Study On Dynamics Of Electromagnetic Rail Launch System

Electromagnetic rail launch system is an advanced accelerating device. Electro-magnetic rail launch use electromagnetic force of the conductor to accelerate object thatis different from the traditional gun. It can accelerate object to hypersonic velocities in ashort time which can greatly improve the velocity and range of projectile.Electromagnetic rail launch is widely applied in researches of national defence,transportation, aerospace, and so on.In this dissertation, electromagnetic force with and without skin effect is studiedrespectively base on distribution of current in the rails. The change of electromagneticforce along with major parameters is discussed. The motion equation of armature forwhole transformation process is presented. Based on electromechanical model ofelectromagnetic rail launch system, the total process of launching is divided into threestages according to change of current in the rails. The expression of energy in each stageis deduced. The expression of total energy and efficiency is achieved. The change ofenergy and efficiency along with main parameters is analyzed. The result shows that themaximal efficiency occurs when the time of each stage is optimized.According to different distribution of current in the rails, electromagnetic forceacting on rails is investigated when considering and not considering skin effect. Bothelectromagnetic forces are calculated respectively. The change of both electromagneticforces along with main parameters is analyzed. Based on the calculated result ofelectromagnetic force, the equation for calculating bending stress of rail on the elasticfoundation is deduced. The stress distribution in rail in different positions of armature isanalyzed. The change of stress along with main parameters is researched. The resultshows that the maximal difference of the stress for tow methods is near the armature.The dynamics model of rail under the running electromagnetic force is established.The free vibration of rail free at two ends, rail simply supported at two ends andcantilever rail on elastic foundation is solved. The complex electromagnetic load isdivided into uniformed load and concentrated force. The equations for the forced responses of rail on elastic foundation to constant velocity load and accelerate load aredeveloped. The dynamic response of rail to the constant velocity load for differentpositions and the different velocity is studied. The influence of critical velocity isdiscussed. The total dynamic response of rail is achieved by adding the dynamicresponses of rail to uniform load and concentrated force. The result shows that thedynamic responses of rail to concentrated force must be considered when the distance ofrails is greater.Considering the change of electromagnetic load along with displacement of rails, theelectromechanical coupled dynamic equations for the rail are given. Using theseequations, the natural frequencies of the electromagnetic rail launch system and theirchanges along with the system parameters are investigated, the vibration modes of theelectromagnetic rail launch system are discussed, and the forced responses of the rail tothe running electromagnetic force are analyzed. The results of coupled and uncoupledequations are compared and analyzed. The change of difference between the forcedresponses with and without considering electromechanical coupled effects along with thesystem parameters is investigated. The result shows that the coupled method is necessaryfor calculating dynamic response of rail when current is larger and elastic coefficient offoundation is smaller.The electromagnetic force acting on rails is simulated by ANSYS software. Thedynamics response of rail to both running electromagnetic forces is simulated by APDL.The electromagnetism-structure FEM simulation for rails carrying current is implementedin load transfer coupled method of the ANSYS software. The maximal differencebetween simulation and theory is9.8%with emphasis on verification of the theoreticalderivation.