Inline Inspection of Wire and Rod


Electromagnetic Acoustic Resonance testing is ideal for defect detection in wire, rod, and small diameter tubing. Resonic leverages its experience inspecting high value fasteners and automotive components to bring new insight and new detection capabilities to producers of those stock materials. A localized acoustic resonance technique offers better defect sensitivity in a smaller equipment footprint. Users of rotary eddy-current systems for in-line seam detection will discover a number of distinct benefits in EMAR.

  • Surface and subsurface flaw detection: cracks, seams, scabs, inclusions, and more
  • Materials: ferrous alloys, non-ferrous alloys, electrically conductive composites
  • Drawn shapes: Round, flat, square, hexagonal, etc.
  • Sizes: 2mm up to 0.75" diameter or equivalent thickness



Resonance fields in a test of wire are both localized and through thickness which offers surface and sub-surface sensitivity in the same test. Surface defects, seams, and internal flaws will cause a normally stable resonance signal to attenuate through the scattering of acoustic waves in the presence of the discontinuity. Simultaneously, even gradual changes in material heat treatment, hardness, or alloy composition will be detected as changes in the frequency of the same resonance signal. The full cross-section of the wire or rod is in resonance with a combination of compressional and shear waves. The wave path of travel through the material is not mono-directional which makes the technique ignorant of the directionality or shapes of defects to be detected.


Test Process

Inside of a rigid or flexible test fixture, 2 EMAT probes are oriented near the surface of the wire 180 degrees opposed. The sensors remain stationary and the length of wire is passed directly between them at a rate of up to 6 in/sec. The active measurement area for wire and rod testing can be imagined as a full cross-sectional cylinder which is slightly longer than the diameter of the probe face, 0.25-.375" depending on the size of the test material. Natural resonant modes are excited and detected at 6-8ms intervals in a narrow frequency band within the range of 2-6 mHz. Defects are automatically identified by observed changes to the modal signature of the wire. In certain cases the type and size of defect can also be identified.

Individual test systems are configured based on a balance of target defect size, test material properties, EMAT selection and line speed. Off-line system configurations are also available for manual feed or fully automated cut-length rod inspection.



  • 5000 Series ARIS Signal Processing Unit
  • LCD display and keyboard
  • Single pair EMATs: Bulk-wave Pencil Probe or compact SH-wave type
  • Passive wire testing fixture or power feed bar testing fixture
floating wire test fixture power feed bar test fixture
Passive and floating EMAT Fixture for continuous wire inspection. Servo driven bar feeding fixture, maintains precision line speed and eliminates material bending during the test.