Effect of the cutting technique on the residual stress distribution of cut edges in FeSi3 transformer sheets

Abstract

Samples of laser-scratched FeSi3 transformer sheets have been investigated. The investigations were carried out by using the Kossel and EBSD techniques in our self-designed multifunctional system. The results show residual stress mappings of the cut edges of FeSi3 transformer sheets and their dependence on the cutting process (conventional plate shears, abrasive water-jet technique, laser cutting).

Experimental study of the impact of punching operations on the high cycle fatigue strength of Fe–Si thin sheets

“…Finally, a burr is observed at the bottom of punched edges because of the metal elongation resulting from the separation into two pieces. This morphology has been observed by various authors on steel sheets with different thicknesses ranging from 0.5 to 15 mm [2,6].…”

“…Large plastic strains, because they result in an increase of the concentration of crystalline defects (e.g. dislocations), are generally responsible for a deterioration of both magnetic [3][4][5] and mechanical properties [6,7] including fatigue strength. Finally, important residual stresses, which significantly affect fatigue resistance, may exist because of punching [8][9][10].…”

High Cycle Fatigue Strength of Punched Thin Fe-Si Steel Sheets

“…2: the roll-over, the sheared zone, the fracture zone and the burr. The same morphology has already been observed by several authors on thicker steel sheets after punching, e.g., on 15 mm and 0.5 mm thick sheets [2,3]. To evaluate the influence of punching operations, some fatigue tests were performed on specimens with polished edges.…”

“…Since rotors are subjected to cyclic loadings, safely designing electrical machines against fatigue failure requires the understanding of the influence of punching operations on the fatigue behavior of Fe-Si thin sheets. As shown in different studies [1][2][3][4][5], important geometrical defects resulting from punching operations are observed on edges. Such defects, because they can be considered as potential fatigue crack initiation sites, are partly responsible for a degradation of the fatigue strength.…”

“…Such defects, because they can be considered as potential fatigue crack initiation sites, are partly responsible for a degradation of the fatigue strength. Also, in addition to geometrical defects, the punching process locally induces both hardening and residual stresses on the edge [3,4,[6][7][8]. These phenomena are observed on either thick (15 mm) or thin (0.23 mm) sheets and contribute to an important degradation of the fatigue resistance [1,2].…”