COMPUTER MODELING AND PREDICTION OF SOLID ARMATURE CONTACT WEAR AND TRANSITIONING IN ELECTROMAGNETIC GUNS

A 30 mm round bore solid armature development and test program has bee n completed at the Electric Armaments Research Center at Picatinny Ars enal, New Jersey, The program has furthered the understanding of solid armature contact wear and how it relates to the subsequent loss of th e solid armature to rail contact, The Army Railgun Modular Simulator ( ARMS) computer code has been improved to provide a 1D model of the par asitic effects of the contact ohmic and the melt layer viscous shear h eating on contact wear at the rail to armature interface, The theoreti cal premise for the simulator asserts that contact wear Is a result of the loss of contact material from a sliding melt layer which forms be tween the armature and the rail, The melt layer interface is sustained by the heat inputs to the armature from both ohmic and viscous shear heating, The net contact force at any time is a resultant of both the mechanical force arising from the contact interference and stiffness p roduct and the induced magnetic force, As the contact wear progresses, the resulting loss of interference between the armature and rail redu ces the net contact force in proportion to the armature stiffness to t he point where the mechanical contact force component ceases to assist the induced magnetic force, Transition of the contact from a low volt age/efficient sliding interface is shown to occur when the mechanical contact force is equal and opposite to the magnetic force, resulting i n near zero contact force, This paper describes the 30 mm armature tes t plan, the computer model theoretical premise, the thermodynamic and electromechanical modeling techniques utilized and compares the simula tion results to the 30 mm armature test cases.