Time-Dependent Fracture Mechanics

The tensile-creep and creep-fracture behavior of as-cast Mg-11Y-5Gd-2Zn-0.5Zr (wt%) (WGZ1152) was investigated at temperatures between 523 and 598 K (0.58-0.66T m ) and stresses between 30 and 140 MPa. The creep stress exponent was close to five, suggesting that dislocation creep was the dominant creep mechanism. The activation energy for creep (233 ± 18 kJ/mol) was higher than that for self-diffusion in magnesium, and was believed to be associated with cross-slip, which was the dominant thermally-aided creep mechanism. This was consistent with the surface observations, which suggested non-basal slip and cross-slip were active at 573 K. The minimum creep rate and fracture time values fit the original and modified Monkman-Grant models. In situ creep experiments highlighted the intergranular cracking evolution. The creep properties and behavior were compared with those for other high-temperature creep-resistant Mg alloys such as WE54-T6 and HZ32-T5.

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“…The creep damage tolerance parameter k measures the tolerance of a material to strain concentrations, and is given by [18].…”

Section: Initial Microstructurementioning

confidence: 99%

Creep and fracture behavior of as-cast Mg–11Y–5Gd–2Zn–0.5Zr (wt%)

et al. 2012

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“…The creep damage tolerance parameter λ measures the tolerance of the material to strain concentrations, and is given by the following equation [20] min…”

Section: Creep Rupturementioning

confidence: 99%

“…[55] The value of λ for engineering alloys ranges from 1 to 20. [20] From Eq. (3), it is evident that when λ=1, fracture occurs as soon as a small amount of damage has occurred and the material is brittle.…”

Section: Creep Rupture Mechanismsmentioning

confidence: 99%

“…With higher values of λ, the material may endure a larger amount of damage before it fails. [20] Theoretical calculation has predicted that when λ ranges from about 1-2.5, grain-boundary cavities and cracks attribute significantly to tertiary creep and final rupture. [55] In the present study, the λ values ranged between 1.4 and 2.5, which implies that grain boundary cavities and cracks may play an important role in the creep rupture.…”

Section: Creep Rupture Mechanismsmentioning

confidence: 99%

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Creep and Fracture Behavior of Peak-Aged Mg-11Y-5Gd-2Zn-0.5Zr (wt pct)

Yin

Wang

Boehlert

et al. 2012

Metall Mater Trans A

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The tensile-creep and creep-rupture behavior of heat-resistant peak-aged Mg-11Y-5Gd-2Zn-0.5Zr (wt.%) (WGZ1152) was investigated at T=523-598K (0.58-0.66T m ) and stresses between 30MPa to 140MPa. The minimum creep rate of the alloy was almost two orders of magnitude lower than that for WE54-T6, and was comparable to that for HZ32-T5. The creep behavior exhibited an extended tertiary creep stage, which was believed to be associated with precipitate coarsening. The creep stress exponent value was 4.5, suggesting that dislocation creep was the rate-controlling mechanism. The activation energy for creep (221±20kJ/mol) was higher than that for self-diffusion in magnesium, and was believed to be associated with the activation of non-basal slip and cross slip. This was consistent with the surface deformation observations, which revealed a transition from basal slip to non-basal slip and cross slip with increasing temperature. The minimum creep rate and rupture time followed the original and modified Monkman-Grant relationships. The microcracks and cavities preferentially nucleated at grain boundaries and at the interface between Mg matrix and the second phase. In-situ creep experiments highlighted the intergranular cracking evolution.

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“…[12] Next we evaluate the function B(T) for the following logarithmic creep functions [Miannay, 2001]:…”

Section: Analysis Of Subcritical Crack Propagation In Viscoelastic Somentioning

confidence: 99%

Magma‐driven subcritical crack growth and implications for dike initiation from a magma chamber

Chen

Jin

2006

Geophysical Research Letters

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[1] The purpose of this paper is to explore a viscoelastic energy dissipation theory for subcritical dike growth from a magma chamber. The theoretical relationship between the dike growth velocity and dike length is established using the viscoelastic subcritical crack growth theory proposed by the first author and the solutions of stress intensity factor at the crack tip derived by a perturbation method. Effects of magma chamber over-pressure, buoyancy and viscoelastic properties of the host rock on the subcritical growth rate are included in the model. The numerical results indicate that the viscous energy dissipation of the host rock could allow a short dike to slowly grow on the order of 10 À7 -10 À5 m/s under modest over-pressure and to accelerate when the stress intensity factor increases close to the fracture toughness, followed by the unstable dike propagation. The proposed theory provides a reasonable understanding of dike initiation process from a magma chamber.Citation: Chen, Z., and Z.-H. Jin (2006), Magma-driven subcritical crack growth and implications for dike initiation from a magma chamber, Geophys.

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Time-Dependent Fracture Mechanics

Cited by 17 publications

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Creep and fracture behavior of as-cast Mg–11Y–5Gd–2Zn–0.5Zr (wt%)

Creep and fracture behavior of as-cast Mg–11Y–5Gd–2Zn–0.5Zr (wt%)

Creep and Fracture Behavior of Peak-Aged Mg-11Y-5Gd-2Zn-0.5Zr (wt pct)

Magma‐driven subcritical crack growth and implications for dike initiation from a magma chamber

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