Research Progress on the Surface Damage Mechanism and Protection of Armature for Electromagnetic Rail Launch
Electromagnetic launch technologies can directly convert electromagnetic energy into the instantaneous kinetic energy required for launching a payload within a short period.This technology has the advantages of high speed,high safety performance,and strong controllability,offering broad prospects for applications.Unlike mechanical and chemical energy,electromagnetic rail launch technology harnesses electromagnetic energy,enabling the achievement of ultrahigh launch velocities exceeding 2 km/s.During an electromagnetic launching process,a system is subjected to extreme launching conditions,such as high currents(～MA level),strong magnetic fields(～T level),high heat(～103 K),and strong forces(～106 N).Electrical energy is transformed into kinetic energy through an armature,making it a critical component of the launch system.However,the armature inevitably undergoes a series of damage during its operational lifespan,leading to significant changes in the contact characteristics between the armature and rail current-carrying friction pairs.This significantly affects the efficiency and precision of the electromagnetic rail launch system.This paper summarizes recent research progress on the surface damage mechanism and protection of armatures for electromagnetic rail launches,including typical damage characteristics and their influencing factors,a simulation and trend analysis of typical damage mechanisms,and the optimization of armature damage protection.Three primary forms of armature damage have been identified in various studies:current-carrying friction and wear,thermal melting,and transition erosion.The categories of current-carrying friction and wear encompass mechanical,current,and arc wear,presenting a distinct"three-stage"damage progression,correlating with the changes in current during the launch process.Thermal melting occurs owing to the contact resistance and friction between the armature and rails,which generate Joule and frictional heat,ultimately causing the armature surface to melt.Transition erosion manifests as a change in the contact mode between the armature and rails,leading to phenomena such as contact loss,which exacerbate the erosion on the armature surface and intensify the thermal melting damage.The severity and morphology of armature damage are influenced by service variables,inherent armature parameters,and their interplay.Simulations of armature damage mechanisms,conducted using finite element analysis software such as ANSYS,ABAQUS,and COMSOL,primarily focused on three aspects:the concentration of contact stress,current density,and heat.The optimization of armature damage protection requires considering various factors such as the structural designs of the armature and rail current-carrying friction substructure,material selection,and surface coating.These considerations aim to mitigate or prevent armature damage during launch.Existing studies have highlighted Al-Zn-Mg-Cu alloy as one of the most preferred materials for armatures,particularly when applies as a coating for surface protection.Currently,the preparation process,application conditions,and micro-mechanism of aluminum alloy armature coatings are not mature enough,especially in the extreme service environment of the launch process,which has a variety of coupled fields of physical quantities.Surface coatings with various impact resistances and other physical properties can meet the relevant standards,but systematic guidance is still lacking.Finally,a summary and outlook regarding the armature surface damage and protection are presented.The lack of a systematic and complete spatiotemporal evolution law in the morphological study of armature surface damage is attributed to the extreme harshness and multi-field coupling characteristics of the electromagnetic rail-launching armature surface damage formation.Further research is required for theoretical analysis,experimental validation of simulation reproduction methods,and correlation with rail damage characteristics.Future research should focus on the profound coupling of multiphysical fields,dynamic evolution of contact states between the armature and rail,development of three-dimensional analysis models under harsh operating conditions and material property evolution,and development of novel materials and structures for both the armature and rail.This study aims to enhance armature efficiency by incorporating insights from research on armature surface damage and protection,the development of new armature materials,and structural design improvements.
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