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Ultrasonic NDT

Friction Weld Inspection

Published on 4th January 2021

Friction Weld Inspection

Friction welding is a solid-state welding process that generates heat through mechanical friction between two work-pieces in relative motion to one another with the addition of a lateral force called “upset” to plastically displace and fuse the materials. This process is commonly used on cylindrical metal or thermoplastic components in aviation and automotive applications.

Typical signal response

The following are outputs from a TOFD inspection demonstrating a good weld, side drilled hole and two flaws.

No Flaw

Side Drill Hole

No Fusion / Stick Weld

Lack of Fusion / Side Crack

There are three potential inspection methods:

  • Conventional single compression probe. This is the simplest method but requires the shaft end to be accessible.
  • Tandem Pitch & Catch. Two conventional probes on angled wedges are used. A good method but more difficult to achieve satisfactory results.
  • Time of Flight Diffraction (TOFD). This is the best method utilising pitch and catch probes on each side of the weld.


Although all three methods can be utilised for such applications, the end of the shaft and the TOFD approach are favoured compared to the tandem pitch & catch method due to the display advantages, the pace in data interpretation and improved repeatability. Inspection can be automated using SDK (software development kit) when using Sonatest VEO+ or Prisma platforms.


  • Oil & Gas
  • Aerospace
  • Automotive

Typical Parts

  • High pressure pipes
  • Metal rods
  • Thermoplastic rods
  • Shafts
  • Billets

Technical Inspection

  • Pulse echo
  • Pitch & catch
  • TOFD
  • Go-NoGo
  • Encoded data

Additional application verification / validation may be required for specific test samples. For further information or support, please contact the Sonatest Applications Team:


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