How NDT-RAM Works
NDT-RAM Systems

The Resonant Acoustic Method uses a form of the method called Resonant Ultrasound Spectroscopy, also popularly known as Resonant Inspection (RI). 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.  Resonant frequencies are determined by dimensions and material properties of the “whole part”.

A Structural Defect results in an out-of-specification condition for dimensions or material properties – 
e.g., a crack reduces stiffness and therefore lowers the resonant frequency.

Degree of shift in resonant frequency correlates to degree of defectiveness.

Resonances Evaluate the Whole Part
no scanning - no indications

Principles

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

The result is a Response Frequency Spectrum that is unique to your part. Using this spectrum, we can look for changes in your parts.

Component A (good)

The principal properties of an object are:
· Mass
· Stiffness
· Damping

If the Mass, Stiffness, or Damping in a component are varied, the response characteristics of an impact will vary.

Component A (flawed)

How NDT-RAM works