Time of flight diffraction (TOFD)

Principle

The depth of the cracks of an aluminiumtest block with seven cracks of different depths (saw cuts) is determined with two methods. During the experiment, the cracks in the material are examined with the aid of the ultrasound angle beam probe and the depth of the cracks is determined with the aid of the signal amplitude and the TOFD method (time of flight diffraction). Both methods are compared based on their measurement results and in view of their performance and detection limits. The test block is scanned in accordance with the TOFD method as well as with a special probe combination so that the corresponding scan image of the crack distribution canb e generated.

Tasks

1. Determine the sound velocity of the shear wave in a test block for the crack depth determination with the angle beam probe based on the corner echoes at half and full skip distance.
2. Prepare a characteristic groove curve for the cracks of the aluminium test block for determining the crack depth based on the echo amplitude.
3. Determine the crack depths of the test block with the TOFD method and compare the results to the results of the echo amplitude method.
4. Scan the test object with a TOFD scanning head and analyse the cracks in the TOFD scan.

What you can learn about

• Non-destructive testing (NDT)
• TOFD method (time of flight diffraction)
• Ultrasonic diffraction
• Sound velocity
• Shear waves (transverse waves)
• Corner echo
• B-scan
• Preferential corrosion measurement

Documentation language: ENG

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