Carel ten Horn, Henk Vegter, Janka Cafollasharefea.com › upload › 2014 › 11 › 16 ›...
Transcript of Carel ten Horn, Henk Vegter, Janka Cafollasharefea.com › upload › 2014 › 11 › 16 ›...
Tata Steel Slide 1Vegter yield locus in MF GenYld + CrachFEMPresentation title, change View >> Header & Footer
MATFEM conference 2014
Increased accuracy for forming and crash simulation using the Vegter yield locus
Carel ten Horn, Henk Vegter, Janka Cafolla
Tata Steel Slide 2Vegter yield locus in MF GenYld + CrachFEM
Fracture in Automotive
Need for cost reduction and fuel efficiency has lead to:
� Increased use of higher strength materials
� Increased reliance on simulations
� Increased importance of accuracy of forming, springback and crash predictions
For HSS, AHSS and UHSS:
� fracture can occur before necking
� fracture limit close to or below forming limit
� predicting fracture has become important
Fracture models have become important for accurate predictions which requires calculated stresses and strains to be accurate
Good fracture predictions require using a good plasticity model
Tata Steel Slide 3Vegter yield locus in MF GenYld + CrachFEM
Plasticity and fracture inextricably linked
Fracture strains only have meaning when they are viewed together with plasticity data
Example: 3 point bending
� 2 materials with same bending angle at fracture but different hardening curves
� due to difference in strain distribution, different strain level at same bending angle
� different fracture strains for same bending angle
� Therefore, fracture strains need plasticity model for proper interpretation
Bending angle
[°]
Fracture strain
[-]
CP800 86 0.53
DP800HpF 85 0.35
0
200
400
600
800
1000
1200
0 0.2 0.4 0.6 0.8
True plastic strain [-]
True stress [MPa]
CP800
DP800HpFCP-grade
DP-grade
CP-grade
DP-grade
CP-grade
DP-grade
Tata Steel Slide 4Vegter yield locus in MF GenYld + CrachFEM
Plasticity model – Yield locus
� Many yield locus models available:
� Hill’48, Hill’90, Barlat1996, Barlat2000, Barlat-Lian, Barlat-Lege-Brem, Dell, Bron-Besson, …
� Standard models (e.g. vonMises, Hill’48, Hill’90, Yld’89) do not always coincide with (yield locus) measurements
� Advanced models require:
� more test data (which may not always be available)
� complicated fitting routines
� Solution: Vegter yield locus
It incorporates all measured points from:
� Uniaxial test
� Plane strain test
� Shear test
� Biaxial test (stack compression or bulge test)
σ2
σ1
Tata Steel Slide 5Vegter yield locus in MF GenYld + CrachFEM
Parameters Vegter yield locus
� Using measured points and strain ratios, an envelope is created
� A Bezier curve connects the points
� Usually tests in 3 direction but up to 10 directions possible in MF GenYld + CrachFEM
� 17 Parameters from 9 tests:
σun(0°) σun(45°) σun(90°)
r0 r45 r90
σps(0°) σps(45°) σps(90°)
α(0°) α(45°) α(90°)
σsh(0°) σsh(45°) σsh(90°)
σbi rbi
� Parameter taken directly from tests except for α
� Second stress component of plane strain point impossible to measure; so assumption: α = 0.5 (i.e. half way between hinge points)
σun(0°)
σun(90°)
"r90"
"r0"
σps(90°)σbi
"rbi"
σps(0°)
σsh(0°)
σsh(90°)
σσσσ1
σσσσ2
αps(0°)
αps(90°)
Tata Steel Slide 6Vegter yield locus in MF GenYld + CrachFEM
Yield locus DX57D+Z
DX57D+Z
0°/90°
-1.5
-1
-0.5
0
0.5
1
1.5
-1.5 -1 -0.5 0 0.5 1 1.5
Hill'48
Hill'90
Barlat2000
Vegter
Measured
σσσσ1/σσσσf
σσσσ2/σσσσfDX57D+Z
45°
-1.5
-1
-0.5
0
0.5
1
1.5
-1.5 -1 -0.5 0 0.5 1 1.5
Hill'48
Hill'90
Barlat2000
Vegter
Measured
σσσσ1/σσσσf
σσσσ2/σσσσf
Tata Steel Slide 7Vegter yield locus in MF GenYld + CrachFEM
Yield locus HX220BD+Z
HX220BD+Z
0°/90°
-1.5
-1
-0.5
0
0.5
1
1.5
-1.5 -1 -0.5 0 0.5 1 1.5
Hill'48
Hill'90
Barlat2000
Vegter
Measured
σσσσ1/σσσσf
σσσσ2/σσσσfHX220BD+Z
45°
-1.5
-1
-0.5
0
0.5
1
1.5
-1.5 -1 -0.5 0 0.5 1 1.5
Hill'48
Hill'90
Barlat2000
Vegter
Measured
σσσσ1/σσσσf
σσσσ2/σσσσf
Tata Steel Slide 8Vegter yield locus in MF GenYld + CrachFEM
Yield locus HX340LAD+Z
HX340LAD+Z
0°/90°
-1.5
-1
-0.5
0
0.5
1
1.5
-1.5 -1 -0.5 0 0.5 1 1.5
Hill'48
Hill'90
Barlat2000
Vegter
Measured
σσσσ1/σσσσf
σσσσ2/σσσσfHX340LAD+Z
45°
-1.5
-1
-0.5
0
0.5
1
1.5
-1.5 -1 -0.5 0 0.5 1 1.5
Hill'48
Hill'90
Barlat2000
Vegter
Measured
σσσσ1/σσσσf
σσσσ2/σσσσf
Tata Steel Slide 9Vegter yield locus in MF GenYld + CrachFEM
Yield locus HCT980X+Z High Yield
HCT980X+Z HY
0°/90°
-1.5
-1
-0.5
0
0.5
1
1.5
-1.5 -1 -0.5 0 0.5 1 1.5
Hill'48
Hill'90
Barlat2000
Vegter
Measured
σσσσ1/σσσσf
σσσσ2/σσσσf HCT980X+Z HY
45°
-1.5
-1
-0.5
0
0.5
1
1.5
-1.5 -1 -0.5 0 0.5 1 1.5
Hill'48
Hill'90
Barlat2000
Vegter
Measured
σσσσ1/σσσσf
σσσσ2/σσσσf
Tata Steel Slide 10Vegter yield locus in MF GenYld + CrachFEM
Aurora Online
� Material data service
� Enabling high-quality support
� Representative of everyday production
� For selected automotive customers
Meeting the material data needs of our Automotive customers
Tata Steel Slide 11Vegter yield locus in MF GenYld + CrachFEM
Aurora Online
� Basic & Advanced properties
� Datasheet PDF-file
� Raw data Excel-file
� Raw data Text-file
� CAE R2R Forming & Crash:
� Material cards for
� PAM-STAMP / PAM-CRASH
� LS-DYNA
� Autoform
� Radioss
� Abaqus
Tata Steel Slide 12Vegter yield locus in MF GenYld + CrachFEM
An example: the cross-die
� Semi-industrial laboratory specimen
� Materials:
� DC04
� DP800
� All runs with MF GenYld + CrachFEM
� Same hardening curves but different yield loci:
� Hill’48 (3 parameters)
� Barlat2000 (9 parameters)
� Vegter (17 parameters)
DC04 DP800
Blank size [mm] 260x260 265x265
Thickness [mm] 1.00 1.20
Blankholder force [kN] 244 823
Height [mm] 61.5 30.2
Tata Steel Slide 13Vegter yield locus in MF GenYld + CrachFEM
Yield locus DC04
� Hill’48 overestimates the anisotropy and the biaxial point
� Barlat2000 much better but plane strain points do not match experiments
� Vegter takes all experimental data into account
DC04 - 0°/90°
-1.5
-1
-0.5
0
0.5
1
1.5
-1.5 -1 -0.5 0 0.5 1 1.5
σσσσ1/σσσσref
σσ σσ2/ σσ σσref
Hill'48Barlat2000VegterMeasured
DC04 - 45°
-1.5
-1
-0.5
0
0.5
1
1.5
-1.5 -1 -0.5 0 0.5 1 1.5
σσσσ1/σσσσref
σσ σσ2/ σσ σσref
Hill'48Barlat2000VegterMeasured
Tata Steel Slide 14Vegter yield locus in MF GenYld + CrachFEM
Results Cross-die DC04
� Major strain distribution for Barlat2000 and Vegter are closer to measurement than Hill’48
Hill’48 Barlat2000 Vegter
Measured
Tata Steel Slide 15Vegter yield locus in MF GenYld + CrachFEM
Results Cross-die DC04
� Hill’48 and Barlat2000 predict (very) safe part but blank size is critical in the experiment
� Vegter model predicts necking will occur at this blank size
Cross-die DC04
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
-0.7 -0.5 -0.3 -0.1 0.1 0.3
Minor strain [-]
Major strain [-]
MeasurementMeasured FLCHill'48Barlat2000Vegter
Tata Steel Slide 16Vegter yield locus in MF GenYld + CrachFEM
Results Cross-die DC04
� Punch force better predicted using Barlat2000 and Vegter than using Hill’48
0
50
100
150
200
250
0 10 20 30 40 50 60
Punch displacement [mm]
Punch force [kN]
Measured
Hill'48
Barlat2000
Vegter
Tata Steel Slide 17Vegter yield locus in MF GenYld + CrachFEM
Yield locus DP800
� Hill’48 overestimates the anisotropy and the underestimates the biaxial point
� Barlat2000 quite close but small differences in plane strain and shear points
� Vegter takes all experimental data into account
DP800 - 0°/90°
-0.5
0
0.5
1
-0.5 0 0.5 1
σσσσ1/σσσσref
σσ σσ2/ σσ σσref
Hill'48Barlat2000VegterMeasured
DP800 - 45°
-0.5
0
0.5
1
-0.5 0 0.5 1
σσσσ1/σσσσref
σσ σσ2/ σσ σσref
Hill'48Barlat2000VegterMeasured
Tata Steel Slide 18Vegter yield locus in MF GenYld + CrachFEM
Results Cross-die DP800
Height 25.6 mm
� experiment: some points above FLC but no necking
� Simulation:
� Strain distribution similar for all yield loci
� Vegter predicts necking is imminent
Hill’48 Barlat2000 Vegter
Cross-die DP800
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2
Minor strain [-]
Major strain [-]
MeasurementMeasured FLCHill'48Barlat2000Vegter
Major strain:
Tata Steel Slide 19Vegter yield locus in MF GenYld + CrachFEM
Results Cross-die DP800
Height 30.2 mm
� experiment: fracture on die radius
� simulation:
� ductile shear fracture risk predicts fracture at correct location
� small differences for different yield loci
Hill’48 Barlat2000 Vegter
Ductile shear fracture risk:
Tata Steel Slide 20Vegter yield locus in MF GenYld + CrachFEM
Conclusions
� A good plasticity model is essential for good fracture predictions
� Small changes in yield locus can have large effect on results
� Vegter yield locus:
� fits experimental data
� provides better forming, crash and fracture predictions
� no complicated fitting routines needed to obtain parameters
� only available for shells
++ Very good
+ Acceptable
- Not good
-- Very bad
von Mises Hill'48 Hill'90 Barlat'91 Vegter Example
Forming steel
LC steel -- - - - ++ DC03
IF -- -- -- - ++ DX56D+Z, DC06
HSS
IF Rephos -- - + - ++ HX220YD
Bake Hardening -- - -- - ++ HX220BD
LC steel Rephos - - - - ++ HX280PD
Micro Alloyed + + + + ++ HX340LAD
AHSS
Dual Phase + - - - ++ DP600, DP800
Complex Phase + + + + ++ CP800
Aluminium -- -- - -- ++ AA5182, AA6016
Tata Steel Slide 21Vegter yield locus in MF GenYld + CrachFEM
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