Generation of elastic waves from line and point sources by a high-current pulse method

Abstract

This paper describes a method of generating both line and point sources of acoustic emission (AE) signals by a powerful, transient Joule heating of a thin, conductive film deposited on an insulating plate or a small diameter metal wire buried inside it. Point-and line-source AE signals are generated by heating a short or a long section of thin film, respectively. The versatility of this method is demonstated by the diversity of AE signals that can be produced by simply changing the rise time, magnitude, and duration of the current pulse that provides the heating. An analysis shows that both the line and the point AE sources are of dipolar type for the case of the heated thin film. The line source resulting from an imbedded long, thin wire appears to be a two-dimensional center of dilatation. Short-duration current pulses generate a step source whose rise time is approximately equal to that of the input electrical power pulse while long-current pulses produce a linear ramp source that resembles the temperature rise of the heated conducting film or wire.