Prediction of long-term creep behaviour of Grade 91 steel at 873 K in the framework of microstructure-based creep damage mechanics approach

Christopher, J.; Choudhary, B.K.

doi:10.1177/1056789518796118

Cited by 16 publications

(10 citation statements)

References 48 publications

(80 reference statements)

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“…The four parameters associated with the model such as trueε˙0, trueω˙0, m and q were optimised by relative least-square error minimisation (Christopher and Choudhary, 2019; Shahsavari et al., 2016). In general, either gradient based or derivative-free methodologies were employed in the optimisation techniques with or without constraints/bounds to obtain the model parameters (Christopher and Choudhary, 2019; Imran et al., 2020; Wardeh and Toutanji, 2017; Yang et al., 2019). The gradient based interior-point technique was adopted in the present investigation due to its fastest convergence of parameter optimisation towards the global minimum.…”

Section: Kachanov–rabotnov Model and Its Numerical Implementationmentioning

confidence: 99%

Influence of varying nitrogen on creep deformation and damage behaviour of type 316L in the framework of continuum damage mechanics approach

Christopher

Praveen

Ganesan

et al. 2020

International Journal of Damage Mechanics

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In the present study, Kachanov–Rabotnov continuum damage model has been employed to describe the steady state and tertiary creep deformation and damage behaviour of 316L austenitic stainless steel with different nitrogen contents of 0.07, 0.11 and 0.22 wt%, at 923 K. For all the nitrogen contents, the model appropriately predicts the creep strain–time data, creep rupture strain and rupture life. The model parameters such as characteristic strain and damage rates systematically decrease with the increase in nitrogen content. The derived iso-damage contours superimposed on creep strain–time data indicate that the evolution kinetics of strain, as well as damage, are unique at each applied stress level. For nitrogen added type 316L SS, the critical damage value ( ωcr) at which creep failure takes place is found to be less than 1 and is in the range of 0.35–0.60. It is observed that the dominance of damage rate ([Formula: see text]) over the strain rate ([Formula: see text]) increases with increasing nitrogen content from 0.07 to 0.22% N for the steel. A direct correlation has been established between the creep rupture ductility and the ratio of strain rate to damage rate, i.e. [Formula: see text]/[Formula: see text] using the Kachanov–Rabotnov model for different nitrogen contents and stress levels.

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Section: Kachanov–rabotnov Model and Its Numerical Implementationmentioning

confidence: 99%

Influence of varying nitrogen on creep deformation and damage behaviour of type 316L in the framework of continuum damage mechanics approach

Christopher

Praveen

Ganesan

et al. 2020

International Journal of Damage Mechanics

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“…The rate of longitudinal true stress evolution is calculated in Figure 5d from the constant volume assumption _ σ yt ¼ σ yt _ ε which is applied in constant-load damage mechanics prior to tertiary necking. [34] Secondly, DIC creep strains are compared with strains measured using traditional linear variable differential transducers (LVDTs) during conventional creep testing at a single temperature and stress. Creep curves at the stress corresponding to the nominal stress applied in the conventional setup were obtained by linearly interpolating the DIC strain fields at y positions that were correlated with the location of the required stress in the FEM model.…”

Section: Validation Of Strain Measurementsmentioning

confidence: 99%

“…Quantitative microstructural characterisation at several stresses from a single specimen are conducive to understanding the coarsening kinetics of creep obstacles in microstructure-based rate equations in CDM formulations. [34]…”

Section: Threshold Stress As a Damage Indicatormentioning

confidence: 99%

Creep deformation measurement of ex‐service 12% Cr steel over nonuniform stress fields using digital image correlation

Rooyen

Forsey

Güngör

et al. 2021

Strain

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Deterioration assessment of materials is essential to the continued effective operation of critical components in thermal power plants. Establishing the degree of creep exhaustion of power engineering alloys operating at high temperatures and stresses guides maintenance strategies to ensure reliable plant operation. Within progressive inspection philosophies, traditional laboratorybased creep testing is often difficult to conduct on ex-service steel due to the limited material availability from which to machine standard specimen geometries. This work investigates a technique for the measurement of creep strain curves at several stresses and at 600 C from a single test using a nontraditional specimen geometry together with full-field strain measurement through digital image correlation (DIC). Of interest is ex-service X20CrMoV12-1 (X20) which is widely used in older, subcritical thermal power plants. The paper aims to show that multiple creep curves can be resolved over a spatially varying stress field using DIC whilst preserving material economy. Differences in creep behaviour between ex-service X20 with varying levels of service exposure are evident from quantitative comparisons of the creep strain and rate curves through threshold stress computation which agrees with hardness measurements and microstructural observation of subgrains and precipitates using electron microscopy. These single-specimen tests yield high densities of creep data which can be used in the calibration of creep damage models for characterisation of ex-service X20.

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“…The mechanical properties reflect the damage resistance of composites under different loading conditions, which is an important index for the safety design of components (Baranger, 2013; Chen et al., 2007; Christopher and Choudhary, 2019; Marcin et al., 2011). It is directly related to the safety and reliability of components in service and the predictability of damage (Bache et al., 2019; Baranger, 2019; Mareau and Morel, 2019; Matta et al., 2019; Yu et al., 2019).…”

Section: Introductionmentioning

confidence: 99%

A time-dependent tensile constitutive model for long-fiber-reinforced unidirectional ceramic-matrix minicomposites considering interface and fiber oxidation

2020

International Journal of Damage Mechanics

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In this paper, a time-dependent tensile constitutive model of long-fiber-reinforced unidirectional ceramic-matrix minicomposites is developed considering the interface and fiber oxidation. The relationship between the time-dependent tensile behavior and internal damage is established. The damage mechanisms of time-dependent matrix cracking, fiber/matrix interface debonding, fiber failure, and the oxidation of the interface and fiber are considered in the analysis of the time-dependent tensile stress–strain curve. The fracture mechanic approach, matrix statistical cracking model, and fiber statistical failure model are used to determine the time-dependent interface debonding length, matrix crack spacing, and the fiber failure probability considering the time-dependent interface and fiber oxidation. The effects of the fiber volume, fiber radius, matrix Weibull modulus, matrix cracking characteristic strength, matrix cracking saturation spacing, interface shear stress, interface debonding energy, fiber strength, fiber Weibull modulus, and oxidation time on the time-dependent tensile stress–strain curves, matrix cracking density, interface debonding, and fiber failure are discussed. The experimental time-dependent tensile stress–strain curves, matrix cracking, interface debonding, and fiber failure of four different unidirectional SiC/SiC minicomposites for different oxidation time are predicted. The composite tensile strength and failure strain increase with the fiber volume, fiber strength, and fiber Weibull modulus, and decrease with the oxidation time; the fiber/matrix interface debonding length increases with the fiber radius and oxidation time and decreases with the interfacial shear stress and interface debonding energy; the fiber/matrix interface oxidation ratio increases with the interfacial shear stress, interface debonding energy, and oxidation time and decreases with the saturation matrix crack spacing.

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Prediction of long-term creep behaviour of Grade 91 steel at 873 K in the framework of microstructure-based creep damage mechanics approach

Cited by 16 publications

References 48 publications

Influence of varying nitrogen on creep deformation and damage behaviour of type 316L in the framework of continuum damage mechanics approach

Influence of varying nitrogen on creep deformation and damage behaviour of type 316L in the framework of continuum damage mechanics approach

Creep deformation measurement of ex‐service 12% Cr steel over nonuniform stress fields using digital image correlation

A time-dependent tensile constitutive model for long-fiber-reinforced unidirectional ceramic-matrix minicomposites considering interface and fiber oxidation

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