期刊
ENGINEERING FRACTURE MECHANICS
卷 174, 期 -, 页码 127-138出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.engfracmech.2016.12.007
关键词
Threshold stress intensity factor range; Shear-mode fatigue crack; Static crack-opening stress; Crack path; Bearing steel
类别
资金
- NSK Foundation for the Advancement of Mechatronics
An investigation was conducted into the influence of statically-applied, mode I, crack opening load on the threshold condition for propagation of a shear-mode fatigue crack in a bearing steel. Torsional fatigue test was carried out at an R of -1 using a hollow cylindrical specimen into which a semi-elliptical, small slit was axially introduced. A static axial compressive stress was simultaneously applied to suppress crack branching. A coplanar, shear-mode, non-propagating fatigue crack emanating from the slit was attained by appropriate control of shear stress amplitude. Internal pressure was then applied to generate a hoop stress as a static crack-opening stress, sigma(theta) (static) Consequently, the threshold shear-mode stress intensity factor range, Delta K-tau th, was significantly decreased with increase of the static mode I stress intensity factor. To further understand the contribution of ao static to the reduction in Delta K-tau th, microstructural observations for the cross-sections of a non-propagating crack were conducted using a scanning electron microscope in conjunction with the electron backscatter diffraction analysis. The results revealed that the excess loading of 60 static accounts for the change in the crack-path, resulting in a further reduction in Delta K-tau th. (C) 2016 Elsevier Ltd. All rights reserved.
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