DESIGN AND DEVELOPMENT OF ULTRASONIC INSTRUMENTATION SYSTEM

Abstract

Non-destructive testing is nowadays becoming a basic inspection tool of industry. It serves an important role in many areas of development and manufacturing of products. These areas include product development, process control, flow detection, quality evaluation , measurement of mecha-nical and physical properties and product improvement. In this dissertation, essentials of piezoelectric transducer assembly required for ultrasonic non-destructive testing of materials have been described. Physical principles of such non-destructive testing techniques-and-notse--problems encountered in ultrasonic instrumentation systems have also been discussed. Two ultrasonic instrumentation systems viz, for flaw detection and for wall thickness gauging have been designed, developed and tested. Pulse-echo method which has been developed in the present work for flow detection system uses a single transducer assem-bly called probe, which acts first as emitter of ultrasonic pulses and then as a receiver to detect echoes from defects or other interfaces. Necessary signal processing is done at both, the transmitting and receiving ends of the probe. The signals are displayed on CRO,time sweep of which is externally driven from separately developed time base generator. Various •echoes obtained at the interfaces and/or flaw locations are displaced in time from transmitted signal indicating the presence or absense of flow• In the case if flaw is present it is possible to estimate its location from either of the ends. The pulsed transit-time method which is utilised in the present work for wall thickness gauging uses dual probe operation with one probe acting as a transmitter whereas another as a receiver. The duration between transmitted and received pulses which corresponds to the thickness of the object under test has been digitally measured and displayed on a seven segment LED display unit. Thickness of the object has been evaluated when number of counts displayed are multiplied by the acoustic velocity of the material.. The design details and test results of these schemes are also given. The test of the flaw detection system is carried out on a specially prepared specimen with artificial flew developed in. it.. The wall thickness gauge is calibrated for steel rods' measurement... The developed instruments operated with reasonable accuracy during testing. In the end suggestions for future work are given.