Experimental investigation into the size effect on the microscale fatigue behaviour of 316L stainless steel

Abstract This study focuses on the microscale fatigue properties of 316L stainless steel. This material is commonly used in the manufacture of medical devices such as stents, which, once implanted, are subjected to hundreds of millions of fatigue cycles. Fatigue testing was carried out on 50 μm, 75 μm, 100 μm and 150 μm 316L specimens with 60 μm thickness. A size effect was shown to exist in the form of a reduced fatigue endurance limit of the 50 μm specimens. In order to determine the cause of this size effect, the outer surfaces and fracture surfaces of failed test specimens were examined using Scanning Electron Microscopy (SEM) techniques. These SEM studies suggest that the process of strain localization was occurring in the specimens and was most pronounced in the 50 μm specimens. The experimentally established surface roughness of the test specimens, measured using white-light interferometry, further confirmed the SEM observation.