Coupled influence of microstructure and atmosphere environment on fatigue crack path in new generation Al alloys

2010 ◽  
Vol 77 (11) ◽  
pp. 1941-1952 ◽  
Author(s):  
S. Richard ◽  
C. Gasquères ◽  
C. Sarrazin-Baudoux ◽  
J. Petit
Keyword(s):  
Fatigue Crack ◽  
Crack Path ◽  
Al Alloys ◽  
New Generation ◽  
Atmosphere Environment

Fatigue Crack Propagation in New Generation Aluminium Alloys

2011 ◽  
Vol 488-489 ◽  
pp. 476-479
Author(s):  
Sébastien Richard ◽  
Christine Sarrazin-Baudoux ◽  
Jean Petit
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Alloy Composition ◽  
Crack Path ◽  
Aging Condition ◽  
Modelling Framework ◽  
Alloy Type ◽  
New Generation ◽  
Atmosphere Environment

The fatigue crack propagation behaviour of a new third generation Al-Cu-Li alloy type 2050-T84 developed for aeronautical applications is studied in comparison to a new generation Al-Cu-Mg alloy type 2022-T851. The alloy resistance against crack growth is shown to depend on alloy composition, aging condition and atmosphere environment. The crack path and the growth rate at moderate DK and in the near-threshold domain are discussed in terms of the slip morphology with respect to the microstructure. The different crack propagation regimes, as identified by mean of micro-fractographic observations and EBSD analysis are discussed on the basis of a modelling framework elaborated for conventional metallic alloys.

Comparison of DBEM and FEM Crack Path Predictions with Experimental Findings for a SEN-Specimen under Anti-Plane Shear Loading

2007 ◽  
Vol 348-349 ◽  
pp. 129-132 ◽  
Author(s):  
Roberto G. Citarella ◽  
Friedrich G. Buchholz
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Front ◽  
Crack Path ◽  
Shear Loading ◽  
Crack Growth Behaviour ◽  
3D Crack Growth ◽  
Corner Points ◽  
Experimental Findings

In this paper detailed results of computational 3D fatigue crack growth simulations will be presented. The simulations for the crack path assessment are based on the DBEM code BEASY, and the FEM code ADAPCRACK 3D. The specimen under investigation is a SEN-specimen subject to pure anti-plane or out-of-plane four-point shear loading. The computational 3D fracture analyses deliver variable mixed mode II and III conditions along the crack front. Special interest is taken in this mode coupling effect to be found in stress intensity factor (SIF) results along the crack front. Further interest is taken in a 3D effect which is effective in particular at and adjacent to the two crack front corner points, that is where the crack front intersects the two free side surfaces of the specimen. Exactly at these crack front corner points fatigue crack growth initiates in the experimental laboratory test specimens, and develops into two separate anti-symmetric cracks with complex shapes, somehow similar to bird wings. The computational DBEM results are found to be in good agreement with these experimental findings and with FEM results previously obtained. Consequently, also for this new case, with complex 3D crack growth behaviour of two cracks, the functionality of the proposed DBEM and FEM approaches can be stated.

Characterization of Crack Tip Damage Zone Formation on Alloy 625 During Fatigue Crack Growth at 750°C by Transmission EBSD Method

2017 ◽  
Author(s):  
Yuji Ozawa ◽  
Tatsuya Ishikawa ◽  
Yoichi Takeda
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Power Plants ◽  
Crack Path ◽  
Damage Zone ◽  
Crack Tip ◽  
Loading Frequency ◽  
Zone Formation ◽  
Alloy 625

In order to clarify the mechanism of fatigue crack growth in alloy 625, which is a candidate material for use in advanced ultra supercritical power plants, the crack tip damage zone formation after a crack growth test conducted in high temperature steam was investigated. It was observed that the oxide thickness at the crack tip tended to increase with decreasing cyclic loading frequency. The crack path was a mix of transgranular and intergranular fractures. According to the grain reference orientation deviation (GROD) maps, it was revealed that the density of geometrically necessary dislocations (GNDs) in the matrix along the crack path and ahead of crack tip increased with an increase in the fatigue crack growth rate (FCGR) due to environmental effects. It was observed that (1) mobile dislocations at the crack surface were blocked due to the thick oxide layer, resulting in an increase in the density of GNDs, and (2) an increase in the density of GNDs might induce stress concentration at the crack tip, deformation twinning, and the acceleration of FCGRs.

Corrosion-Fatigue Crack Growth in Age-Hardened Al Alloys: Examples of Failures and Explanations for Fractographic Observations

2014 ◽  
Vol 891-892 ◽  
pp. 248-253 ◽  
Author(s):  
Rohan Byrnes ◽  
Noel Goldsmith ◽  
Mark Knop ◽  
Stan Lynch
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Corrosion Fatigue ◽  
Compact Tension ◽  
Al Alloys ◽  
Corrosion Fatigue Crack ◽  
Crack Tips ◽  
Corrosion Fatigue Crack Growth ◽  
Additional Support

The characteristics of corrosion-fatigue in age-hardened Al alloys, e.g. brittle striations on cleavage-like facets, are described, with reference to two examples of component failure. Mechanisms of corrosion fatigue (and explanations for fracture-surface features) are then reviewed. New observations of corrosion-fatigue crack growth for 7050-T7451 alloy compact-tension specimens tested in aqueous environments using a constant (intermediate) ΔK value but different cycle frequencies are then described and discussed. These observations provide additional support for a hydrogen-embrittlement process involving adsorption-induced dislocation-emission from crack tips.

Effects of Hydrogen on Fatigue Crack Growth of Iron Aluminides

1994 ◽  
Vol 364 ◽  
Author(s):  
A. Castagna ◽  
N.S Stoloff
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Al Alloys ◽  
Moist Air ◽  
Stress Intensity Range ◽  
Low Levels ◽  
Structural Iron ◽  
Fatigue Crack Growth Testing ◽  
Crack Growth Rates

AbstractThree Fe-Al alloys, FAP-Y, FA-129, and Fe-35a%Al, containing 16, 28, and 35a%Al, respectively, have been subjected to fatigue crack growth testing in moist air, in oxygen, and in gaseous hydrogen. In each case hydrogen and air were embrittling. Crack growth rates increased significantly as frequency decreased. Fatigue crack growth results have been compared with those for other structural iron-base alloys. Surprisingly, FAP-Y displays the highest crack growth rate of any alloy examined, except at very low levels of stress intensity range. The mechanisms for embrittlement by hydrogen and by moisture in air are discussed.

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