Dynamic Tension Experimental Technique Of Electromagneticall Driven Expanding Metal Ring

The electromagnetically driven ring as a dynamic tensile test technique was suggested inthe middle of the1960s, in which, the force on the specimen is a body force, and the waveeffects that inevitably arise from the application of mechanical forces can be avoided. In thispaper, the electromagnetic ring expanding process, assessment of stress\strain state, and thetemperature rising of the of ring specimen were studied by the electrodynamics and finite elementmethod, which is able to provide references for the designing of electromagnetic ring expansionexperiment system, experimental results measure and analysis.In this paper, based on the electrodynamics and mechanics equations obtained by WilliamH.Gourdin, the induced currents, as well as the deformation, strain rate and the temperature risingof the expanding ring specimen are discussed. The results show that:(1) the strain rate of the metalring’ specimen can reach to1041/s order of magnitude, the technique of electromagneticall driveexpanding ring can be designed for metal tensile test in a high strain rate.(2) the strain loading rateof ring specmen can be controlled by varying the characteristics of discharge voltage upondriving solenoid and and the inductance of coil.(3) the temperature rising of specimen in theexperiment which the solenoid discharge voltage is4kv can reach to197oc, its effect to materialbehavior would be considered in experimental data analysis.The dynamic tension process of electromagneticall driven expanding metal ring wereanalysed by the three-dimensional ANSYS-Multiphysical FEM code. The FEM results show that:(1) The expanding ring specimen isn’t as one-dimensional stress state in the early deformationstages whether the solenoid currents cut off or not. The electromagnetic expanding ring could beseem as uniaxial tension only when the ring’s deformation is in stage of free expanding motionafter the solenoid currents cut off.(2) The flow stress calculated by the of motion equation ofexpanding ring agree with material constitutive, but fluctuate along the constitutive curve. Thephenomenon needs further research.Furthermore, the dynamic tensile experimental system of electromagneticall expanding ringwas set up, which the EMF10/7-Ⅱelectromagnetic forming machine in our laboratory is utilized asan energy storage device. The experimental data measuring and analysis method are discussed.