Validation Of Plasticity Models

Validation of a multi-physics code Plasticity models & Taylor Impact

Biswajit Banerjee University of Utah

McMat 2005, June 2005, Baton Rouge

Outline  The

UINTAH multi-physics code  Verification & Validation  Materials & Models  Taylor Impact Test  Validation Metrics  Results  Conclusions

The UINTAH code

Verification  Comparisons

with exact solutions  Rate of convergence of the truncation error (theory vs. code)  Manufactured test problems  Monitoring of conserved parameters  Preservation of symmetry  Comparisons with existing codes

Validation  Comparisons

with experiments

 Level

1: Experiments to validate individual component physics  Level 2: Experiments to validate combinations of components  Level 3: Experiments to validate the complete simulation

experiments designed to validate large codes.

 Need

Goals  Determine

plasticity model best suited for fire-steel interaction  Strain

rates - 0.001/s to 108/s  Temperatures - 230 K - 800 K  Validate

Plasticity Models

 Taylor

Impact Tests  Flyer-Plate Impact Tests

Materials & Models 

Materials OFHC Copper (Annealed)  6061-T6 Aluminum Alloy  4340 Steel Alloy 



Yield Stress Models: Johnson-Cook (JC)  Steinberg-Cochran-Guinan-Lund (SCG)  Zerilli-Armstrong (ZA)  Mechanical Threshold Stress (MTS)  Preston-Tonks-Wallace (PTW) 



Shear Modulus/Melting Temp. Models: Nadal-Le Poac  Follansbee-Kocks  Steinberg-Cochran-Guinan 

OFHC-Copper - strain rate

JC vs MTS

JC vs PTW

JC vs SCG

JC vs ZA

OFHC-Copper - temperature JC vs MTS

JC vs PTW

JC vs SCG

JC vs ZA

OFHC-Copper - moduli/melting Equation of State

Shear Modulus

Melt Temp.

Taylor Impact Test

Experiments - OFHC Copper

Experiments - 6061-T6 Al

Experiments - 4340 Steel

Validation Metrics           

Eyeball-norm Final Length Elastic Length (green) Final vertical length (red+green) Mushroom Diameter Diameter at 0.2 L (x) Final area Final volume Centroid (1st moment) Moment of Inertia Time of impact

Final Profiles: OFHC Copper

210 m/s, 295K

188 m/s, 718K

181 m/s, 1235K

Error Metrics: OFHC Copper

188 m/s, 718K

Time Metrics: OFHC Copper

188 m/s, 718K

Range of States: OFHC Copper

188 m/s, 718K

Final Profiles: 6061-T6 Al

373 m/s, 294K

194 m/s, 635K

354 m/s, 655K

Error Metrics: 6061-T6 Al

194 m/s, 635K

Final Profiles: 4340 Steel

308 m/s, 295K

312 m/s, 725K

160 m/s,1285K

Error Metrics: 4340 Steel

312 m/s, 725K

Conclusions  Thermal

softening is inadequate in the physically based models  Johnson-Cook is the best bet among the models investigated  More high temperature data are needed in the high rate regime  A temperature sensitive length scale may be needed to prevent spurious mesh sensitivity