Influence of loading frequency on the rules and mechanisms of fatigue crack growth in titanium alloys. Report 1

1988 ◽  
Vol 20 (1) ◽  
pp. 19-24 ◽  
Author(s):  
L. E. Matokhnyuk ◽  
V. S. Ordynskii
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Titanium Alloys ◽  
Crack Growth ◽  
Loading Frequency

scholarly journals Structural Reliability Prediction Using Acoustic Emission-Based Modeling of Fatigue Crack Growth

2018 ◽  
Vol 8 (8) ◽  
pp. 1225 ◽  
Author(s):  
Azadeh Keshtgar ◽  
Christine Sauerbrunn ◽  
Mohammad Modarres
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Titanium Alloys ◽  
Crack Growth ◽  
Structural Reliability ◽  
Bayesian Regression ◽  
Model Parameters ◽  
Loading Frequency ◽  
Proposed Model ◽  
Crack Growth Model

In this paper, AE signals collected during fatigue crack-growth of aluminum and titanium alloys (Al7075-T6 and Ti-6Al-4V) were analyzed and compared. Both the aluminum and titanium alloys used in this study are prevalent materials in aerospace structures, which prompted this current investigation. The effect of different loading conditions and loading frequencies on a proposed AE-based crack-growth model were studied. The results suggest that the linear model used to relate AE and crack growth is independent of the loading condition and loading frequency. Also, the model initially developed for the aluminum alloy proves to hold true for the titanium alloy while, as expected, the model parameters are material dependent. The model parameters and their distributions were estimated using a Bayesian regression technique. The proposed model was developed and validated based on post processing and Bayesian analysis of experimental data.

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.

Effect of Loading Frequency on Fatigue Crack Growth Behaviour and Microstructural Damage in P92 HAZ

2007 ◽  
Vol 120 ◽  
pp. 21-24
Author(s):  
Bum Joon Kim ◽  
Byeong Soo Lim
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Low Frequency ◽  
Growth Behavior ◽  
Frequency Effect ◽  
Crack Growth Behavior ◽  
Loading Frequency ◽  
Crack Growth Behaviour ◽  
Microstructural Damage

Various hold periods in a cyclic wave of fatigue load were introduced to investigate loading frequency effects on crack growth behavior and microstructural damage. The crack growth path and microstructural damage characteristics at 600°C in tempered martensitic 9Cr-2W (P92) HAZ of welded steel were studied. Generally, low frequency effect with increasing hold periods affects microstructural damage with microvoids/cavities nucleation due to the effect of creep. Results showed that the fatigue crack growth behavior was sensitive to the loading frequency. As frequency decreased, the fatigue crack growth rate increased and the crack path mode changed from transgranular to intergranular in terms of microstructural damage. As the loading frequency decreased, it was found that the microvoids /cavities and microcracks that formed along the prior austenite grain boundaries ahead of the main crack contributed to the intergranular crack growth.

Full Size Fatigue Crack-Growth Testing for Girth Welds

2004 ◽  
Author(s):  
Paulo Gioielli ◽  
Jaime Buitrago
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Production Quality ◽  
Small Scale ◽  
Loading Frequency ◽  
Growth Data ◽  
Girth Welds ◽  
Crack Growth Modeling ◽  
Fatigue Crack Growth Testing

Fatigue crack-growth modeling has a significant impact in establishing defect acceptance criteria for the inspection of fracture-critical, girth-welded components, such as risers and tendons. ExxonMobil has developed an experimental technique to generate crack-growth data, in actual welded tubulars, that account for the particular material properties, geometry, and residual stresses. The technique is fully compatible with conventional fracture mechanics models. It uses a series of pre-designed notches made around the welds on a production quality, full-scale specimen that is tested efficiently in a resonant fatigue setup. The crack development from notches is monitored during testing and evaluated post-mortem. Given its simplicity and high loading frequency, the technique provides growth data germane to the component at hand at a lower cost and faster than standard, small-scale tests.

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