|About this Abstract
||2016 TMS Annual Meeting & Exhibition
||Fatigue in Materials: Fundamentals, Multiscale Modeling and Prevention
||What Causes the Formation of Crack Initiation Characteristic Region for Very-High-Cycle Fatigue of Metallic Materials?
||Youshi Hong, Xiaolong Liu, Zhengqiang Lei, Chengqi Sun
|On-Site Speaker (Planned)
For high-strength steels, the crack initiation of very-high-cycle fatigue (VHCF) is commonly at material interior with the morphology of fish-eye (FiE) containing a rough region of fine granular area (FGA) surrounding an inclusion as crack origin. In this paper, we carefully examined the FGA and FiE regions for a high-strength steel subjected to rotary bending by TEM and SEM. The observations reveal that the nature of FGA is a thin layer of nano-sized grains. We propose the formation mechanism of FGA is due to numerous cyclic pressing (NCP) at originated crack surfaces. The results of a second set investigation (for a similar material with ultrasonic axial cycling at stress ratios of R=‒1, ‒0.5, 0.1 and 0.3) show that the cases of negative stress ratios exhibit nanograin layer in FGA region and this tendency vanishes for the cases of positive stress ratios, which verifies the proposed NCP model.
||Planned: Publication Outside of TMS (Indicate publication title and publisher if known.)