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Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing, UT

Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing

Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing

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Attenuation can be determined by evaluating the multiple backwall reflections<br />

seen in a typical A-scan display like the one shown in the image at the bottom.<br />

The number of decibels between two adjacent signals is measured and this<br />

value is divided by the time interval between them. This calculation produces<br />

a attenuation coefficient in decibels per unit time Ut. This value can be<br />

converted to nepers/length by the following equation.<br />

Where v is the velocity of sound in meters per<br />

second and Ut is in decibels per second.

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