Ultrasonic Phased Array Testing
The ultrasonic phased array testing method is an advanced non-destructive testing method used in the industrial field. Single-element probes, called monolithic transducers, emit a beam in a fixed direction. To test a high-volume material, a conventional probe must be physically moved or rotated to scan the beam throughout the area of interest.
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.
Using Ultrasound Waves for Thickness Measurement
Ultrasonic waves propagate in a given material at a specific speed. A sample of the same material and of known thickness is used to calibrate the thickness gauge. An ultrasonic wave is emitted by a mono- or bi-element longitudinal wave transducer through the material and is reflected by the opposite face of the wall.
After a penetration time of 15 to 20 minutes at room temperature, the excess penetrant is removed by washing. After drying, a white developer is applied to the surface to be tested. The penetrant contained in the possible defects then bleeds out into the developer. Defect images appear immediately or up to 30 minutes after applying the developer.
Magnetic Particle Testing
Magnetic particle testing consists in subjecting the area to be tested to the action of a continuous or alternative magnetic field. Possible defects create a leakage field at the surface of the component. This leakage field is made visible to the human eye using a very fine ferromagnetic powder sprayed onto the surface to be examined, where it is attracted at right angles to the defects by the magnetic forces.
Visual testing is the simplest and foremost testing procedure. It must precede any other type of investigation. It consists in examining the surface of the materials, welds, and equipment with the naked eye under satisfactory lighting conditions and at the appropriate distance.