Influence of the magnetising field frequency and the analysis frequency bands on Barkhausen measurements to improve grinding burn detection and induction hardened layer depth characterization

Speaker:
Lasaosa, Aitor; CEIT, University of Navarra; Spain

Authors:
Lasaosa, A.; CEIT; Spain
Gurruchaga, K.; CEIT; Spain
Arizti, F.; CEIT; Spain
Martinez-De-Guerenu, A.; CEIT; Spain

ID: ECNDT-0184-2018
Download: PDF
Session: Magnetic Methods - Barkhausen 1
Room: R2
Date: 2018-06-11
Time: 14:30 - 14:50

The magnetic Barkhausen noise (MBN) is emitted from few micrometres up to several millimetres below the surface of the sample depending on the frequency of the magnetisation waveform and on the acquisition frequency band of the MBN. Additionally, the envelope of the MBN signal can present several peaks when several layers of ferromagnetic materials with different magnetic properties are present in the analysed region.

In this work, samples with an induction hardened layer and a final grinding process are studied. During the grinding, a superficial defect called grinding burn can happen and produce a three-layer structure. The upper layer contains the hardened layer affected by the grinding burn (which can present softer or harder hardness or more tensile residual stresses than samples without grinding burns), the second layer presents the hardened layer not affected by the grinding burn and the third layer or core, corresponds to the soft material.

MBN envelopes obtained from induction hardened samples with and without grinding burns using different magnetisations and acquisition configurations, are analysed. Different magnetisation frequencies are applied and the MBN signal is analysed in several frequency bands. With these configurations, more knowledge of the relation between the magnetisation and acquisition configurations and the layers present in the material can be obtained. As a result, an improvement of both the grinding burn detection and the characterisation of the induction hardened layer is obtained.