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J M Cabrera - One of the best experts on this subject based on the ideXlab platform.
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a simple zerilli armstrong constitutive equation for modeling and prediction of hot Deformation Flow stress of steels
Mechanics of Materials, 2016Co-Authors: Tina Mirzaie, Hamed Mirzadeh, J M CabreraAbstract:Abstract Generally, the dislocation-mechanics-based constitutive relations are applicable at high strain rates and relatively low temperatures. However, for expressing Flow stress at elevated temperatures, it is required to account for the diffusion processes, namely softening effects of dynamic recovery (DRV) and dynamic recrystallization (DRX). In the current work, the Zerilli–Armstrong constitutive equation for face-centered cubic materials was appropriately modified by incorporation of peak strain and consideration of both hardening and softening phenomena. The developed constitutive relation was successfully applied to model the hot Flow stress of a typical carbon steel and it was revealed that there is no need to alter the physically-based nature of the Zerilli–Armstrong constitutive equation by extensive modifications.
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A simple Zerilli–Armstrong constitutive equation for modeling and prediction of hot Deformation Flow stress of steels
Mechanics of Materials, 2016Co-Authors: Tina Mirzaie, Hamed Mirzadeh, J M CabreraAbstract:Abstract Generally, the dislocation-mechanics-based constitutive relations are applicable at high strain rates and relatively low temperatures. However, for expressing Flow stress at elevated temperatures, it is required to account for the diffusion processes, namely softening effects of dynamic recovery (DRV) and dynamic recrystallization (DRX). In the current work, the Zerilli–Armstrong constitutive equation for face-centered cubic materials was appropriately modified by incorporation of peak strain and consideration of both hardening and softening phenomena. The developed constitutive relation was successfully applied to model the hot Flow stress of a typical carbon steel and it was revealed that there is no need to alter the physically-based nature of the Zerilli–Armstrong constitutive equation by extensive modifications.
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Modeling and Prediction of Hot Deformation Flow Curves
Metallurgical and Materials Transactions A, 2011Co-Authors: Hamed Mirzadeh, J M Cabrera, Abbas NajafizadehAbstract:The modeling of hot Flow stress and prediction of Flow curves for unseen Deformation conditions are important in metal-forming processes because any feasible mathematical simulation needs accurate Flow description. In the current work, in an attempt to summarize, generalize, and introduce efficient methods, the dynamic recrystallization (DRX) Flow curves of a 17-4 PH martensitic precipitation hardening stainless steel, a medium carbon microalloyed steel, and a 304 H austenitic stainless steel were modeled and predicted using (1) a hyperbolic sine equation with strain dependent constants, (2) a developed constitutive equation in a simple normalized stress-normalized strain form and its modified version, and (3) a feed-forward artificial neural network (ANN). These methods were critically discussed, and the ANN technique was found to be the best for the modeling available Flow curves; however, the developed constitutive equation showed slightly better performance than that of ANN and significantly better predicted values than those of the hyperbolic sine equation in prediction of Flow curves for unseen Deformation conditions.
Hamed Mirzadeh - One of the best experts on this subject based on the ideXlab platform.
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a simple zerilli armstrong constitutive equation for modeling and prediction of hot Deformation Flow stress of steels
Mechanics of Materials, 2016Co-Authors: Tina Mirzaie, Hamed Mirzadeh, J M CabreraAbstract:Abstract Generally, the dislocation-mechanics-based constitutive relations are applicable at high strain rates and relatively low temperatures. However, for expressing Flow stress at elevated temperatures, it is required to account for the diffusion processes, namely softening effects of dynamic recovery (DRV) and dynamic recrystallization (DRX). In the current work, the Zerilli–Armstrong constitutive equation for face-centered cubic materials was appropriately modified by incorporation of peak strain and consideration of both hardening and softening phenomena. The developed constitutive relation was successfully applied to model the hot Flow stress of a typical carbon steel and it was revealed that there is no need to alter the physically-based nature of the Zerilli–Armstrong constitutive equation by extensive modifications.
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A simple Zerilli–Armstrong constitutive equation for modeling and prediction of hot Deformation Flow stress of steels
Mechanics of Materials, 2016Co-Authors: Tina Mirzaie, Hamed Mirzadeh, J M CabreraAbstract:Abstract Generally, the dislocation-mechanics-based constitutive relations are applicable at high strain rates and relatively low temperatures. However, for expressing Flow stress at elevated temperatures, it is required to account for the diffusion processes, namely softening effects of dynamic recovery (DRV) and dynamic recrystallization (DRX). In the current work, the Zerilli–Armstrong constitutive equation for face-centered cubic materials was appropriately modified by incorporation of peak strain and consideration of both hardening and softening phenomena. The developed constitutive relation was successfully applied to model the hot Flow stress of a typical carbon steel and it was revealed that there is no need to alter the physically-based nature of the Zerilli–Armstrong constitutive equation by extensive modifications.
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a simple constitutive model for predicting Flow stress of medium carbon microalloyed steel during hot Deformation
Materials & Design, 2015Co-Authors: Zohreh Akbari, Hamed Mirzadeh, J M CabreraAbstract:The constitutive behavior of a medium carbon microalloyed steel during hot working over a wide range of temperatures and strain rates was studied using the Johnson-Cook (JC) model, the Hollomon equation, and their modifications. The original JC model was not able to predict the softening part of the Flow curves and the subsequent modifications of the JC model to account for the softening stage and the strain dependency of constants were not satisfactory owing to the uncoupled nature of the JC approach regarding strain rate and temperature. The coupled effect of these variables was considered in the form of Zener-Hollomon parameter (Z) and the constants of the Hollomon equation were related to Z. This modification was found to be useful for the hardening stage but the overall consistency between the experimental Flow curves and the calculated ones was not good. Therefore, a simple constitutive model was proposed in the current work, in which by utilization of the peak stress and strain into the Hollomon equation, good prediction abilities were attained. Conclusively, the proposed model can be considered as an efficient one for modeling and prediction of hot Deformation Flow curves. (C) 2015 Elsevier Ltd. All rights reserved.
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A Simplified Approach for Developing Constitutive Equations for Modeling and Prediction of Hot Deformation Flow Stress
Metallurgical and Materials Transactions A, 2015Co-Authors: Hamed MirzadehAbstract:A comparative study was carried out on the appropriateness of hyperbolic sine, power, and exponential descriptions of Zener–Hollomon parameter (Z) in prediction of high-temperature Flow stress by consideration of the effect of strain. It was shown that the main problem of the conventional strain compensation approach is the implementation of the constitutive equations to find the strain-dependent material constants, especially the hot Deformation activation energy (Q), at constant strain values, which arises from the change in the microstructure of the material at a given strain for different Deformation conditions (different Z values). Subsequently, a simplified approach for each constitutive equation, mainly by taking Q from the peak stress analysis, was proposed to solve this issue. This also resulted in significantly better prediction abilities for unseen Deformation conditions and effectively simplified the required calculations.
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constitutive modeling and prediction of hot Deformation Flow stress under dynamic recrystallization conditions
Mechanics of Materials, 2015Co-Authors: Hamed MirzadehAbstract:Abstract Simple modeling approaches based on the Hollomon equation, the Johnson–Cook equation, and the Arrhenius constitutive equation with strain-dependent material’s constants were used for modeling and prediction of Flow stress for the single-peak dynamic recrystallization (DRX) Flow curves of a stainless steel alloy. It was shown that the representation of a master normalized stress–normalized strain Flow curve by simple constitutive analysis is successful in modeling of high temperature Flow curves, in which the coupled effect of temperature and strain rate in the form of the Zener–Hollomon parameter is considered through incorporation of the peak stress and the peak strain into the formula. Moreover, the Johnson–Cook equation failed to appropriately predict the hot Flow stress, which was ascribed to its inability in representation of both strain hardening and work softening stages and also to its completely uncoupled nature, i.e. dealing separately with the strain, strain rate, and temperature effects. It was also shown that the change in the microstructure of the material at a given strain for different Deformation conditions during high-temperature Deformation is responsible for the failure of the conventional strain compensation approach that is based on the Arrhenius equation. Subsequently, a simplified approach was proposed, in which by correct implementation of the hyperbolic sine law, significantly better consistency with the experiments were obtained. Moreover, good prediction abilities were achieved by implementation of a proposed physically-based approach for strain compensation, which accounts for the dependence of Young’s modulus and the self-diffusion coefficient on temperature and sets the theoretical values in Garofalo’s type constitutive equation based on the operating Deformation mechanism. It was concluded that for Flow stress modeling by the strain compensation techniques, the Deformation activation energy should not be considered as a function of strain.
Tina Mirzaie - One of the best experts on this subject based on the ideXlab platform.
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a simple zerilli armstrong constitutive equation for modeling and prediction of hot Deformation Flow stress of steels
Mechanics of Materials, 2016Co-Authors: Tina Mirzaie, Hamed Mirzadeh, J M CabreraAbstract:Abstract Generally, the dislocation-mechanics-based constitutive relations are applicable at high strain rates and relatively low temperatures. However, for expressing Flow stress at elevated temperatures, it is required to account for the diffusion processes, namely softening effects of dynamic recovery (DRV) and dynamic recrystallization (DRX). In the current work, the Zerilli–Armstrong constitutive equation for face-centered cubic materials was appropriately modified by incorporation of peak strain and consideration of both hardening and softening phenomena. The developed constitutive relation was successfully applied to model the hot Flow stress of a typical carbon steel and it was revealed that there is no need to alter the physically-based nature of the Zerilli–Armstrong constitutive equation by extensive modifications.
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A simple Zerilli–Armstrong constitutive equation for modeling and prediction of hot Deformation Flow stress of steels
Mechanics of Materials, 2016Co-Authors: Tina Mirzaie, Hamed Mirzadeh, J M CabreraAbstract:Abstract Generally, the dislocation-mechanics-based constitutive relations are applicable at high strain rates and relatively low temperatures. However, for expressing Flow stress at elevated temperatures, it is required to account for the diffusion processes, namely softening effects of dynamic recovery (DRV) and dynamic recrystallization (DRX). In the current work, the Zerilli–Armstrong constitutive equation for face-centered cubic materials was appropriately modified by incorporation of peak strain and consideration of both hardening and softening phenomena. The developed constitutive relation was successfully applied to model the hot Flow stress of a typical carbon steel and it was revealed that there is no need to alter the physically-based nature of the Zerilli–Armstrong constitutive equation by extensive modifications.
M. Rakhshkhorshid - One of the best experts on this subject based on the ideXlab platform.
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A SVM model to predict the hot Deformation Flow curves of AZ91 magnesium alloy
2017Co-Authors: M. Rakhshkhorshid, Nader Mollayi, A.r. MaldarAbstract:Abstract In this work, a support vector machine (SVM) model was developed to predict the hot Deformation Flow curves of AZ91 magnesium alloy. The experimental stress-strain curves, obtained from hot compression testing at different Deformation conditions, were sampled. Consequently, a data base with the input variables of the Deformation temperature, strain rate and strain and the output variable of Flow stress was prepared. To develop the support vector machine (SVM) model, the overall data was divided into two subsets of training and testing (randomly selected). Root mean square error (RMSE) criterion was used to evaluate the prediction performance of the developed model. The low RMSE value calculated for the developed model showed the robustness of it to predict the hot Deformation Flow curves of tested alloy. Also, the performance of the SVM model was compared with the performance of some previously used constitutive equations. The overall results showed the better performance of the SVM model over them.
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A Robust RBF-ANN Model to Predict the Hot Deformation Flow Curves of API X65 Pipeline Steel
2017Co-Authors: M. RakhshkhorshidAbstract:Abstract In this research, a radial basis function artificial neural network (RBF-ANN) model was developed to predict the hot Deformation Flow curves of API X65 pipeline steel. The results of the developed model was compared with the results of a new phenomenological model that has recently been developed based on a power function of Zener-Hollomon parameter and a third order polynomial function of strain power m (m is a constant). Root mean square error (RMSE) criterion was used assess the prediction performance of the investigated models. According to the results obtained, it was shown that the RBF-ANN model has a better performance than that of the investigated phenomenological model. Very low RMSE value of 0.41 MPa was obtained for RBF-ANN model that shows the robustness of it to predict the hot Deformation Flow curves of tested steel. The results can be further used in mathematical simulation of hot metal forming processes.
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Constitutive Modeling of Warm Deformation Flow Curves of an Eutectoid Steel
Journal of Materials Engineering and Performance, 2017Co-Authors: H. Rastegari, M. Rakhshkhorshid, Mahesh C. Somani, David PorterAbstract:The capabilities of the commonly encountered Johnson-Cook and Arrhenius-type constitutive equations to describe the warm Deformation Flow curves of an eutectoid steel undergoing dynamic spheroidization have been compared based on the warm compression test data. Warm compression tests were conducted over the temperature range 620-770 °C and strain rates in the range of 0.01-10 s−1. The average absolute relative error values for the Johnson-Cook and Arrhenius-type constitutive equations were 44.03 and 6.50%, respectively, thereby showing that the Arrhenius-type constitutive equation is to be preferred. It is also shown that in contrast to the Arrhenius-type constitutive equation, the softening caused by dynamic spheroidization cannot be modeled using the Johnson-Cook equation.
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Exponential-type Constitutive Equation in Order to Use in Modeling the Warm Deformation of a Eutectoid Steel
international journal of iron and steel society of iran, 2016Co-Authors: M. Rakhshkhorshid, H. RastegariAbstract:The main contribution of the present work is to investigate the capability of exponential-type constitutive equationto model the warm Deformation Flow curves of a eutectoid steel in the temperature range of 620-770 °C andat the strain rates in the range of 0.01-10 s-1 conducted on a Gleeble-1500 thermomechanical simulator. WarmDeformation in this temperature range facilitates the occurrence of dynamic spheroidization of cementite lamellaeas a softening process as well as some instabilities and microstructural defects. The prediction capability of theexamined model was assessed using the average absolute relative error (AARE) criterion. The obtained AAREwith the value of 7.39% for warm Deformation modeling of the tested steel showed the acceptable performance ofthe examined model.
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Neural Network Prediction of Warm Deformation Flow Curves in Ferrite+ Cementite Region
international journal of iron and steel society of iran, 2016Co-Authors: M. Rakhshkhorshid, H. RastegariAbstract:Many efforts have been made to model the the hot Deformation (dynamic recrystallization) Flow curves of different materials. Phenomenological constitutive models, physical-based constitutive models and artificial neural network (ANN) models are the main methods used for this purpose. However, there is no report on the modeling of warm Deformation (dynamic spheroidization) Flow curves of any kind of steels. In this work, a neural network with feed forward topology and Bayesian regularization training algorithm was used to predict the warm Deformation Flow curves of a eutectoid steel. The experimental data was provided by sampling the dynamic spheroidization Flow curves of the tested steel obtained from warm compression tests conducted over a temperature range of 620-770 °C with different strain rates in the range of 0.01-10 s-1. To develop the neural network model, the overal data was divided into three categries of training, validation and testing. The scatter diagrams together with the root mean square error (RMSE) criterion were used to evaluate the prediction performance of the developed model. The low calculated RMSE value of 4.15 MPa for the overall data showed the robustness of the developed ANN model in predicting the warm Deformation Flow curves of the tested steel. The results can be further used in the mathematical simulation of warm metal forming processes.
Z.y. Zhong - One of the best experts on this subject based on the ideXlab platform.
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Slow Cooling Treatment of High-Alloyed Superalloy
Advanced Materials Research, 2012Co-Authors: Q. Deng, Z.y. ZhongAbstract:The very poor hot workability of high-alloyed GH4742 superalloy is represented in the aspects of very narrow available Deformation temperature range, high Deformation-resistant force and poor ductility. In this paper, a special heat treatment to change the ingot microstructure is proposed to improve the hot workability of the GH4742 superalloy. The' phase with a appropriate size and morphology and tortuous grain boundary were obtained by slow cooling in the ' two phases region after solution treatment. Modified microstructure induces that the hot Deformation Flow stress of GH4742 superalloy was decreased effectively and hot Deformation plasticity was increased obviously.
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Effect of slow cooling treatment on microstructure of difficult Deformation GH4742 superalloy
Journal of Alloys and Compounds, 2008Co-Authors: Q. Deng, J.y. Zhuang, Z.y. ZhongAbstract:Abstract For the difficult Deformation of GH4742 superalloy, hot working of the γ + γ′ two phases region is inevitable. The dispersed small size γ′ phase markedly increases hot Deformation Flow stress and at the same time decreases the plasticity. In this paper, the effect of slow cooling treatment in γ + γ′ two phases region after homogenization on precipitation behavior of γ′ phase was evaluated. The relationships between grain boundary morphology, the size, morphology and distribution of γ′ phase and cooling rate were also investigated. The results showed that the little dendritic-type γ′ phase, γ matrix of lower solution strengthening effect and tortuous grain boundary after slow cooling treatment decreased the hot Deformation Flow stress of the GH4742 superalloy and increased hot Deformation plasticity obviously.