Relevance of Nonlinear Fracture Mechanics to Creep Cracking

Nikbin, Kamran; Webster, G. A.; Turner, C. E.

doi:10.1520/stp28637s

Cited by 124 publications

(63 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…A major feature of these studies is the development of a parameter that characterizes the crack tip fields as well as crack propagation. Under steady state creep conditions, the so called C * -integral (Landes and Begley 1976;Nikbin et al 1976;Ohji et al 1976) (i.e. the creep J -integral, Rice 1978) can be used to characterize the crack tip fields and creep crack growth.…”

Section: Introductionmentioning

confidence: 99%

“…Riedel 1981;Tvergaard 1984) or strain-rate field (e.g. Cocks and Ashby 1981;Nikbin et al 1984) is the same as that for the undamaged material and used either empirical or mechanistic damage growth laws to determine the crack growth rate. In the strain based models the critical damage at the crack tip is expressed in terms of a material ductility (strain to failure) which is a function of the local stress state.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A theoretical and computational framework for studying creep crack growth

Elmukashfi

Cocks

2017

Int J Fract

View full text Add to dashboard Cite

In this study, crack growth under steady state creep conditions is analysed. A theoretical framework is introduced in which the constitutive behaviour of the bulk material is described by power-law creep. A new class of damage zone models is proposed to model the fracture process ahead of a crack tip, such that the constitutive relation is described by a traction-separation rate law. In particular, simple critical displacement, empirical Kachanov type damage and micromechanical based interface models are used. Using the path independency property of the C * -integral and dimensional analysis, analytical models are developed for pure mode-I steady-state crack growth in a double cantilever beam specimen (DCB) subjected to constant pure bending moment. A computational framework is then implemented using the Finite Element method. The analytical models are calibrated against detailed Finite Element models. The theoretical framework gives the fundamental form of the model and only a single quantityĈ k needs to be determined from the Finite Element analysis in terms of a dimensionless quantity φ 0 , which is the ratio of geometric and material length scales. Further, the validity of the framework is examined by investigating the crack

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A theoretical and computational framework for studying creep crack growth

Elmukashfi

Cocks

2017

Int J Fract

View full text Add to dashboard Cite

show abstract

“…The creep crack growth being an inelastic process, net section stress on (2) and reference stress 0 r (3) have been used to correlate with creep crack growth rates. In 1976, based on the modification of the J integral, a C* integral was suggested to be an appropriate parameter for creep crack growth (4)(5)(6)(7). However, the C* integral represents only the amplitude of the stress strain field ahead of the crack tip when a material is in steady state creep, but the stress relaxation around the crack tip due to creep deformation and crack propagation causes a nonsteady state creep process.…”

Section: Introductionmentioning

confidence: 99%

Creep Crack Growth Behaviour of Alloy 718

Liu¹,

Yan²,

Yan³

et al. 1991

Superalloys 718, 625 and Various Derivatives (1991)

View full text Add to dashboard Cite

The creep crack growth behaviour of Alloy 718 at 923K has been investigated. It is found that its creep crack growth is controlled by stress intensity factor regardless of load level, loading change and crack growing history. The metallographic analysis indicates that the creep crack growth mechanism of this alloy at 923K comprises three stages. Based on this mechanism, a creep crack growth model has been developed where crack growth rates relate with the effective driving force in sinh function. In addition, the effect of microstructure on the creep crack growth behaviour of Alloy 718 has been studied. The results reveal that the crack growth rates strongly depend on the grain size and the carbide structure. These phenomena have been explained by the diffusion and tearing process in the creep crack growth mechanism.

show abstract

“…Consequently, the creep crack growth rates measured from C(T) and M(T) specimens differed from each other. Attempts to find J-like parameters to correlate creep crack growth rates were also made in Europe (Nikbin et al 1976) and in Japan (Taira et al 1979) but the association with crack tip stress fields was not recognized in these studies. Saxena (1980) showed that creep crack growth rates were uniquely correlated with C * -Integral for C(T) and M(T) specimens for 304 stainless steel at 594 • C (1,100 • F) because the necessary conditions of widespread steady-state creep (a term interchangeably used with secondary creep in the literature and here) were established shortly after loading and the creep crack growth rate occurred primarily under this tailor-made conditions for C * to describe the crack tip conditions.…”

Section: Early Developments In Tdfmmentioning

confidence: 99%

Creep and creep–fatigue crack growth

Saxena

2015

Int J Fract

View full text Add to dashboard Cite

Creep and creep-fatigue considerations are important in predicting the remaining life and safe inspection intervals as part of maintenance programs for components operating in harsh, high temperature environments. Time-dependent deformation associated with creep alters the crack tip stress fields established as part of initial loading which must be addressed in any viable theory to account for creep in the vicinity of crack tips. This paper presents a critical assessment of the current state-of-the-art of time-dependent fracture mechanics (TDFM) concepts, test techniques, and applications and describes these important developments that have occurred over the past three decades. It is concluded that while big advances have been made in TDFM, the capabilities to address some significant problems still remain unresolved. These include (a) elevated temperature crack growth in creep-brittle materials used in gas turbines but now also finding increasing use in advanced power-plant components (b) in predicting crack growth in weldments that inherently have cracks or crack-like defects in regions with microstructural gradients (c) in development of a better fundamental understanding of creep-fatigue-environment interactions, and (d) in prognostics of high temperature A. Saxena (B) College of Engineering, University of Arkansas, 130 A John A. White Hall, 790 W. Dickson Street, Fayetteville, AR 72701, USA e-mail: asaxena@uark.edu component reliability. It is also argued that while these problems were considered intractable a few years ago, the advances in technology do make it possible to systematically address them now and advance TDFM to its next level in addressing the more difficult but real engineering problems.

show abstract

Relevance of Nonlinear Fracture Mechanics to Creep Cracking

Cited by 124 publications

References 11 publications

A theoretical and computational framework for studying creep crack growth

A theoretical and computational framework for studying creep crack growth

Creep Crack Growth Behaviour of Alloy 718

Creep and creep–fatigue crack growth

Contact Info

Product

Resources

About