127 research outputs found
Two new mathematical models to predict the flow stress at hot deformation
No full textBased on both linear and non-linear estimations of work hardening rate versus strain curves, two mathematical models have been developed to predict the flow curves under hot working conditions up to the peak. The models were tested for a mechanically alloyed Al6063/0.75Al2O3/0.75Y2O3 nanocomposite under different hot forming conditions. The predicted results from both models are found to be in accord with the experimental flow stress curves. However, the linear model (with an average error of 0.81%) predicted the flow stress more accurate than the non-linear model (with an average error of 1.94%)
Revisiting the Common Practice of Sellars and Tegart’s Hyperbolic Sine Constitutive Model
Full text linkThe Sellars and Tegart’s hyperbolic sine constitutive model is widely practiced in describing stress–strain curves of metals in hot deformation processes. The acceptance of this phenomenological model is owed to its versatility (working for a wide range of stress values) and simplicity (being only a function of strain, strain rate, and temperature). The common practices of this model are revisited in this work, with a few suggestions to improve its results. Moreover, it is discussed that, with the progress of data-driven models, the main reason for using the Sellars and Tegart’s model should be to identify reliable activation energies, and not the stress–strain curves. Furthermore, a piece of code (Hot Deformation Fitting Tool) has been created to automate the analysis of stress–strain curves with various models
ACTAS: A New Framework for Mechanical and Frictional Characterization in Axisymmetric Compression Test
Full text linkThere are two common methods to interpret the results of an Axisymmetric Compression Test (ACT): the Cylindrical Profile Model (CPM) and the Avitzur model; however, both of the two and all other models available in the literature ignore the unavoidable foldover phenomenon, which breaks the models to provide reliable friction-free flow stress curves. Here, a novel numerical framework (called ACTAS) is presented that incorporates the foldover. ACTAS can be used to both simulate and analyze ACT. Ten finite element models are used to benchmark ACTAS. The results show the reliability of the proposed method in estimating the average and pointwise stress-strain curves and friction factors. Moreover, a new solution is provided by coupling the CPM and the Avitzur model (called A-CPM), to obtain reliable average flow curves even after the onset of foldover
Evaluation of coefficient of friction in bulk metal forming
No full textIn this study an upper bound analysis for cylindrical "Barrel Compression Test" (BCT) is developed. BCT method is a very simple method which can be utilized in order to evaluate quantitatively the coefficient of friction by means of just one cylindrical specimen in an upsetting test. The method is checked by a series of finite element method (FEM) simulations and by means of the results of FEM simulations the method is modified
Determination of flow stress and the critical strain for the onset of dynamic recrystallization using a hyperbolic tangent function
No full textA new model has been developed to estimate the flow stress under hot deformation conditions up to the peak of the stress-strain curves. This model is derived from the general form of hyperbolic function by introducing an additional parameter to bring the results to a more acceptable level. Stress-strain curves and the critical strain of a '304 austenitic stainless steel' are determined with an average percentage error of 1.24. The model is also used to obtain an equation which has the ability of predicting the critical strain for the onset of dynamic recrystallization. (C) 2013 Elsevier Ltd. All rights reserved
Nanotribology investigations with classical molecular dynamics
Full text linkThis thesis presents a number of nanotribological problems investigated by means of classical molecular dynamics (MD) simulations, within the context of the applicability of continuum mechanics contact theories at the atomic scale. Along these lines, three different themes can be recognized herein: measuring the contact area in atomistic simulations, the applicability of continuum mechanics theories for describing nanocontacts, and the topography of rough surfaces at the atomic scale
Determination of flow stress and the critical strain for the onset of dynamic recrystallization using a sine function
No full textA new model has been developed to estimate the flow stress under hot deformation conditions up to the peak of the stress-strain curves. The model is constructed on the basis of the general form of sine functions by introducing an additional exponent. Besides, an equation is derived from the model, which could be used to predict the critical strain for the onset of dynamic recrystallization. The model has been examined for a 304 austenitic stainless steel. The estimated flow stress had an average percentage error of %1.66
Corrigendum to “Determination of flow stress under hot deformation conditions” [Mater. Sci. Eng. A 552 (2012) 566–568]Corrigendum to “Determination of flow stress under hot deformation conditions” [Mater. Sci. Eng. A 552 (2012) 566–568]
Full text linkHDFT
No full textThe fitting and figure generator functions are updated to work with the new output file format.If you use HDFT in your work, please cite it using the following metadat
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