Mechanism of fine granular area and white etching crack formation in AISI 52100 bearing steel
THEORETICAL AND APPLIED FRACTURE MECHANICS
Authors: Averbeck, Stefan; Spriestersbach, Daniel; Kerscher, Eberhard
Abstract
Fine Granular Area (FGA) and White Etching Cracks (WEC) are two types of fatigue damage phenomena which are characterised by the development of cracks accompanied by a local microstructural transformation. The resulting microstructures share many properties, chiefly a strong reduction in grain size. In this study, the thickness of the transformed zones along the crack formed during FGA and WEC experiments is investigated. It is shown that in WEC, similar to earlier results on the FGA, the size of the transformed zones increases with increasing crack length. For further analysis of the more complex WEC case, an approach is presented that uses the results of a critical plane analysis for the calculation of key figures in fracture mechanics. The results are shown to be very similar to those of the FGA. Drawing on these and earlier results, it is proposed that a common mechanism of WEC and FGA formation exists. In addition, some important differences of the two phenomena are explained within the framework of the common mechanism.
Gravity anomalies and lithospheric flexure around the Longmen Shan deduced from combinations of in situ observations and EGM2008 data
EARTH PLANETS AND SPACE
Authors: She, Yawen; Fu, Guangyu; Wang, Zhuohua; Liu, Tai; Xu, Changyi; Jin, Honglin
Abstract
The current work describes the combined data of three field campaigns, spanning 2009-2013. Their joint gravity and GPS observations thoroughly cover the sites of lithospheric flexure between the Sichuan Basin and the Eastern Tibetan Plateau. The study area's free-air gravity anomalies (FGAs) are updated by using a remove-and-restore algorithm which merges EGM2008 data with in situ observations. These new FGAs show pairs of positive and negative anomalies along the eastern edges of the Tibetan Plateau. The FGAs are used to calculate effective elastic thickness (T-e) and load ratios (F) of the lithosphere. Admittance analysis indicates the Te of Longmen Shan (LMS) to be 6 km, and profile analysis indicates that the T-e of the Sichuan Basin excesses 30 km. The load ratio (F-1 = 1) confirms that the lithospheric flexure of the LMS area can be attributed solely to the surface load of the crust.