scholarly journals Development of an integrated approach combining artificial neural network material based on modeling with finite element analysis of forming processes

2005 ◽  
Author(s):  
◽  
Brian Scott Kessler
Keyword(s):  
Finite Element ◽  
Flow Stress ◽  
Strain Rate ◽  
Strain Hardening ◽  
Integrated Approach ◽  
Hot Forming ◽  
Energy Materials ◽  
Softening Mechanism ◽  
Wide Range ◽  
Early Strain

The use of a finite element model for design and analysis of a metal forming processes is limited by the incorporated material model's ability to predict deformation behavior over a wide range of operating conditions. Conventionally generated rheological models prove deficient in several respects due to the difficulty in establishing complicated relations between many parameters. More recently, artificial neural networks (ANN) have been suggested as an effective means to overcome these difficulties. To this end, a robust ANN with the ability to determine flow stresses based on strain, strain rate, and temperature is developed and linked with finite element based simulation model. Comparisons of this novel method with conventional means are carried out to demonstrate the advantages of this approach as applied to industrial applications. The flow stress curves generated using the developed ANN method for 6061 alumimum show the typical behavior of high stacking fault energy materials, where the controlling softening mechanism is dynamic recovery (early strain hardening followed by a smooth transition to a plateau of stress). In contrast, the flow stress behavior of nickel aluminide exhibits the typical behavior of low stacking fault energy materials, where the controlling softening mechanism in hot working is dynamic recrystallization (early strain hardening to a peak stress followed by drop and oscillation of the flow stress about a steady average value). A thermo-mechanical coupled finite element method (FEM) using the commercial code ABAQUS as a platform for development is introduced to simulate hot forming processes. The FEM model is integrated with the developed ANN material based model in order to account for the effects of strain, strain rate, and temperature variations within the material during hot-forming. An industrial case study involves hot forging of an aftermarket automotive wheel made out of 6061 aluminum is used to evaluate the effectiveness of the integrated approach. The load-displacement curves predicted by the developed virtual model are in good agreement with the experimental observations of an industrial forging process. The developed approach and knowledge gained from the present work, has a wide range of application in general, and is not limited to hot forming of the investigated materials. The new approach is applicable to all hot forming processes of different alloy systems.

Sensitivity Analysis of the Material Flow Stress in Machining

Manufacturing ◽  
2003 ◽  
Author(s):  
Ning Fang
Keyword(s):  
Sensitivity Analysis ◽  
Flow Stress ◽  
Aluminum Alloys ◽  
Strain Rate ◽  
Strain Hardening ◽  
Material Flow ◽  
Chemical Compositions ◽  
Wide Range ◽  
Strain Rate Hardening ◽  
Factor Governing

Among the effects of strain hardening, strain-rate hardening, and temperature softening, it has long been argued about which effect is predominant in governing the material flow stress in machining. This paper compares four material constitutive models commonly employed, including Johnson-Cook’s model, Oxley’s model, Zerilli-Armstrong’s model, and Maekawa et al.’s model. A new quantitative sensitivity analysis of the material flow stress is performed based on Johnson-Cook’s model covering a wide range of engineering materials, including plain carbon steels with different carbon contents, alloyed steels, aluminum alloys with different chemical compositions and heat treatment conditions, copper and copper alloys, iron, nickel, tungsten alloys, etc. It is demonstrated that the first predominant factor governing the material flow stress is either strain hardening or thermal softening, depending on the specific work material employed and the varying range of temperatures. Strain-rate hardening is the least important factor governing the material flow stress, especially when machining aluminum alloys.

scholarly journals Analytical Descriptions of Dynamic Softening Mechanisms for Ti-13Nb-13Zr Biomedical Alloy in Single Phase and Two Phase Regions

2017 ◽  
Vol 62 (4) ◽  
pp. 2029-2043
Author(s):  
G.-Z. Quan ◽  
X. Wang ◽  
Y.-L. Li ◽  
L. Zhang
Keyword(s):  
Flow Stress ◽  
Kinetic Model ◽  
Strain Rate ◽  
Single Phase ◽  
Dual Phase ◽  
Compression Tests ◽  
Two Phase ◽  
Softening Mechanism ◽  
Wide Range ◽  
Dynamic Softening

AbstractDynamic softening behaviors of a promising biomedical Ti-13Nb-13Zr alloy under hot deformation conditions across dual phaseα+βand single phaseβregions were quantitatively characterized by establishing corresponding dynamic recovery (DRV) and dynamic recrystallization (DRX) kinetic models. A series of wide range hot compression tests on a Gleeble-3500 thermo-mechanical physical simulator were implemented under the strain rate range of 0.01-10 s−1and the temperature range of 923-1173 K. The apparent differences of flow stress curves obtained in dual phaseα+βand single phaseβregions were analyzed in term of different dependence of flow stress to temperature and strain rate and different microstructural evolutions. Two typical softening mechanisms about DRV and DRX were identified through the variations of a series of stress-strain curves acquired from these compression tests. DRX is the dominant softening mechanism in dual phaseα+βrange, while DRV is the main softening mechanism in single phaseβrange. The DRV kinetic model for single phaseβregion and the DRX kinetic model for dual phaseα+βregion were established respectively. In addition, the microstructures of the compressed specimens were observed validating the softening mechanisms accordingly.

Study on Dynamic Mechanical Response of TC21 Alloy

2011 ◽  
Vol 88-89 ◽  
pp. 674-678
Author(s):  
Shuang Zan Zhao ◽  
Xing Wang Cheng ◽  
Fu Chi Wang
Keyword(s):  
Flow Stress ◽  
High Strain Rate ◽  
Strain Rate ◽  
Strain Hardening ◽  
High Strain ◽  
Dynamic Flow ◽  
Dynamic Mechanical ◽  
Hardening Effect ◽  
High Strain Rate Deformation ◽  
Binary Morphology

Some results of an experimental study on high strain rate deformation of TC21 alloy are discussed in this paper. Cylindrical specimens of the TC21 alloys both in binary morphology and solution and aging morphology were subjected to high strain rate deformation by direct impact using a Split Hopkinson Pressure Bar. The deformation process is dominated by both thermal softening effect and strain hardening effect under high strain rate loading. Thus the flow stress doesn’t increase with strain rate at the strain hardening stage, while the increase is obvious under qusi-static compression. Under high strain rate, the dynamic flow stress is higher than that under quasi-static and dynamic flow stress increase with the increase of the strain rate, which indicates the strain rate hardening effect is great in TC21 alloy. The microstructure affects the dynamic mechanical properties of TC21 titanium alloy obviously. Under high strain rate, the solution and aging morphology has higher dynamic flow stress while the binary morphology has better plasticity and less prone to be instability under high strain rate condition. Shear bands were found both in the solution and aging morphology and the binary morphology.

Tensile Deformation Behavior of 5A90 Al-Li Alloy Sheet at Elevated Temperature

2011 ◽  
Vol 66-68 ◽  
pp. 70-75 ◽  
Author(s):  
Gao Shan Ma ◽  
Song Yang Zhang ◽  
Han Ying Wang ◽  
Min Wan
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Deformation Behavior ◽  
Tensile Deformation ◽  
Alloy Sheet ◽  
Hot Forming ◽  
Uniaxial Tensile ◽  
Sensitivity Index ◽  
Tensile Deformation Behavior ◽  
Increasing Temperature

Uniaxial tensile deformation behavior of 5A90 aluminium-lithium alloy sheet is investigated in the hot forming with the temperature range of 200-450°C and strain rate range of 0.3×10-3-0.2×10-1s-1. It is found that the flow stress of 5A90 Al-Li alloy in uniaxial tension increase with increasing strain rate and decrease with increasing temperature, however, the tendency of total elongation is just the reverse, and the optimum forming temperature is 400°C. The strain rate sensitivity index (m-value) remarkably increases with increasing temperature for a given strain rate. It is shown that 5A90 Al-Li alloy sheet displays the sensitivity to the strain rate at elevated temperatures. For a given strain rate, the strain hardening index (n-value) decreases with increasing temperature, whereas the n-value increases above 350°C. The constitutive equation of stress, strain and strain rate for 5A90 Al-Li alloy at any temperature is obtained by fitting the experimental data, which gave a good flow stress model for the FEM simulation of hot forming.

scholarly journals Avrami Kinetic-Based Constitutive Relationship for Armco-Type Pure Iron in Hot Deformation

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 365 ◽  
Author(s):  
Yan Zhang ◽  
Qichao Fan ◽  
Xiaofeng Zhang ◽  
Zhaohui Zhou ◽  
Zhihui Xia ◽  
...  
Keyword(s):  
Kinetic Equation ◽  
Strain Rate ◽  
Strain Hardening ◽  
Pure Iron ◽  
Constitutive Relationship ◽  
Structure Evolution ◽  
Wide Range ◽  
Z Parameter ◽  
Time Exponent ◽  
Fractional Softening

The work presents a full mathematical description of the stress-strain compression curves in a wide range of strain rates and deformation temperatures for Armco-type pure iron. The constructed models are based on a dislocation structure evolution equation (in the case of dynamic recovery (DRV)) and Avrami kinetic-based model (in the case of dynamic recrystallization (DRX)). The fractional softening model is modified as: X = ( σ 2 − σ r 2 ) / ( σ d s 2 − σ r 2 ) considering the strain hardening of un-recrystallized regions. The Avrami kinetic equation is modified and used to describe the DRX process considering the strain rate and temperature. The relations between the Avrami constant k ∗ , time exponent n ∗ , strain rate ε ˙ , temperature T and Z parameter are discussed. The yield stress σ y , saturation stress σ r s , steady stress σ d s and critical strain ε c are expressed as the functions of the Z parameter. A constitutive model is constructed based on the strain-hardening model, fractional softening model and modified Avrami kinetic equation. The DRV and DRX characters of Armco-type pure iron are clearly presented in these flow stress curves determined by the model.

A Modified Double Multiple Nonlinear Regression Constitutive Equation for Modeling and Prediction of High Temperature Flow Behavior of BFe10-1-2 Alloy

2018 ◽  
Vol 37 (1) ◽  
pp. 75-87
Author(s):  
Jun Cai ◽  
Kuaishe Wang ◽  
Jiamin Shi ◽  
Wen Wang ◽  
Yingying Liu
Keyword(s):  
Flow Stress ◽  
Constitutive Equation ◽  
Strain Rate ◽  
Nonlinear Regression ◽  
Flow Behavior ◽  
Strain Rate Range ◽  
Compression Tests ◽  
Constitutive Analysis ◽  
Average Absolute Relative Error ◽  
Wide Range

AbstractConstitutive analysis for hot working of BFe10-1-2 alloy was carried out by using experimental stress–strain data from isothermal hot compression tests, in a wide range of temperature of 1,023~1,273 K, and strain rate range of 0.001~10 s–1. A constitutive equation based on modified double multiple nonlinear regression was proposed considering the independent effects of strain, strain rate, temperature and their interrelation. The predicted flow stress data calculated from the developed equation was compared with the experimental data. Correlation coefficient (R), average absolute relative error (AARE) and relative errors were introduced to verify the validity of the developed constitutive equation. Subsequently, a comparative study was made on the capability of strain-compensated Arrhenius-type constitutive model. The results showed that the developed constitutive equation based on modified double multiple nonlinear regression could predict flow stress of BFe10-1-2 alloy with good correlation and generalization.

Artificial Neural Network for Predicting the Flow Behaviors of Hot Compressed 2124-T851 Aluminum Alloy

2010 ◽  
Vol 146-147 ◽  
pp. 720-723
Author(s):  
Yong Cheng Lin ◽  
Xiao Min Chen ◽  
Yu Chi Xia
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Aluminum Alloy ◽  
Flow Stress ◽  
Strain Rate ◽  
Learning Algorithm ◽  
Ann Model ◽  
Wide Range ◽  
Feed Forward Network ◽  
Artificial Neural

The compressive deformation experiments of 2124-T851 aluminum alloy were carried out over a wide range of temperature and strain rate. An artificial neural network (ANN) model is developed for the analysis and simulation of the correlation between the flow behaviors of hot compressed 2124-T851 aluminum alloy and working conditions. The input parameters of the model consist of strain rate, forming temperature and deformation degree whereas flow stress is the output. A three layer feed-forward network with 15 neurons in a single hidden layer and back propagation (BP) learning algorithm has been employed. Good performance of the ANN model is achieved. The predicted results are consistent with what is expected from fundamental theory of hot compression deformation, which indicates that the excellent capability of the developed ANN model to predict the flow stress level, the strain hardening and flow softening stages is well evidenced.

Finite-Element Analysis of Rate-Dependent Buckling and Postbuckling of Viscoelastic-Layered Composites

2015 ◽  
Vol 83 (3) ◽  
Author(s):  
Kashyap Alur ◽  
Thomas Bowling ◽  
Julien Meaud
Keyword(s):  
Finite Element ◽  
Strain Rate ◽  
Volume Fraction ◽  
Acoustic Metamaterials ◽  
Layered Composites ◽  
Element Analysis ◽  
Rate Dependent ◽  
Wide Range ◽  
Compressive Loads ◽  
Deformation Mechanics

The buckling and postbuckling responses of viscoelastic-layered composites are investigated using finite-element simulations. These composites consist of alternating layers of a stiff elastic constituent and of a soft viscoelastic constituent. In response to compressive loads in the layer direction, elastic instabilities significantly affect the finite deformation mechanics of these composites. The dependence of the critical strain and critical wavenumber on strain rate is analyzed. In the postbuckling regime, the wavenumber of the mode of deformation is found to be highly dependent on strain rate and time and can be used to identify three different regimes that depend on the volume fraction of the stiff constituent. Interestingly, a transition from a wrinkling mode to a longwave mode can be observed when the strain rate is varied for moderate volume fractions of the stiff material. Analytical formulae for the buckling and postbuckling of the elastic-layered composites are used to interpret numerical results obtained for viscoelastic-layered composites. Viscoelastic-layered composites exhibit a wide range of rate-dependent mechanical behavior and could have applications in vibration damping and acoustic metamaterials.

Constitutive flow stress formulation for aeronautic aluminum alloy AA7075-T6 at elevated temperature and model validation using finite element simulation

2016 ◽  
Vol 230 (6) ◽  
pp. 994-1004
Author(s):  
Uma Maheshwera Reddy Paturi ◽  
Suresh Kumar Reddy Narala
Keyword(s):  
Finite Element ◽  
Aluminum Alloy ◽  
Flow Stress ◽  
Elevated Temperatures ◽  
Constitutive Models ◽  
Absolute Error ◽  
Machining Process ◽  
Strain Rates ◽  
Average Absolute Error ◽  
Wide Range

A judicious material constitutive model used as input to the numerical codes to denote elastic, plastic, and thermomechanical behavior under elevated temperatures and strain rates is essential to analyze and design a process. This work describes the formulation of different constitutive models, such as Johnson–Cook, Zerilli–Armstrong, Arrhenius, and Norton–Hoff models for high-strength aeronautic aluminum alloy AA7075-T6 under a wide range of deformation temperatures and strain rates. The adeptness of the formulated models is evaluated statistically by comparing the value of the correlation coefficient and average absolute error between experimental and predicted flow stress results, and numerically when simulating AA7075-T6 machining process. Though all the models show a reasonable degree of accuracy of fit, based on the average absolute error of the data and finite element predictions when simulating the AA7075-T6 machining process, Zerilli–Armstrong model can offer an accurate and precise estimate and is very close to the experimental results over the other models.

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