Coupling Experiment and Simulation in Electromagnetic Forming Using Photon Doppler Velocimetry

Modeling electromagnetic forming processes is in many ways simpler than modeling traditional metal forming processes. In electromagnetic forming the problem is often dominated by inertial acceleration by a magnetic field. This problem is better posed than the more common ones in metal forming that are often dominated by complex three-dimensional constitutive behavior and frictional effects. However, important aspects of the problem are dominated by the constitutive properties of the material, and often electromagnetic forming is performed in a regime where there is little reliable material strength data. Strain rates are often high (10(2) to 10(4) s(-1) is the typical range for electromagnetic forming). Also, heat is generated both by Joule heating as well as by plastic deformation, and peak temperatures can be quite high. Also, while high-temperature, high-strain-rate data is scarce, there is very little data in cases where temperature rises significantly over very short time periods (tens of micro-seconds) as in electromagnetic metal forming. This rapid temperature rise is very important to the material response because the short time scales largely preclude the material from recovery and recrystallization processes, and precipitates cannot dissolve as they normally would in an age-hardening alloy in these time scales. This paper will show how advanced instrumentation, particularly the Photon Doppler Velocimeter (PDV) can be coupled with electromagnetic forming and provide both avenues to characterize the high strain rate strength of the material as well as to provide clear experimentally measured data that can be used to compare experiments with numerical models.