Case Study: Subsurface Defect Analysis of Small Diameter Copper Rod

Two samples of solid copper rod of approximately .30” diameter were tested in a 3 wavelength (N: 3) resonance mode EMAT (RM-EMAT). Transducer ID was .410” nominal. One of the samples has had a .040” hole end drilled approximately 1.25” deep. This sample was tested on an ARIS lab unit hand fed through a variable diameter transducer mount. The resonant frequency was calculated for a copper rod of this diameter and verified by test.

 The first chart depicts the surface resonance of the “unflawed” surface of the end-drilled rod.

The Second chart depicts the second order resonance of this same rod. The end-drilled hole causes a complete loss of resonant activity in the sample approaching and over the location of the hole.

Two Screen plots of the ARIS unit were taken of the resonant signals of a separate .3” dia. rod with indicator holes approximately .042” dia. x .1” deep drilled transversely into the rod 

The first graphic is of normal resonance in an unflawed region

The second graphic depicts the decay or loss of resonance over one of these holes.