Optimal design and evaluation criteria for acoustic emission pulse signature analysis

Abstract

Design of pulse-recording systems and evaluation criteria (method of analyzing the pulse signature) are investigated with the objective of defining optimal approaches to pulse signal analysis. A representative situation which this paper addresses is the modeling of acoustic emission (AE) pulse analysis as a nondestructive means of failure detection in which pulse density counting is presently the most common evaluative criterion. The instrumentation is modeled and selected analytical pulses are passed through the system. Two alternatives are considered here: frequency spectrum analysis, and time domain reconstruction of the pulse or pulse train (deconvolution). The pulse recording/analysis problem is modeled, and the various analysis techniques are considered. Within practical constraint optimal system designs are defined. It is shown that deconvolution of a pulse is a superior approach for transient pulse analysis. Reshaping of a transducer output back of the original input pulse is possible and gives an accurate representation of the generating pulse in the time domain. Frequency spectrum analysis methods and AE measurement systems have potential for segregation of different pulse shapes. Using deconvolution, in principle any definable transducer and filter system can be used to reconstruct pulse characteristics, i.e., to generate time domain signature. A number of major conclusions about the selection of design variables are made for general usage. In addition there are families of optimal selections for transducer and filter system parameters which give superior deconvoluted output signals. These may be significant when working with actual hardware and unknown characteristics. The optimal design results are new and possibly different from the expectations of engineers accustomed to working in the field of signal conditioning. In obtaining these results modern rational design techniques on a rather complex design problem are demonstrated.