scholarly journals Application of an Incremental Constitutive Model for the FE Analysis of Material Dynamic Restoration in the Rotary Tube Piercing Process

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4289
Author(s):  
Alberto Murillo-Marrodán ◽  
Eduardo García ◽  
Jon Barco ◽  
Fernando Cortés
Keyword(s):  
Constitutive Model ◽  
Material Flow ◽  
Twist Angle ◽  
State Parameter ◽  
Material Model ◽  
Fe Analysis ◽  
Incremental Model ◽  
Mathematical Expressions ◽  
Accumulated Strain ◽  
Tube Piercing Process

In the numerical simulation of hot forming processes, the correct description of material flow stress is very important for the accuracy of the results. For complex manufacturing processes, such as the rotary tube piercing (RTP), constitutive laws based on both power and exponential mathematical expressions are commonly used due to its inherent simplicity, despite the limitations that this approach involves, namely, the use of accumulated strain as a state parameter. In this paper, a constitutive model of the P91 steel derived from the evolution of dislocation density with strain, which takes into account the mechanisms of dynamic recovery (DRV) and dynamic recrystallization (DRX), is proposed for the finite element (FE) analysis of the RTP process. The material model is developed in an incremental manner to allow its implementation in the FE code FORGE®. The success of this implementation is confirmed by the good correlation between results of the simulation and experimental measurements of the manufactured tube (elongation, twist angle, mean wall thickness and eccentricity). In addition, this incremental model allows addressing how the restoring mechanisms of DRV and DRV occur during the RTP process. The analysis puts into evidence that DRV and DRX prevail over each other cyclically, following an alternating sequence during the material processing, due mainly to the effect of the strain rate on the material.

scholarly journals Modelling Texturised Cast Structures in the Forging of Superalloys

2011 ◽  
Vol 278 ◽  
pp. 210-215
Author(s):  
Jan Terhaar ◽  
Nikolaus Blaes ◽  
Dieter Bokelmann ◽  
Hendrik Schafstall
Keyword(s):  
Flow Stress ◽  
Material Flow ◽  
Cylindrical Specimen ◽  
Material Model ◽  
Growth Direction ◽  
Solidification Structure ◽  
Vacuum Arc ◽  
Correct Prediction ◽  
Dendrites Growth ◽  
Stress Dependency

The main objective of remelting processes commonly used in the production of super¬alloys is to obtain a columnar dendritic solidification structure throughout the whole ingot. Besides reduced microsegregation, this cast structure features a preferred orientation, which is depending on the primary dendrites’ growth direction and therefore closely related to the ingot’s pool shape. As a result, non-isotropic material behaviour can be observed during initial forging operations. Since the correct prediction of material flow is a prerequisite for the further analysis of forging processes by means of numerical simulation, the solidification texture’s influence on plastic flow was accounted for by the application of an anisotropic material model. The model according to Barlat was used to scale the flow stress with respect to the crystal orientations observed in the examination of vacuum arc remelted alloy 718, thereby considering the flow stress’ dependency on strain, strain rate and temperature. The parameters defining the material's anisotropy could be determined by the upsetting of cylindrical specimen from a remelted ingot.

A Constitutive Model for Jointed Rock Mass With Orthogonal Sets of Joints

1989 ◽  
Vol 56 (1) ◽  
pp. 25-32 ◽  
Author(s):  
E. P. Chen
Keyword(s):  
Constitutive Model ◽  
Material Model ◽  
Jointed Rock ◽  
Rate Equations ◽  
Strain Partitioning ◽  
Additional Material ◽  
The Subject ◽  
Nonlinear Normal ◽  
Elastic Rock ◽  
The Continuum

The development and numerical implementation of a constitutive model for jointed rock media is the subject of investigation in this paper. The constitutive model is based on the continuum assumption of strain-partitioning among the elastic rock matrix and joint sets with nonlinear normal and shear responses. Rate equations for the stress-strain response of the jointed media have been formulated. A numerical incremental solution scheme to these equations has been developed. It has been implemented into the finite element code JAC as an additional material model. Several sample problems have been solved for demonstration purposes. Interpretation and discussion of these results are presented.

Indentation Tests Based on Gelatin Phantom

2013 ◽  
Vol 483 ◽  
pp. 386-390
Author(s):  
Lei Song ◽  
Tong Su ◽  
Li Ying Gao ◽  
Qin He Zhang
Keyword(s):  
Constitutive Model ◽  
Least Squares Method ◽  
Fem Simulation ◽  
Indentation Test ◽  
Target Material ◽  
Fem Analysis ◽  
Material Model ◽  
Fem Model ◽  
Indentation Tests ◽  
Viscoelastic Characteristics

In order to improve the accuracy of biopsy, an accurate FEM model is quite essential. To get the coefficients of the puncture target material which will be used in the Abaqus FEM analysis, the paper performed indentation test on gelatin phantom which is more stable than normal biological tissue. The Neo-Hookean and the improved Kelvin constitutive model were used to describe the mechanical properties of gelatin phantom demonstrated in the tests, including the hyperelastic and viscoelastic characteristics, then least squares method was used to fit the experimental data, finally the parameters of each constitutive model were achieved, which will be used to establish the material model in the further Abaqus FEM simulation.

Effect of Friction conditions on Material Flow in FE Analysis of Al Piston Forging Process

2019 ◽  
Vol 20 (10) ◽  
pp. 1643-1652 ◽  
Author(s):  
Seong-Won Lee ◽  
Jae-Wan Jo ◽  
Man-Soo Joun ◽  
Jung-Min Lee
Keyword(s):  
Material Flow ◽  
Fe Analysis ◽  
Forging Process

A Methodology to Determine Work Material Flow Stress and Tool-Chip Interfacial Friction Properties by Using Analysis of Machining

2004 ◽  
Author(s):  
Tug˘rul O¨zel ◽  
Erol Zeren
Keyword(s):  
Flow Stress ◽  
Material Flow ◽  
Orthogonal Cutting ◽  
Material Model ◽  
Interfacial Friction ◽  
Frictional Stress ◽  
Rake Face ◽  
Friction Characteristics ◽  
Work Material ◽  
1045 Steel

In this paper, we develop a methodology to determine flow stress at the machining regimes and friction characteristics at the tool-chip interface from the results of orthogonal cutting tests. We utilize metal cutting analysis originally developed by late Oxley and present some improvements. We also evaluate several temperature models in calculating the average temperatures at primary and secondary deformation zones and present comparisons with the experimental data obtained for AISI 1045 steel through assessment of machining models (AMM) activity. The proposed methodology utilizes measured forces and chip thickness obtained through a basic orthogonal cutting test. We conveniently determine work material flow stress at the primary deformation zone and the interfacial friction characteristics along tool rake face. Calculated friction characteristics include parameters of the normal and frictional stress distributions on the rake face. Determined flow stress data from orthogonal cutting tests is combined with the flow stress measured through split-hopkinson pressure bar (SHPB) tests and the Johnson-Cook work material model is obtained. Therefore, with this methodology, we extend the applicability of Johnson-Cook work material model to machining regimes.

Newest Developments on the Manufacture of Helical Profiles by Hot Extrusion

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Nooman Ben Khalifa ◽  
A. Erman Tekkaya
Keyword(s):  
Material Flow ◽  
Twist Angle ◽  
Hot Extrusion ◽  
Extrusion Process ◽  
Die Design ◽  
3D Fem ◽  
Extrusion Dies ◽  
Application Fields ◽  
Twisting Angle ◽  
Screw Rotors

A new innovative direct extrusion process, helical profile extrusion (HPE) is presented, which increases the flexibility of aluminum profile manufacturing processes. The application fields of such profiles can be seen in screw rotors for compressors and pumps. The investigations concentrate on experimental and numerical analyses by 3D-FEM simulations to analyze the influence of friction and the material flow on the twisting angle and contour accuracy. By means of finite-element method (FEM), the profile shape could be improved by modifying the die design. The numerical results were validated by experiments. For these investigations, a common aluminum alloy AA6060 was used. Mainly, the friction in the die influences the twist angle and the shape of the helical profile. Two die coatings were analyzed, but the friction was not substantially decreased in any of these cases. Although there is no efficient practical solution for reducing the friction in extrusion dies using tested die coatings, the required profile contour could be achieved by new die designing and by modifying the material flow. However, increasing the twist angle is limited due to geometrical aspects of this technology, namely, by the ratio of the volume to the contact area with the die for the displaced metal.

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