NDTnet - December 1996, Vol.1 No.12

Characterization of Reflectors by Ultrasonic Methods

By U. Schlengermann


Abstract

Here is a comprehensive review of the methods being used at present or under development, for qualitative interpretation of reflectors by means of pulse-echo techniques.


1. Introduction

2. The pulse-echo method - general remarks

    It is essential in the evaluation of a reflector that one has scanned for it and detected it (1).
    The procedure can be divided into the following steps:

    • A reflector is detected.
    • A simple evaluation can be made of the pulse echo characteristics, for example, the transit time or the maximum echo amplitude.
    • A rough classification of the type of reflector can be made with additional effort. In this case a combination of different characteristics from a number of echoes during a scan procedure (signal analysis) must be linked in order to determine the type of reflector.
    • A precise classification of the reflector according to type, position and size can be attemped by means of ultrasonic imaging. However, besides being quite difficult, these methods are often constrained by the limits of physics.

Fig. 1 - Information of the pulse echo method

3. Simple evaluation methods

4. Evaluation of diffracted and converted sound waves



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