Surface discontinuities only Generally only large discontinuities Misinterpretation of scratches

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Locate surface defects only Rough or porous surfaces interfere with test Part preparation required (removal of finishes and sealant, etc.) High degree of cleanliness required Direct visual detection of results required

Portable Inexpensive Sensitive to very small discontinuities 30 min. or less to accomplish Minimum skill required

MAGNETIC PARTICLE

Can be portable Inexpensive Sensitive to small discontinuities Immediate results Moderate skill required Detects surface and subsurface discontinuities Relatively fast

AJR Product Page

Surface must be accessible Rough surfaces interfere with test Part preparation required (removal of finishes and sealant, etc.) Semi-directional requiring general orientation of field to discontinuity Ferro-magnetic materials only Part must be demagnetized after test.

What is Ultrasonic Testing?

Similar to the ultrasonic principles used by an OB/GYN during pregnancy and naval SONAR, the ultrasonic non-destructive testing method uses high frequency sound waves traveling through a part to detect discontinuities. If the sound traveling through a part hits material with different acoustical impedance, some of the sound will reflect back. Once received by the sending unit, it will represent as an indication on the screen. Knowing the velocity at which sound travels through a part, along with the time of travel, will allow the technician to determine the distance to the indicated material with a change in acoustic impedance.

Sound waves are introduced to the part via a transducer made up of a piezoelectric crystal that converts electrical current to sound waves. The two most commonly used types of sound waves are Compression (Longitudinal or Straight Beam) and Shear wave (Transverse or Angle Beam).

What are the Advantages and Disadvantages of Ultrasonic Testing?

Advantages of Ultrasonic Testing Techniques:

• Portability
• Consistent
• Detects surface and subsurface defects
• Only limited access needed
• Instant results

Disadvantages of Ultrasonic Testing Techniques:

• Training is more extensive than other methods
• More expensive than other methods
• Difficult to use on thin materials
• Part Geometry can cause complications
• Needs relatively smooth surface to couple transducer
• Must know velocity of part and have a reference to calibrate against for equipment set-up

TXNDT facilitates an in-depth ultrasonic testing training course. Our sole aim is for trainees to receive quality ultrasonic inspection training.

If you want to learn more, please visit our website Ndt Flaw Detector.