1. School of Electrical Engineering Xi’an Jiaotong University Xi’an 710049 China; 2. Baoding Power Supply Subsidiary Company of State Grid Hebei Electric Power Supply Co. Ltd Baoding 071000 China
Abstract：The armature erosion during the electromagnetic launching process disrupts the contact between the armature and the rails, significantly impairing the performance of the launch. Joule heating and frictional heating, originating from different mechanisms, affect armature erosion in distinct ways. Current research on armature erosion focuses on current-induced Joule heating, with relatively limited studies on erosion caused by frictional heating. This paper establishes an armature surface erosion model that incorporates the effects of frictional heating. The model analyzes the impact of both Joule and frictional heating on armature surface erosion during the early stages of the launch and validates the results with experimental data. Firstly, the contact state between the armature and the rails under the influence of contact pressure is analyzed. The contact pressure distribution on the contact surface is significantly non-uniform in the early stages of the launch, with the contact conductance distribution corresponding closely to the contact pressure distribution. Subsequently, the Joule and frictional heat fluxes at the armature-rail interface are calculated separately. Due to differences in the electrical conductivity of the armature and rail materials, the distribution of Joule heat flux is shifted approximately 10 mm towards the armature head compared to the distribution of contact pressure. In contrast, the distribution of frictional heat flux closely aligns with the distribution of contact pressure. As the velocity of the armature increases during the launch, frictional heating initially contributes less than Joule heating but eventually surpasses it. The temperature distribution characteristics on the armature surface are studied. The results indicate that the armature’s maximum surface temperature exceeds the melting point of the armature material before the maximum frictional heat flux surpasses the maximum Joule heat flux. With the rapid increase in frictional heat during the launch process, the location of the maximum surface temperature shifts from the position of the maximum Joule heat flux density to that of the maximum frictional heat flux density. The Stefan condition for phase transition is used to investigate the erosion process on the armature surface. The results demonstrate that during the initial stage of the launch, surface erosion first occurs at the point of maximum Joule heat flux, presenting as localized current erosion. As the armature velocity increases, the erosion region expands from the rear edges towards the center, with the maximum erosion depth shifting to the point of maximum frictional heat flux. A low-speed, low-current electromagnetic launch experiment is conducted by the Huazhong University of Science and Technology team. Based on the parameters of this experiment, the simulated armature erosion profile closely matches the experimental results, with the maximum surface erosion depth measured at 0.44 mm in the experiment and 0.46 mm in the simulation. Analysis of the armature surface erosion profiles at different time points indicates that during the low-speed phase, Joule heating predominantly governs armature erosion, with initial erosion primarily attributed to Joule heating. As the armature velocity increases, the influence of frictional heating on armature erosion gradually surpasses that of Joule heating, making frictional heating the primary factor in determining the maximum erosion depth.
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2025, Vol. 40 
