PSI - Issue 13

Tatiana Oršulová et al. / Procedia Structural Integrity 13 (2018) 1689–1694 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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materials in one graph. This comparison showed non-linear dependences between applied plastic deformation and the intrinsic magnetic field response. In fact, this is also in correlation with theory, which describes this phenomenon from the material engineering point of view. Based on the results, it can be concluded that the most suitable material for nondestructive evaluation purposes is AISI 304. Generally, all of the inspected materials can be evaluated, but with respect to the sensitivity of the sensor and the deformation level.

Fig. 3 Experimental results: residual magnetic field - maximum module gained values

b)

a)

Fig. 4 Results from device Magnet Physik: a) comparison of magnetic properties of investigated steels in initial state; b) magnetic properties of the AISI 304 after different degrees of deformation

Measurements realized on device Magnet Physic have demonstrated that from three chosen materials, only one has got significant magnetic behavior - the AISI 304. It is caused by the presence of plastic deformation after previous forming in evaluated material. This measurement failure was also caused by the low sensitivity of the measuring device; it is possible to measure only specimens with stronger magnetism. On the other hand, this device was able to record the results from slightly magnetic steel AISI 304. Fig. 4b) shows significant increase of magnetism after the plastic deformation.

5. Conclusion

This article presented a study of electromagnetic nondestructive evaluation of austenitic stainless steels after previous plastic deformation. Three different steel grades were evaluated with presence of the seven specific levels of the plastic deformation. The commercially available 1D GMR sensor was used in the first step of research. Each of the 3D coordinate systems components was sensed, so the sensor was rotated three times for the scanning