Analysis on Fatigue Crack Propagation and Fractography of A7075 Aluminum Alloy

2012 ◽  
Vol 217-219 ◽  
pp. 390-394 ◽  
Author(s):  
Xu Chao ◽  
Shang Lei Yang
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Stress Amplitude ◽  
High Stress ◽  
Great Influence ◽  
Optical Microscope ◽  
Secondary Cracks ◽  
Fatigue Fractography

The fatigue fractography and surface of A7075 aluminum alloy was investigated by means of optical microscope, scanning electron microscope and technology of metallurgic replica. The results show that the fatigue crack generally initiated in the surface or near the surface of the sample area, such as hole and inclusion. The crack propagation regions under high stress amplitude was characterized by furrow and hollow, and obviously presented fine ripple vein. While lots of fatigue striations and sidesteps with the holes and secondary cracks generated in the crack propagation regions of low stress amplitude. Fatigue transient breaking area is a mixed fracture of brittle and ductile fracture. In the fatigue crack propagation stage, with the increasing of cycle times, secondary cracks gradually merged into primary crack on the path of crack propagation. The dislocation of crack tip,grain boundaries and different grain orientations have great influence on the path of crack growth, which can make cracks bending.

Characteristics of Microscopic Inclusions and their Influence on Fatigue Crack Propagation in FGH96 Superalloy

2017 ◽  
Vol 898 ◽  
pp. 505-516 ◽  
Author(s):  
Jie Hou ◽  
Jian Xin Dong
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Low Cycle Fatigue ◽  
Energy Dispersive Spectrometer ◽  
Aircraft Engine ◽  
Optical Microscope ◽  
The Finite Element Method ◽  
Heat Treated ◽  
Secondary Cracks

FGH96 superalloy has been used in aircraft engine turbine discs due to the superior damage tolerance. This work investigated the characteristics of microscopic inclusions and their influence on fatigue crack propagation in hot isostatic pressed and heat treated commercial FGH96 superalloy. Low cycle fatigue crack growth tests were conducted. Several kinds of microscopic inclusions were identified by optical microscope (OM), scanning electric microscope (SEM) and energy dispersive spectrometer (EDS). Microscopic inclusions and secondary cracks were analyzed near the main cracks. Combined with the finite element method (FEM) results, it can be proposed that the microscopic inclusions have no critical influence on fatigue crack propagation in the specimens.

scholarly journals 4005 Property for fatigue crack propagation of friction stir welded 2024-T3 aluminum alloy

2008 ◽  
Vol 2008.5 (0) ◽  
pp. 331-332
Author(s):  
Takao Okada ◽  
Kazuya Kuwayama ◽  
Toshiya Nakamura ◽  
Motoo Asakawa ◽  
Shigeru Machida
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Friction Stir

Description of Small Fatigue Crack Propagation in ODS Steel

2014 ◽  
Vol 891-892 ◽  
pp. 911-916
Author(s):  
Pavel Hutař ◽  
Ivo Kuběna ◽  
Miroslav Šmíd ◽  
Martin Ševčík ◽  
Tomáš Kruml ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
High Stress ◽  
Oxide Dispersion Strengthened ◽  
Ods Steel ◽  
Small Fatigue Crack ◽  
Propagation Law

The oxide dispersion strengthened (ODS) steels are widely studied as possible candidate material for fission and fusion technology. Due to application of the ODS materials, mainly low cycle fatigue is important. Therefore, small crack initiation and propagation for rather high stress amplitude are in focus. The main aim of the presented work is description of the small fatigue crack propagation for ODS-EUROFER steel. Due to limited quantity of ODS steel special miniaturized cylindrical specimens for fatigue testing were designed. Crack propagation law based on plastic part of J-integral is presented and applied for mentioned material. The resulting fatigue crack propagation rates for ODS-EUROFER steel and EUROFER 97 are compared and discussed.

LOW CYCLE FATIGUE BEHAVIOR OF Zn-22Al ALLOY IN SUPERPLASTIC REGION AND NON-SUPERPLASTIC REGION

2008 ◽  
Vol 22 (31n32) ◽  
pp. 5477-5482 ◽  
Author(s):  
ATSUMICHI KUSHIBE ◽  
TSUTOMU TANAKA ◽  
YORINOBU TAKIGAWA ◽  
KENJI HIGASHI
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Crack Tip ◽  
The Other ◽  
Al Alloy ◽  
Cycle Fatigue ◽  
Secondary Cracks

The crack propagation properties for ultrafine-grained Zn -22 wt % Al alloy during low cycle fatigue (LCF) in the superplastic region and the non-superplastic region were investigated and compared with the corresponding results for several other materials. With the Zn - 22 wt % Al alloy, it was possible to conduct LCF tests even at high strain amplitudes of more than ±5%, and the alloy appeared to exhibit a longer LCF lifetime than the other materials examined. The fatigue life is higher in the superplastic region than in the non-superplastic region. The rate of fatigue crack propagation in the superplastic region is lower than that in the other materials in the high J-integral range. In addition, the formation of cavities and crack branching were observed around a crack tip in the supereplastic region. We therefore conclude that the formation of cavities and secondary cracks as a result of the relaxation of stress concentration around the crack tip results in a reduction in the rate of fatigue crack propagation and results in a longer fatigue lifetime.

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