a conventional C-shaped armature (CCA), a rounded leading edge Cshaped armature (LCA), a rounded trailing edge C-shaped armature (TCA), and a rounded incorporate edge C-shaped armature (ICA). A novel low-speed experiment was constructed and tested. The armatures were eroded and recovered to compare the improved effect. Then finite element simulations according to the experiments were taken to analyze the further results.It is proved that the curved edge of the armature could reduce the nonuniformity of current density and temperature distribution greatly. LCA and ICA showed less erosion on the contact surface due to the rounded leading edge. The trailing edge could improve the uniform of the current on the interface. ICA is the best choice of the four armatures which combines the effect of LCA and TCA. Erosion and transition mechanism were analyzed at last. A detailed description of the experiments and simulations will be presented in this paper.

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“…Kinetic friction force also must be concerned in the experiment. Reference [12] suggested a equation about the solid friction in a railgun. The friction coefficient could be written as:…”

Section: A Design Of the Experimentsmentioning

confidence: 99%

Effect of geometry change on solid C shaped armature

Zhang

Ruan

Liao³

et al. 2012

2012 16th International Symposium on Electromagnetic Launch Technology

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“…The transverse contact force on each railarmature contact surface was calculated to be about 90 % of the axial electromagnetic force on the armature. The model of the friction coefficient was adopted from [3,4]. The chosen values of static, kinetic, and attenuation coefficient to explain the measured result were almost the same as those used in [4].…”

Section: Electromagnetic Launch Experimentsmentioning

confidence: 99%

Modeling and circuit analysis of an electromagnetic launcher system for transient current waveforms

Kim

Lee

et al. 2014

2014 17th International Symposium on Electromagnetic Launch Technology

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An electromagnetic launcher with a 4.8 MJ pulsed power supply has been fabricated, and experimental tests were started. Through the experiments and calculations, the effects influencing on the electrical properties and the performance of the launcher have been investigated. The electromagnetic launcher system includes pulse-forming inductors in the power supply and rails in the launcher which are made of massive conductors showing a prominent skin effect for a transient current. For these conductors constant impedance values or those defined per unit length have difficulties in calculating correct voltages appearing between the terminals of them. In addition, the frictional force between the rail and armature could not be ignored for a better estimation of the armature motion. To obtain solutions close to the measured ones, the diffusion of the magnetic flux density or current density was taken into account, and the history of the armature motion was reflected in the electrical modeling of the rails. These effects were implemented as voltage correction terms in the circuit equations with the help of the electromagnetic responses for a step-function current. In the equation of the armature motion a reasonable form of the frictional force was modeled considering the velocity skin effect and the structural analysis. In this paper, the application of the voltage correction method into rails and the calculated result of the modified circuit equations for the constructed electromagnetic launcher system are presented.

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“…The VDM in reference [13] ignores atmosphere drag which is less than three percent of the electromagnetic force. The function of VDM is:…”

Section: A Drag Model Associated With Velocity (Vdm)mentioning

confidence: 99%

“…IDM is used widely in railgun research which takes current, friction, preload and velocity into account [7], [8], [13]- [15]. For a solid armature, the solid-solid friction force is the domain drag force which is proportional to the normal force as follows:…”

Section: Synthesis Models Of the Solid Armature (Idm)mentioning

confidence: 99%

Nonlinear scaling study of a railgun

Zhang

Ruan

Liao

et al. 2012

2012 16th International Symposium on Electromagnetic Launch Technology

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Scaling method has been used widely in railgun technology. But nonlinear problem is seldom studied because of the complexity and uncertainty. In order to employ the scaling method better, the paper brings the nonlinear drag model to the solid armature railgun circuit.Several drag functions were compared including drag model associated with velocity (VDM), drag model associated with current (CDM), and drag force associated with integrated factors (IDM). Scaling relationships of these drag models were discussed. And then, a novel experiment was constructed to compare the drag models at low velocity. Further simulations at high velocity are also studied. At last, the nonlinear scaling method was verified by an example at high velocity.It shows that VDM is far from satisfactory at high velocity. The scaling conditions of VDM are too strict to use in practice. CDM is workable only in high velocity condition which satisfies conditions of linear scaling method (LSM) in nature. But it is worthless when the velocity is less than about 0.5 km/s. Although a bit complex, IDM is very accurate at any condition. Coefficient α in IDM should be taken considering different test conditions. Scaling relationships of IDM could not be derived at low velocity due to nonlinearity. While at high velocity, IDM could be simplified to CDM and realize LSM. Further research indicates that IDM could use the scaling method directly and realize approximate LSM at high velocity. Due to the work range of the solid armature is usually 1~2km/s, nonlinear scaling method could be used in a railgun with IDM. What should be noted is that the velocity scaling factor must be controlled above about one quarter to avoid the nonlinear field. A detailed analysis of the experiments and simulations will be presented in this paper.

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Friction and ablation measurements in a round bore railgun

Cited by 40 publications

References 2 publications

Effect of geometry change on solid C shaped armature

Effect of geometry change on solid C shaped armature

Modeling and circuit analysis of an electromagnetic launcher system for transient current waveforms

Nonlinear scaling study of a railgun

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