Constitutive Modeling of Stress-Strain Curves of IF Austenite

2007 ◽  
Vol 539-543 ◽  
pp. 4202-4207
Author(s):  
Roney Eduardo Lino ◽  
Ronaldo Barbosa
Keyword(s):  
Constitutive Modeling ◽  
Hot Deformation ◽  
Stress Strain ◽  
A Value ◽  
Strain And Strain Rate ◽  
Precise Knowledge ◽  
Model Predictions ◽  
Deformation Processes ◽  
Predicted Values ◽  
Usual Process

Industry hot deformation processes such as hot rolling are complex in nature. Setting up a rolling mill requires precise knowledge of the loads needed to shape the metal. This in turn, demands the ability to predict the strength of the material when deformed to a value of strain and strain rate at a given temperature. On and off-line models need, however, to be fed with constitutive equations relating the stresses required to deform a certain metal under the usual process variables. This paper shows how a set of stress-strain curves can be modeled so that both hardening and softening mechanisms commonly present during hot deformation are taken into account. The model predictions are compared to a set of literature data in order to be validated. Reasonable agreement between published results and predicted values were obtained indicating how efficiently the model can assess values of stresses under hot working conditions.

scholarly journals Calculation Model of Resistance to Hot Deformation in Consideration of Metallurgical Phenomena in Continuous Hot Deformation Processes

1984 ◽  
Vol 70 (10) ◽  
pp. 1392-1399 ◽  
Author(s):  
Takehide SENUMA ◽  
Hiroshi YADA ◽  
Yoshikazu MATSUMURA ◽  
Shuichi HAMAUZU ◽  
Koe NAKAJIMA
Keyword(s):  
Hot Deformation ◽  
Calculation Model ◽  
Deformation Processes

The Constitutive Model for High Temperature Flow Behavior of SiC/6168Al Composite

2015 ◽  
Vol 1089 ◽  
pp. 37-41
Author(s):  
Jiang Wang ◽  
Sheng Li Guo ◽  
Sheng Pu Liu ◽  
Cheng Liu ◽  
Qi Fei Zheng
Keyword(s):  
Constitutive Model ◽  
Hot Deformation ◽  
Flow Behavior ◽  
Type Equation ◽  
Strain Rate Range ◽  
Compression Tests ◽  
Stress Strain ◽  
Hollomon Parameter ◽  
Proposed Model ◽  
Relationship Of

The hot deformation behavior of SiC/6168Al composite was studied by means of hot compression tests in the temperature range of 300-450 °C and strain rate range of 0.01-10 s-1. The constitutive model was developed to predict the stress-strain curves of this composite during hot deformation. This model was established by considering the effect of the strain on material constants calculated by using the Zenter-Hollomon parameter in the hyperbolic Arrhenius-type equation. It was found that the relationship of n, α, Q, lnA and ε could be expressed by a five-order polynomial. The stress-strain curves obtained by this model showed a good agreement with experimental results. The proposed model can accurately describe the hot flow behavior of SiC/6168Al composite, and can be used to numerically analyze the hot forming processes.

Study on Dynamic Recrystallization Behavior in Deformed Austenite of 52100 Steel by Using JMAK-Model

2013 ◽  
Vol 275-277 ◽  
pp. 1833-1837
Author(s):  
Ke Lu Wang ◽  
Shi Qiang Lu ◽  
Xin Li ◽  
Xian Juan Dong
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Hot Deformation ◽  
Volume Fraction ◽  
True Strain ◽  
Strain And Strain Rate ◽  
Average Grain Size ◽  
Dynamic Recrystallization Behavior ◽  
Simulation And Experiment ◽  
Good Agreement

A Johnson-Mehl-Avrami-Kolmogorov (JMAK)-model was established for dynamic recrystallization in hot deformation process of 52100 steel. The effects of hot deformation temperature, true strain and strain rate on the microstructural evolution of the steel were physically studied by using Gleeble-1500 thermo-mechanical simulator and the experimental results were used for validation of the JMAK-model. Through simulation and experiment, it is found that the predicted results of DRX volume fraction, DRX grain size and average grain size are in good agreement with the experimental ones.

Impact of random soil properties on stress–strain response

2004 ◽  
Vol 41 (2) ◽  
pp. 351-355 ◽  
Author(s):  
Dieter Stolle ◽  
Peijun Guo ◽  
Gabriel Sedran
Keyword(s):  
Soil Properties ◽  
Constitutive Modelling ◽  
Soil Parameters ◽  
Strain Response ◽  
Constitutive Behaviour ◽  
Stress Strain ◽  
Deterministic Analysis ◽  
Model Predictions ◽  
Random Variability ◽  
The Impact

This paper analyzes the impact of natural random variation of soil properties on the constitutive modelling of geomaterial behaviour. A theoretical framework for accommodating variation in soil properties is presented. The framework is then used to examine the consequence of parameter variability on stress–strain relations. An important observation is that average soil parameters from a series of tests on small specimens, in which density of the specimens varies randomly, do not necessarily reflect the average constitutive behaviour of soil. Model predictions are shown to be consistent with the experimental data.Key words: random variability, deterministic analysis, soil parameters, constitutive model.

Construction and Experimental Study of an Elevation Linear Fresnel Reflector

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
J. D. Nixon ◽  
P. A. Davies
Keyword(s):  
Heat Loss ◽  
Thermal Efficiency ◽  
Theoretical Models ◽  
Loss Coefficient ◽  
Heat Transfer Fluid ◽  
Stagnation Temperature ◽  
Model Predictions ◽  
The Difference ◽  
Predicted Values ◽  
Linear Fresnel Reflector

This paper outlines a novel elevation linear Fresnel reflector (ELFR) and presents and validates theoretical models defining its thermal performance. To validate the models, a series of experiments were carried out for receiver temperatures in the range of 30–100 °C to measure the heat loss coefficient, gain in heat transfer fluid (HTF) temperature, thermal efficiency, and stagnation temperature. The heat loss coefficient was underestimated due to the model exclusion of collector end heat losses. The measured HTF temperature gains were found to have a good correlation to the model predictions—less than a 5% difference. In comparison to model predictions for the thermal efficiency and stagnation temperature, measured values had a difference of −39% to +31% and 22–38%, respectively. The difference between the measured and predicted values was attributed to the low-temperature region for the experiments. It was concluded that the theoretical models are suitable for examining linear Fresnel reflector (LFR) systems and can be adopted by other researchers.

scholarly journals Evolution of specimen strain rate in split Hopkinson bar test

2019 ◽  
Vol 233 (13) ◽  
pp. 4667-4687 ◽  
Author(s):  
Hyunho Shin ◽  
Jong-Bong Kim
Keyword(s):  
Strain Rate ◽  
Rate Equation ◽  
Constant Strain Rate ◽  
Strain Curve ◽  
Hopkinson Bar ◽  
Stress Strain ◽  
Split Hopkinson Bar ◽  
Specimen Diameter ◽  
Strain And Strain Rate ◽  
Split Hopkinson

The specimen strain rate in the split Hopkinson bar (SHB) test has been formulated based on a one-dimensional assumption. The strain rate is found to be controlled by the stress and strain of the deforming specimen, geometry (the length and diameter) of specimen, impedance of bar, and impact velocity. The specimen strain rate evolves as a result of the competition between the rate-increasing and rate-decreasing factors. Unless the two factors are balanced, the specimen strain rate generally varies (decreases or increases) with strain (specimen deformation), which is the physical origin of the varying nature of the specimen strain rate in the SHB test. According to the formulated strain rate equation, the curves of stress–strain and strain rate–strain are mutually correlated. Based on the correlation of these curves, the strain rate equation is verified through a numerical simulation and experiment. The formulated equation can be used as a tool for verifying the measured strain rate–strain curve simultaneously with the measured stress–strain curve. A practical method for predicting the specimen strain rate before carrying out the SHB test has also been presented. The method simultaneously solves the formulated strain rate equation and a reasonably estimated constitutive equation of specimen to generate the anticipated curves of strain rate–strain and stress–strain in the SHB test. An Excel® program to solve the two equations is provided. The strain rate equation also indicates that the increase in specimen stress during deformation (e.g., work hardening) plays a role in decreasing the slope of the strain rate–strain curve in the plastic regime. However, according to the strain rate equation, the slope of the strain rate–strain curve in the plastic deformation regime can be tailored by controlling the specimen diameter. Two practical methods for determining the specimen diameter to achieve a nearly constant strain rate are presented.

Constitutive Modeling for the Prediction of Peak Stress in Hot Deformation Processing of Al Alloy Based Nanocomposite

2011 ◽  
Vol 328-330 ◽  
pp. 1602-1605 ◽  
Author(s):  
V. Senthilkumar ◽  
A. Balaji Abhishek ◽  
Hafeez Ahamed
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Constitutive Modeling ◽  
Hot Deformation ◽  
Constitutive Models ◽  
Peak Stress ◽  
Percentage Error ◽  
Al Alloy ◽  
Measured Flow ◽  
Deformation Tests

Hot deformation tests were carried out on Al5083 – 2 %(vol) TiC nanocomposite in a temperature range of 250 – 450°C at varying strain rate of 0.01 – 1.0 sec-1. Constitutive models were developed for the prediction of peak flow stress relating strain rate, true stress, temperature and activation energy. The percentage error between measured flow stress and constitutive model values were calculated to analyse the efficacy of the model in the prediction of peak stress. Finally, a window of working of the selected nanocomposite is established for finding out the safer region of working.

Stratospheric ozone depletion - an overview of the scientific debate

1995 ◽  
Vol 19 (1) ◽  
pp. 1-17 ◽  
Author(s):  
Frances Drake
Keyword(s):  
Ozone Depletion ◽  
Stratospheric Ozone ◽  
Ozone Layer ◽  
Scientific Uncertainty ◽  
Perceived Threat ◽  
Stratospheric Ozone Depletion ◽  
Scientific Debate ◽  
Supersonic Transport ◽  
Model Predictions ◽  
Predicted Values

For almost half a century it was widely believed that the photochemistry of the stratosphere and hence ozone distribution were well understoood. As observations revealed a gap between observed and predicted values it was recognized that a number of substances acted as catalysts thereby increasing the destruction of ozone and that humanity could augment those catalysts and affect the ozone layer. Initial concern focused on nitrogen oxides from the exhausts of supersonic transport, but attention switched in the mid-1970s to chlorofluorocarbons (CFCs). Although the theory of anthropogenic ozone depletion by CFCs found widespread scientific support the perceived threat was minimized in particular by successive model predictions downgrading the amount of depletion. The appearance of the ozone hole over Antarctica in the mid-1980s reopened the debate as to whether such depletion was anthropogenic or natural in origin. It also highlighted the model's inadequate treatment of the processes occurring in the stratosphere and the importance of dynamics and radiative transfer in stratospheric ozone destruction. Scientific consensus again favours the anthropogenic depletion of the ozone layer. In conclusion it is considered that the degree of consensus outweighs the image of scientific uncertainty that is often portrayed in relation to the issue of stratospheric ozone depletion.

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