Mid Sweden University

Ultrasonic non-destructive testing are widely used in many branches of the indus-

try for measurements of materials characteristics.  In some cases there is a need

for  ultrasonic  transducers  to  measure  at  higher  temperatures,  but  these sensors lack proper sensing quality at elevated temperatures.  With the years it has been developed  several  approaches  to  make  ultrasonic  transducers  able  to  measure  at higher temperatures.

During this thesis an ultrasonic transducer with a delay line will be used to measure

thickness of a steel pipe at temperatures up to 300C, the delay line will work as a

temperature estimator and use the estimated temperature to compensate measure-

ment errors which is created from higher temperatures.  A measurement system is

created to make the ultrasonic transducer gather thickness and temperature data,

this system will then be placed inside ovens for testing.

At  higher  temperatures  a  problem  with  high  attenuation  of  signal  occurred  due to bad coupling and made it hard to find thickness values,  but the temperature

estimations showed good results at stable temperatures.