AUTOMATION of ULTRASONIC TESTING PROCEDURES

INTRODUCTION Automation of ultrasonic testing procedures is a kind of non-destructive testing procedures, which is involves the use of both longitudinal and transverse high-frequency sound waves for the exploration and/or mapping of both surface and sub-surface defect or irregularities. Of course the material thickness or the material loss (corrosions/ erosions) can also be observed by the concept of feed back echo of the ultrasonic wave. Easily using the ultrasonic beam produced by the ultrasonic testing machine, we can locate down the position where the deformation occurred and hence progress a more detail observation. This technique are widely used for the quality control inspection for the finished component such as seam weld of a steel plate, as well as for the inspection of part processed material. The technique is also used for the in-service testing of parts and assemblies as well as on-site testing for the respective structures. Basically the objectives of this project is to perform a typical automation of ultrasonic testing procedures, which aims to: 1. Determine the location of defects in the specimen 2. Determine the size of defects in the specimen 3. Determine the acceptability of the defects (interference) in the specimen The range of the frequency of audible sound is between 10Hz to 20KHz. The sound waves have a frequency higher than 20KHz are referred as ultrasonic or ultrasound. However the sound waves used for non-destructive testing of materials are usually having a frequency range of 0.5MHz to 20MHz. By using the equation V=λf, which λ is referred to wavelength and f is referred to the frequency of the wave, it can be known that ultrasonic waves have an extremely short wavelength and strong penetrating power. For example if a defect in a material is expected equal to 0.30mm, the ultrasonic beam used in the testing procedure must have a wavelength smaller than 0.30mm. When a normal (90ْ) ultrasonic beam travel through the interface of two different media, reflection and transmission occur due the acoustic impedance Z1 Z2. Therefore, any discontinuity inside a uniform material will be detected because of the different time feedback echo of the ultrasonic waves. By using an ultrasonic flaw detector, the defect signal can be screened on a cathode ray oscilloscope so the location and the size of the defect can be observed in order to produce further analysis. Fig 1 is a typical graph obtains from a CRT using ultrasonic flaw detector.