Very high cycle fatigue crack initiation in electroplated Ni films under extreme stress gradients

2012 ◽  
Vol 67 (1) ◽  
pp. 45-48 ◽  
Author(s):  
E.K. Baumert ◽  
O.N. Pierron
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Fatigue Crack Initiation ◽  
Cycle Fatigue ◽  
Stress Gradients ◽  
Extreme Stress ◽  
Very High Cycle Fatigue ◽  
Very High

On Fatigue Crack Initiation in the Matrix in Very High Cycle Fatigue Regime

2014 ◽  
Vol 783-786 ◽  
pp. 2266-2271 ◽  
Author(s):  
Guo Cai Chai
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Fatigue Damage ◽  
Strain Localization ◽  
High Cycle Fatigue ◽  
High Strain ◽  
Fatigue Crack Initiation ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Very High

In very high cycle fatigue, VHCF, regime, fatigue crack initiation can occur at subsurface defects such as inclusion or subsurface non-defect (matrix) origin. This paper provides a study on the fatigue crack initiation mechanisms at subsurface non-defect (matrix) origin in two metallic materials using electron backscatter diffraction and electron channeling contrast imaging. The results show that the strains in the material in the VHCF regime were highly localized, where the local maximum strain is greatly higher than the average strain value. This high strain localization can lead to the formation of fine grain zone and also fatigue damage or fatigue crack initiation at grain boundaries or twin boundaries by impingement cracking. High strain localization is caused by strain accumulation of each very small loading, and also increases the local hardness of the material. This may start quasi-cleavage crack origin, and consequently the formation of subsurface fatigue crack initiations. The results also show that fatigue damage and crack initiation mechanisms in the VHCF regime can be different in different metals due to the mechanisms for local plasticity exhaustion.

The most Influential Articles in Very High Cycle Fatigue

2015 ◽  
Vol 664 ◽  
pp. 3-11 ◽  
Author(s):  
Q.Y. Wang ◽  
Muhammad Kashif Khan
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Web Of Science ◽  
Fatigue Crack Initiation ◽  
Experimental Studies ◽  
Cycle Fatigue ◽  
Science Data ◽  
Very High Cycle Fatigue ◽  
Very High

The most influential articles in Very high cycle fatigue (VHCF) during last 20 years have been identified from web of science data. It has been found that VHCF is an important category of fatigue damage and has produced the highest impact in the field. The number of articles and their citations is continuously increasing in the overall published papers in the field of fatigue. In VHCF field, it was found that the participants of VHCF conferences from VHCF 1 to 5 are the main contributors in all the VHCF papers and in its top 100 influential papers. Majority of the articles were experimental studies. The fatigue crack initiation in the VHCF domain is considered the most important area in the field. In VHCF, the most influential papers till date have been identified. This may prove helpful to trainees mastering the most influential literature of the field as well as more established professionals searching for starting points for new investigations

Partition of Cyclic Plasticity in an Austenitic-Ferritic Duplex Stainless Steel and its Significance for Fatigue Crack Initiation under High and Very High Cycle Fatigue Loading Conditions

2014 ◽  
Vol 891-892 ◽  
pp. 1424-1429 ◽  
Author(s):  
Benjamin Dönges ◽  
Marcus Söker ◽  
Alexander Giertler ◽  
Ulrich Krupp ◽  
Claus Peter Fritzen ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Fatigue Crack Initiation ◽  
Cycle Fatigue ◽  
Slip Bands ◽  
Very High Cycle Fatigue ◽  
Microcrack Initiation ◽  
Austenite Grains ◽  
Very High

The present study documents that at loading amplitudes close to the fatigue limit, cyclic irreversible plastic deformation in form of slip band generation in the austenitic-ferritic duplex stainless steel X2CrNiMoN22-5-3 (318 LN) mainly takes place in few austenite grains without any microcrack initiation in these grains. This was shown by means of focused ion beam (FIB) cutting in combination with high resolution scanning electron microscopy (SEM) at pronounced extrusion-intrusion-pairs in several austenite grains. Investigations by means of confocal laser scanning microscopy (CLSM) revealed that the slip band density in these grains increases with the number of loading cycles and remains constant in the very high cycle fatigue (VHCF) regime. Under such loading conditions, fatigue cracks frequently initiate in the ferrite phase due to anisotropy stresses which are strongly superimposed by stress intensifications at the tip of austenite slip bands. TEM investigations revealed that austenite slip bands, which are piling up against phase boundaries, cause localized dislocation generation and motion in neighboring ferrite grains. The cyclic irreversible motion of these dislocations on several parallel slip planes is correlated with the stage of fatigue crack initiation. A crystal plasticity model based on a finite element program, which considers anisotropic elasticity, allows for the determination of crack initiation sites in real microstructures according to the above mentioned mechanisms. Crystallographic orientations, measured by means of the electron back scatter diffraction (EBSD) technique, serve as input parameters for the calculations regarding microcrack initiation as well as for the analysis of the subsequent short fatigue crack propagation, which is strongly affected by microstructural barriers such as grain and phase boundaries.

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