Multi-Physics Numerical Modeling and Experimental Characterization of Materials

1. Multi-Physics Numerical Modeling and Experimental Characterization of Materials Vincent Y. Blouin Assistant Professor Materials Science and Engineering Clemson University MILMI Bordeaux June 15, 2010

2. Background Post-doc (Mech. Eng.) Research Assistant Professor Assistant Professor Diplome d’ingenieur (Hydrodynamic naval) PhD (Marine Engineering) 2/36

3. Research Activities Multi-Physics Numerical Modeling Characterization of Material Properties Calibration Validation 3/36

4. Hunley Submarine 1/25

5. Corrosion-Erosion 5/25

6. Thermal Behavior of Buildings Coupling between CFD and FEA. 6/36 FEA Transient thermal analysis Input: Heat fluxes Output: Wall temperatures CFD Steady state fluid flow analysis Input: Wall temperatures Output: Heat fluxes

7. Cooling of Precision Glass Molding Glass lens Cooling channels (N2 flow) 7/36

8. 3D heat transfer model of assembly 8/36

9. Coupled 3D fluid flow / thermal analysis Surface temperatures N2 flow rates • Thermal analysis (FEA) • Required parameters: • Material properties • Surface conductance values • Fluid flow analysis (CFD) • Required parameters: • Material properties Surface heat fluxes Boundary conditions 9/36

10. Temperature profile • Gradient of 10oC through the lens • This validates the axisymmetric assumption 10/36

11. Heat fluxes • Can visualize heat fluxes • Heat is drawn to the center of the assembly (inlet of cooling channels) 1/25

12. Modeling Precision Glass Molding • Precision glass molding requires full understanding of • Thermal properties • Interaction properties • Friction coefficient • Heat exchange • Viscosity as function of temperature • Structural relaxation • Stress relaxation 12/36

13. Creep test Constant force Glass sample 13/25

14. Experimental Characterization of Stress Relaxation Properties • Three issues • Separate shear and hydrostatic behavior • Manufacture samples • Numerical treatment to extract stress relaxation properties 14/36

15. A considerable experimental effort is required to define visco-elastic behavior of glass Separate stress into shear and hydrostatic parts Shear constitutive law Hydrostatic constitutive law (Prony Series) Relaxation functions:

16. Stress Relaxation Basics Strain produced by viscous flow. The viscosity is related to the slope. Instantaneous Elastic Strain Delayed Elastic Strain Delayed Elastic Strain Strain due to viscous flow CREEP RECOVERY Instantaneous Elastic Strain 16/36

17. Shear and Hydrostatic Deformations Shear or deviatoric Hydrostatic or dilatation Shape change Volume change Comparatively easy to conduct experiments involving pure shear Experiments involving pure hydrostatic component is complicated 17/36

18. Shear and Uni-axial Tests Shear test Uni-axial test Shear deformation only (pure shear) Hydrostatic deformation Shear deformation +

19. Literature Rekhson S.M. (1980) Extension of theory of linearity to complex glasses and temperature dependent viscosity values of Pyrex® glass Scherer. G (1986) Fundamentals of viscoelasticity Gy R. et al. (1994) Retardation to Relaxation conversions Gy R. et al. (1996) Concept of viscoelastic moments and constants Duffrène et al. (1997) Overview of creep testing, methodology and experimental requirements Pascual M.J. et al. (2001) Temperature dependent viscosity data for Pyrex® glass Spinner S. (2006) Temperature dependent mechanical properties of Pyrex® glass 19/36

20. Overview of Characterization Process

21. Creep tests on Helical Spring sample (At different loads and temperatures) Displacement(mm) 21/36 Time (sec)

22. Curve Fitting

23. Stress Relaxation Module Create dog-bone specimen Create spring specimen Conduct creep relaxation test at various temperatures Conduct creep relaxation test at diff. temperatures Strain vs time data Displacement vs time data Data processing based on Mathematical formulations

24. Alternative Geometries Helical spring (pure shear) Tension/compression uniaxial test (shear + hydrostatic) 3-point bending (shear + hydrostatic) Shaft under torsion (pure shear) 24/36

25. Equipment Creep frame Parallel-plates viscometer (PPV)

26. Manufacturing Samples Pyrex BK7 LBAL35

27. Glass Manufacturing 27/36

28. Manufacturing Samples of Low Tg Glass Manufacturing process Short thick rod Wrap long rod around metal rod to create spring Create ball Stretch into long rod • Heat treatment and large deformations may alter optical and thermo-mechanical properties • BK7 was successful with some defects • L-BAL35 was not successful BK7

29. Glass Manufacturing 29/36

30. Glass Manufacturing 30/36

31. Glass Manufacturing

32. Glass Manufacturing

33. Glass Manufacturing

34. Glass Manufacturing

35. Optical Glasses (Low Tg) • Sensitive to thermal shocks • Impossible to fix once broken • Optical glasses usually come as short rods (<20cm x 1cm) • Prone to formation of bubbles when melted and extended • Sand-blasted finish is harder to work with than smooth finish • Current and future work: • Use simpler geometries (not as accurate, requires more numerical treatment) • Develop setup to manufacture samples at controlled temperature 35/36

36. Current and Future Work • Use simpler geometries (not as accurate, requires more numerical treatment) • Develop setup to manufacture samples at controlled temperature • Experimental validation of numerical simulation • Development of automatic numerical treatment of experimental data for extracting properties • Use PPV for better temperature control (small samples) 36/36