Small punch testing of P91 steel

Milička, K.; Dobeš, F.

doi:10.1016/j.ijpvp.2006.07.009

Cited by 90 publications

(76 citation statements)

References 14 publications

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“…Fig. 22 Experimental results and lifetimes predicted by the upper and lower bounds for a large number of tempered martensitic materials at temperatures between 500 and 700 • C (CEA/SRMA, Abe et al 2001;Milicka and Dobes 2006;Sklenička et al 2003;Gaffard 2005;Sawada et al 2001;Abe 2008) This is due to the use of the lower and upper limits of δ D r under the exponent k(≈ 90) that leads to a difference by a factor 2.5, and lower and upper bounds of the fraction t min /t R that causes a difference by a factor 1.6. Therefore, to improve lifetime prediction, the time fraction, t min /t R , and (if possible) the initial variation of the diameter δ D should be more accurately measured.…”

Section: Derivation Of Simple Lower and Upper Boundsmentioning

confidence: 99%

Modelling and experimental study of the tertiary creep stage of Grade 91 steel

et al. 2011

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International audienceThis article addresses experimental studies and analytical simulations of the tertiary creep stage of Grade 91 steel tested at various stresses and temperatures between 500°C (up to 160 × 103 h) and 600°C (up to 94 × 103 h). The strain rate increases after its minimum mainly because of the softening of the material which microstructure evolves strongly during creep deformation. An interrupted creep test shows that necking significantly affects the acceleration of the reduction in cross-section only during the last 10% of the creep lifetime. The Hoff model based on homogeneous reduction of cross-section correctly predicts lifetimes only for high applied stress. The Hart necking model using the Norton power-law allows fair predictions of lifetimes up to 60 × 103 h at 500°C. The necking model using a modified Norton power-law combined with a material softening term allows predictions of lifetimes for all creep tests, differing from the experimental results by less than 50%, which is consistent with the experimental scatter. The evolution of the cross-section predicted by this model is in agreement with measurements carried out during the interrupted creep test. Two prediction rules for the lifetime prediction are deduced from the necking model that takes into account the material softening. For a large number of tempered martensitic steels, these two criteria bound the experimental lifetimes up to 200 × 103 h at 500-700°C

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Section: Derivation Of Simple Lower and Upper Boundsmentioning

confidence: 99%

Modelling and experimental study of the tertiary creep stage of Grade 91 steel

et al. 2011

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“…pre L pre = yield L yield (20) Expressing equation (20) in the form of equation (21), it is possible to derive d pre as in equation (22) (22) L pre and L yield are given in equation (23) and in equation (24), respectively, where L 0 is the initial specimen gauge length.…”

Section: Plastic Part Of Pre-strainingmentioning

confidence: 99%

“…Specimen designs are simple (a disk) and therefore far easier to manufacture than, say, the miniature samples proposed by the Electrical Power Research Institute (EPRI) [1]. Unlike other creep samples, such as the small ring specimen [2], the small punch creep test specimen is taken to failure, therefore it is expected that creep rupture data can also be evaluated using SPCT [14][15][16][17][18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Analysis of Initial Plasticity in P91 Steel Small Punch Creep Samples

et al. 2017

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To date, the complex behaviour of small punch creep test (SPCT) specimens has not been completely understood, making the test hard to numerically model and the data difficult to interpret. This paper presents a novel numerical model able to generate results that match the experimental findings. For the first time, pre-strained uniaxial creep test data of a P91 steel at 600 • C have been implemented in a conveniently modified Liu and Murakami creep damage model in order to simulate the effects of the initial localised plasticity on the subsequent creep response of a small punch creep test specimen. Finite element (FE) results, in terms of creep displacement rate and time to failure, obtained by the modified Liu and Murakami model are in good agreement with experimental small punch creep test data. The rupture times obtained by the FE calculations which make use of the non-modified creep damage model are one order of magnitude shorter than those obtained by using the modified constitutive model. Although further investigation is needed, this novel approach has confirmed that the effects of initial localised plasticity, taking place in the early stages of small punch creep test, cannot be neglected. The new results, obtained by using the modified constitutive model, show a significant improvement with respect to those obtained by a 'state of the art' creep damage constitutive model (the Liu and Murakami constitutive model) both in terms of minimum load-line displacement rate and time to rupture. The new modelling method will

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“…The proportionality factor k is probably independent on the temperature; however, it is dependent on the thickness of the disc θ 0 and the geometry of the actual small-punch device, which has recently been confirmed by Milička and Dobeš [18]. In this paper we tried to use an improved powerlaw, stress-dependent, energy-barrier model to describe the creep behaviour of 9Cr-1Mo-0.2V steel during small-punch creep testing.…”

Section: Introductionmentioning

confidence: 77%

“…The value of this stress is not known, since only the load P is measured for a particular disc thickness and geometry of the small-punch testing device. Since Milička and Dobeš [17,18] experimentally determined the linear dependence between the stress σ during a conventional, uniaxial, tensile creep test and the load P during a smallpunch creep test, which results in an identical time-to rupture t r (Eq. (3)), Eq.…”

Section: Resultsmentioning

confidence: 99%

An improved, stress-dependent, energy-barrier model for the creep of 9Cr-1Mo-0.2V steel under disc-bend loading

Nagode¹,

Ule²,

Kosec³

et al. 2010

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In this paper we describe the creep behaviour of 9Cr-1Mo-0.2V steel under disc-bend loading, also known as the small-punch method. An improved power-law, stress-dependent, energy-barrier model was used to describe the creep behaviour of 9Cr-1Mo-0.2V steel because the characteristics of this steel cannot be accurately described using a simple, Arrhenius-type power law. A good correlation between the calculated values from the improved model and the experimental data was obtained for discs of different thickness, i.e., 0.50 mm, 0.47 mm and 0.44 mm. We found that the optimum disc thickness for our small-punch device was 0.50 mm. The stress-dependent, apparent activation energy of creep for a disc thickness of 0.50 mm decreased from ∼ 543 kJ mol

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Small punch testing of P91 steel

Cited by 90 publications

References 14 publications

Modelling and experimental study of the tertiary creep stage of Grade 91 steel

Modelling and experimental study of the tertiary creep stage of Grade 91 steel

Experimental and Numerical Analysis of Initial Plasticity in P91 Steel Small Punch Creep Samples

An improved, stress-dependent, energy-barrier model for the creep of 9Cr-1Mo-0.2V steel under disc-bend loading

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