Ratchetting strain as a driving force for fatigue crack growth

Tong, Jie; Li, Zhao; Lin, Bing

doi:10.1016/j.ijfatigue.2012.01.003

Cited by 52 publications

(22 citation statements)

References 24 publications

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“…Here, two parameters, namely the accumulated inelastic strain and oxygen concentration, were used to represent the viscoplastic deformation and the oxidation effect, respectively. The accumulated inelastic strain, highly localised to the crack tip [27,37], has been successfully used to predict crack growth rate in vacuum (without oxidation) [52,53]. The idea proposed here is to use the two parameters to construct a failure curve from which crack growth prediction under fatigue-oxidation may be made.…”

Section: Failure Curvementioning

confidence: 99%

Oxygen diffusion and crack growth for a nickel-based superalloy under fatigue-oxidation conditions

Karabela

Lin

et al. 2013

Materials Science and Engineering: A

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Advanced microscopy characterisation and numerical modelling have been carried out to investigate oxygen diffusion and crack growth in a nickel-based superalloy under fatigue-oxidation conditions. Penetration of oxygen into the material and the associated internal oxidation, which leads to material embrittlement and failure, have been found from Focused Ion Beam (FIB) examinations. Applied fatigue loading tends to enhance the extent of internal oxidation for temperatures at 750°C and above. Using a submodelling technique, finite element analyses of oxygen penetration at grain level have been carried out to quantify the fatigue-oxidation damage and calibrate the diffusion parameters based on the measurements of maximum depth of internal oxidation. The grain microstructure was considered explicitly in the finite element model, where the grain boundary was taken as the primary path for oxygen diffusion. A sequentially coupled mechanical-diffusion analysis was adopted to account for the effects of deformation on diffusion during fatigue loading, for which the material constitutive behaviour was described by a crystal plasticity model at grain level. Prediction of oxidation-assisted crack growth has also been carried out at elevated temperature from the finite 2 element analyses of oxygen diffusion near a fatigue crack tip. A failure curve for crack growth has been constructed based on the consideration of both oxygen concentration and accumulated inelastic strain near the crack tip. The predictions from the fatigue-oxidation failure curve compared well with the experimental results for triangular and dwell loading waveforms, with significant improvement achieved over those predicted from the viscoplastic model alone.

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Section: Failure Curvementioning

confidence: 99%

Oxygen diffusion and crack growth for a nickel-based superalloy under fatigue-oxidation conditions

Karabela

Lin

et al. 2013

Materials Science and Engineering: A

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“…Progressive accumulation of strain was found in a compact tension (CT) specimen under cyclic loading conditions. Further extensive modelling work has since been carried out using a number of constitutive modelling tools, including visco-plasticity [8][9][10], crystal-plasticity [10,11] and Discrete Dislocation Dynamics [12], in both two and three dimensions, selected materials (nickel alloys, titanium alloy), specimen geometries (CT, single edge notch tension and 3D aerofoil specimen) and temperatures (room temperature, 300, 650°C) and at variable loading conditions. Encouragingly, strain ratchetting was found common in all the cases examined.…”

Section: Introductionmentioning

confidence: 99%

In Situ Experimental Study of Near-Tip Strain Evolution of Fatigue Cracks

Lupton

Zhu

et al. 2015

Exp Mech

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Near crack tip strain fields in a stationary and a growing fatigue crack have been studied in situ using the Digital Image Correlation (DIC) technique in a compact tension specimen of stainless steel 316 L under tensiontension cyclic loading. The evolution of near-tip strains normal to the crack plane was monitored at selected locations ahead of the crack tip in consecutive cycles during fatigue crack growth experiments. A stationary crack was examined first to provide a baseline reference whilst the evolution of the strain field ahead of a growing crack was monitored in situ at peak loads during fatigue cycling. The results show that strain accumulation with loading cycle occurred at all tracked locations in both cases, and it is particularly evident close to the crack tip. Moreover, a higher strain accumulation rate was found near the growing crack tip than that near the stationary crack tip. The results on near-tip strain evolution were collected for the first time in situ during the fatigue crack growth experiments, which may hopefully inform a physical-based modelling strategy of fatigue crack growth.

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“…Usually, wheel fatigue failure modes are divided into three failure types that correspond with different initiation locations: surface, sub-surface and deep-surface [10,11]. With surfaceinitiated cracks, one of the damage mechanisms is called ratchetting [12,13] and typically occurs on the surface layers of wheels. The main causes of surface ratchetting are high friction loads that act parallel to the surface.…”

Section: Introductionmentioning

confidence: 99%