A new strategy to clarify the thickness effect on the fatigue crack growth rate in high‐strength steels

Abstract

It is generally recognized that the fatigue failure of the cracked engineering components is a crucial issue, especially considering the sample thickness effect. Although numerous methods have been proposed, it is still unclear about the sample thickness effect on the fatigue crack growth (FCG) rate of metallic materials. Based on the plasticity-induce crack closure and crack tunneling effect, we established an improved FCG model with a thickness factor T by the load analysis near the crack tip. The thickness factor could clarify the sample thickness effect on the FCG rate of high-strength steels. Numerous fatigue data demonstrates that the improved model displays a fairly good relationship between the sample thickness and FCG rate. It would provide a new strategy to the FCG rate prediction of cracked structures through small size specimen.

Investigation on the Fatigue Crack Growth Behaviors of AISI 4340 Steel with Different Strength–Toughness Combinations

“…The FCG rate tests were performed to follow the ASTM‐E647 standard method. So as to eliminate the influence of specimen size, [ 27 ] the standard CT specimen dimensions in this study are 10 mm in thickness and 40 mm in width, which are the same to those of 18Ni maraging steel. [ 25 ] The sinusoidal load‐controlled ( R = 0.1, f = 10 Hz) room temperature FCG rate tests were carried out on the Instron 8874 testing machine, and two specimens were tested in each state.…”

Subsurface fatigue crack tip strains in 7475‐T7351 aluminium alloy measured using stroboscopic neutron diffraction

“…9,10 However, the distribution of strain at the surface of a thick specimen can differ significantly from the distribution at the mid-thickness. Higher stress triaxiality occurs at this mid-thickness plane strain region, and since higher triaxiality normally favors crack growth in high-cycle fatigue, [11][12][13][14][15] this region may control the material's overall fatigue crack growth behavior. Secondly, these techniques only measure total strain, and it is not possible to isolate the elastic component of strain (i.e., the part that relates to the material's stress state) without additional assumptions.…”