Modelling the initiation of cleavage fracture of ferritic steels

Roberts, Steve; Noronha, S. J.; Wilkinson, Angus J.; Hirsch, P. B.

doi:10.1016/s1359-6454(01)00425-6

Cited by 38 publications

(29 citation statements)

References 37 publications

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“…The model gave a similar grain size dependence of T C to that given by Petch [13] except for T C increasing with increase in carbide thickness. More recently, Roberts, Noronha, Wilkinson and Hirsch have employed an analogous relation to equation (3.4), with addition of a plastic work term, w p , to γ C and specified σ * C to be determined by emission of dislocations from the cracked carbide [49]. Consideration of any grain size effect was excluded.…”

Section: (B) Carbide Crackingmentioning

confidence: 99%

Material grain size and crack size influences on cleavage fracturing

Armstrong

2015

Phil. Trans. R. Soc. A.

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A review is given of the analogous dependence on reciprocal square root of grain size or crack size of fracture strength measurements reported for steel and other potentially brittle materials. The two dependencies have much in common. For onset of cleavage in steel, attention is focused on relationship of the essentially athermal fracture stress compared with a quite different viscoplastic yield stress behaviour. Both grain-size-dependent stresses are accounted for in terms of dislocation pile-up mechanics. Lowering of the cleavage stress occurs in steel because of carbide cracking. For crack size dependence, there is complication of localized crack tip plasticity in fracture mechanics measurements. Crack-size-dependent conventional and indentation fracture mechanics measurements are described also for results obtained on the diverse materials: polymethylmethacrylate, silicon crystals, alumina polycrystals and WC-Co (cermet) composites.

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Section: (B) Carbide Crackingmentioning

confidence: 99%

Material grain size and crack size influences on cleavage fracturing

Armstrong

2015

Phil. Trans. R. Soc. A.

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“…A dislocation is emitted from the source when τ res (z 01 ) exceeds a critical value. The friction shear stress, τ f , the material resistance against the dislocation movement, is used for the critical value in the same consideration as the other researchers (7), (8), (10) . When the dislocation emission criterion is satisfied, a new dislocation will be emitted and allowed to move away from the source.…”

Section: Dislocation Emission and Movement From The Crack Tipmentioning

confidence: 99%

“…Dislocations subjected to the resolved shear stresses larger than τ f will move at a certain traveling velocity along the inclined slip line. The empirical dislocation traveling velocity law (7), (8) , which is related to the resolved shear stress at each dislocation position, is used in this work: The first equation shows that if the resolved shear stress τ res (z ij ) is less than the critical stress, the dislocation does not move. The second equation shows that if the resolved shear stress is greater than the critical stress, the dislocation will move at the velocity proportional to excess extend from the critical value and the m -th power of the resolved shear stress.…”

Section: Dislocation Emission and Movement From The Crack Tipmentioning

confidence: 99%

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Experimental and Discrete Dislocation Dynamics Approach to Initiation of Cleavage Fracture under Short Pulse Loads

Tran

Homma

2009

JMMP

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Mode I crack initiation properties under stress intensity pulses with durations of 25, 50 and 100 µs are investigated by experiment and discrete dislocation dynamics. The cleavage fracture initiation is examined under the consideration of the pile-up of dislocations against an obstacle ahead of the crack tip and the coalescence of piled-up dislocations. In the experiment, under very short pulse loads with the duration of less than 50 µs, the dynamic fracture toughness, K Id remarkably increases and the crack tip opening displacement is closely correlated with K Id . The numerical results are compared with the experimental ones in reasonable agreement.

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“…Dynamic models use moving dislocations that have been emitted from a dislocation source at or near the crack tip to describe the plastic flow. Dynamic models have been used to study brittle-ductile transitions for long mode I cracks such as (Tanaka et al 2008;Hirsch et al 1989); small double ended microcracks (Roberts et al 2002) and fatigue cracks under mode I and II loading (e.g. Wilkinson et al 1998;Riemelmoser et al 1997).…”

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confidence: 99%

Dislocation modeling of quasi-static crack propagation in an elasto-plastic medium

Stoll

Wilkinson

2010

Int J Fract

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A dislocation model for simulating twodimensional quasi-static crack propagation is presented. The crack and plastic flow along slip planes are described using dislocation dipoles. A stationary crack can be modeled as well as a propagating crack along a straight line inclined at an arbitrary angle to a free surface of a semi-infinite medium. Cracks are also allowed to kink. A superdipole algorithm is introduced to save simulation time without loosing important information and necessary geometric details. It reduces the number of dislocation dipoles on slip planes in the plastic wake. The paper gives results on crack shapes for stationary and advancing cracks as well as it describes how the size of the plastic zone depends on crack inclination angles. Results on stress intensity factors (SIF) are given using two different approaches as well as kinking cracks are introduced and SIF at kinked crack tips are calculated.

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Modelling the initiation of cleavage fracture of ferritic steels

Cited by 38 publications

References 37 publications

Material grain size and crack size influences on cleavage fracturing

Material grain size and crack size influences on cleavage fracturing

Experimental and Discrete Dislocation Dynamics Approach to Initiation of Cleavage Fracture under Short Pulse Loads

Dislocation modeling of quasi-static crack propagation in an elasto-plastic medium

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