Computation of the Diffusional Transformation of Continuously Cooled Austenite for Predicting the Coefficient of Thermal Expansion in the Numerical Analysis of Thermal Stress.

Boyadjiev, I I; Thomson, Peter Frederic; Lam, Yee Cheong

doi:10.2355/isijinternational.36.1413

Cited by 26 publications

(21 citation statements)

References 2 publications

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“…Accordingly, for each cooling curve we will take X 2 = 0.9999 for a temperature T X2 = T f + 1°C. The sensitivity of this assumption was checked in [22] with acceptable results.…”

Section: Fe-stress/displacement Modelmentioning

confidence: 99%

“…For the hypoeutectoid steel used for the rails, the phase transformation region comprises two phases: ferrite and austenite. Therefore, the thermal expansion coefficient can be given as a mean value, weighted according to the fraction of ferrite and austenite present during the perlite reaction [22] : (1) where, X is the "volume fraction of intended phase at T temperature". The process for calculating α th , according to Boyadjiev et al [22] , was based on the determination of X in the multiphase region.…”

Section: Fe-stress/displacement Modelmentioning

confidence: 99%

“…Therefore, the thermal expansion coefficient can be given as a mean value, weighted according to the fraction of ferrite and austenite present during the perlite reaction [22] : (1) where, X is the "volume fraction of intended phase at T temperature". The process for calculating α th , according to Boyadjiev et al [22] , was based on the determination of X in the multiphase region. using a numerical method involving the equation by Kamamoto et al [23] : (2) where, -X is the "volume fraction of intended phase at T temperature", -X 0 is the "volume fraction of intended phase at transformation termination", -T s is the transformation start temperature, -T f is the transformation finish temperature, and -n, b are constant values.…”

Section: Fe-stress/displacement Modelmentioning

confidence: 99%

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Analysis of rail cooling strategies through numerical simulation with instant calculation of thermal expansion coefficient

et al. 2010

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This article describes a new methodology to simulate the cooling process for an asymmetrical Ri60 grooved rail, designed for city tramways, in a more realistic manner than that conducted previously by other authors for long steel sections. The approach considers the phase transformation of the steel and the forced convection cooling. The process is modelled as an uncoupled thermo-mechanical problem. First, the rail's temperature history is obtained from a computer fluid dynamic model and subsequently introduced in the finite element model, in order to model the stresses and displacements. This second stage involves the calculation of the thermal expansion coefficient, for each element and at each iteration. The calculation is made according to the continuous cooling transformation diagram. These results lead to the extremely reliable determination of residual stresses as proved by the comparison with experimental data obtained in the industrial plant. The methodology allows for an accurate study of two types of cooling strategies for the Ri60 and the selection of the more suitable one. KeywordsResidual stresses; Section manufacturing; Thermal expansion coefficient. Análisis de estrategias de enfriamiento de raíles mediante simulación numérica con cálculo instantáneo del coeficiente de expansión térmica ResumenEn este artículo se describe una nueva metodología para simular el proceso de enfriamiento de un rail asimétrico Ri60, diseñado para tranvías, de una forma mucho más realista que lo realizado hasta ahora para perfiles largos de acero. La propuesta considera los efectos de la transformación de fases del acero y el enfriamiento por convección forzada. El proceso es simulado como un proceso termo-mecánico desacoplado. Primero, las curvas de enfriamiento del rail son obtenidas a partir de un modelo basado en dinámica de fluidos computacional y posteriormente introducidas en el modelo de elementos finitos para calcular las tensiones y desplazamientos. En esta segunda fase se calcula, para cada elemento finito y en cada iteración, el coeficiente de dilatación térmica lineal según el diagrama de curvas de enfriamiento continuo. Estos resultados permiten determinar las tensiones residuales al final del proceso con muy buena fidelidad respecto a los datos experimentales obtenidos en la planta industrial. La metodología permite estudiar con precisión dos tipos de estrategias de enfriamiento del Ri60 y seleccionar la más conveniente. Palabras claveTensiones residuales; Fabricación de perfiles; Coeficiente de dilatación térmica lineal.

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“…Accordingly, for each cooling curve we will take X 2 = 0.9999 for a temperature T X2 = T f + 1°C. The sensitivity of this assumption was checked in [22] with acceptable results.…”

Section: Fe-stress/displacement Modelmentioning

confidence: 99%

Section: Fe-stress/displacement Modelmentioning

confidence: 99%

Section: Fe-stress/displacement Modelmentioning

confidence: 99%

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Analysis of rail cooling strategies through numerical simulation with instant calculation of thermal expansion coefficient

et al. 2010

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“…While in a single-phase region the thermal expansion coefficient is a function of temperature, in a multiphase region it depends not only on the temperature change but also of the volume and relative amounts of phases because of the development of new phases with different specific volumes [10].…”

Section: Transformations Study By Dilatometrymentioning

confidence: 99%

Microstructure Evolution at Different Cooling Rates of Low Carbon Microalloyed Steels

Brandaleze¹,

Ramírez²,

Ávalos³

2017

JCCE

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Abstract:In low carbon microalloyed steels (C  0.1%), the content of V, Nb and Ti affects the phases transformation kinetic during cooling in the rolling process. The final microstructure determines the required mechanical properties such as high formability, high toughness and adequate strength. For this reason it is relevant to identify and determine the volume fraction of the ferrite, bainite and martensite present in the structure. The microalloying elements: V, Nb and Ti promote carbides precipitation during cooling. The precipitates control the grain size refinement during hot rolling process and the mechanical properties of the steel. In this sense it is necessary to increase the knowledge on the microstructure evolution at different cooling rates. In this paper, the results obtained on two low carbon microalloyed steels (with C contents between 0.11%-0.06%) are reported. An integrated methodology including dilatometry in combination with microscopy techniques was applied. By EBSD (Electron Backscatter Diffraction) technique and microhardness measurements, the structural study was completed. Through a thermodynamic simulation using Fact Sage the type of precipitates in the studied steels structure at the temperature range between 950 °C and 450 °C, were predicted. The information on the evolution of the steel structure at rolling process conditions is relevant to consider changes in processing conditions.

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“…To predict the onset of δ precipitation, an existing TTT diagram can be used in conjunction with a Scheil calculation [14][15][16]. Equation 1 shows the Scheil additive function, where t is the time required to initiate precipitation at a given temperature, and ∆t is the time spent at that temperature.…”

Section: Prediction Of δ Precipitationmentioning

confidence: 99%

Modelling Microstructural Transformations of Nickel Base Superalloy in 718 During Hot Deformation

Guest¹,

Tin

2005

Superalloys 718, 625, 706 and Various Derivatives (2005)

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A new Inconel 718 microstructural evolution model that works in tandem with finite element software is described, and is then used to predict the microstructure during the production of a typical two-stage forging route. The model works by grouping similar grains into grainsets and predicting the dislocation density within these grainsets during thermomechanical processing. The model is shown to accurately predict both the grain size and presence of δ precipitates during the processing route, and displays results both numerically and graphically.

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Computation of the Diffusional Transformation of Continuously Cooled Austenite for Predicting the Coefficient of Thermal Expansion in the Numerical Analysis of Thermal Stress.

Cited by 26 publications

References 2 publications

Analysis of rail cooling strategies through numerical simulation with instant calculation of thermal expansion coefficient

Analysis of rail cooling strategies through numerical simulation with instant calculation of thermal expansion coefficient

Microstructure Evolution at Different Cooling Rates of Low Carbon Microalloyed Steels

Modelling Microstructural Transformations of Nickel Base Superalloy in 718 During Hot Deformation

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