Numerical predictions of carburisation and crack evolution using a combined diffusion rate and remaining multi-axial creep ductility damage model

The multiaxial thermomechanical fatigue properties for nickel-based superalloy GH4169 in aeroengine turbine discs are investigated in this paper. Four types of axial–torsional thermomechanical fatigue experiments were performed to identify the cyclic deformation behavior and the damage mechanism. The experimental results showed that the creep damage can be generated under thermally in-phase loading while it can be ignored under thermally out-of-phase loading, and the responded stress increasing phenomenon, that is, non-proportional hardening, can be shown under the mechanically out-of-phase strain loading. Based on the analysis of cyclic deformation behavior and damage mechanism, a life prediction method was proposed for multiaxial thermomechanical fatigue, in which the pure fatigue damage, the creep damage, and the interaction between them were simultaneously considered. The pure fatigue damage can be calculated by the isothermal fatigue parameters corresponding to the temperature without creep; the creep damage can be calculated by the principle of subdivision, and the creep–fatigue interaction can be determined by creep damage, fatigue damage, and an interaction coefficient which is used to reflect the creep–fatigue interaction strength. The predicted results showed that the proposed method is reasonable.

Section: Introductionmentioning

confidence: 99%

Thermomechanical fatigue life prediction method for nickel-based superalloy in aeroengine turbine discs under multiaxial loading

Shang

Zhang

et al. 2019

“…This law is usually written as a differential equation. For polycrystalline material, which is of particular interest, the material structure can be described by some additional parameters introduced into this equation (cf., e.g., Cocks and Ashby, 1982;Biglari and Nikbin, 2017). The author proposes another form of such a law, written as a set of cellular automata (CA) rules.…”

Section: Introductionmentioning

confidence: 99%

Application of a nonlocal grid model for analysis of the creep damage of metals

Nowak

2019

The paper presents a model of creep damage development in polycrystalline material. The model operates at two scales: micro and macro. The microscale is appropriate for simulation of the damage development phenomenon. Engineering structures operate and experimental tests are performed at the macroscale. For a polycrystalline material, damage development is strictly dependent on the structure of the material. At the microscale, the model uses a tool called cellular automata that enables the description of this dependence. The macroscopic results, required for comparison with the experimental results and for the analysis of engineering structures, are achieved by means of the finite element method. The model connects the cellular automata damage model with the deformation model implemented in the finite element system to realize the multiscale cellular automata finite element model. This connection is made using a nonlocal approach to avoid a solution dependence on the finite element mesh. The nonlocal grid method is considered the most suitable for the discrete cellular automata model. The model has been verified with the experimental results of a uniaxial tension test for copper at elevated temperature. The effectiveness and different variants of the nonlocal grid method for creep crack growth problems have been examined.

“…The continual improvement in understanding of underlying microstructure variables in 9% Cr steels has led to the development of new constitutive models or modification in existing models. Applicability of constitutive relationships associated with the single or multiple state variables towards the description of creep behaviour of tempered martensitic steels can be found elsewhere (Biglari and Nikbin, 2017;Christopher and Choudhary, 2018;Christopher et al, 2012;Dyson and McLean, 1998;Eisentra¨ger et al, 2017;Hore and Ghosh, 2011;Liu and Pons, 2018;McLean and Dyson, 2000;Murchu´et al, 2017;Naumenko et al, 2011aNaumenko et al, , 2011bOruganti et al, 2011;Semba et al, 2008;Wang et al, 2016;Yin and Faulkner, 2006). Most of the creep models were based on the works of Dyson and McLean (1998) and McLean and Dyson (2000).…”

Section: Introductionmentioning

confidence: 99%

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

Christopher

Choudhary

2018

A detailed analysis has been performed for the prediction of long-term creep behaviour of tempered martensitic Grade 91 steel at 873 K using the microstructure-based creep damage mechanics approach. Necessary modifications have been made into the original kinetic creep law proposed by Dyson and McLean in order to account for the influence of microstructural damages arising from the coarsening of M23C6 and conversion of useful MX precipitates into deleterious Z-phase on creep behaviour of the steel. An exponential rate relationship has been introduced for the evolution of number density of MX precipitates with time. It has been shown that the developed model adequately predicts the experimental long-term creep strain–time as well as creep rate-time data. The role of Z-phase on long-term creep behaviour of Grade 91 steel has also been discussed.