Creep Fracture in Nimonic 80A Under Triaxial Tensile Stressing

Dyson, B. F.; Loveday, M S

doi:10.1007/978-3-642-81598-0_27

Cited by 36 publications

(25 citation statements)

References 7 publications

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“…Grain boundary cavity formation is a kinetic phenomenon and its influence on deformation resistance and on fracture mode under arbitrary stress state depends critically on cavity nucleation rate and growth rate. When both rates are high, there is a potential for a strong coupling between cavitation and creep rate through the mechanism of creep constrained cavity growth, leading to rapid tertiary creep (Dyson and Loveday, 1981). This damage normally occurs during long-term high temperature creep at low stress levels.…”

Section: Damage Due To Creep Constrained Cavity Nucleation and Growthmentioning

confidence: 99%

A Review on Damage Mechanisms, Models and Calibration Methods under Various Deformation Conditions

Lin

Liu

Dean

2005

International Journal of Damage Mechanics

144

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The development of microdamage under the deformation conditions of high temperature creep, cold metal forming, superplastic forming, and hot metal forming has been reviewed and discussed, and typical constitutive equations developed to model the individual damage mechanisms are summarized. Based on the microstructural analysis of the key damage features for metallic materials under a wide range of deformation conditions, a set of schematic diagrams is designed to illustrate the major types of damage mechanisms. This helps researchers and engineers to understand the major cause of failure of materials under different deformation conditions and to select simple and appropriate mechanism-based damage equations to predict the damage evolution. Further discussions are carried out on the dominant damage mechanisms in hot metal forming conditions and it is concluded that the dominant damage mechanism can be 'grain boundary (creeptype) damage' or 'plasticity-induced (ductile) damage' depending on the material microstructure and deformation rate. In the case of grain boundary damage in hot forming, the shape of microdefects is different from those in high temperature creep and superplastic forming although all of those result in intergranular failure of materials. Furthermore, damage calibration techniques for different conditions of plastic deformation are summarized and discussed.KEY WORDS: damage mechanisms, damage calibrations, creep and viscoplasticity, cold and hot metal forming.

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Section: Damage Due To Creep Constrained Cavity Nucleation and Growthmentioning

confidence: 99%

A Review on Damage Mechanisms, Models and Calibration Methods under Various Deformation Conditions

Lin

Liu

Dean

2005

International Journal of Damage Mechanics

144

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“…Dyson and Loveday [7]. Their tests were under long durations when the stationary conditions for stresses were maintained and the creep strain rate was uniform along the entire cross section.…”

Section: -"mentioning

confidence: 99%

“…." equivalent stress should be used as the reference stress to determine the creep rupture behavior under multiaxial loading condition has been studied by several authors [3,5,6,7]. Hayhurst [3] has found that for cross section of test specimens.…”

Section: -"mentioning

confidence: 99%

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Finite Element and Experimental Studies of Creep Crack Initiation of RENE-95 Superalloy.

Pian¹,

Sifre²,

Lee³

1985

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“…These laws have been developed to describe the behaviour of nickel-base superalloys which are used in the fabrication of load-bearing and thermally-stressed gas turbine components. Computer modelling of the creep rupture behaviour, using these constitutive laws, has been carried out by Othman et al (1994) for notched tension bars, and the results have been compared with experimental data reported by Dyson and Loveday (1981). It has been found from the experimental results that, at low stress levels (r N ffi 0.2r y where r N is the net section stress at the notch, and r y is the material yield stress) damage evolution starts at the notch surface/root and progresses inwards towards the notch centre-line (outside-in failure), which is consistent with the computer modelling results using the physically-based two-damage variable sinh-constitutive equations.…”

Section: Introductionmentioning

confidence: 99%

Failure in notched tension bars due to high-temperature creep: Interaction between nucleation controlled cavity growth and continuum cavity growth

Hayhurst

Lin

Hayhurst

2008

International Journal of Solids and Structures

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For axi-symmetrically notched tension bars [Dyson, B.F., Loveday, M.S., 1981, Creep Fracture in Nimonic 80A under Tri-axial Tensile Stressing, In: Ponter A.R.S., Hayhurst, D.R. (Eds.), Creep in Structures, Berlin, show two types of damage propagation are shown: for low stress, failure propagates from the outside notch surface to the centre-line; and for high stress, failure propagates from the centre-line to the outside notch surface. The objectives of the paper are to: identify the physics of the processes controlling global failure modes; and, describe the global behaviour using physics-based constitutive equations.Two sets of constitutive equations are used to model the softening which takes place in tertiary creep of Nimonic 80A at 750°C. Softening by multiplication of mobile dislocations is firstly combined, for low stress, with softening due to nucleation controlled creep constrained cavity growth; and secondly combined, for high stress, with softening due to continuum void growth. The Continuum Damage Mechanics, CDM, Finite Element Solver DAMAGE XX has been used to study notch creep fracture. Low stress notch behaviour is accurately predicted provided that the constitutive equations take account of the effect of stress level on creep ductility. High stress notch behaviour is accurately predicted from a normalized inverse cavity spacing d/2' = 6, and an initial normalized cavity radius r hi /' = 3.16 · 10 À3 , where 2' is the cavity spacing, and d is the grain size; however, the constants in the strain rate equation required recalibration against high stress notch data. A void nucleation mechanism is postulated for high stress behaviour which involves decohesion where slip bands intersect second phase grain boundary particles. Both equation sets accurately predict experimentally observed global failure modes. Nomenclature Stress r 1Uni-axial stress r ij Stress tensor r e (=3r ij r ij /2) 1/2 Effective stress r 0Normalizing stress S ij Stress deviation tensor J 1 Normalized first stress invariant R ij ð¼ r ij =r 0 Þ Normalized stress tensor S ij ð¼S ij =r 0 Þ Normalized stress deviation tensor R e (=r e /r 0 ) Normalized effective stress Strain _ e 1 Uni-axial creep strain rate _ e ij Creep strain rate tensor _ e o ð¼ A ¼ P Þ Steady-state uni-axial strain rate e o (= r 0 /E) Normalizing strain k ij (= e ij /e o ) Normalized strain tensor _ e e ð¼ 2_ e ij _ e ij =3Þ 1=2 Effective creep strain rate tensor

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Creep Fracture in Nimonic 80A Under Triaxial Tensile Stressing

Cited by 36 publications

References 7 publications

A Review on Damage Mechanisms, Models and Calibration Methods under Various Deformation Conditions

A Review on Damage Mechanisms, Models and Calibration Methods under Various Deformation Conditions

Finite Element and Experimental Studies of Creep Crack Initiation of RENE-95 Superalloy.

Failure in notched tension bars due to high-temperature creep: Interaction between nucleation controlled cavity growth and continuum cavity growth

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