The influence of loading frequency and heat treatment on the rate of fatigue crack growth in 45 steel in impregnation with hydrogen

1980 ◽  
Vol 15 (6) ◽  
pp. 654-655
Author(s):  
M. M. Shved ◽  
L. M. Bilyi
Keyword(s):  
Heat Treatment ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Loading Frequency

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.

Characteristic Dependency of Hydrogen-Affected Fatigue Crack Growth and Crack Tip Plasticity on Low Loading Frequency in α-Iron

2020 ◽  
Vol 51 (8) ◽  
pp. 4313-4326
Author(s):  
Tomoki Shinko ◽  
Gilbert Hénaff ◽  
Damien Halm ◽  
Guillaume Benoit ◽  
Hadi Bahsoun
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Tip ◽  
Loading Frequency ◽  
Crack Tip Plasticity

scholarly journals Probabilistic Evaluation of Fatigue Crack Growth Rate for Longitudinal Tungsten Inert Gas Welded Al 6013-T4 Under Various PostWeld Heat Treatment Conditions

2019 ◽  
Vol 130 ◽  
pp. 01016 ◽  
Author(s):  
I Made Wicaksana Ekaputra ◽  
Gunawan Dwi Haryadi ◽  
Stefan Mardikus ◽  
Rando Tungga Dewa
Keyword(s):  
Heat Treatment ◽  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Postweld Heat Treatment ◽  
Inert Gas ◽  
Probabilistic Assessment

In this study, a Monte Carlo method (MCM) was applied on the fatigue crack growth rate (FCGR) curves to evaluate a probabilistic assessment for the welded longitudinal Al 6013-T4 aluminum alloy under various post-weld heat treatment (PWHT) conditions. The welded CT specimens were manufactured by a tungsten inert gas (TIG) welding, and the fatigue crack growth (FCG) tests were conducted by following ASTM E647. Before conducting the FCG test, the PWHT conditions were applied to the welded CT specimens under three different aging times of 6 h, 18 h, and 24 h at 175 C. The FCGR curves were generated from the FCG data and plotted on the da/dN versus Δk curves. The constants C and m were determined by drawing the fitting line on the FCGR curves. A sizeable random number was generated from the obtained constants by MCM. By plotting these constants, the probabilistic assessment of FCGR was determined on the da/dN versus Δk curves. The results showed that the confidence interval was appeared on the FCGR curves and limited by the upper and lower probabilistic lines. It was found that the lower and upper probabilistic lines were formed at 1 % and 90 %, respectively.

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.

Reliability Analysis of Corrosion Fatigue Crack Growth for 2024-T3 Aluminum Alloy

2008 ◽  
Vol 44-46 ◽  
pp. 105-110
Author(s):  
Sen Ge ◽  
Zhong Li ◽  
J.G. Zhang ◽  
Y.C. Xiao ◽  
G.Q. Liu ◽  
...  
Keyword(s):  
Growth Rate ◽  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Reliability Analysis ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Loading Frequency ◽  
Corrosive Environment

Fatigue crack growth rate experiments of center-cracked tension (CCT) specimens of the 2024-T3 aluminum alloy under constant-amplitude load in corrosive environment are carried out with 3 kinds of loading frequency. The fatigue crack growth rates in 3.5% NaCl solution are obtained by using seven-point incremental polynomial method. A probabilistic approach is presented for fatigue crack growth rate in corrosive environment with log-normal random variable model. The reliability analysis of crack propagation is conducted based on the experimental data. The crack exceedance probability at given service time and the distribution of the service time at given crack size are obtained by using the reliability analysis approach. The effect of loading frequency on crack propagation is studied. It is shown that the fatigue crack growth rate is increasing with loading frequency decreasing in corrosive environment. The predicted results by the presented method match the experimental results very well.

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