Ultrasonic Testing

Ultrasonic Testing

INSPECTION AND TESTING METHODS

Principle

Ultrasounds are mechanical waves generated from a piezoelectric element excited at a frequency comprised, for many applications, between 2 and 5 MHz. This element is often fixed to a plastic sole on one side and to a shock absorber on the other side, constituting together what is called the transducer.

The ultrasound waves are transmitted in the component to be tested through a coupling medium and propagate at a speed which depends on the material.

When the ultrasonic waves encounter a defect favourably oriented with respect to the incident wave, an echo returns to the transducer. This reflected mechanical energy is transformed into an electrical signal by the piezoelectric element and is displayed as an echo on the visualization system of the ultrasonic device. The position of the echo makes it possible to determine the depth of the indication in the component as well as appreciate whether it is two- or three-dimensional.

Advantages

• Access to only one side of the component is required.
• Highly sensitive for the detection of flat defects.
• The position of the detected indications is located within the thickness.
• Estimation of the size of an indication using its reflecting power (reflection testing) or the degree of attenuation (transmission testing).