Acoustic Emission and Signal Analysis

Acoustic emission (AE) is one of the most recent entries into the field of nondestructive evaluation. Due to the uniqueness of the basic principle and the potential for tackling a wide range of applications, the technique has gone through rapid strides in a very short time. Thus, today, two decades after the first application of the technique, AE is used in various industries, such as petro-chemical, refinery , nuclear , transportation and aerospace. While, some of the applications can be dealt with by current state-of-the-art, through simple methods of measurement and analysis, the entire potential of the technique still remains to be exploited as extraction of complete information contained in the signal is not possible with the adaption of only simple data analysis procedures. Currently several scientists in many countries are involved in evolving and~mplementing advanced concepts for AE signal analysis. These along with the approach adopted by us are discussed in this paper . I. SOME ASPECTS OF ACOUSTIC EMISSION 1.1 The Phenomenon Acoustic emissions are pressure waves generated due to transient release of energy when a material is subjected to mechanical, thermal or chemical changes causing irreversible deformations or changes in atomic arrangement. Cracking of timber, tin cry , noise generated before rock and mine collapses are some of the examples of acoustic emission (AB) which have been intuitively utilized as warning signals. Local dynamic movements such as initiation and propagation of cracks, twinning, slip dislocation movements, phase transformation, and fusion (welding) are Received 20 January, 1990 55