Non-contact measurement of impact load due to collision of ferromagnetic projectile based on electromagnetic induction

Abstract

A non-contact measurement method of the impact load due to collision of a ferromagnetic projectile with a non-magnetic target was proposed and validated by conducting steel bar collision tests with an acrylic bar. In the measurement system, one coil connected to a stabilized power supply was set near the collision point to generate a magnetic field and the other was set near the magnet coil to measure the electromotive force induced by the disturbance of the magnetic field due to passing a ferromagnetic projectile through the coils. Because the induced electromotive force is proportional to the projectile velocity in accordance with Faraday's law of electromagnetic induction, the measured velocity of the projectile was differentiated to obtain the acceleration, which was then multiplied by the mass of the projectile to analyze the impact load. In the tests, a steel bar was collided with an acrylic bar to determine how well the proposed method could measure the impact load. The impact load analyzed from the electromotive force was compared with the impact load measured by strain gauges set on the acrylic bar and the two were found to be in good agreement. These results demonstrate that the proposed method is effective for measuring the impact load resulting from collision of a small projectile, where conventional sensors are not applicable.