Abstract
This study presents the fatigue response of 304 stainless steel foil, cold-rolled to a thickness of 3.2 μm with 87 percent cold work at orientations of 0, 45, and 90 degrees to the direction of rolling. Fatigue specimens were fabricated by laminating a supportive layer of 20-μm polyimide film to one side of the foil and patterning 242 crack initiation features by photolithographic process. Progression of fatigue damage was determined through electrical resistance measurement. The fatigue response was demonstrated to be largely affected by anisotropy existing between the rolling direction and the off-axis orientations. Fatigue cracks that traveled in a direction parallel to the elongated grains (cyclic loads applied at 90-degree orientation to foil rolling direction) had the most fatigue response (undesirable characteristic). The construction of the specimens with thin foil supported by a film backing contributed to high fatigue threshold.
Highlights
Fatigue test results can be sensitive to a number of factors including test method, surface finish, notch sensitivity, etc
This study presents the fatigue response of 304 stainless steel foil, cold-rolled to a thickness of 3.2 μm with 87 percent cold work at orientations of 0, 45, and 90 degrees to the direction of rolling
Fatigue cracks that traveled in a direction parallel to the elongated grains had the most fatigue response
Summary
Fatigue test results can be sensitive to a number of factors including test method, surface finish, notch sensitivity, etc. One conservative design rule suggests 304 stainless steel be assigned an endurance limit of about 240 MPa or about 50 percent of the ultimate tensile strength [1]. The cold rolling process can increase the tensile strength of the material and the fatigue strength has been reported to be considerably greater than the design rule. One study reported 300 μm thick cold-rolled strip had an endurance limit of about 600 MPa [2].
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