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FE-Simulation Of Hemming In The Automotive Industry
Mats Sigvant *,*** and Kjell Mattiasson **,***
* Volvo Cars Body Components Dept 34406 Sheet Materials
Technology
SE 293 80 Olofstrm, Sweden e-mail : [email protected]
** Volvo Car Corporation
Dept 91420 Crash Simulation SE 405 31 Gteborg, Sweden
*** Department of Applied Mechanics Chalmers University of
Technology
SE 412 96 Gteborg, Sweden
Abstract. This paper summarizes and presents the most important
results from a research project on FE simulation of hemming carried
out at Volvo Cars Body Components and Chalmers University of
Technology. In the automotive industry, hemming is used to join two
sheet metal panels by bending the flange of the outer panel over
the inner one. The final goal of the project was to simulate all of
the hemming steps of production parts. In order to make
three-dimensional simulations of hemming possible within reasonable
simulation times, it is necessary to use shell elements and not
solid elements. On the other hand, the radius of curvature of the
outer part in the folded area is very small, normally of the same
order of magnitude as the sheet thickness. This fact raises the
question if shell elements are applicable in FE simulation of
hemming. One part of the project was therefore a thorough
investigation of the order of magnitude of the errors resulting
from the use of shell elements in FE simulation of hemming. Another
part of the project was devoted to three-dimensional simulations of
the hemming of an automotive hood. The influence on the roll-in
from several parameters, such as shell element formulation,
adhesives, and anisotropy was studied. Finally, results from a
forming simulation were also mapped to the flanging and hemming
models in order to study the influence from the stamping of the
outer panel on the roll-in.
INTRODUCTION
There is a strong demand in the automotive industry today to
develop new products in a shorter time and at lower cost. A way to
facilitate this is to carry out simulations of manufacturing
processes in early stages of car projects, to assure that the
process chosen will work in production. During the past ten years,
simulations of sheet metal forming with explicit FE methods have
grown rapidly, and today they are commonly used in the automotive
industry. The results show good agreement with practical tests.
Together with parallel computing, it is now possible to get results
fast, even for very large FE models.
Since sheet metal forming is just one of many processes used in
the manufacturing of automotive body parts, it is also of interest
to simulate other processes. This paper deals with simulations of
hemming, which is a method used to join two sheet metal panels by
bending the flange of the outer panel over the inner panel.
Therefore, hemming is considered by many people to be a joining
method. Nevertheless, as hemming also has many properties in common
with sheet metal forming, knowledge gained in research on sheet
metal forming can also be applied to hemming and vice versa. The
method is described in Atzema et al. [1], Livatyali et al. [2],
Svensson [3] and Sigvant [11].
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Hemming is used mainly for assembly of closures in automotive
bodies. The advantage of this assembly method is that it gives a
neat and compact joint. Such a joint is not as strong as a welded
joint, but it is possible to combine hemming with other assembly
methods, for instance adhesive bonding, to increase its
strength.
Although there are different ways to make a hem, all of the
methods have in common that the hemming operation is performed in
two steps. First, the flange of the outer panel is bent down to an
angle of approximately 45 from the visible surface, the pre-hemming
operation, and in a second step the flange of the outer part is
bent down to the final position, the final hemming.
There are several defects associated with the hemming operation.
The work presented in this paper concentrates on predicting the
reduction in size of the outer panel during the operation, known as
roll-in. This reduction in size has to be compensated for in the
flange die for the outer panel, to get an assembled part with the
correct dimensions.
PRESENTATION OF THE WORK
The work presented in this paper is divided in two studies, one
considering a two-dimensional approach, and one considering
three-dimensional hemming. The two-dimensional one studies hemming
of a flat test panel with a straight flange, while the three
dimensional one analyses hemming of the hood of the previous Volvo
70-series.
The Two-Dimensional Study
The purpose of this study was to investigate the order of
magnitude of the errors resulting from the use of shell elements in
FE simulation of hemming. The study involves the hemming of a 290
mm long test panel, used at Volvo Cars Body Components to evaluate
both new hemming methods and new materials. Four different
materials are used in the study; DC06, ZStE220P, ZstE260 and
AA6016. Furthermore, four different set-ups of the hemming unit was
studied.
The hemming experiments were performed by means of a bi-axial
MTS machine located at Chalmers University of Technology, see
Figure 1. Pre- and final hemming are done with two kinds of test
equipment. Common for both types is a plate with three clamps,
an adjustable support, and two guiding pins. The test panels are
clamped to the plate during the experiment. The plate is then
mounted on top of either of two shelves depending on whether pre-
or final hemming is to be performed. The pre-hemming shelf has an
inclination of 30, giving an angle of attack of 30, while the final
hemming shelf is horizontal. The tip of the pre-hemming steel has a
radius of 1.5 mm and can be adjusted so that different strike
heights can be tested. The angle of the flange after pre-hemming is
adjusted by altering the maximum displacement of the horizontal
cylinder. The final hemming steel is a flat surface. During the
experiments both roll-in and forces are measured continuously.
Furthermore, all panels are measured before and after each
operation in three sections in a CMM.
FIGURE 1. The MTS machine, at Chalmers University of Technology,
used for the hemming experiments). The photograph shows the set-up
for a pre-hemming experiment.
The Three-Dimensional Study
The purpose of this study was to verify that it is possible to
predict all of the roll-in for a part. Therefore, all parts used in
this study are manufactured with production dies, and assembled in
the production line. Twenty hoods were used in this study, of which
ten were made with adhesives and ten without. To join the outer and
the inner parts before the first measurements, five hoods of each
type were hemmed completely at the front and rear edges, while the
other five were completely hemmed along the sides. The parts that
were hemmed at the front and rear edges were then used for
measurements on the sides. Similarly, the parts that were hemmed on
the sides were used for measurements at front and rear edges.
The parts were measured after each operation, i.e. after
joining, after pre hemming, and after final hemming. During the
measurements the hoods were placed in an inspection fixture, the
same as the one used for inspecting the outer panel in production,
and
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the experimental results were obtained with a CMM. The accuracy
of these measurements in this study is 0.05 mm.
THE FE-MODELS
All flanging and hemming FE-models used in the project have
several common features. All the simulations were performed with
the explicit software LS-DYNA. In order to reduce the simulation
time, all tooling surfaces modelled by shell elements were given
rigid properties. The speed of each tool was also increased
compared to reality. Furthermore, mass scaling was also used to
further reduce simulation time.
The Two-Dimensional Models
The FE model represents the centre cross section of the test
panel with plane strain boundary conditions. The deformable parts,
i.e. the outer and the inner panel, are modelled using either fully
integrated, first order shell elements with five integration points
through the thickness or first order, 8-node, hexahedron solid
elements with eight integration points.
The outer part has an adaptive mesh with both shell and solid
elements. In the shell element model the free nodes are constrained
to the midpoints along the edges of the neighbouring larger
elements. In the solid element model the free nodes in the mesh are
constrained to the surface of the neighbouring larger elements.
The Hill 48 material model is used for steel grades, and the
Barlat and Lian model for the aluminium in the shell element model.
The solid model uses an implementation of the Barlat '91 material
model assuming plane strain conditions.
The Three-Dimensional Model
The hood, see Figure 2, was assumed to be symmetrical.
Consequently, only one half of the hood was modelled with symmetric
boundary conditions on the symmetry plane. The FE-analyses were
divided in two separate FE models, the first FE model simulated the
flanging of the outer panel, while the second one simulated all
hemming of the hood. The final geometry, stresses, and effective
plastic strain in the
outer panel after flanging were transferred from the first model
and entered as input to the second one. The surfaces of the FE
models were based on the CAD data of the outer and the inner
panels, the flange dies, and the hemming equipment. These FE models
were then modified so that the geometries of the panels in the
simulation were the same as in the corresponding experiments. The
roll-in was measured both after pre-hemming and after final
hemming. The simulation results were finally compared with those
from the corresponding experiments.
FIGURE 2. The FE model of the hood in the three-dimensional
study.
RESULTS
The results presented below are only the most important ones.
More information about the project and the results from the studies
can be found in Sigvant [11].
The Two-Dimensional Study
The presentation in this paper will focus on the mild steel
results, but the conclusions are similar for the other three
grades, unless anything else is stated.
Figure 3 shows the calculated roll-in from solid elements and
shell elements, together with the CMM measurements for the mild
steel. The numerical results, from both solid and shell elements,
show good agreement with experimental results. Generally, the
agreement is better after pre-hemming than after final hemming.
Furthermore, the divergence between shell and solid element results
is generally very small after pre-hemming, but somewhat larger
after final hemming. Finally, the influence of the m-exponent in
the Barlat '91 material model, on the roll-in is small.
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0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1, Pre 2, Pre 3, Pre 4, Pre 1, Final 2, Final 3, Final 4,
FinalCase
Roll-
in [m
m]
Experimental resultsSolid elements, m=2Solid elements, m=6Shell
elements
FIGURE 3. Roll-in after both pre- and final hemming with solid
and shell elements together with CMM measurements for the mild
steel.
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
6.5Displacement [mm]
Forc
e [kN
]
Experimental resultsSolid elements, m=2Solid elements, m=6Shell
elements
FIGURE 4. Pre-hemming forces for the mild steel in Case 3. The
upper curves are horizontal forces, while the lower ones are
vertical forces.
-5.00.05.0
10.015.020.025.030.035.040.045.050.055.060.065.070.075.080.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5
8.0 8.5Displacement [mm]
Forc
e [kN
]
Experimental resultsSolid elements, m=2Solid elements, m=6Shell
elements
-4.0-3.5-3.0-2.5-2.0-1.5-1.0-0.50.00.51.01.52.02.53.03.54.0
0 1 2 3 4 5 6 7 8 9
FIGURE 5. Final hemming forces for the mild steel in Case 3. The
upper curves are vertical forces, while the lower ones are
horizontal forces.
The pre-hemming forces in Case 3 are presented in Figure 4 and
the final hemming forces are presented in Figure 5. There is a
marked difference between the deforming forces, i.e. horisontal
forces during pre-hemming and vertical forces during final hemming,
calculated with solid and shell elements. The solid elements yield
the highest force. The explenation can either be that shell
elements are used here in an application that is beyond the limits
for the shell
theory, or that the fully integrated solid elements are too
stiff, which means that they yield forces that are too large.
Clearly, the element type has a greater influence on the calculated
forces than on the roll-in.
The simulations also underestimate the forces in comparison with
the experimental ones. This can be explained by problems with the
measuring equipment and technique. It is a difficult task to
accurately measure forces during the experiments: for instance, the
force gauges are subjected to bending moments during the
experiments, which are not accounted for.
The study also showed that the supporting forces, i.e. the
vertical force during pre-hemming, and the horizontal force during
final hemming, are largely influenced by the friction conditions
during these operations. These results could therefore indicate
that the assumption of constant friction coefficients during the
hemming operations is too crude. Numerical tests with different
friction coefficients in different areas of the hemming steel
improved the accuracy of the simulations, which underlines the
conclusion above. An interesting observation was that the agreement
between the calculated and experimental vertical force curves
during pre-hemming for the aluminium alloy were excellent.
Finally, the study showed that the deforming forces are
determined by the mechanical properties of the material. The
difference between simulated forces and measured forces could
therefore also indicate that the tensile test data are incorrect
and/or the constitutive model cannot accurately model the material
behaviour is this application. The m exponent in the material
model, has also a strong influence on the horizontal forces in
pre-hemming, and this underlines the conclusion above.
The Three-Dimensional Study
The two tested versions of LS-DYNA, the serial and the MPP
version, give almost identical roll-in and hemming forces.
Consequently, the MPP version can be used for these simulations.
Without the possibility of parallel processing, the computation
time would be devastating.
Four underintegrated shell elements were tested in order to
determine which one was preferable. No major differences in results
were obtained with initial tensile test data. But in a model with a
uniformly pre-strained outer panel the flange along the side showed
large wrinkles during pre-hemming with the Belytschko-Leviathan
element, see Figure 6. This was
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a problem since no wrinkles were observed after pre-hemming in
the experiments. On the other hand, the same model using fully
integrated elements displayed no wrinkles. Similar results, i.e.
wrinkles with underintegrated elements and no wrinkles with fully
integrated elements, has also been observed when simulating the
hemming of aluminium panels. Based on these results the fully
integrated element was used for the rest of this study.
FIGURE 6. The shape of the flange along the side of the hood
with 5 % pre-straining. The left picture shows the results with the
Belytschko-Leviathan element and the right figure shows the results
with the fully integrated element.
A model with planar anisotropy improved the accuracy of the FE
results for some cross sections in comparison with a model with
normal anisotropy. This indicates that a material model with full
anisotropy should be used in three-dimensional simulations of
hemming.
The effects on roll-in of the adhesives between the panels were
modelled with a smaller friction coefficient for the contacts
between the two parts. The roll-in in the simulations was almost
unaffected by this modification, but the experimental results
showed a dissimilar influence of the adhesives in different areas.
When adhesives were included the agreement between simulation and
experimental results was better along the sides of the hood, but
were poorer at the rear edge. Since the adhesives function as a
lubricant between the parts, and also reinforce the complete part,
the experimental results from hoods with adhesives are probably
more reliable than those from ones without them.
It was also considered to be of great interest to investigate
the effects of including the real strain distribution after
forming. To do this, the first stamping operation of the outer
panel was simulated
with the implicit FE code AUTOFORM. Thereafter, the sheet
thickness and effective plastic strain after forming were mapped
from the AUTOFORM result file to the mesh used for flanging and
hemming simulation in LS-DYNA. The results after final hemming of
the side are presented in Figure 7
0.0
0.5
1.0
1.5
2.0
2.5
1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300
2400
x-coordinate [mm]
Roll-
in [m
m]
Test results, left sideTest results, right sideSimulation
results without forming resultsSimulation results, mapped forming
results
FIGURE 7. Roll-in after final hemming along the sides of the
hood. Effects of mapping of stamping results of the outer panel
.
The results from this simulation show that the agreement between
the results from the FE model, taking the preceding sheet metal
forming into account, and the experimental results is good along
the sides and acceptable at the rear edge. It is also evident that
the difference between these results and the previous ones is
small. The only exception is at the rear edge, where the new
results show a little better agreement with experiments than the
previous ones. Nevertheless, these results are encouraging, and it
would be interesting to continue this work with other parts to
investigate the effects of the forming process on the roll-in. For
certain shapes of panels and/or certain sheet materials, e.g.
aluminium, the influence from stamping can be large.
CONCLUSIONS
The predicted roll-in, after both pre- and final hemming,
modelled with solid and shell elements, was almost identical for
all four materials in the two-dimensional study. Furthermore, the
agreement between predicted roll-in from the FE simulations and
measured roll-in from experiments was generally good. Surprisingly,
for the mild steel the accuracy of the results from shell elements
was a bit higher than that from the solid and plane strain
elements.
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There was a deviation between the predicted forces for solid and
shell elements, respectively. This deviation can maybe be
attributed to the fact that, due to the high curvature/thickness
ratio, shell elements are used beyond its theoretical range of
applicability. The study also showed that friction mainly
influences the supporting forces and that the friction conditions
are very complecated. An interesting observation is, though, that
the differences in results are much more pronounced for forces than
for roll-in.
The conclusion drawn from all the results in this project is
that shell elements in combination with a plane stress material
model can be used, with acceptable accuracy, for the simulation of
hemming of anisotropic materials, even though all conditions for
the shell theory to be valid are not fulfilled. This way of
modelling the problem has major advantages, such as shorter
simulation times and smaller model sizes.
Mapping the results from the forming of the outer panel to the
mesh in the FE-models for the flanging and hemming simulations was
done in the three-dimensional study. The roll-in in this simulation
showed acceptable agreement with experimental results, and the
conclusion drawn is, therefore, that it is possible to simulate all
steps in the manufacturing of closures. In fact, the overall
accuracy of the three-dimensional simulation results is judged to
be good enough to motivate the use of numerical simulations as an
efficient, industrial tool to predict roll-in for the hemming of
real production parts. Including the influence of the preceding
stamping operations has further improved the accuracy of this
technique.
The final result from this project is a technique for simulating
all hemming steps of a closure to an automotive body. Nevertheless,
further research and development is recommended in order to make it
easier and faster to perform the hemming simulation and to further
improve the accuracy. It would also be interesting to develop
similar methods for other types of hemming than tabletop hemming,
which was the method used in the current work. An example of a new
hemming method that should be interesting to simulate is robot
hemming. In this method, the hemming tool is displaced along the
edge of the part by a robot.
ACKNOWLEDGMENTS
The authors like to thank Volvo Car Corporation and Chalmers
University of Technology for giving us the opportunity to perform
this study. Volvo Car Corporation and The Swedish Research Council
should also be acknowledged for its financial support.
REFERENCES
1. E.H.Atzema, R. Baartman & A.J.H. Klomp, Finite element
simulations of the hemming process, Proceedings of NUMIFORM98,
933-939,Balkema (1998).
2. H. Livatyali, Computeraided process design of selected sheet
metal bending processes: flanging and hemming, Dissertation, The
Ohio State University, Ohio ( 1998 ).
3. M. Svensson, Hemming Simulation, Proceedings of NUMIFORM '98,
925-931, (1998).
4. C. Holmr, C. and A. Larbrant, Finite Element analyses of the
hemming process, Master thesis, Department of Mechanical
Engineering, University of Karlskrona/Ronneby, Karlskrona ( 2000
)
5. M. Svensson and K. Mattiasson, Simulation of hemming of
automotive body components with the explicit FE-method, Proceedings
of ECCOMAS 2000, (2000).
6. M. Svensson and K. Mattiasson, Simulation of hemming with
different element formulations and time integration methods,
Proceedings of NUMIFORM 2001, (2001).
7. M. Svensson, FE-simulation of hemming in the automotive
industry, Thesis for the degree of Licentiate of Engineering,
Department of Structural Mechanics, Chalmers University of
Technology, (2001).
8. M. Svensson and K. Mattiasson, Three-dimensional simulation
of hemming with the explicit FE-method, Journal of Materials
Processing Technology 128, 142-154, (2002).
9. J.O. Hallquist,. LS-DYNA Theoretical Manual. LSTC (1998)
10. J.O. Hallquist,. LS-DYNA Keyword Users Manual, Version 970.
LSTC (2003).
11. M Sigvant, The Hemming Process, A Numerical and Experimental
Study, Ph.D.-thesis, Computational Mechanics, Department of
Structural Design and Mechanics, Chalmers University of Technology,
(2003).
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Welcome ScreenPART A: Main MenuTitle
PageCopyrightPrefaceAcknowledgmentsOrganization of NUMISHEET
2005
PART B: Main MenuTitle PageCopyrightPreface
ContentsPART A: GENERAL PAPERSCHAPTER 1. KEYNOTE PROGRAM
LECTURESOverview - Simulation of Sheet Metal FormingTechnology
Innovation and Future Research Needs in Net Shape
ManufacturingExperimentally- and Dislocation-Based Multi-scale
Modeling of Metal Plasticity Including Temperature and Rate
EffectsAdvances of Plasticity Experiments on Metal Sheets and Tubes
and Their Applications to Constitutive ModelingDirect Design Method
Based on Ideal Forming Theory for Hydroforming and Flanging
Processes
CHAPTER 2. COMPUTER AIDED DIE TRYOUTImpact of Simulation
Technology on Die and Stamping BusinessCAE Based Die Face
Engineering Development to Contribute to the Revitalization of the
Tool & Die IndustryFinite Element Simulation of the
Stretch-Forming of Aircraft SkinsDraw-in MapA Road Map for
Simulation-Guided Die Tryout and Stamping Process ControlIntegrated
Stamping Simulation Using State of the Art Techniques to Fulfill
Quality Assessment RequirementsEvolutions of Advanced Stamping
CAETechnology Adventures and Business Impact on Automotive Dies and
StampingDevelopment of JSTAMP-Works/NV and HYSTAMP for Multipurpose
Multistage Sheet Metal Forming SimulationSimulation of Stamping
Process of Automotive Panel Considering Die DeformationIntegrated
Forming Simulations and Die Structural Analysis for Optimal Die
DesignsModelling and Simulation of the Influence of Forming
Processes on the Structural Behavior of High Strength SteelsA
Benchmark Study for Different Numerical Parameters and their Impact
on the Calculated Strain Levels for a Model Part Door
OuterEvaluation and Visualization of Surface DefectsA Numerical and
Experimental Study on Sheet-Metal PartsComparison of the Deep
Drawability of Aluminum and Steel using Numerical Simulation
ExperimentsControlled FEM Simulation Ways of Blank Holding Force in
Sheet Metal Forming ProcessObtaining Formability Characteristics of
Automotive Materials Using On-Line Strain Imaging SystemEvaluating
the Dynamic Character of Friction during Metal Forming
CHAPTER 3. FINITE ELEMENT ANALYSISVisualization of the
Invisible, Explanation of the Unknown, Ruggedization of the
UnstableMassively Parallel Processing for Fast and Accurate
Stamping SimulationsStiffness Simulation using Non-linear FEAFEA
and Multivariate Statistical Data Analysis of Polypropylene Tube
Forming ProcessCrashworthiness Assessment of Auto-Body Members
Considering the Fabrication HistoriesApplication of the Incremental
Volumetric Remapping Method in the Simulation of Multi-Step Deep
Drawing ProcessesNumerical Simulation of Temperature Controlled
Solid Phase Forming Process of Polymeric PlateFinite Element
Simulation of Sheet Metal Forming Process Using Local Interpolation
for Tool SurfacesFE-Analysis of the Sheet Metal Forming Processes
using Continuous Contact TreatmentSimulation of Roll Forming with
Dynamic Explicit Finite Element MethodMechanical Field
Interpolation
CHAPTER 4. SPRINGBACK PREDICTIONAdvances in SpringbackDesign of
Experiments and Springback Prediction for AHSS Automotive
Components with Complex GeometryThrough-Thickness Residual Stress
Measurements on Springback Test SpecimensSpringback Prediction on
Slit-Ring TestInfluence of Stamping Rate upon SpringbackModeling
and Simulation of Induced Anisotropic Hardening and Springback in
Sheet Metals during Non-Proportional LoadingEffect of Plastic
Deformation and Strain History on X-ray Elastic ConstantsAn
Anisotropic Hardening Model for Springback PredictionProbabilistic
Design of Aluminum Sheet Drawing for Reduced Risk of Wrinkling and
FractureStudy on the Influence of the Work Hardening Models
Constitutive Parameters Identification in the Springback
PredictionModeling Pseudo-elastic Behavior of SpringbackA Study of
FEA Springback Predictability with Channel Draw TestRobustness
Evaluation and Tolerance Prediction for a Stamping Process with
Springback Calculation by the FEMA Sensitivity Analysis on the
Springback Behavior of the Unconstrained Bending ProblemSpringback
Prediction in Sheet Metal Forming Process Based on the Hybrid
SASpringback Calibration using Pulsed Electronmagnetic
FieldSpringback Simulation: Impact of Some Advanced Constitutive
Models and Numerical Parameters
CHAPTER 5. SPRINGBACK COMPENSATIONPossibilities and Strategies
for Simulations and Compensation for SpringbackSpringback Reduction
in Stamping of Front Side Member with a Response Surface
MethodStructure of Complementary Surface and Numerical Simulation
on Forming Process of Cover PanelDie Face Engineering Based
Springback Compensation Strategy and ImplementationCompensating
Springback in the Automotive Practice using MASHALIterative
Springback Compensation of Numisheet Benchmark #1Springback
Simulation and Tool Surface Compensation Algorithm for Sheet Metal
FormingSpringback Prediction and Compensation for a High Strength
Steel Side Impact BeamSpringback Prediction, Compensation and
Correlation for Automotive Stamping
CHAPTER 6. CONSTITUTIVE MODELSConstitutive Modeling for Sheet
Metal FormingSuitability of the Yield Criterion in Numerical
Simulation of Stretch Bending of Aluminum ExtrusionsAdvancing
Material Models for Automotive Forming SimulationsModel
Identification and FE Simulations: Effect of Different Yield Loci
and Hardening Laws in Sheet FormingExplicit Analysis of
Transversely Anisotropic and Axisymmetric Sheet Metal Forming
Process using 6-Component Barlat Yield FunctionDirect Measurement
of Multiaxial Yield Loci as a Function of Plastic
StrainDetermination of Anisotropic Hardening of Sheet Metals by
Shear TestsOn the Influence of the Yield Locus Shape in the
Simulation of Sheet Stretch FormingLS-DYNA Simulation of
Hemispherical-Punch Stamping Process Using an Efficient Algorithm
for Continuum Damage Based Elastoplastic Constitutive Equation
CHAPTER 7. MICRO-LEVEL AND MULTILEVEL MODELSAnalysis of Texture
Evolution and Hardening Behavior during Deep Drawing with an
Improved Mixed Type FEM ElementMulti-Scale Sheet Metal Forming
Analyses by Using Dynamic Explicit Homogenized Finite Element
MethodMulti Scale Finite Element Analyses by Using SEM-EBSD
Crystallographic Modeling and Parallel ComputingUnit Cell
Definition of Polycrystal Sheet Material based on SEM-EBSD
AnalysesGrain Interactions in Crystal PlasticityTexture Evolution
of FCC Sheet Metal during Deep Drawing Based on Rate Independent
FEM AnalysisEffects of Texture on Mechanical Properties of Aluminum
Alloy Sheets and Texture Optimization StrategyParallel Computing of
Multi-scale Finite Element Sheet Forming Analyses Based on
Crystallographic Homogenization Method
CHAPTER 8. FORMING LIMITSA Path-Independent Forming Limit
Criterion for Stamping SimulationsForming Limits in Sheet Metal
Forming for Non-Proportional Loading Conditions Experimental and
Theoretical ApproachRecent Developments in the Formability of
Aluminum AlloysA Comparative Study between Strain and Stress Based
Forming Limit Analysis by Applying Several Phenomenological Yield
CriteriaForming Limit Stresses of Sheet Metal under Proportional
and Combined LoadingsAdvanced Line Die Forming Simulation
Technology and its Impact on Stamping Automotive Body PanelsForming
Limit Diagram of Titanium and Stainless Steel Alloys to Study the
Formability of Hydro-Mechanical Deep Drawing PartsMaterial
Selection for an Ultra High Strength Steel Component Based on the
Failure Criteria of CrachFEMAnalytical Prediction of Forming Limits
for Thermoplastic TubesA Simulation for the Punchless Piercing
Process Using Lemaitre Damage ModelApplication of an Extended
Stress-based Flow Limit Curve to Predict Necking in Tubular
Hydroforming
CHAPTER 9. HYDROFORMING PROCESSESFundamental Issues in
Hydroforming of Deep Drawing ProcessesHydroforming of Patchwork
Blanks - Numerical Modeling and Experimental ValidationResearch on
the Effect of the Local Constraints on Sheet Hydroforming with the
Movable DieDesign of Hydroforming Processes for Metallic Liners
Used in High Pressure Hydrogen StorageDeep Drawing for High LDR by
a New Hydro-Rim Forming Process with Differential
Temperature-Analysis and ExperimentsNumerical Investigation on
Formability of Ellipse Deep Drawing by Sheet HydroformingAn
Improved Hydroforming Process for "Unlimited" Drawing RatiosShear
Deformation and Thickness Stress in Corner FillComparison of
Conventional Deep Drawing, Hydromechanical Deep-Drawing and High
Pressure Sheet Metal Forming by Numerical ExperimentsNumerical
Study of Hydroforming with Tailor-Welded Tubular BlanksHydroforming
Simulations and Applications in Product Design, Die Development,
and Production Trouble ShootingNumerical Simulation of
Hydro-Mechanical Deep Drawing A Study on the Effect of Process
Parameters on Drawability and Thickness VariationOptimization of
Tube Hydroforming with Consideration of Manufacturing Effects on
Structural PerformanceDesign and Optimization of Sheet Hydroforming
Process for Manufacturing Oil TankNumerical Simulation of
Hydroforming a Double Conical TubeNumerical Self-Regulation of
Time-Dependent Parameters in Tube Hydroforming Processes
CHAPTER 10. SUPERPLASTIC AND WARMING FORMINGAnalytical
Formability Model for Elevated Temperature Sheet Metal Forming
ProcessesMaterial Behavior Based Hybrid Process for Sheet
Draw-Forging Thin Walled Magnesium AlloysStamping of Thin-Walled
Structural Components with Magnesium Alloy AZ31 SheetsModeling for
the FE-Simulation of Warm Metal Forming ProcessesFinite Element
Analysis on Warm Hydroforming of Rectangular Mg Alloy Cups with a
Step CavityWarm Forming of Aluminum Alloys Using a Coupled
Thermo-Mechanical Anisotropic Material Model
CHAPTER 11. NON-HOMOGENEOUS MATERIALSNumerical Simulations of
Formability of Multiphase SteelsInfluence of Normal Anisotropy
Ratio on Lateral Normal Stress In Aluminum-Steel Clad Materials
CHAPTER 12. DRAWBEAD AND CYCLIC DEFORMATIONDrawbeads: To Be or
Not to BeNon-Uniform Pressure Distribution in Draw-Bend Friction
Test and its Influence on Friction MeasurementCyclic Bending and
Stationary Drawing Deformation of Metal Sheets: Experiments and
Associated Numerical Simulations
CHAPTER 13. HEMMING AND FLANGINGFE-Simulation of Hemming in the
Automotive IndustryGuidelines for Stretch Flanging Advanced High
Strength SteelsDevelopment of Sharp Flanging Technology for
Aluminum PanelsNumerical Simulation of the Hemming Process in the
Case of Al Alloys
CHAPTER 14. TAILOR WELDED BLANKSFormability Studies on
Transverse Tailor Welded BlanksSimulation Based Control of Weld
Line Movement in Tailor Welded Blanks
CHAPTER 15. METAL PACKAGINGConvolute Cut-Edge Design for an
Earless Cup in Cup DrawingOptimum Design of Aluminum Beverage Can
Ends Using Structural Optimization TechniquesErgonomics Designs of
Aluminum Beverage Cans & BottlesUse of the Inverse Approach for
the Manufacture and Decoration of Food Cans
CHAPTER 16. ELEMENT TECHNOLOGYOne Point Quadrature Shell Element
with Through-Thickness StretchEffectiveness of Rotation-Free
Triangular and Quadrilateral Shell Elements in Sheet-Metal Forming
SimulationsFully Integrated EAS-Based Solid-Shell Finite Elements
in Implicit Sheet Metal Forming SimulationsDevelopment of a
One-Point Quadrature EAS Solid-Shell Element for Sheet
FormingEnhanced Shell Elements for the Numerical Simulation of
Industrial ProcessesAn ALE Model for Numerical Simulation of Cold
Roll Forming ProcessThe Effect of Element Formulation on the
Prediction of Boost Effects in Numerical Tube BendingMesh-Free
Simulation of Automotive Decklid Inner Panel
CHAPTER 17. OPTIMIZATION AND INVERSE METHODSAnalytic
Differentiation of Barlat/s 2D Criteria for Inverse
ModelingAdvanced Gradient Based Optimization Techniques Applied on
Sheet Metal FormingOn the Development of Multi-Step Inverse FEM
with Shell ModelFast Simulation of 3-D Surface Flanging and
Prediction of the Flanging Lines Based on One-Step Inverse Forming
AlgorithmSensitivity Analysis of the Sheet Metal Stamping Processes
Based on Inverse Finite Element Modeling and Monte Carlo
SimulationApplication of Six Sigma Robust Optimization in Sheet
Metal FormingRecent Advances in Process Optimization and Control
for the Design of Sheet and Tube Hydroforming ProcessesFormability
Predictions in Stamping and Process Parameter Optimization Based on
the Inverse Approach Code Fast_StampTrimming Line Design using New
Development Method and One Step FEMAutomatic Process Optimization
of Sheet Metal Forming with Multi-ObjectiveOptimization of the
Blankholder Force Distribution with Application to the Stamping of
a Car Front Door Panel (Numisheet/99)Study of Various Initial Blank
Shapes to Minimize the Earing in the Different Shaped Formed Parts
using Finite Element AnalysisA Draw-In Sensor for Process Control
and OptimizationProbabilistic Design in a Sheet Metal Stamping
Process under Failure AnalysisFinite Element Analysis and
Optimization for the Multi-Stage Deep Drawing of Molybdenum
Sheet
PART B: BENCHMARK STUDY REPORTCHAPTER 1. BENCHMARK PHYSICAL
TRYOUT REPORTSExperimental Test for Benchmark 1Deck Lid Inner
PanelBackground and Tryout Report for BM2: Underbody Cross
MemberDescription of Numisheet 2005 Benchmark #3 Stage-1: Channel
Draw with 75% Drawbead PenetrationExperimental Procedures and
Results for Benchmark 3: Stage 2 Forming Process
CHAPTER 2. BENCHMARK ANALYSISBenchmark Simulation Results:
Automotive Deck Lid Inner Panel (Benchmark 1)Numisheet 2005
Benchmark Analysis on Forming of an Automotive Deck Lid Inner
Panel: Benchmark 1Benchmark Simulation Results: Automotive
Underbody Cross Member (Benchmark 2)Numisheet 2005 Benchmark
Analysis on Forming of an Automotive Underbody Cross Member:
Benchmark 2Benchmark Simulation Results: Channel Draw/Cylindrical
Cup 2-Stage Test (Benchmark 3)
APPENDICESSpecification for BM1: Decklid Inner
PanelSpecification for BM2: Underbody Cross Member
PanelSpecification for BM3: Two-Stage Channel/Cup DrawSpecification
for Benchmark MaterialsCharacterizations of Aluminum Alloy Sheet
Materials: Numisheet 2005
ADDITIONAL BENCHMARK MATERIALDescription of additional data on
aluminum alloysGeneral instructions for all benchmarksMeasured
standard data of aluminum alloy 6111 (XLS)Measured standard data of
bake-hardenable steel (XLS)Geometry files for BM1 in IGES format
(ZIP)Instructions for Benchmark # 1Experimental results for
Benchmark # 1 (XLS)Measured standard data of aluminum alloy AL 5182
(XLS)Uniaxial tension data in 15 degree intervals of Aluminum 5182
(XLS)Experimental crystal orientations of Aluminum 5182
(XLS)Measured standard data of 600 MPa Dual Phase Steel
(XLS)Measured standard data of 965 MPa Dual Phase Steel
(XLS)Geometry files for BM2 in IGES and NASTRAN format
(ZIP)Instructions for Benchmark # 2Experimental results for
Benchmark # 2 (XLS)Measured standard data of aluminum alloy AL6022
(XLS)Uniaxial tension data in 15 degree intervals of Aluminum 6022
(XLS)Experimental crystal orientations of Aluminum 6022
(XLS)Measured standard data of 600 MPa Dual Phase Steel
(XLS)Measured standard data of low carbon mild steel (XLS)Measured
standard data of high strength low alloy steel (XLS)Instructions
for Benchmark # 3Experimental results for Benchmark # 3 (XLS)
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