An engineer uses an ultrasonic flaw detector to inspect a steel railway axle. A short ultrasonic pulse is sent from one end of the axle along its length. A second pulse is received by the detector after a total time of 120μs. The speed of sound in steel may be taken as 5.0×103ms−1.
a. (i) Calculate the distance from the detector to the reflecting flaw inside the axle.
b. (ii) Explain briefly why two separate pulses (instead of one) are observed on the detector screen when a flaw is present.
c. (iii) State two advantages of using ultrasound rather than dismantling the axle for internal inspection.