Non-Destructive Test

Principles

Principles fo NDT-RAM

Detection

The Resonant Acoustic Method uses a form of the method called Resonant Ultrasound Spectroscopy, also popularly known as Resonant Inspection (RI). The ASTM E-2001-08 standard addresses resonant inspection.  NDT-RAM can detect imperfections such as variances in overall shape, weight, cracks, and density of parts. It can also detect if any process has been missed, such as a machine or heat treating process.

Unique Vibration Signature

Every part has its unique vibration signature (its resonant frequency). This resonance will be almost exactly the same from good part to part. However it will change when there is an internal or external change or imperfection.
Pipe organs, bells, carillons and xylophones are examples of how controlled incremental changes in a part create incremental changes in "resonance" or tone.
When a bell cracks however, it doesn’t have a clear ring, it is flat or dull sounding. It looses the ability to hold it’s Tone.
The same is true of a part that has a flaw.

Typical Time Response

Converting from Time Domain to Frequency Domain

Using a Fast Fourier Transform (FFT) process, the response signal is separated into discrete frequencies.

Typical Frequency Response

• Overview

• Analyze
• Equipment
• Advantages

• Powdered Metal Example Application

Back to NDT