Validation of Material Models in Uintah. Biswajit Banerjee August 16, 2005

Transcription

1 Validation of Material Models in Uintah Biswajit Banerjee August 16, 2005

2 Outline Validation Process Copper 4340 Steel One-dimensional tests Taylor impact tests Model parameters One-dimensional tests Future Work

3 Validation Process : Goals Determine Model Error Determine Numerical Algorithm Error Minimize Errors

4 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

5 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

6 Validation Process : Step 1 Verification of material models Validation 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. Do the material models reflect reality? What is the percentage error? Reality in this step means: Controlled tests, usually 1-D

7 Validation Process : Step 2 Validation of material models under more complex loading conditions Examples: Non-uniform strain rate Unloading of the material 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.

8 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

9 Validation Process : Step 4 Interaction with burn models and fluidstructure 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.

10 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)

11 Verification Tests: Copper (JC)

12 Verification Tests: Copper (SCG)

13 Verification Tests: Copper (ZA)

14 Verification Tests: Copper (MTS)

15 Verification Tests: Copper (PTW)

16 1-D Validation Tests: Copper (JC)

17 1-D Validation Tests: Copper (SCG)

18 1-D Validation Tests: Copper (ZA)

19 1-D Validation Tests: Copper (MTS)

20 1-D Validation Tests: Copper (PTW)

21 1-D Tests: Summary PTW models data best Stage IV hardening not captured by any model What happens during an overdriven shock?

22 2-D Taylor Tests: Cu Profile 1

23 2-D Taylor Tests: Cu Profile 2

24 2-D Taylor Tests: Cu Profile 3

25 2-D Taylor Tests: Cu Energy 1

26 2-D Taylor Tests: Cu Energy 2

27 2-D Taylor Tests: Cu Energy 3

28 2-D Taylor Tests: Metrics

29 2-D Taylor Tests: Metrics Cu 1

30 2-D Taylor Tests: Metrics Cu 2

31 2-D Taylor Tests: Metrics Cu 3

32 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.

33 4340 Steel Validation Tests: Cp

34 4340 Steel Validation Tests: Tm

35 4340 Steel Validation Tests: µ

36 4340 Steel Validation Tests: EOS

37 4340 Steel Validation: JC Rc 30

38 4340 Steel Validation: JC Rc 38

39 4340 Steel Validation: JC Rc 45

40 4340 Steel Validation: JC Rc 49

41 4340 Steel Validation: MTS Rc 30

42 4340 Steel Validation: MTS Rc 38

43 4340 Steel Validation: MTS Rc 45

44 4340 Steel Validation: MTS Rc 49

45 4340 Steel Validation: Summary MTS fits data better overall. Easier to determine parameters for MTS. All submodels perform reasonably well.

46 4340 Steel Predictions: Rc /s

47 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!