Evaluation of residual stresses and plastic deformations for iron-based materials by leakage magnetic flux sensors

The purpose of this paper is to present the results of stress damage observation using a giant magnetoresistive sensor and a high performance measuring system. Selected digital signal processing algorithms were applied in order to enhance the obtained signals and extract parameters suitable for quantitative stress evaluation. The experimental verification of the developed technique is done and the selected results are presented.

Evaluation of stress loaded steel samples using GMR magnetic field sensor

The magnetic leakage flux, multifrequency eddy current and Barkhausen noise methods were used to evaluate changes in materials properties induced by stress. Seven samples made of ferromagnetic low carbon steel with different stress level were prepared. The results showed tensile deformed samples at room temperature with a yield at around 350 MPa, residual strain between 0.7% and 14% and tensile stress from 100 MPa to 389 MPa.

Fusion of electromagnetic inspection methods for evaluation of stress loaded steel samples

Magnetization processes in iron-based materials with edge dislocations were simulated using Monte Carlo method for the purpose of analyzes of the magnetic nondestructive evaluation. RKKY-type exchange interaction was assumed in this simulation using the Heisenberg Hamiltonian of the metal magnetism. The temperature and magnetic field dependence of magnetization were calculated for spin cell system of 31/sup 3/=29791 with some edge dislocations. We found anisotropic influences of edge dislocations on magnetic domain formations.

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Monte Carlo simulation for magnetic materials including dislocations

Monte Carlo simulations of the dynamic magnetic processes were performed for spin systems with various lattice imperfections. From a physical point of view, the presented method might be the more useful tool for the analysis of the magnetic processes rather than those by Preisachs model.

Monte Carlo simulation of dynamic magnetic processes for spin system with local defects

Nondestructive evaluations of iron-based material (A533B) have been investigated on the leakage flux from the surface by using Hall elements, on magnetic noises, on sub-micron deformations by Ar-laser speckle interferometry and on residual stresses by X-ray diffraction. A high resolution and high sensitivity for spatial inhomogeneity observation were attained as small as 200μm for residual strains less than 0.5 %.

Sinnichi Shoji

Papers

Nondestructive Cross Evaluations of Iron-based Material by Magnetic Sensors and by Laser Speckle Interferometry