The Multi-Physical Fields Coupling Analysis For The High Speed Forming Process And Measurement Technology Study Of Electromagnetic Ring Expansion

Electromagnetic forming technology is one of the most potential technology to overcome the defects of the traditional technology of lightweight aluminum alloy forming manufacturing. However, the process of electromagnetic forming is a process under the couple actions of many physical fields such as electromagnetic field, structure field and temperature field. This process is very complex, the formability of the material will also be changed under such physical fields. The underlying mechanism is complicated. The electromagnetic ring expansion, however, which can be considered as an electromagnetic forming process in uniaxial tensile state, has highly symmetrical structure and very even distribution of physical distribution. These featuress make the process of the electromagnetic ring expansion much simplified to analyzed. Therefore, the study is based on electromagnetic ring expansion experiment, to analysis all the physical fields and build the finite element simulation of the process.This paper adopts the electromagnetic ring expansion as the research model to analyze the physical fields like electromagnetic field, structure field and temperature field in the electromagnetic forming process. Then the circuit model of the electromagnetic ring expansion experiment platform is constructed. And for the electromagnetic field, electromagnetic process between the forming coil and the metal ring workpiece is analyzed, for the structure field, both the mechanical process and motion state of metal ring are studied, for the temperature heat source and influence of temperature on materials are discussed. Finally, by using COMSOL Multiphysics finite element software, the 2D-axisymmetric finite elements model of electromagnetic ring expansion is built to numerically simulate electromagnetic ring expansion process.In Electromagnetic Ring Expansion experiment, eddy currents are induced in ring due to current change in the forming coil, which results into generation of electromagnetic forces on metal ring. Measurement of this eddy current is essential to calculate the stress and strain on metal ring to get the constitutive relationships in this high speed forming process. Due to any mechanical contact to the living circuit will have influence to generation of eddy currents, the Rogowski coil is a feasible transducer for measuring currents. The paper presents a method of eddy currents measurement. Experiments to measure the induced currents in metal ring are performed using the coils. Experimental values of eddy currents are compared with the COMSOL simulation results.For the displacement measurement problem of the electromagnetic driven high-speed deformation behavior, the thesis presents an electromagnetic probe based high-speed displacement measurement method for electromagnetic ring expansion. By analyzing its measuring principle, a Rogowski coil and electromagnetic probes based high-speed displacement measuring system has been designed. By measuring the magnetic flux in the electromagnetic probe generated by the induced eddy current in the metal ring, the magnetic field distribution of the eddy current is obtained. Then by using the property that the magnetic flux in the electromagnetic probe is zero when the metal ring is going above this electromagnetic probe, the real-displacement curve of the metal ring is measured. The program provides the high-speed deformation behavior an effective and simple method of measurement.