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

Abstract

a b s t r a c tIn this paper, the impact of punching operations on the high cycle fatigue strength of Fe-Si thin sheets is investigated. High cycle fatigue tests are performed on both punched and polished edge specimens. Results show a significant decrease of the fatigue strength in the case of punched specimens. Different factors are found to be responsible for this degradation. First, according to SEM observations of fracture surfaces and to 3D surface topography, fatigue crack initiation is strongly governed by the geometrical defects resulting from punching operations. Second, important tensile residual stresses, which are analyzed using X-ray diffraction techniques, are observed on punched edges. Depending on the loading conditions, it is possible for the residual stress field to be redistributed as a result of cyclic plasticity.

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

“…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].…”

A non-local approach to model the combined effects of forging defects and shot-peening on the fatigue strength of a pearlitic steel

“…• Microstructure Surface integrity is very dependant on the process being used, so studies on this subject usually focus on a specific process: machining [1,2,3], stamping [4], punching [5]. A large number of papers also deal with the impact of localised natural or artificial defects on fatigue strength.…”

Experimental study of the impact of geometrical defects on the high cycle fatigue behavior of polycrystalline aluminium with different grain sizes

“…In metallic alloys, defects can originate from material elaboration [1], manufacturing processes [2,3] or foreign-object impacts [4]. These defects have either 4 a geometrical (e.g.…”