Electromagnetic testing emt-mft chapter 9b

Depth of decarburization was analyzed by varying the frequency of the
excitation field, thus changing the skin depth in the material. Experiments
were performed with both artificial samples containing two layers of different
carbon content and industrial samples in which carbon concentration varied
smoothly with distance from the surface. It was shown that certain features of
both Barkhausen noise and incremental permeability data can be correlated
with depth of decarburization. The Barkhausen noise method showed a
somewhat stronger sensitivity to depth, but was useful over a smaller range of
depths than the incremental permeability method. It can be concluded that
both methods are useful, with the optimum choice depending on accuracy
requirements and the expected depth of decarburization.
Charlie Chong/ Fion Zhang