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T Goshima - One of the best experts on this subject based on the ideXlab platform.
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on the initiation and growth behavior of Corrosion Pits during Corrosion fatigue process of industrial pure aluminum
International Journal of Fatigue, 2008Co-Authors: Sotomi Ishihara, T Goshima, Z Y Nan, A J Mcevily, Satoshi SunadaAbstract:It is well known that the fatigue limit in air disappears in a corrosive environment. This is often because Corrosion Pits initiate and grow in the early stage of Corrosion fatigue process, and a final failure of specimen is brought by crack initiation and propagation from the grown Pits, even if the applied stress amplitudes are small. Therefore, it is important to study the initiation and growth characteristics of Corrosion Pits in order to predict the Corrosion fatigue lives of machines and structures that operate in corrosive environments. In this study we carry out Corrosion fatigue experiments with an industrial-grade pure aluminum and two different types of Corrosion methods. The initiation and growth characteristic of the Corrosion Pits were investigated by successive observations during the Corrosion fatigue process using a replica technique. It was found that effect of stress amplitude differed depending on the Corrosion method. It was also found that the growth characteristics of Corrosion Pits could be estimated quantitatively by changes in time of both the Corrosion current density and the Corrosion Pit density.
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Corrosion fatigue behavior of extruded magnesium alloy az31 in sodium chloride solution
International Journal of Fatigue, 2008Co-Authors: T GoshimaAbstract:Abstract In the present study, Corrosion fatigue experiments were done using the extruded magnesium alloy AZ31 in the 3% sodium chloride solution to clarify the Corrosion fatigue characteristics of the material. Corrosion fatigue lives greatly decreased as compared with those in laboratory air. It was also clarified that most of the Corrosion fatigue life (70–80%) at the lower stress amplitude is occupied with the period of the Corrosion Pit growth. Corrosion fatigue lives were evaluated quantitatively by dividing the Corrosion fatigue process into the following two periods, i.e. (1) the Corrosion Pit growth period preceding the crack initiation from the Pit and (2) the crack growth period before the specimen failure. In the analysis, the law of the Corrosion Pit growth proposed by authors was used to deal with the above first period. The evaluated results corresponded well to the experimental results.
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prediction of Corrosion fatigue lives of aluminium alloy on the basis of Corrosion Pit growth law
Fatigue & Fracture of Engineering Materials & Structures, 2006Co-Authors: Sotomi Ishihara, T Goshima, Z Y Nan, S Saka, Satoshi SunadaAbstract:ABSTRACT Tension-compressionandrotating-bendingfatiguetestswerecarriedoutusingaluminiumalloy 2024-T3, in 3% NaCl solution. The Corrosion Pit growth characteristics, and alsothe fatigue crack initiation and propagation behaviour were investigated in detail. Theresults obtained are summarized as follows: (i) Most of Corrosion fatigue life (60–80%)is occupied with a period of Corrosion Pit growth at low-stress amplitude. The CorrosionPit growth law can be expressed as functions of stress amplitude σ a and an elapsed time t . (ii) The critical stress intensity factor for crack initiation from the Corrosion Pit wasdetermined as 0.25 MPa√m. This value is the same as the threshold stress intensity factorrange for crack propagation. (iii) Corrosion fatigue life can be estimated on the basis ofCorrosion Pit growth law and crack propagation law. The estimated fatigue lives agree wellwith the experimental data. Keywords Corrosion fatigue; Corrosion Pit; stress amplitude; stress frequency.INTRODUCTIONAluminium alloys have been widely used as structuralmembersoftransportmachines,suchasshipsandaircraftsfor the purpose of reducing their weight. Such structuresare usually exposed to the natural environment during theoperation.It is well known that metal fatigue life is lowered sub-stantially by the action of a corrosive environment whencompared with that in an inert atmosphere. This is be-cause a Corrosion Pit can generate and grow on the mate-rial surface, followed by crack initiation and propagationin corrosive environments, even at very low-stress ranges.Therefore, for quantitative analysis of the Corrosion fa-tigue life, it is very important to clarify the Corrosion Pitgrowth characteristics and the crack initiation behaviourfrom the Corrosion Pit. Until now, many researches onCorrosion Pit growth characteristics, and crack initiationand propagation behaviour have been made.Wan
D L Duquesnay - One of the best experts on this subject based on the ideXlab platform.
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Corrosion fatigue behaviour of 7075 t651 aluminum alloy subjected to periodic overloads
International Journal of Fatigue, 2007Co-Authors: R M Chlistovsky, Patrick J Heffernan, D L DuquesnayAbstract:Abstract The Corrosion-fatigue behaviour of 7075-T651 aluminum alloy subjected to periodic overloads was examined. This aluminum alloy is typically used in aerospace structural components such as the wing spars of aircraft. Axial fatigue specimens were subjected to a loading spectrum that consisted of a fully reversed periodic overload of near-yield magnitude followed by 200 smaller cycles at high R-ratio. The specimens were fatigue tested while they were fully immersed in an aerated and recirculated 3.5 wt% NaCl simulated seawater solution. The results for the Corrosion-fatigue testing were compared to data obtained for the same overload spectrum applied in laboratory air. A damage analysis showed that the presence of the corrosive environment accelerated the damage accumulation rate to a greater extent than that observed in air, particularly at low stress ranges. This resulted in a reduction in the fatigue strength of the material when it was simultaneously subjected to overloads and a corrosive environment. It is believed that the reduced fatigue life was due primarily to Corrosion Pit formation and a combination of anodic dissolution at the crack tip and hydrogen embrittlement. For practical purposes, the endurance-limit of the material disappears under these conditions.
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fatigue crack growth from Corrosion damage in 7075 t6511 aluminium alloy under aircraft loading
International Journal of Fatigue, 2003Co-Authors: D L Duquesnay, P R Underhill, H J BrittAbstract:This paper investigates the growth behaviour of fatigue cracks initiated at Corrosion Pits in laboratory coupons of 7075-T6511 aluminium alloy subjected to a transport aircraft loading spectrum. Corrosion Pits were artificially introduced by exposing the coupons to EXCO solution for a variety of periods to produce Corrosion damage varying from mild to severe. In general, the presence of Corrosion damage reduced the fatigue lives of components to a severe extent. It was found that the depth of the Corrosion Pit was a suitable parameter for characterizing the Corrosion damage and for predicting the fatigue life of the coupons using commercial fatigue crack growth software. It is suggested that for practical purposes the size of the deepest Corrosion Pit in the area of Corrosion damage on an aircraft, or similar structure, can be used as the metric for predicting fatigue life.
Ryuichiro Ebara - One of the best experts on this subject based on the ideXlab platform.
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Corrosion fatigue crack initiation behavior of stainless steels
Procedia Engineering, 2010Co-Authors: Ryuichiro EbaraAbstract:Abstract Corrosion fatigue crack initiation behavior of various kinds of stainless steels is reviewed mainly on the basis of the author’s experimental results. The role of Corrosion Pit in the Corrosion fatigue crack initiation process of martensitic, ferritic, austenitic, duplex and preciPitation-hardening stainless steels is briefly summarized. The recent investigation of an electrochemical noise measurement method is demonstrated for 12%Cr martensitic stainless steel and 2.5%Mo containing high strength austenitic stainless steels. Finally a couple of future problems to be solved in Corrosion fatigue crack initiation are touched on briefly.
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Corrosion fatigue crack initiation in 12 chromium stainless steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Ryuichiro EbaraAbstract:Characteristics of Corrosion fatigue failures of steam turbine blades derived from failure analysis are summarized. Then Corrosion fatigue variables on Corrosion fatigue strength of 12% chromium stainless steel are briefly reviewed. The paper emphasizes initiation and growth of Corrosion Pits in the Corrosion fatigue crack initiation process. A recent investigation of the early stages of Corrosion Pit initiation by use of electrochemical noise measurement is demonstrated. Finally, some recommendations are given how to clarify the Corrosion fatigue crack initiation process.
Scott Fawaz - One of the best experts on this subject based on the ideXlab platform.
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test method for Corrosion Pit to fatigue crack transition from a corner of hole in 7075 t651 aluminum alloy
International Journal of Fatigue, 2016Co-Authors: Saravanan Arunachalam, Scott FawazAbstract:Abstract The paper presents a protocol to develop a Corrosion Pit of the order 120–180 μm and characterize the Pit to fatigue transition at three stress levels 70, 120 and 180 MPa. The study was carried out using 7075-T651 aluminum alloy and the Pit location was at the corner of the hole, simulating damage at the corner of a fastener hole. The study includes effort undertaken to develop micro Pits of various size and consistency in obtaining a narrow size range. In addition, the paper presents analysis of the direct current potential drop (dcPD) data from a propagating fatigue crack to assess the crack nucleation and growth phenomenon from these Corrosion micro Pits. A stress ratio ( R ) of 0.65 was used for the above mentioned stress levels. Marker bands were used to determine the crack front as a function of cycles and to study the crack shape evolution from the post-test fracture surface analysis using a scanning electron microscope (SEM). The crack growth data from experimental crack dimensions “ a ” and “ c ” (where “ a ” is the dimension through the thickness and “ c ” the dimension along the specimen width) are in agreement with predictions using (AFGROW, 2014) [1]. Crack growth rates were also compared with that obtained from the Structural Integrity Prognosis System (SIPS) program (Papazian and Anagnostou, 2009) for similar test conditions, and the results are in good agreement.
Shinpei Iwakami - One of the best experts on this subject based on the ideXlab platform.
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Corrosion fatigue behavior of extruded magnesium alloy az61 under three different corrosive environments
International Journal of Fatigue, 2008Co-Authors: Md Shahnewaz Bhuiyan, Yoshiharu Mutoh, Tsutomu Murai, Shinpei IwakamiAbstract:Abstract Corrosion fatigue process of extruded AZ61 magnesium alloy has been investigated under three different corrosive environments: (a) high humidity environment (80% relative humidity), (b) 5 wt% NaCl solution environment, and (c) 5 wt% CaCl2 solution environment. The fatigue strength drastically reduced under the three different corrosive environments: the reduction rates of fatigue limit under high humidity, NaCl and CaCl2 environments were 0.22, 0.85 and 0.77, respectively. The drastic reduction in fatigue limit under corrosive environments resulted from Pit formation and growth to the critical size for fatigue crack nucleation. It is suggested that the NaCl environment enhances Pit formation and growth more than the CaCl2 environment, due to the high Cl− concentration and low pH value. It is also found that the Corrosion Pit grows during fatigue cycles and the fatigue crack starts when the Pit reaches a critical size for crack nucleation. The critical size is attained when the stress intensity factor range reaches the threshold value. The ratio between Pit growth life to fatigue crack nucleation and total fatigue life was about 30%.
