NONLINEAR VIBRATION IN ELECTRICALLY DRIVEN NICHROME WIRE

The goal of this paper is to explain the nonlinear amplitude modulation seen when electro-dynamically driving NiCr wire. In general, electro-dynamic transduction and string vibration are governed by well understood linear equations. Under typical excitation conditions this system should follow the linear equations of a fixed-fixed string and have a very clearly defined frequency response based upon the wire’s tension and linear density. Hence the system was initially assumed to possess a linear frequency response; however, early experimentation by Garrett showed evidence of amplitude modulation under certain drive conditions. Through further experimentation, it has been determined that the system exhibits a seemingly linear frequency response away from resonance, but near resonance single frequency excitation inputs result in multi-frequency oscillations. As a result of these multi-frequency oscillations, beating occurs which appears to the naked eye as amplitude modulations. The experimental results indicate a nonlinear effect, but the mathematics and theory associated with the phenomena are not fully understood.