Creep–fatigue–oxidation interactions in a 9Cr–1Mo martensitic steel. Part I: Effect of tensile holding period on fatigue lifetime

Fournier, Benjamin; Sauzay, Maxime; Caës, Christel; Noblecourt, Michel; Mottot, Michel; Bougault, Annick; Rabeau, Véronique; André, Pascal

doi:10.1016/j.ijfatigue.2007.05.007

Cited by 147 publications

(73 citation statements)

References 110 publications

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“…This process is much similar to what has been observed in high temperature LCF of stainless steels [79][80][81], for which it has been demonstrated that small cracks, often denoted as oxide intrusions [57,82,83], are initiated through the fracture of the oxide scale formed due to the high temperature oxidation. These oxide intrusions extend circumferentially for smooth cylindrical specimens and produce oxide ridges above and beneath the crack mouth; resulting in a resemblance to furrows of a ploughed field on the specimen surface [79,80].…”

Section: Elevated Temperaturessupporting

confidence: 77%

Fatigue of Heavy-Vehicle Engine Materials: Damage Mechanisms, Laboratory Experiments and Life Estimation

Norman¹

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Due to increasing demands on sustainability exerted by end-costumers and policy makers, heavy-vehicle manufacturers are urged to increase the engine efficiency in order to reduce the exhaust gas emission. However, increasing the efficiency is also associated with an elevated fatigue rate of the materials constituting the engine parts, which consequently reduces the engine service life. The aim of the present thesis is therefore to confront the expected increase by studying the fatigue behaviour and damage mechanisms of the materials typically employed in heavy-vehicle diesel engines. With this knowledge, this work seeks to guide the development of new heavy-vehicle engine materials, as well as to develop improved life estimation methods designated to assist the mechanical design of durable heavy-vehicle engines.In essence, a large set of thermo-mechanical fatigue (TMF) and combined thermo-mechanical and high-cycle fatigue (TMF-HCF) tests is conducted at engine load conditions on laboratory specimens of lamellar, compacted and spheroidal graphite iron. In this way, the fatigue performance and associated damage mechanisms are investigated. In particular, a new fatigue property is identified, the TMF-HCF threshold, which quantifies how resistant a material is to superimposed high-cycle fatigue.The damage mechanism at low temperatures ( 500 o C) is confirmed to consist of the initiation, propagation and coalescence of numerous microcracks. Based on this, a successful fatigue life estimation model is formulated, allowing accurate estimations of TMF and TMF-HCF tests on smooth specimens, and TMF tests on notched specimens. In the latter case, the microcrack growth behaviour in non-uniform cyclic stress fields and its implications for life estimation are clarified. At elevated temperatures ( 500 o C), surface oxidation is shown to govern the fatigue performance of cast iron grades intended for exhaust manifolds. It is observed that oxide intrusions are induced, from which surface fatigue cracks are initiated. Consequently, an optimal material at these conditions should have a low oxide growth rate and few casting defects at the surface, as these factors are found to stimulate the growth of intrusion.iii Populärvetenskaplig sammanfattningMen anledning av ökande krav på hållbarhet från slutkunder och beslutsfattare pressas tillverkare av tunga lastbilar att öka drivlinans verkningsgrad och minska utsläppen av luftföroreningar. För dieselmotorn som är den vanligaste motortypen i tunga lastbilar förväntas i dagsläget det största bidraget till att möta kraven vara att öka motorns verkningsgrad. Högre verkningsgrad innebär lägre bränsleförbrukning, vilket i sin tur står i direkt proportion till mängden utsläppt koldioxid. Denna eftertraktade förbättring åstadkoms generellt genom att öka kompressionsförhållandet, vilket medför en ökning i det maximala förbränningstrycket och temperaturen i förbränningskam-maren. Till följd av detta uppkommer även ett ökat slitage av motorkomponenterna, i tekniska sammahang kallat utma...

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Section: Elevated Temperaturessupporting

confidence: 77%

Fatigue of Heavy-Vehicle Engine Materials: Damage Mechanisms, Laboratory Experiments and Life Estimation

Norman¹

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“…3. However, according to the previous reports [15][16][17][18][19], the fatigue life of the 9-12Cr martensitic steels obtained in vacuum was longer than that Fig. 3 Relationship between total strain range (Δε t ) and number of cycles to failure (N f ) of RB-1 specimen tested at R.T. in air [1] and tested at 550…”

Section: Resultsmentioning

confidence: 77%

High Temperature Fatigue Life Evaluation Using Small Specimen

Nogami

Hisaka

Fujiwara

et al. 2017

Plasma and Fusion Research

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For developing the high temperature fatigue life evaluation method using small specimen, the effect of specimen size and test environment on the high temperature fatigue life of the reduced activation ferritic/martensitic steel, F82H-IEA, was investigated at 550• C under the total strain range of 0.5 -1.2 % using a new high temperature low cycle fatigue testing machine for the small round-bar specimen. No significant effect of the test environment (oxidation) on the fatigue life was observed in the standard-size specimen, whereas the slight reduction of the fatigue life due to that was indicated in the small-size specimen, especially at the final fracture stage of the test. It could be concluded that the new high temperature low cycle fatigue testing machine of the present study could satisfy the minimum requirements for the high temperature low cycle fatigue life evaluation using small specimen because the fatigue life data obtained using this testing machine could be acceptable based on the comparison with the previous studies data. To improve the reliability and the applicability of this test technology, further evaluations under the wider test temperature and strain conditions are expected in future.

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“…However for the purposes of this analysis the constants determined from [17] are used as they provide more conservative results (shorter lives). The constants C and β are found to be 4.5×10 3 and -1.6, respectively (for stress in units of MPa).…”

Section: Representation Of Multiaxial Fatigue Damagementioning

confidence: 94%

“…Work carried out in [3] has recognised that repeated start and stop operations lead to creep-fatigue loading on power plant components. In [4], thermo-mechanical modelling of P91steel in complex power plant geometries, including…”

Section: Introductionmentioning

confidence: 99%

“…Current header design does not consider cyclic thermal stresses and load cycling that can lead to creep-fatigue damage [2]. Work carried out in [3] has recognised that repeated start and stop operations lead to creep-fatigue loading on power plant components. In [4], thermo-mechanical modelling of P91steel in complex power plant geometries, including 2 effects of varying thermal and mechanical loads representative of plant start-up was carried out using an elastic-plastic material model (without strain-rate effects).…”

Section: Introductionmentioning

confidence: 99%

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Development of life assessment procedures for power plant headers operated under flexible loading scenarios

Farragher

Scully²,

O’Dowd

et al. 2013

International Journal of Fatigue

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Publication InformationFarragher, TP, Scully, S, O Dowd, NP, Leen, SB (2013) 'Development of life assessment procedures for power plant headers operated under flexible loading scenarios'. International Journal Of Fatigue, 49 :50-61. PublisherElsevier ScienceDirect 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 Abstract A finite element methodology for thermomechanical fatigue analysis of a subcritical power plant outlet header under realistic loading conditions is presented. The methodology consists of (i) a transient heat transfer model, (ii) a sequential anisothermal cyclic viscoplastic model and (iii) a multiaxial, criticalplane implementation of the Ostergren fatigue indicator parameter. The methodology permits identification of the local thermomechanical stress-strain response at critical locations and prediction of fatigue life and cracking orientation for complex transient, anisothermal, cyclic elastic-plastic-creep material behaviour. Measured plant data, in the form of steam and pipe temperature transients and steam pressure data, are employed to identify heat transfer constants and validate the predicted thermal response, with particular attention given to plant start-up and attemperation effects. The predictions indicate out-of-phase temperature-strain response at the header inside surface and in-phase response on the outside surface. Cooling transients are predicted to control damage and crack initiation at the inner bore, whereas heating transients are predicted to have a more damaging effect at weld locations. A representative test cycle is presented, which is shown to capture the salient thermo-mechanical cyclic damage of the realistic cycle. The predicted results correlate well with industrial experience in terms of crack (initiation) orientation, location and life. IntroductionThere is a need to understand the performance of candidate power plant materials for higher temperatures and pressures. 9-12% Cr steels are an example of such candidate materials, owing to their excellent mechanical properties, and steels such as P91 and P92 are already being utilised in power generation plant [1]. There is an increasing trend towards shifting of energy supply from conventional fossil fuel power plant to sustainable energies, e.g. wind power. To allow for the variable nature of renewable energy supply, there is a requirement to operate existing plant, designed for 'base-load' operation, with relatively infrequent shutdown and start-up, in 'load-following' mode, characterised by increased frequency of shutdown and start-up. This issue has increased the importance of design and assessment of materials and components for high temperature, pressurised plant with respect to thermomechanical fatigue (TMF) and creep-fatigue failure.Current header design does not consider cyclic thermal stresses and load cycling that can lead to creep-f...

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Creep–fatigue–oxidation interactions in a 9Cr–1Mo martensitic steel. Part I: Effect of tensile holding period on fatigue lifetime

Cited by 147 publications

References 110 publications

Fatigue of Heavy-Vehicle Engine Materials: Damage Mechanisms, Laboratory Experiments and Life Estimation

Fatigue of Heavy-Vehicle Engine Materials: Damage Mechanisms, Laboratory Experiments and Life Estimation

High Temperature Fatigue Life Evaluation Using Small Specimen

Development of life assessment procedures for power plant headers operated under flexible loading scenarios

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