Detection of Grinder Burn Area on Surfaces of Ferromagnetic Material by Eddy Current, Barkhausen Noise and Multi Technical 3MA Methods

Decitre, Jean-Marc; CEA Saclay; France

Decitre, J.-M.; CEA, LIST; France
Delabre, B.; CEA, LIST; France
Zhang, F.; CETIM; France
Samet, N.; CETIM-CERMAT; France

ID: ECNDT-0502-2018
Download: PDF
Session: Magnetic Methods - Barkhausen 1
Room: R2
Date: 2018-06-11
Time: 14:10 - 14:30

One of the issues in Nondestructive Testing by electromagnetic technique concerns its high sensitivity for detecting surface defects, or defects close to the surface in conductive materials, both nonmagnetic and ferromagnetic. These examinations are commonly used in many industrial sectors such as aerospace, energy and metallurgy.
A new recurrent request from industry concerns the non-destructive characterization of mechanical properties such as hardness or residual stress, which may occur after bad heat treatment or due to heating during operation. The classical applications are gears in turbine, motors and compressors. Thanks to a link between electromagnetic properties (conductivity, permeability, a hysteresis loop of material) and mechanical properties, electromagnetic methods are candidates to this study.
In this paper, the application deals with plate mock-ups in ferromagnetic material, representative to material used for gears. These mock-ups include grinder burn area with different intensities obtained by appropriate rectifications. Two principal techniques are used. First, Barkhausen noise is evaluated, thanks to a 3MA device, and seems particularly well-suited due to its sensitivity to the microstructure and the stress. Secondly, the Eddy Current (EC) technique is implemented. The EC pattern is optimized thanks to the CIVA platform to obtain, on the one hand a straight response in the complex plane for electrical conductivity variations, and on the other hand a huge sensitivity to the material’s conductivity.
The conclusion is that the behavior of the EC signal in function of the burning intensity is similar to Barkhausen noise and 3MA data, and that the EC signal and hardness are in good correlation.