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Dynamore GmbHIndustriestraße 2
70565 Stuttgarthttp://www.dynamore.de
Recent Enhancements to the GISSMO Failure Model in LS-DYNA
André Haufe1, Markus Feucht2, Frieder Neukamm2, Paul DuBois3
1 DYNAmore GmbH, 70565 Stuttgart, Germany2 Daimler AG, EP/SPB, 71059 Sindelfingen, Germany3 Consultant, 63065 Offenbach, Germany
2European LS-DYNA Conference 2011 - Strasbourg
Weight Composites
High strength steel
Light alloys
Polymers
Safety requirements
Cost effectiveness
New materials
Design to the point
New power train
technology
Technological challenges in the automotive industry
3European LS-DYNA Conference 2011 - Strasbourg
Technological challenges in the automotive industry
Damage
σ σ
m axε
E
Failure
=fail true
E
σ σ
Anisotropyc
a
b
η
ε( )eE
σ σ
σ y
Fracture growthDebonding
Weight Composites
High strength steel
Light alloys
Polymers
Safety requirements
Cost effectiveness
New materials
Design to the point
New power train
technology
Plasticity
4European LS-DYNA Conference 2011 - Strasbourg
???
Forming simulation
Closing the process chain
� v. Mises or Gurson model
� Strain rate dependency
� Isotropic hardening
� Damage evolution
� Failure models
(damage variable necessary!!)
IIσ
Iσ
IIIσ
� Hill based models
� Anisotropiy of yield surface
� Kinematic/Isotropic hardening
� Failure by FLD
(post-processing)
� No computation of damage
IIσ
IσIIIσ
IIσ
Iσ
IIIσ
Crash simulation
5European LS-DYNA Conference 2011 - Strasbourg
Different ways to realize a consistent modeling
One Material Model for Forming and Crash Simulation
� Requirements for Forming
Simulations: Anisotropy, Exact
Description of Yield Locus,
Kinematic Hardening, etc.
� Requirements for Crash
Simulation: Dynamic Material
Behavior, Failure Prediction,
Energy Absorption, Robust
Formulation
� Leads to very complex model
Modular Concept for the Description of Plasticity and Failure
� Plasticity and Failure Model are
treated separately
� Existing Material Models are kept
unaltered
� Consistent modeling through the
use of one damage model for
forming and crash simulation
*MAT_ADD….(damage)
6European LS-DYNA Conference 2011 - Strasbourg
Produceability to Serviceability
Gurson
Barlat Gurson
Forming simulation Crash simulation
000,0,,, ftplεσ
fplεσ ,
Mapping
tpl ,,εσ
background
Fo
rtra
n-P
rog
ram
� Anisotropy� Yield locus
� Damage� Dynamic effects
Schmeing, Haufe & Feucht [2007]
Neukamm, Feucht & Haufe [2007]
Incompatible Models:Isochoric plastic behavior
7European LS-DYNA Conference 2011 - Strasbourg
Produceability to Serviceability: Modular Concept
Damage model
Material model Material model00,
, tplε
plεσ ,
Mapping
tpl ,ε
D D
Damage model
plεσ ,
Forming simulation Crash simulation
D D
Modular Concept:
•Proven material models for both disciplines are retained
•Use of one continuous damage model for both
8European LS-DYNA Conference 2011 - Strasbourg
GISSMO
Barlat Mises00,0
,, tplεσ
plεσ ,
Mapping
tpl ,,εσ
Fo
rtra
n-P
rog
ram
D DGISSMO
plεσ ,
Forming simulation Crash simulation
Ebelsheiser, Feucht & Neukamm [2008]
Neukamm, Feucht, DuBois & Haufe [2008-2010]
Produceability to Serviceability: Modular ConceptCurrent status in 971R5
9European LS-DYNA Conference 2011 - Strasbourg
J. Lemaitre, A Continuous Damage
Mechanics Model for Ductile Fracture
Overall Section Area containing micro-defects
Reduced (“effective“) Section Area
SS <ˆS S
SSD
ˆ−=
Measure of
Damage
Reduction of effective cross-section leads to reduction of tangential stiffness
� Phenomenological description( )D−= 1
*σσ
GISSMO – a short descriptionEffective stress concept (similiar to MAT_81/224 etc.)
10European LS-DYNA Conference 2011 - Strasbourg
Gurson
Mises
FormingCrash
GISSMO
Damage Evolution
Damage overestimated for linear damage accumulation
Failure Curve
Neukamm, Feucht, DuBois & Haufe [2008-2010]
GISSMO - a short description Ductile damage and failure
triaxiality
11European LS-DYNA Conference 2011 - Strasbourg
Gurson
Mises
Forming
Crash
Evolution of Instability Material Instability
Material Instability
( )v
n
locv
Fn
F εε
∆=∆− 11
,
Tensile test specimen DIN
EN 12001
GISSMO – a short description Engineering approach for instability failure n
t
1
2ψ
triaxiality
Neukamm, Feucht, DuBois & Haufe [2008-2010]
12European LS-DYNA Conference 2011 - Strasbourg
GISSMO – a short descriptionInherent mesh-size dependency of results in the post-critical region
0,0
0,2
0,4
0,0 0,1 0,2 0,3 0,4 0,5
Engineering Strain
En
gin
ee
rin
g S
tre
ss
Experiment
0,5mm
1mm
2,5mm
Simulations of tensile test specimen with different mesh sizes
Regularization of mesh-size dependency
element size
Influence of damage in postcritical region
13European LS-DYNA Conference 2011 - Strasbourg
DMGTYP: Flag for coupling (Lemaitre)
( )D−= 1* σσ
DCRIT, FADEXP: Post-critical behavior
0
0
True Strain
Tru
e S
tress
GISSMO dmgtyp2
MAT_024
0
0True Strain
Tru
e S
tress
m=2
m=5
m=8
−
−−=
FADEXP
CRIT
CRIT
D
DD
11
* σσ
GISSMO – a short description Generalized Incremental Stress State dependent damage MOdel
14European LS-DYNA Conference 2011 - Strasbourg
To be considered:
8 Specimen geometries
5 Discretisations
GISSMO Identification of damage parameters: Range of experiments and simulations
15European LS-DYNA Conference 2011 - Strasbourg
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
1,6
1,8
2,0
-0,1 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7
Element size 1mm
GISSMO Equivalent plastic strain vs. triaxiality
fε
triaxiality
16European LS-DYNA Conference 2011 - Strasbourg
Flachzugproben DIN EN 10002
0,00
0,10
0,20
0,30
0,40
0,50
0,60
0,00 0,10 0,20 0,30 0,40
Mini-Flachzugproben ungekerbt
0,00
0,10
0,20
0,30
0,40
0,50
0,60
0,0 0,2 0,4 0,6 0,8
Mini-Flachzugproben Kerbradius 1mm
0,0
0,1
0,2
0,3
0,4
0,5
0,6
-0,10 0,10 0,30 0,50
Arcan
0
2
4
6
8
10
12
0,0 0,5 1,0 1,5
Scherzugproben Kerbradius 1mm, 0°
0,00
0,10
0,20
0,30
0,40
0,50
0,60
0,00 0,05 0,10 0,15 0,20
Scherzugproben Kerbradius 1mm, 15°
0,00
0,10
0,20
0,30
0,40
0,50
0,00 0,05 0,10 0,15 0,20
Versuch
GISSMO
Gurson
constant (v. Mises)
Small tensile test specimen Notched tensile specimen, notch radius 1mm Shear test, inclined 15
Tensile specimen DIN EN 12001 Shear test, straight
GISSMO vs. Gurson vs. 24/81 Comparison of experiments and simulations
17European LS-DYNA Conference 2011 - Strasbourg
GISSMO� Failure Strain constant� Fracture energy constant� Identification of Damage Parameters
is more straight-forward
Gurson� Resultant Failure Strain constant� Failure energy depending on el. size� Identification of damage parameters
is difficult
Gurson vs. GISSMO – “regularized” Regularization of element size dependency
18European LS-DYNA Conference 2011 - Strasbourg
Example: tension rod
damage
instability
GISSMO input
19European LS-DYNA Conference 2011 - Strasbourg
Example: Arcan shear test
instabilitydamage
damage
triaxiality
20European LS-DYNA Conference 2011 - Strasbourg
� Constant failure criterion � Linear damage accumulation� Failure not predicted correctly
� GISSMO-Criterion� Linear accumulation
of damage� Possibly overestimated
damage
� GISSMO-Criterion� Nonlinear damage
accumulation� Rupture predicted correctly
GISSMO Deep-draw simulation of cross-die using GISSMO
21European LS-DYNA Conference 2011 - Strasbourg
Forming simulation:*MAT_36 (Barlat 89)*MAT_ADD_EROSION
(GISSMO)
Crash Simulation:*MAT_24 (Mises)*MAT_ADD_EROSION
(GISSMO)
Plast. strains Thickness distribution Damage
Mapping
Process chain with GISSMO
22European LS-DYNA Conference 2011 - Strasbourg
GISSMOFailure criterion extd. for 3D solids
Lode
Parameter-1
1
0
-0.5
0.5
0.50
-1-0.5
1Triaxialität
Bru
chdehnung
Triaxialität
Bru
chdeh
nung
-0.5 0 0.5 11
� For shells (2D with the assumption of plane stress ) triaxility
and Lode angle depend on each other.
� fracture strain is a function of the triaxiality
� For Solids (3D) both the Lode angle and triaxiality are
independent
� fracture strain is a function of triaxiality and Lode angle
Shells (2D) Solids (3D)
Baseran [2010]
η
ηη
ξξ
23European LS-DYNA Conference 2011 - Strasbourg
Parameter definition
1
3
m
vM vM
Iση
σ σ= =
3
3
27
2vM
Jξ
σ=
3 1 2 3J s s s=mit
[Source: Wierzbicki et al.]
Stress domain in
sheet metal forming
GISSMOFailure criterion extd. for 3D solids
1 60orξ θ= − = − °
0 0orξ θ= = °
1 60orξ θ= = °
24European LS-DYNA Conference 2011 - Strasbourg
Parameter definition
1
3
m
vM vM
Iση
σ σ= =
3
3
27
2vM
Jξ
σ=
3 1 2 3J s s s=mit
[Source: Wierzbicki et al.]
Stress domain in
sheet metal forming
ξ
η
Xue
Hutchinson
Gurson std.
Xue
Hutchinson
Gurson std.
η
fε
[Experimental data by Wierzbicki et al.]
GISSMOFailure criterion extd. for 3D solids
25European LS-DYNA Conference 2011 - Strasbourg
Summary
� Features of GISSMO:
� The use of existing material models and respective parameters
� The constitutive model and damage formulation are treated separately
� Allows for the calculation of pre-damage for forming and crashworthiness
simulations
� Characterization of materials requires a variety of tests
� Automatic method for identification of parameters is to be developed
� Offers features for a comprehensive treatment of damage
in forming simulations
� Available in LS-DYNA V9.71 R5
� Verification und validation of concepts are under way
26European LS-DYNA Conference 2011 - Strasbourg
END