scholarly journals Influence of Pitting Corrosion on Fatigue and Corrosion Fatigue of Ship and Offshore Structures, Part II: Load - Pit - Crack Interaction

2015 ◽  
Vol 22 (3) ◽  
pp. 57-66 ◽  
Author(s):  
Marek Jakubowski
Keyword(s):  
Fatigue Crack ◽  
Corrosion Fatigue ◽  
Stress Concentrator ◽  
Offshore Structures ◽  
General Corrosion ◽  
Crack Interaction ◽  
Anticorrosion Protection ◽  
Pit Nucleation ◽  
Corrosion Pits ◽  
Crack Transition

Abstract In the paper has been discussed influence of stresses on general corrosion rate and corrosion pit nucleation rate and growth , whose presence has been questioned by some authors but accepted by most of them. Influence of roughness of pit walls on fatigue life of a plate suffering pit corrosion and presence of the so called „ non-damaging” pits which never lead to initiation of fatigue crack, has been presented. Possibility of prediction of pit-to-crack transition moment by two different ways, i.e. considering a pit a stress concentrator or an equivalent crack, has been analyzed. Also, influence of statistical distribution of depth of corrosion pits as well as anticorrosion protection on fatigue and corrosion fatigue has been described.

Lifetime Enhancement of Propulsion Shafts Against Corrosion-Fatigue by Laser Peening

2018 ◽  
Author(s):  
Lloyd A. Hackel ◽  
Jon E. Rankin
Keyword(s):  
Corrosion Fatigue ◽  
Fatigue Testing ◽  
Salt Water ◽  
Fatigue Cracks ◽  
Water Immersion ◽  
High Energy ◽  
General Corrosion ◽  
Laser Peening ◽  
Corrosion Pits ◽  
Deep Pits

This paper reports substantially enhanced fatigue and corrosion-fatigue lifetimes of propulsion shaft materials, 23284A steel and 23284A steel with In625 weld overlay cladding, as a result of shot or laser peening. Glass reinforced plastic (GRP) coatings and Inconel claddings are used to protect shafts against general corrosion and corrosion pitting. However salt water leakage penetrating under a GRP can actually enhance pitting leading to crack initiation and growth. Fatigue coupons, untreated and with shot or laser peening were tested, including with simultaneous salt water immersion. Controlled corrosion of the surfaces was simulated with electric discharge machining (EDM) of deep pits enabling evaluation of fatigue and corrosion-fatigue lifetimes. Results specifically show high energy laser peening (HELP) to be a superior solution, improving corrosion-fatigue resistance of shaft and cladding metal, reducing the potential for corrosion pits to initiate fatigue cracks and dramatically slowing crack growth rates. At a heavy loading of 110% of the 23284A steel yield stress and with 0.020 inch deep pits, laser peening increased fatigue life of the steel by 1370% and by 350% in the corrosion-fatigue testing.

Corrosion Fatigue Crack Propagation Characteristics of TMCP Steel in Synthetic Seawater Condition under Wave Period

2007 ◽  
Vol 345-346 ◽  
pp. 1043-1046 ◽  
Author(s):  
Won Beom Kim ◽  
Jeom Kee Paik
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Corrosion Fatigue ◽  
Steel Plate ◽  
Offshore Structures ◽  
Correlation Factor ◽  
Propagation Characteristics ◽  
Synthetic Seawater ◽  
Corrosion Fatigue Crack

In this research, corrosion fatigue tests using 490MPa TMCP steel were performed in synthetic seawater condition to investigate the corrosion fatigue crack propagation characteristics of TMCP steel plate which is often used for ships and offshore structures from its weldability and weight reduction purpose. In addition, relationships between boundary correlation factor F(α,β) and α(= 2a/W) of the fracture mechanics formula for the test specimen which was exerted by the pin load were calculated for the evaluation of da/dN-.K. To get the boundary correlation factor F(α,β), the calculation of J as a path-independent line integral was carried out. The solutions of J integral showed similar value in spite of the different path. Crack propagation tests for the same steel in air condition was carried out also for comparison. Finally, it was clear from the crack propagation test results that the propagation rate of TMCP steel plate in synthetic seawater condition is faster than that of in air condition at least twice.

The Effect of Ralstonia pickettii on Environmental Fatigue Crack Growth of 7xxx Series Aluminum Alloys

2014 ◽  
Vol 891-892 ◽  
pp. 224-229
Author(s):  
Sarah E. Galyon Dorman ◽  
Benjamin K. Hoff ◽  
Timothy A. Reid ◽  
Sarah E. Collins ◽  
Daniel H. Henning
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Corrosion Fatigue ◽  
Fatigue Loading ◽  
The United States ◽  
General Corrosion ◽  
Negative Consequences ◽  
Metal Sequestration ◽  
Ralstonia Pickettii

As more industries and nations focus on environmental protection, the desire to develop non-toxic, sustainable coatings to protect against corrosion becomes a primary focus. One of the areas on the cutting edge of new coating development is the use of bacteria in corrosion prevention coatings. For many years the focus in the corrosion community was on microbial influenced corrosion with the assumption that all bacteria had negative consequences for corrosion and corrosion fatigue. More recently it has been documented that a variety of bacteria can protect against general surface corrosion. None of the work to date on bacteria preventing general corrosion has shown that the inhibitive effects could also be applied to corrosion fatigue. Researchers at the United States Air Force Academy discovered that a bacteria, Ralstonia pickettii, is capable of reducing the fatigue crack growth rate of AA7075-T651 and AA7475-T7351 in 0.06M NaCl to near that of chromate. In cycles to failure testing in 0.06M NaCl the sample life was extended approximately 5 to 6 times depending on the fatigue loading variables compared to samples in 0.06M NaCl without the bacteria. The mechanism behind the corrosion fatigue protection is being investigated in hopes that it could lead to the development of new coatings to reduce corrosion fatigue. The current theories behind how the bacteria slows corrosion fatigue crack propagation are (1) presence of a biofilm, (2) metal sequestration and replating on the crack surface, (3) desalination of the test solution, and (4) oxide layer development and repair.

Development of a Probabilistic Methodology for Predicting Hot Corrosion Fatigue Crack Growth Life of Gas Turbine Engine Disks

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Kwai S. Chan ◽  
Michael P. Enright ◽  
Jonathan P. Moody
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Gas Turbine ◽  
Crack Growth ◽  
Corrosion Fatigue ◽  
Hot Corrosion ◽  
Corrosion Fatigue Crack ◽  
Fatigue Crack Growth Life ◽  
Corrosion Fatigue Crack Growth ◽  
Corrosion Pits

Advanced Ni-based gas turbine disks are expected to operate at higher service temperatures in aggressive environments for longer time durations. Exposures of Ni-based alloys to alkaline-metal salts and sulfur compounds at elevated temperatures can lead to hot corrosion fatigue crack growth in engine disks. Type II hot corrosion involves the formation and growth of corrosion pits in Ni-based alloys at a temperature range of 650 °C to 750 °C. Once formed, these corrosion pits can serve as stress concentration sites where fatigue cracks can initiate and propagate to failure under subsequent cyclic loading. In this paper, a probabilistic methodology is developed for predicting the corrosion fatigue crack growth life of gas turbine engine disks made from a powder-metallurgy Ni-based superalloy (ME3). The key features of the approach include: (1) a pit growth model that describes the depth and width of corrosion pits as a function of exposure time, (2) a cycle-dependent crack growth model for treating fatigue, and (3) a time-dependent crack growth model for treating corrosion. This set of deterministic models is implemented into a probabilistic life-prediction code called DARWIN. Application of this approach is demonstrated for predicting corrosion fatigue crack growth life in a gas turbine disk based on the ME3 properties from the literature. The results of this study are used to assess the conditions that control the transition of a corrosion pit to a fatigue crack and to identify the pertinent material parameters influencing corrosion fatigue life and disk reliability.

Analysis of Corrosion Fatigue Crack Growth in Welded Tubular Joints

1985 ◽  
Vol 107 (2) ◽  
pp. 212-219 ◽  
Author(s):  
S. J. Hudak ◽  
O. H. Burnside ◽  
K. S. Chan
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Corrosion Fatigue ◽  
Offshore Structures ◽  
Corrosion Fatigue Crack ◽  
Tubular Joints ◽  
Mechanics Model ◽  
Weld Toe

An improved fracture mechanics model for fatigue crack growth in welded tubular joints is developed. Primary improvements include the use of a wide-ranged equation for the fatigue crack growth rate properties and the incorporation of the influence of local weld-toe geometry into the stress intensity factor equations. The latter is shown to explain the dependence of the fatigue life on the size of tubular joints. Good agreement between predicted and measure fatigue lives of full-scale joints tested in air further supports the applicability of the fracture mechanics approach to offshore structures. Although the model should also be applicable to corrosion fatigue, additional imput data and verification testing are needed under these conditions. Factors which could improve the model are discussed.

Development of a Probabilistic Methodology for Predicting Hot Corrosion Fatigue Crack Growth Life of Gas Turbine Engine Disks

2013 ◽  
Author(s):  
Kwai S. Chan ◽  
Michael P. Enright ◽  
Jonathan P. Moody
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Gas Turbine ◽  
Crack Growth ◽  
Corrosion Fatigue ◽  
Hot Corrosion ◽  
Corrosion Fatigue Crack ◽  
Fatigue Crack Growth Life ◽  
Corrosion Fatigue Crack Growth ◽  
Corrosion Pits

Advanced Ni-based gas turbine disks are expected to operate at higher service temperatures in aggressive environment for longer time durations. Exposures of Ni-based alloys to alkaline-metal salts and sulfur compounds at elevated temperatures can lead to hot corrosion fatigue crack growth in engine disks. Type II hot corrosion involves the formation and growth of corrosion pits in Ni-based alloys at a temperature range of 650°C to 750°C. Once formed, these corrosion pits can serve as stress concentration sites where fatigue cracks can initiate and propagate to failure under subsequent cyclic loading. In this paper, a probabilistic methodology is developed for predicting the corrosion fatigue crack growth life of gas turbine engine disks made from a powder-metallurgy Ni-based superalloy (ME3). Key features of the approach include (1) a pit growth model that describes the depth and width of corrosion pits as a function of exposure time, (2) a cycle-dependent crack growth model for treating fatigue, and (3) a time-dependent crack growth model for treating corrosion. This set of deterministic models is implemented into a probabilistic life-prediction code called DARWIN. Application of this approach is demonstrated for predicting corrosion fatigue crack growth life in a gas turbine disk based on ME3 properties from the literature. The results of this study are used to assess the conditions that control the transition of a corrosion pit to a fatigue crack, and to identify the pertinent material parameters influencing corrosion fatigue life and disk reliability.

scholarly journals Corrosion Fatigue Characteristics of 316L Stainless Steel Fabricated by Laser Powder Bed Fusion

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1046
Author(s):  
Balachander Gnanasekaran ◽  
Jie Song ◽  
Vijay Vasudevan ◽  
Yao Fu
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Corrosion Fatigue ◽  
Fatigue Properties ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Corrosion Properties ◽  
Powder Bed ◽  
Fatigue Characteristics

Laser powder bed fusion (LPBF) has been increasingly used in the fabrication of dense metallic structures. However, the corrosion related properties of LPBF alloys, in particular environment-assisted cracking, such as corrosion fatigue properties, are not well understood. In this study, the corrosion and corrosion fatigue characteristics of LPBF 316L stainless steels (SS) in 3.5 wt.% NaCl solution have been investigated using an electrochemical method, high cycle fatigue, and fatigue crack propagation testing. The LPBF 316L SSs demonstrated significantly improved corrosion properties compared to conventionally manufactured 316L, as reflected by the increased pitting and repassivation potentials, as well as retarded crack initiation. However, the printing parameters did not strongly affect the pitting potentials. LPBF samples also demonstrated enhanced capabilities of repassivation during the fatigue crack propagation. The unique microstructural features introduced during the printing process are discussed. The improved corrosion and corrosion fatigue properties are attributed to the presence of columnar/cellular subgrains formed by dislocation networks that serve as high diffusion paths to transport anti-corrosion elements.

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