Phased Array

Tim ARMITT, Lavender International NDT, Sheffield, UK

Abstract. Phased Array has been the buzz for the last few years within the

NDT world but is it any good? We frequently read papers on applications or

receive literature from suppliers of equipment expressing the excellence of

ultrasonic phased array technology but seldom does any of this contain

information as to limitations of phased array technology.

This presentation has been prepared from a realistic perspective giving a

practical insight into the world of phased arrays and discusses the usefulness

of this technology including clarification of misnomers found throughout our

industry.

1. Introduction

Phased arrays have been banded about for some time now but few people know that

the first phased array unit was actually patented in 1959. The medical industry has

been pioneering many of our industrial imaging systems for years and phased arrays

are no exception. Our industry however has been relatively slow to grasp the new

technology, most of which can be attributed to two main factors, computer power and

cost! Only this last decade have we more readily been utilising the phased array

technology to expedite inspection solutions previously unobtainable.

Thanks to our medical colleges and some large industrial organisations we are

now able to obtain at reasonable cost detection capabilities and imaging solutions that

may revolutionise the way we perform NDT. This of course sounds great but is this

real or just the fantasy of a brilliant marketing machine?

This paper is aimed at giving a balanced assessment of phased array

technology from a non-sales bias and pointing out some typical misconceptions that

some of our NDT fraternity circulate. The paper will guide you through some of the

myths, misnomers and terminology that surround the ‘black art’ of ultrasonic phased

array technology.

2. One scan sees all

Firstly one myth that unfortunately has been used by some individuals is that use of

one swept angle (other wise known as sectorial) scan ranging though a wide range of

angles can detect all defects in a component or weldment in one single line pass from

either side of the joint! This simply is not true! Phased array technology is not

changing the laws of physics but merely exploiting some