On the viscous flow in metals, and allied phenomena

Andrade, E. N. Da C.

doi:10.1098/rspa.1910.0050

Cited by 487 publications

(85 citation statements)

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“…For deformations at constant stress and temperature, it can be reasonably well described by the phenomenological relation [Andrade, 1910] e ¼ e 0 þ bt…”

Section: Introductionmentioning

confidence: 99%

Elastoviscoplastic micromechanical modeling of the transient creep of ice

et al. 2008

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[1] A salient feature of the rheology of isotropic polycrystalline ices is the decrease of the strain rate by more than 2 orders of magnitude during transient creep tests to reach a secondary creep regime at a strain which is systematically of $1%. We use a recent (socalled ''affine'') version of the self-consistent mean-field theory to model the elastoviscoplastic behavior of ice. The model aims at bridging scales between the rheology of single grain and the one of polycrystals by evaluating the intergranular interactions. It takes into account the long-term memory effects, which manifests itself by the fact that local stress and strain rate in grains depend on the whole mechanical history of the polycrystal. It is shown that the strong hardening amplitude during the transient creep is entirely explained by the stress redistribution within the specimen, from an almost uniform stress distribution upon instantaneous loading (purely elastic response) to strong interphase and intraphase heterogeneities in the stationary regime (purely viscoplastic response). The experimental hardening kinetic is much too slow to be explained by the same process; it is attributed to the hardening of hard glide slip systems (prismatic slip) in the transient regime. Moreover, the model very well reproduces the permanent creep rate of several highly anisotropic specimens of the Greenland Ice Core Project ice core (pronounced crystallographic textures), when accounting for a single-grain rheology that well matches the experimental one. Our results are consistent with recent findings concerning dislocation dynamics in ice.

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“…For deformations at constant stress and temperature, it can be reasonably well described by the phenomenological relation [Andrade, 1910] e ¼ e 0 þ bt…”

Section: Introductionmentioning

confidence: 99%

Elastoviscoplastic micromechanical modeling of the transient creep of ice

et al. 2008

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“…3), climb 4 (n* = 4-7) or lattice-diffusion 5 (n* = 8). The threshold stress, σ , o was estimated by plotting SSCR 1/n* against σ, and linearly extrapolating these creep data to a zero value of the creep rate (the interaction of the extrapolated line with the X-axis gives the threshold stress at a particular temperature).…”

Section: Creep Behaviour Analysismentioning

confidence: 99%

“…Following Andrade [4], three stages can be considered in a typical creep curve: the reduced stage, the steady-state stage and the accelerated stage. Studying these three stages helps in understanding the whole creep process.…”

Section: Introductionmentioning

confidence: 99%

Investigation of short-term creep deformation mechanisms in MarBN steel at elevated temperatures

Benaarbia

Sun

et al. 2018

Materials Science and Engineering: A

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This paper reports the short-term creep behaviour at elevated temperatures of a MarBN steel variant. Creep tests were performed at three different temperatures (625°C, 650°C and 675°C) with applied stresses ranging from 160 MPa to 300 MPa, and failure times from 1 to 350 h. Analysis of the macroscopic creep data indicates that the steady-state creep exhibits a power-law stress dependence with an exponent of 7 and an activation energy of 307 kJ mol, suggesting that dislocation climb is the dominant rate-controlling creep mechanism for MarBN steel. Macroscopic plastic instability has also been observed, highlighted by an obvious necking at the rupture region. All the macroscopic predictions have been combined with microstructural data, inferred from an examination of creep ruptured samples, to build up relations between macroscopic features (necking, damage, etc.), and underlying microstructural mechanisms. Analysis of the rupture surfaces has revealed a ductile fracture mode. Electron Backscatter Diffraction (EBSD) analysis near to the rupture surface has indicated significant distortion and refinement of the original martensitic substructure, which is evidence of long-range plastic flow. Dislocation pile-ups and tangles from TEM were also observed near substructure boundaries and precipitate particles. All of these microstructural observations suggest that creep is influenced by a complex interaction between several elements of the microstructure, such as dislocations, precipitates and structure boundaries. The calculated stress exponent and activation energy have been found to agree quantitatively with the highlighted microstructural features, bearing some relationships to the true observed creep microstructures.

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“…Lämmönjohtavuus k voi riippua lämpötilasta 6 . Tässä artikkelissa esitetään virumisvaurion mallintamiseen kaksi mallia, joista parametrien suhteen monimuotoisempi kuvataan potentiaaleilla…”

Section: Tarkasteltavat Mallitunclassified

Metallien virumismurron ja virumisväsymisen mallintaminen

Kauppila

Kouhia²,

Ojanperä

et al. 2017

RakMek

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Tiivistelmä. Artikkelissa tarkastellaan metallien korkealämpötilan virumismurron ja virumisväsymisen mallintamista. Aluksi esitetään lyhyt katsaus virumisen fysikaalisiin perusteisiin ja virumismalleihin. Käytetyn termodynaamisesti konsistentin materiaalimallin konstitutiiviset yhtälöt esitetään varsin perusteellisesti. Mallin materiaaliparametrit määritetään 7CrMoVTiB10-10 teräkselle lämpötila-alueella 500 − 600 • C. Malli on implementoitu ANSYS elementtimenetelmäohjelmiston USERMAT-aliohjelmaksi. Johdanto Ekologinen, kestävän kehityksen mukainen energiantuotanto on yhdistelmä hyvin monimuotoisista energian lähteistä. Tästä johtuen erilaisten energiantuottomuotojen käyttö on joustavaa ja näiden toimintasyklit muodostuvat epäsäännöllisistä prosessien toimintaajoista. Täten sähköä ja lämpöä tuottavien lauhdevoimalaitoskattiloiden painerungon osat altistuvat käyttöikänsä aikana -aikaisempaa useampien -kylmäkäynnistysten, korkeiden käytönaikaisten lämpötilojen ja höyrynpaineiden sekä toisiinsa liitettyjen osien erisuuruisten lämpötilojen aiheuttamien lämpöjännitysten vuoksi yhdistetylle virumis-ja väsymiskuormitukselle, joka erityisesti voimalaitoksen kuumimmissa tulistinkammioissa voi aiheuttaa vaurioita voimalaitoksen käyttöiän aikana. Voimalaitosten tehojen ja kokojen jatkuvasti kasvaessa vaaditaan niiden suunnittelussa aiempaa tarkempaa tietoa erityisesti tulistinkammioiden virumisväsymisen syistä ja mekanismeista. Lisäksi tulistinkammioiden virumisväsymismitoitukseen tarvitaan entistä tarkempia laskentamenetelmiä, joiden perusteella voidaan määritellä yhä parempia tulistinkammioiden suunnitteluperiaatteita.Tässä artikkelissa lähestytään virumisväsymisen mallintamista vauriomekaniikan keinoin ja vallitsevat konstitutiiviset yhtälöt johdetaan termodynaamisesti konsistentilla tavalla. Malli on ohjelmoitu kaupalliseen elementtimenetelmäohjelmaan käyttäjän määrit-telemällä materiaalialiohjelmalla. Mallin vaatimat materiaaliparametrit määritetään materiaalivalmistajan tietojen perusteella ja mallia sovelletaan tulistinkammion aisan väsy-1 Vastuullinen kirjoittaja. reijo.kouhia@tut.fi 420

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On the viscous flow in metals, and allied phenomena

Cited by 487 publications

References 0 publications

Elastoviscoplastic micromechanical modeling of the transient creep of ice

Elastoviscoplastic micromechanical modeling of the transient creep of ice

Investigation of short-term creep deformation mechanisms in MarBN steel at elevated temperatures

Metallien virumismurron ja virumisväsymisen mallintaminen

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