Validation of Material Modelsin Uintah

Biswajit BanerjeeAugust 16, 2005

Outline

● Validation Process● Copper

– One-dimensional tests– Taylor impact tests

● 4340 Steel– Model parameters– One-dimensional tests

● Future Work

Validation Process : Goals

● Determine Model Error● Determine Numerical Algorithm Error● Minimize Errors

Validation Process : Models 1

● Elastic Models– Equation of state (for pressure)– Shear modulus model– Melting temperature model– Thermal expansion model

● Plastic Models– Shear modulus model– Melting temperature model– Model for heating due to plastic work– Specific heat model– Flow stress model– Yield condition model

Validation Process : Models 2

● Damage Models– Scalar damage model– Porosity model

● Failure Models– Energy balance – modifications of J-Integral

model– TEPLA-F empirical model– Material stability model

Validation Process : Step 1

● Verification of material models– Are the models correctly implemented ?– The material stress update algorithm is examined

and errors are quantified using 1-D tests or exact solutions.

● Validation of material models– Do the material models reflect “reality”?– What is the percentage error?

● “Reality” in this step means:– Controlled tests, usually 1-D

Validation Process : Step 2

● Validation of material models under more complex loading conditions– Non-uniform strain rate– Unloading of the material

● Examples:– Moderate strain rate: Taylor Impact Tests– High strain rate: Flyer Plate Impact Tests– Expansion of Copper and Steel Rings.

● The problem geometry is simple – May be 1-D or 2-D.

Validation Process : Step 3

● Coupling constitutive models with damage and failure– Taylor Impact Tests with Failure– Flyer Plate Impact Tests with Spall– Implosion/Explosion of 2-D cylinder (uniform load)– Impact of ball with plate– Fracture of cylinder due to expansion

● The tests are well characterized and involve simple geometries

Validation Process : Step 4

● Interaction with burn models and fluid-structure coupling (no fire)– Detonation and copper sleeve– Explosive fragmentation – Other tests ?

● The tests are complex but still simple enough to be well characterized in certain aspects.

● The final step is the full Monty.

Validation Tests: Copper

● Why copper ?– Well characterized and relatively simple material– A lot of experimental data – Useful for all the validation steps

● Verification and Validation steps– 1-D verification of plastic models– Taylor impact tests– Flyer plate tests (expt. mostly 6061-T6 Al )– Exploding ring (expt. mostly Al and Steel)– Detonation (Jim's simulations)

Verification Tests: Copper (JC)

Verification Tests: Copper (SCG)

Verification Tests: Copper (ZA)

Verification Tests: Copper (MTS)

Verification Tests: Copper (PTW)

1-D Validation Tests: Copper (JC)

1-D Validation Tests: Copper (SCG)

1-D Validation Tests: Copper (ZA)

1-D Validation Tests: Copper (MTS)

1-D Validation Tests: Copper (PTW)

1-D Tests: Summary

● PTW models data best● Stage IV hardening not captured by any

model● What happens during an overdriven shock ?

2-D Taylor Tests: Cu Profile 1

2-D Taylor Tests: Cu Profile 2

2-D Taylor Tests: Cu Profile 3

2-D Taylor Tests: Cu Energy 1

2-D Taylor Tests: Cu Energy 2

2-D Taylor Tests: Cu Energy 3

2-D Taylor Tests: Metrics

2-D Taylor Tests: Metrics Cu 1

2-D Taylor Tests: Metrics Cu 2

2-D Taylor Tests: Metrics Cu 3

2-D Taylor Tests: Summary

● Low temperature tests predicted well by Johnson-Cook.

● Higher temperature tests predicted best by Preston-Tonks-Wallace.

● Validation metrics should include different moments of the geometry – centroid, moment of inertia and higher order moments.

4340 Steel Validation Tests: Cp

4340 Steel Validation Tests: Tm

4340 Steel Validation Tests: µ

4340 Steel Validation Tests: EOS

4340 Steel Validation: JC Rc 30

4340 Steel Validation: JC Rc 38

4340 Steel Validation: JC Rc 45

4340 Steel Validation: JC Rc 49

4340 Steel Validation: MTS Rc 30

4340 Steel Validation: MTS Rc 38

4340 Steel Validation: MTS Rc 45

4340 Steel Validation: MTS Rc 49

4340 Steel Validation: Summary

● MTS fits data better overall.● Easier to determine parameters for MTS.● All submodels perform reasonably well.

4340 Steel Predictions: Rc 38 1000/s

Future Work

● Fit parameters for 4340 steel for PTW, SCG, ZA.

● Get parameters for 6061-T6 Al. Needed for a number of validation tests which are not available for 4340 steel. Anup's thesis.

● Validate damage and failure models.● Develop extended FEM-like fracture model to

create cracks – current approach does not do too well.

● Lot's of work .. so little time !