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| Influence of Aluminum Deposition Layers on Sliding Electrical Contact at the Pivot-Rail Interface under Repetitive Emission |
| Xing Zexi, Wang Jian, Li Hongjian, Han Zhiyun, Li Qingmin |
| State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Beijing 102206 China |
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Abstract The electromagnetic rail launch process exists in high current, ultra-high speed, high temperature-rise, strong friction, and extreme impact conditions. The high heat generated causes the surface of the aluminum armature to melt, resulting in a transition at the pivot-rail interface from solid-solid electrical contact to a solid-liquid-solid melt process. Eventually, molten aluminum solidifies on the rail surface, forming a complex deposition layer. This deposition layer has implications for the performance of the pivot rail system during subsequent launches. The operational environment characterized by ultra-high-speed friction during repeated launches results in a low melting point in the armature. A portion of molten material forms a liquid transferred onto the rail, enhancing the interface and diminishing the electromagnetic rail's longevity. Consequently, it is imperative to investigate the impact of the aluminum deposition layer on the sliding electrical contact at the pivot-rail interface.
This study conducted small-diameter electromagnetic launching tests with varying launching times to examine the carrier friction wear behavior of the friction sub-material of the pivot rail. The results revealed that a significant amount of molten aluminum was transferred to the rail surface after multiple launches, increasing the roughness of the pivot-rail interface due to the residual deposit layer. As a result, the pivot-rail friction sub-contact deteriorated, characterized by organizational features such as gouges and cracks on the rail surface. The wear intensity escalated with an increase in the number of launches. However, after a certain number of launches, the aluminum alloy oxide layer on the rail surface reached a critical thickness, reducing the wear on the rail body. Nonetheless, mechanical and electrical wear simultaneously intensified the environmental conditions at the pivot-rail contact surface.
Finally, a liquid film fusion deposition model at the pivot-rail interface was developed, and the deposited layer’s impacts on the operational dynamics of the liquid film and the electrical contact condition of the pivot-rail interface were studied. The study involved the calculation of the thickness of the deposited layer and the deposition efficiency for varying launch times. During high-speed launches, the aluminum liquid layer experienced significant viscous forces, and pronounced velocity variations of the liquefied layer at the armature tail exit increased viscous dissipation forces. With multiple launches, heightened interfacial friction can counteract the viscous forces within the aluminum liquid layer, destabilizing the interfacial liquid film. Thickening the aluminum deposition layer on the rail surface can exert extrusion effects on the liquid film, introducing destabilizing factors to the flow of the liquefied layer. Consequently, the aluminum liquid layer, which serves as a lubricant between the armature and the rail, may be extruded from the interface. Therefore, the armature’s normal operation is compromised, and the rail's longevity is diminished.
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Received: 09 May 2024
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2025, Vol. 40 
