Research Of Electromagnetic And Heat Characteristics On The Armature/Rail Interface With Imperfect Contact

The electromagnetic launch technology is at the stage to practical application, which solution of high-speed sliding electrical contact interface damage is critical. Due to the large current and high velocity, combined with the uneven distribution of contact pressure and current, the A/R(armature /rail) interface temperature rises severely because of local heat concentration, which results in interface damage such as armature melting and rail grooving. In order to control the interface damage and increase electromagnetic launch performance, reveal of electromagnetic and thermal characteristics is necessary. But,it is hard to direct observe the interface in the environment with such huge magnetic, current and thermal, so numerical simulation is a major way to study the interface characteristics.First, the 3-D electromagnetic diffusion and thermal diffusion mathematical model were analyzed. In order to reveal the actual process, the electromagnetic model coupled the contact resistance model,which considering contact pressure distribution. In thermal model, heat transfer equation, heat source distribution and heat partitioning were analyzed. Particularly Stefan condition was introduced to implement the interface melting simulation. Electromagnetic diffusion model and heat transfer model were established in COMSOL.Electromagnetic diffusion model consists of electromagnetic module and mechanical module. Contact pressure distribution and current density distribution were calculated. The current concentration phenomenon and the reasons were analyzed. With the joule heat obtain from the electromagnetic model and the frictional heat calculated with the contact pressure and the motion equation, the temperature and melting morphology on the interface were calculated in the heat transfer model. Mechanisms of armature melting and rail grooving were discussed. The effects of current rise time, bore size and material properties on the electromagnetic and thermal characteristics were also discussed.Finally, experiments to research electromagnetic and thermal characteristics on the interface were designed and implemented. Control experimental conditions, recycle experiment armatures, and analyze interface physical process through surface morphology. Experiments of impacts of current amplitude and launch mass on the interface melting were carried out at a lab-scale rail launcher. Models and part of conclusions were verified.