Ultrasonic testing-UT

Ultrasonic testing (UT)

Ultrasonic material inspection is one of the most popular non-destructive testing methods for inspecting internal discontinuities, high frequency ultrasonic waves are transmitted into the material under test. Most ultrasonic testing methods are performed in the 0.5 – 20 MHz frequency range. This frequency is much higher than the human hearing frequency range of 20Hz – 20KHz. Ultrasonic waves propagate through a material accompanied by a loss of energy (attenuation) due to the properties of the material. The intensity of the sound wave is measured either after reflection (pulse echo) at the interfaces (defects) or measured at the opposite surface of the test object (transmission pulses). The reflected sound wave beam is detected and analyzed to determine the presence of the defect and its location. The degree of reflection depends heavily on the physical properties of the material, the reflective surface, for example, ultrasonic waves are reflected almost completely at the metal-gas interface. Partial reflection at the metal-liquid interface or metal-solid. Ultrasonic material inspection has a greater penetration depth than radiographic inspection and we can detect cracks deep inside the object (about 6-7 m deep inside the steel block). ). It is also very sensitive to minor defects and allows precise determination of the location, size and nature of the defect. The basic principle of the ultrasonic inspection method is shown in Figure 4.8. Ultrasonic material inspection has a greater penetration depth than radiographic inspection and we can detect cracks deep inside the object (about 6-7 m deep inside the steel block). ). It is also very sensitive to minor defects and allows precise determination of the location, size and nature of the defect. The basic principle of the ultrasonic inspection method is shown in Figure 4.8. Ultrasonic material inspection has a greater penetration depth than radiographic inspection and we can detect cracks deep inside the object (about 6-7 m deep inside the steel block). ). It is also very sensitive to minor defects and allows precise determination of the location, size and nature of the defect. The basic principle of the ultrasonic inspection method is shown in Figure 4.8.

 Ultrasonic material inspection method:

(1) Mostly used to detect defects in materials.

(2) Widely used in thickness measurement and delamination test.

(3) Used to determine the mechanical properties and grain structure of materials.

(4) Used to evaluate the transformation of materials.

Some advantages of ultrasonic inspection method:

(1) Has high sensitivity to detect small defects.

(2) High penetration capacity (up to 6 -7 m deep inside the steel block) allows inspection of very thick sections.

(3) High accuracy in determining the location, size and nature of defects.

(4) Gives quick response thus enabling fast and automated testing.

(5) Only one side of the object to be tested needs to be exposed.

Limitations of the ultrasound method:

(1) The shape of the test object can make inspection work difficult.

(2) Difficult to test materials with complex internal structure.

(3) This method requires the use of a coupling agent.

(4) The probe must be in proper contact with the sample surface during the test.

(5) The direction of the defect has an effect on the defect detection ability.

(6) Equipment is very expensive.

(7) Inspection personnel need to have a lot of experience.

Video clip for reference:  https://www.youtube.com/watch?v=1aA-qdOfWDw