Fatigue life improvements of the AISI 304 stainless steel ground surfaces by wire brushing |
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Authors: | Nabil Ben Fredj Mohamed Ben Nasr Amir Ben Rhouma Habib Sidhom Chedly Braham |
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Affiliation: | (1) Laboratoire de Mécanique, Matériaux et Procédés, LAB-STI-03, ESSTT, 5, Avenue Taha Hussein, 1008 Tunis, Tunisia;(2) Laboratoire de Microstructure et Mécanique des Matériaux, ENSAM, CNRS ESA 8006, 75013 Paris, France |
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Abstract: | The surface and subsurface integrity of metallic ground components is usually characterized by an induced tensile residual
stress, which has a detrimental effect on the fatigue life of these components. In particular, it tends to accelerate the
initiation and growth of the fatigue cracks. In this investigation, to deliberately generate compressive residual stresses
into the ground surfaces of the AISI 304 stainless steel (SS), wire brushing was applied. It was found that under the experimental
conditions selected in this investigation, while the surface roughness was slightly improved by the brushing process, the
surface residual stress shifted from a tensile stress (σ‖=+450 MPa) to a compressive stress (σ‖=−435 MPa). On the other hand, the work-hardened deformation layer was almost two times deeper after wire brushing. Concerning
the fatigue life, an improvement of 26% in terms of endurance limit at 2×106 cycles was realized. Scanning electron microscope (SEM) observations of the fatigue fracture location and size were carried
out to explain the fatigue life improvement. It was found that the enhancement of the fatigue strength could be correlated
with the distribution and location of the fatigue fracture nucleation sites. Concerning the ground surfaces, it was seen that
the fatigue cracks initiated at the bottom of the grinding grooves and were particularly long (150–200 μm). However, the fatigue
cracks at the brushed surfaces were shorter (20–40 μm) and appeared to initiate sideways to the plowed material caused by
the wire brushing. The results of the wire-brushed surface characterization have shown that significant advantages can be
realized regarding surface integrity by the application of this low-cost process compared to shot peening. |
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Keywords: | fatigue life grinding residual stress wire brushing |
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