Crack growth in the presence of limited creep deformation

Kwon, Oh Geon; Nikbin, Kamran; Webster, G. A.; Jata, Kumar V.

doi:10.1016/s0013-7944(98)00081-2

Cited by 14 publications

(9 citation statements)

References 13 publications

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“…In accordance w ith [19], t'in is the tim e from the instant o f load application to the crack increm ent by 0.2 m m , w hich can be determ ined approxim ately using the technique described earlier [14]. In addition, this m agnitude o f the increm ent corresponds to the onset o f the steady-state grow th o f the creep crack, as noted by m any researchers [4,16,19].…”

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confidence: 90%

Theoretical-experimental model for predicting crack growth rate in structural alloys under combined action of fatigue and creep

et al. 2009

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[4][5][6]. Also, there is a lack o f experimental data and theoretical generalization on crack propagation for a trapezoidal load cycle w ith various hold periods under m aximum load [7,8]. The m ajority of researchers in this case restrict them selves to the use o f the linear dam age sum m ation hypothesis based on the independent dam aging effect o f fatigue and creep [2,9]. Som etim es, they determ ine the m aterial susceptibility to a certain m ode o f fracture (fatigue or tim e-dependent) and, on this basis, choose the fracture m echanics param eters to describe experim ental crack grow th rate data [10,11]. It is notew orthy that such approaches do not always yield satisfactory results and require further experim ental and physical substantiation.E arlier [12,13], on the basis o f the experim ental data obtained and calculations perform ed, it was show n that the m ost com m only used approaches give no w ay o f predicting the crack grow th kinetics in the alloys under study to sufficient accuracy. In this paper, w e w ill discuss the m ethods proposed for the solution o f the above problem .R esea rch T ask S ta tem en t. H igh-tem perature nickel-based alloys EP742 and EP962 for aircraft applications w ere used as m odel m aterials. Their m echanical properties and other characteristics as w ell as the experim ental procedure w ere detailed earlier in [12,14]. The m aterials under study are used to m anufacture long-life aircraft gas-turbine engine (A G TE) disks. The service conditions (flight cycle) involve operation o f the m aterial under cyclic loading w ith long hold periods at m axim um load in a cycle. The solution o f this problem m akes it

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Theoretical-experimental model for predicting crack growth rate in structural alloys under combined action of fatigue and creep

et al. 2009

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“…The limits set in equation (4) can be practically utilised to identify the relative limits of the applicability of the parameter C* [5,12]. It is found that creep crack growth rate a & can be correlated satisfactorily in terms of C* by the relation [11,12] …”

Section: Model For Creep Crack Growthmentioning

confidence: 99%

“…For plane stress conditions the appropriate failure strain * f ε is taken to be the uniaxial failure strain, ε f , and for plane strain situations * f ε can be as low as ε f /30 [11][12]. Experimentally it has been shown that the upperbound of 30 is conservative for most creep ductile situations.…”

Section: Model For Creep Crack Growthmentioning

confidence: 99%

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Justification for meso-scale modelling in quantifying constraint during creep crack growth

Nikbin

2004

Materials Science and Engineering: A

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Abstract.Meso-scale models over a range of 50-500 μm are employed for predicting crack growth in the creep range. They make use of fracture mechanics, creep damage mechanics under multiaxial loading and limit analysis techniques. A study is made of the several levels of approximations and validations in the modelling process that are needed in order to make the method an acceptable tool for use in a safe defect assessment procedure. The NSW mesoscale model developed previously has been used to compare crack growth rate in a 316H Preliminary results using two-dimensional modelling of a CCP specimen under plane strain conditions suggest that the method could be used to predict conservative estimates for crack growth rates when compared to experimental results. Further numerical analysis using threedimensional models of actual geometric sizes are necessary to confirm the usefulness of the two parameter method in defect assessment procedures.

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“…A crack extension at high temperatures under susas engineering materials especially for high-temperature tained load is characterized by an incubation period, a period structural applications, thanks to beneficial attributes, such of decreasing crack growth rates ("transient regime"), a period as low density and high high-temperature strength and moduof steady-state crack growth rate, and final failure. [12][13][14][15][16][17][18][19][20][21][22][23][24] In lus retention, as well as advances in processing. [1][2][3][4] For the creep-brittle materials, [14,18,21,23] it has been shown that the last 10 years, low-temperature property evaluations have incubation period and the transient regime can be quite a been extensive worldwide; however, the increasing need substantial portion of the total life.…”

Section: Introductionmentioning

confidence: 99%

Crack growth in a nearly fully-lamellar gamma TiAl alloy at 650 °C and 800 °C under constant load conditions

Kim

Jata

2002

Metall Mater Trans A

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The crack growth behavior of a gamma titanium aluminide alloy, K5S, was investigated at 650 ЊC and 800 ЊC under constant load conditions in a nearly fully-lamellar microstructural form. Crack growth at both temperatures ensues at stress intensities (K ) much higher than anticipated from the R curves. At 650 ЊC, creep crack extension occurs through the formation of microcracks (interlamellar (IL) separation) and their joining to the main crack tip through ligament fracture. This results in a mainly transgranular (TG) fracture with occasional IL separation. This process features a rapid initial crack growth but at decreasing growth rate, followed by a nearly no-growth stage. At 800 ЊC, crack extension is accompanied by extensive plastic deformation and consists of an initial rapid transition period and a subsequent steady state. For similar K's, crack extension and growth rate are greater at 800 ЊC than at 650 ЊC, but even these are very slow processes for this alloy. The resistance to crack propagation at 650 ЊC is explained in terms of work hardening that arises during the extended primary creep deformation occurring ahead of the crack tip. Increased crack propagation at 800 ЊC is accredited to grain boundary and lamellar-interface weakening and extensive post primary creep damage in the plastic zone. The resulting fracture at 800 ЊC is mainly boundary fracture, which consists of IG fracture involving formation and coalescence of voids, and IL separation.

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Crack growth in the presence of limited creep deformation

Cited by 14 publications

References 13 publications

Theoretical-experimental model for predicting crack growth rate in structural alloys under combined action of fatigue and creep

Theoretical-experimental model for predicting crack growth rate in structural alloys under combined action of fatigue and creep

Justification for meso-scale modelling in quantifying constraint during creep crack growth

Crack growth in a nearly fully-lamellar gamma TiAl alloy at 650 °C and 800 °C under constant load conditions

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