Slip and Crack Initiation Behavior of Carbon Steel Thin Films under Cyclic In-Plane Shear Loading

Abstract

In the same materials, film and bulk materials show different mechanical properties. Slip and crack initiation is rare in steel thin films. The slip that does occur is also dependent on the influence of the pearlite volume ratio and the film thickness directional constraint. The slip is reported to have an in-plane shear component and an out-plane shear component. Therefore, in this study we conducted fatigue tests under in-plane pure shear loading on specimens with steel films pasted to acrylic bar. As a result, two types of slips were observed: wavy slip and single linear slip and more wavy slip occurred in pure iron and S10C, while more single linear slip occurred in S45C. Crack initiation ratio and single linear slip initiation ratio showed similar increasing behavior. In addition, wavy slips in the grain were found to be in the out-plane direction, and a single linear slip in the grain was in the in-plane direction. Wavy slip (out-plane slip) is considered to occur only in ferrite that deformation is restrained by grains existing in the thickness direction. Single linear slip (in-plane slip) is considered to be caused by concentrated slip deformation or separation of slip planes in ferrite where plastic deformation is inhibited by hard pearlite, resulting in cracks.