An Impact Velocity Measurement System for Electromagnetic Forming Process

Electromagnetic forming (EMF) is a high-speed process that uses pulsed electromagnetic force to drive metal forming. The impact velocity significantly affects the deformation behavior of the workpiece in the die and it can be used to guide the process parameters design. Due to the constraints of narrow space, it is difficult to construct a suitable optical path for noncontact measurement methods. The tactile measurement device is another low-cost and effective method, but most designs currently used in EMF have the shortcomings of inconsequence contact probe structure and low signal-to-noise ratio (SNR), which limit their application in the EMF process. To improve the performance and broaden the application scope of the low-cost tactile measurement method, a more durable contact probe structure and easily implemented external circuit topology connected to probes are introduced in this article. The influence of the characteristic parameters of the probe structure on the measurement results is investigated through finite element simulation and the structure is optimized. The equivalent circuit diagram of the measurement system is constructed and the analytical expression of the output signal is derived. The influence of the circuit parameters on the output signal is analyzed, and the stability and SNR of the measurement system are improved by optimizing the circuit parameters. Therefore, a robust and low-cost impact velocity measurement system for the EMF experiment is constructed. The accuracy and feasibility are confirmed through high-speed camera experiments and simulation analysis. The experimental results show that the maximum relative error of the collision moment and impact velocity is 3.32% and 7.34%, respectively, which shows good performance and confirms the potential for application in the EMF process.