Constitutive Modelling of Anisotropy, Hardening and Failure of Sheet Metals

2011 ◽  
Vol 473 ◽  
pp. 631-636 ◽  
Author(s):  
Ivaylo N. Vladimirov ◽  
Yalin Kiliclar ◽  
Vivian Tini ◽  
Stefanie Reese
Keyword(s):  
Kinematic Hardening ◽  
Plastic Anisotropy ◽  
Forming Limit Diagram ◽  
Material Model ◽  
Constitutive Modelling ◽  
Forming Limit ◽  
Isotropic Hardening ◽  
Continuum Damage ◽  
Aluminium Sheets ◽  
Good Agreement

The paper discusses the application of a newly developed coupled material model of finite anisotropic multiplicative plasticity and continuum damage to the numerical prediction of the forming limit diagram at fracture (FLDF). The model incorporates Hill-type plastic anisotropy, nonlinear Armstrong-Frederick kinematic hardening and nonlinear isotropic hardening. The numerical examples investigate the simulation of forming limit diagrams at fracture by means of the so-called Nakajima stretching test. Comparisons with test data for aluminium sheets display a good agreement between the finite element results and the experimental data.

Prediction of Forming Limit Diagram Based on Damage Coupled Kinematic-Isotropic Hardening Model Under Nonproportional Loading

2002 ◽  
Vol 124 (2) ◽  
pp. 259-265 ◽  
Author(s):  
C. L. Chow ◽  
X. J. Yang ◽  
E. Chu
Keyword(s):  
Damage Mechanics ◽  
Kinematic Hardening ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Isotropic Hardening ◽  
Strain History ◽  
Sheet Metals ◽  
Nonproportional Loading ◽  
Localized Necking ◽  
Theory Of Damage

Based on the theory of damage mechanics, an anisotropic damage coupled mixed isotropic-kinematic hardening plastic model for the prediction of forming limit diagram (FLD) is developed. The model includes the formulation of nonlinear anisotropic kinematic hardening. For the prediction of limit strains under nonproportional loading, a damage criterion for localized necking of sheet metals subjected to complex strain history is proposed. The model is employed to predict the FLDs of AL6111-T4 alloy. The predicted results agree well with those determined experimentally.

scholarly journals Insight into the Influence of Punch Velocity and Thickness on Forming Limit Diagrams of AA 6061 Sheets—Numerical and Experimental Analyses

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 2010
Author(s):  
Sasan Sattarpanah Karganroudi ◽  
Shahab Shojaei ◽  
Ramin Hashemi ◽  
Davood Rahmatabadi ◽  
Sahar Jamalian ◽  
...  
Keyword(s):  
Finite Element ◽  
Fe Simulation ◽  
Forming Limit Diagram ◽  
Material Model ◽  
Forming Limit ◽  
Forming Limit Diagrams ◽  
Punch Velocity ◽  
Experimental Analyses ◽  
Insight Into ◽  
Good Agreement

In this article, the forming limit diagram (FLD) for aluminum 6061 sheets of thicknesses of 1 mm and 3 mm was determined numerically and experimentally, considering different punch velocities. The punch velocity was adjusted in the range of 20 mm/min to 200 mm/min during the Nakazima test. A finite element (FE) simulation was carried out by applying the Johnson–Cook material model into the ABAQUSTM FE software. In addition, a comparison between the simulation and the experimental results was made. It was observed that by increasing the punch velocity, the FLD also increased for both thicknesses, but the degree of the improvement was different. Based on these results, we found a good agreement between numerical and experimental analyses (about 10% error). Moreover, by increasing the punch velocity from 20 mm/min to 100 mm/min in 1 mm-thick specimens, the corresponding FLD increased by 3.8%, while for 3 mm-thick specimens, this increase was 5.2%; by increasing the punch velocity from 20 mm/min to 200 mm/min in the 3 mm-thick sheets, the corresponding FLD increased by 9.3%.

Explicit Simulation of Forming Processes Using a Novel Solid-Shell Concept Based on Reduced Integration

2012 ◽  
Vol 504-506 ◽  
pp. 425-430 ◽  
Author(s):  
Mara Pagani ◽  
Stefanie Reese ◽  
Umberto Perego
Keyword(s):  
Kinematic Hardening ◽  
Plastic Anisotropy ◽  
Material Model ◽  
Isotropic Hardening ◽  
Element Formulation ◽  
Solid Shell ◽  
Explicit Integration ◽  
Assumed Strain ◽  
Shell Finite Element ◽  
Assumed Natural Strain

The contribution deals with the simulation of sheet metal forming processes by means of a recently developed hexahedral solid-shell finite element. In contrast to this earlier work, we pursue here explicit integration. The element formulation has the following features. In order to avoid undesired effects of locking an enhanced assumed strain (EAS) concept using only one EAS degree-of-freedom has been implemented. In addition, by means of the assumed natural strain (ANS) method an excellent performance in bending situations is obtained. A key point of the element formulation is the construction of the hourglass stabilization by means of different Taylor expansions. This procedure leads to the important advantage that the sensitivity of the results with respect to mesh distortion is noticeably reduced. Further the hourglass stabilization is in this way designed that locking is eliminated and numerical stability guaranteed. The finite strain material model for plastic anisotropy and non-linear kinematic and isotropic hardening is motivated by a rheological model including Armstrong-Frederick kinematic hardening. The element formulation has been implemented into the academic code FEAP. Some standard benchmark examples are computed.

Failure modelling in metal forming by means of an anisotropic hyperelastic-plasticity model with damage

2014 ◽  
Vol 23 (8) ◽  
pp. 1096-1132 ◽  
Author(s):  
Ivaylo N Vladimirov ◽  
Michael P Pietryga ◽  
Yalin Kiliclar ◽  
Vivian Tini ◽  
Stefanie Reese
Keyword(s):  
Metal Forming ◽  
Plastic Anisotropy ◽  
Forming Limit Diagram ◽  
Ductile Damage ◽  
Forming Limit ◽  
Isotropic Hardening ◽  
Work Piece ◽  
Plasticity Model ◽  
Anisotropic Plasticity ◽  
Isotropic Damage

In metal forming, formability is limited by the evolution of ductile damage in the work piece. The accurate prediction of material failure requires, in addition to the description of anisotropic plasticity, the inclusion of damage in the finite element simulation. This paper discusses the application of an anisotropic hyperelastic-plasticity model with isotropic damage to the numerical simulation of fracture limits in metal forming. The model incorporates plastic anisotropy, nonlinear kinematic and isotropic hardening and ductile damage. The constitutive equations of the proposed model are numerically integrated both implicitly and explicitly, and the model is implemented as a user material subroutine UMAT in the commercial solvers ABAQUS/Standard and LS-DYNA, respectively. The numerical examples investigate the potential of the constitutive framework regarding the prediction of failure in metal forming processes such as, e.g. cross-die deep drawing. In particular, simulations of the Nakazima stretching test with varying specimen geometry are utilized to simulate the forming limit diagram at fracture and the numerical results are compared to experimental data for aluminium alloy sheets.

On the Modeling of Evolving Elastic and Plastic Anisotropy in the Finite Strain Regime – Application to Deep Drawing Processes

2012 ◽  
Vol 504-506 ◽  
pp. 679-684 ◽  
Author(s):  
Ivaylo N. Vladimirov ◽  
Michael P. Pietryga ◽  
Vivian Tini ◽  
Stefanie Reese
Keyword(s):  
Deep Drawing ◽  
Evolution Equations ◽  
Finite Strain ◽  
Kinematic Hardening ◽  
Plastic Anisotropy ◽  
Material Model ◽  
Internal Variables ◽  
Time Step ◽  
Finite Element Software ◽  
Structure Tensors

In this work, we discuss a finite strain material model for evolving elastic and plastic anisotropy combining nonlinear isotropic and kinematic hardening. The evolution of elastic anisotropy is described by representing the Helmholtz free energy as a function of a family of evolving structure tensors. In addition, plastic anisotropy is modelled via the dependence of the yield surface on the same family of structure tensors. Exploiting the dissipation inequality leads to the interesting result that all tensor-valued internal variables are symmetric. Thus, the integration of the evolution equations can be efficiently performed by means of an algorithm that automatically retains the symmetry of the internal variables in every time step. The material model has been implemented as a user material subroutine UMAT into the commercial finite element software ABAQUS/Standard and has been used for the simulation of the phenomenon of earing during cylindrical deep drawing.

Advanced High Strength Steel Sheet Forming and Springback Simulation

2010 ◽  
Vol 97-101 ◽  
pp. 200-203 ◽  
Author(s):  
Ke Chen ◽  
Jian Ping Lin ◽  
Mao Kang Lv ◽  
Li Ying Wang
Keyword(s):  
High Strength Steel ◽  
Yield Criterion ◽  
Kinematic Hardening ◽  
Sheet Material ◽  
High Strength ◽  
Material Model ◽  
Sheet Forming ◽  
Isotropic Hardening ◽  
Advanced High Strength Steel ◽  
Springback Prediction

With the increasing use of finite element analysis method in sheet forming simulations, springback predictions of advanced high strength steel (AHSS) sheet are still far from satisfactory precision. The main purpose of this paper was to provide a method for accurate springback prediction of AHSS sheet. Material model with Hill’48 anisotropic yield criterion and nonlinear isotropic/kinematic hardening rule were applied to take account the anisotropic yield behavior and the Bauschinger effect during forming processes. U-channel forming and springback simulation was performed using ABAQUS software. High strength DP600 sheet was investigated in this work. The simulation results obtained with the proposed material model agree well with the experimental results, which show a remarkable improvement of springback prediction compared with the commonly used isotropic hardening model.

Analysis of Tube Hydroforming by Means of an Inverse Approach1

2003 ◽  
Vol 125 (2) ◽  
pp. 369-377 ◽  
Author(s):  
Ba Nghiep Nguyen ◽  
Kenneth I. Johnson ◽  
Mohammad A. Khaleel
Keyword(s):  
Tube Hydroforming ◽  
Forming Limit Diagram ◽  
Computational Time ◽  
Forming Limit ◽  
Hydraulic Pressure ◽  
Computational Tool ◽  
Incremental Method ◽  
Inverse Approach ◽  
Initial Geometry ◽  
Good Agreement

This paper presents a computational tool for the analysis of freely hydroformed tubes by means of an inverse approach. The formulation of the inverse method developed by Guo et al. [1] is adopted and extended to the tube hydroforming problems in which the initial geometry is a round tube submitted to hydraulic pressure and axial feed at the tube ends (end-feed). A simple criterion based on a forming limit diagram is used to predict the necking regions in the deformed workpiece. Although the developed computational tool is a stand-alone code, it has been linked to the Marc finite element code for meshing and visualization of results. The application of the inverse approach to tube hydroforming is illustrated through the analyses of the aluminum alloy AA6061-T4 seamless tubes under free hydroforming conditions. The results obtained are in good agreement with those issued from a direct incremental approach. However, the computational time in the inverse procedure is much less than that in the incremental method.

Prediction of Limiting Strains for Square Pattern – Square Hole Perforated Commercial Pure Aluminium Sheets

2012 ◽  
Vol 548 ◽  
pp. 382-386 ◽  
Author(s):  
G. Venkatachalam ◽  
S. Narayanan ◽  
Narayanan C. Sathiya
Keyword(s):  
Sheet Metal ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Pure Aluminium ◽  
Element Analysis ◽  
Material Condition ◽  
Geometrical Features ◽  
Perforated Sheet ◽  
Commercial Aluminium ◽  
Aluminium Sheets

Forming limit diagram (FLD) is the most appropriate tool used to obtain the safe strain region in sheet metal forming industries. This FLD is based on limiting values of major and minor strains. This Limiting strain is the strain at the onset of fracture / necking in a sheet metal. It is influenced by the material / condition of the material, strain condition in geometrical features of a sheet metal. In this paper, square pattern – square holed, perforated commercial aluminium sheets are considered for the study. The limiting strain for the above perforated sheet metals is predicted using finite element analysis. It is found that the limiting strain is controlled by percentage of open area, ligament ratio and hole size.

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