Characterization of stable crack growth through AISI 4340 steel using cohesive zone modeling and CTOD/CTOA criterion

Jadhav, Dipti; Maiti, Sukumar

doi:10.1016/j.nucengdes.2009.11.042

Cited by 10 publications

(10 citation statements)

References 27 publications

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“…Such a behaviour can be simulated best with a model capable of showing softening before final failure, and a Hillerborg et al [44] type cohesive zone model might be used for this purpose. Such cohesive models require the shape of the traction-separation law, cohesive energy, maximum stress and critical displacement at which the softening behaviour starts, though it has been shown that the shape of the tractionseparation law has little effect on the crack initiation load, specially when the cohesive energy is low and constant [45][46][47]; this would be appropriate for graphite. Comprehensive studies by Cornet et al [48] and later Schwalbe et al [49] have shown that for quasi-brittle materials such as graphite, the cohesive energy can be considered equal to the energy release rate measured from a standard high constraint fracture test and the maximum stress in the cohesive model can be considered to be equal to the tensile strength.…”

Section: Discussionmentioning

confidence: 99%

Fracture behaviour of an anisotropic polygranular graphite (PGA)

Mostafavi

Schmidt

Marsden

et al. 2012

Materials Science and Engineering: A

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a b s t r a c tThis paper reports a numerical and experimental study on the mechanical and fracture properties of an anisotropic polygranular graphite: extruded nuclear grade Pile Grade A (PGA). The dynamic elastic moduli and Poisson's ratios were measured by the ultrasonic method and the fracture toughness was investigated using compact tension (CT) specimens: both as a function of orientation relative to the material grain direction. Digital image correlation was applied to monitor the full displacement field of the surface of the CT specimens, allowing the propagating crack and the fracture process zone around the tip of the crack to be observed and quantified. Rising fracture resistance (R-curve) behaviour is observed before unstable fracture, commensurate with the observed fracture process zone. We show that to accurately obtain the fracture resistance, the material anisotropy must be properly accounted for. This is demonstrated by comparing the experimental data for specimen compliance with finite element simulations for isotropic and orthotropic material properties. Digital image correlation validated the crack dimensions that were obtained from specimen stiffness, which was dominated by the lower of the anisotropic elastic moduli for all orientations. The use of a numerical method to evaluate fracture resistance, based on the incremental work done with crack extension (after Turner and Kolednik) is shown to be not reliable when the crack extension increments are insufficiently small relative to the gradient of the fracture resistance curve. There is a significant difference between the fracture properties of PGA with respect to the extrusion direction; cracks propagating across the extrusion direction (i.e. against the grain direction) have a fracture resistance that is approximately 50% higher than that for cracks propagating in a plane containing the extrusion direction.

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Section: Discussionmentioning

confidence: 99%

Fracture behaviour of an anisotropic polygranular graphite (PGA)

Mostafavi

Schmidt

Marsden

et al. 2012

Materials Science and Engineering: A

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“…A blunt notch geometry would need to be used in the model to improve the agreement between numerical and experimental P versus LLD results. In addition, it is generally expected that full three‐dimensional analyses (rather than the present plane strain analyses) would be needed to reproduce a closer agreements …”

Section: Finite Element Simulationsmentioning

confidence: 99%

“…It has been used extensively in analysing crack propagation in the aircraft industry for aluminium alloys 6,7 and in the nuclear industry for pressure vessel steels. 8,9 Several researchers have simulated ductile crack growth with CZM and extracted CTOA for pipeline steels. For example, the group of researchers in Engineering Mechanics Corporation of Columbus 10 used the classical cohesive zone (CZ) model discussed by Tvergaard and Hutchinson.…”

Section: N O M E N C L a T U R E A = Crack Lengthmentioning

confidence: 99%

“…In addition, it is generally expected that full three-dimensional analyses (rather than the present plane strain analyses) would be needed to reproduce a closer agreements. 6,9,13,22 Crack-tip opening angle For DWTT simulations, the crack tip position was located and CTOA measured using the same procedures described in Results for SSY Simulations. CTOA versus Δa data for the four TH materials are plotted in Fig.…”

Section: Load Versus Load-line Displacement Curvesmentioning

confidence: 99%

“…For this purpose, the cohesive zone modelling (CZM), originally developed by Tvergaard and Hutchinson, can be used. It has been used extensively in analysing crack propagation in the aircraft industry for aluminium alloys and in the nuclear industry for pressure vessel steels . Several researchers have simulated ductile crack growth with CZM and extracted CTOA for pipeline steels.…”

Section: Introductionmentioning

confidence: 99%

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Simulation of ductile crack propagation and determination of CTOAs in pipeline steels using cohesive zone modelling

Dunbar

Wang

Tyson

et al. 2014

Fatigue Fract Eng Mat Struct

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This paper presents recent results of numerical studies on stable crack extension of high toughness steels typical of those in modern gas pipelines using cohesive zone modelling (CZM). The main focus of the work is on the determination of crack‐tip opening angles (CTOAs) of these steels from CZM. Two sets of materials are modelled. The first material set models a typical structural steel, with variable toughness described by four traction–separation (TS) laws. The second set models an X70 pipe steel, with three different TS laws. For each TS law, there are three defining parameters: the maximum cohesive strength, the final separation and the work of separation. The specimens analysed include a crack in an infinite plate (small‐scale yielding, SSY) and a standard drop‐weight tear test (DWTT). Fracture propagation characteristics and values of CTOA are obtained from these two types of specimens. It is shown that cohesive zone models can be successfully used to simulate ductile crack propagation and to numerically measure CTOAs. The ductile crack propagation characteristics and CTOAs obtained from SSY and DWTT specimens are compared for each set of steels. In addition, the CTOA results from numerical CZM of DWTT specimens of X70 steel are compared with those from laboratory tests.

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