Eddy current testing

A test procedure to eliminate the finest cracks in the screw head.
Eddy current testing is an electrical method for non-destructive testing for the finest shear and hairline cracks in electrically conductive screws. In our eddy current machines, an alternating magnetic field is generated by a coil, which induces eddy currents in the head of the screw to be tested.
The induced magnetic field causes the current to flow evenly in the head of the screw. If there is a crack in the head, this represents a material separation, as a result of which the eddy currents must flow around the crack. This leads to a deflection of the amplitude, whereby screws with this defect pattern are reliably rejected.

Eddy current test method
The screw to be tested is gripped at the top and bottom by the automatic testing machine and rotated 360° in front of the eddy current probe. The probe is positioned at the height of the bolt head so that an alternating magnetic field can be generated on the bolt head. Eddy currents are then induced in the head of the screw.
For this comparative measurement, our customers ideally provide poor samples in order to calibrate the automatic testing machine to the defect and adjust the sensitivity of the eddy current unit so that an optimum result can be achieved.
This crack test enables us to guarantee a 10 ppm purity for this test characteristic.

The screw is rotated in front of the probe.