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Multi-Physics Numerical Modeling and Experimental

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Multi-Physics Numerical Modeling and Experimental Powered By Docstoc
					       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
                       Background
                                                 Post-doc (Mech. Eng.)
 Diplome d’ingenieur           PhD            Research Assistant Professor
(Hydrodynamic naval)   (Marine Engineering)       Assistant Professor




                                                                     2/36
              Research Activities
Multi-Physics Numerical Modeling
                                   Characterization of
Calibration                        Material Properties
Validation        Mechanical



              Thermal     Fluids


                                                     3/36
Hunley Submarine




                   1/25
Corrosion-Erosion




                    5/25
Thermal Behavior of Buildings




          CFD                                   FEA
          Steady state fluid flow analysis      Transient thermal analysis
          Input: Wall temperatures              Input: Heat fluxes
          Output: Heat fluxes                   Output: Wall temperatures


                             Coupling between CFD and FEA.
                                                                         6/36
Cooling of Precision Glass Molding
                 Glass lens




                  Cooling
                  channels
                  (N2 flow)




                                     7/36
3D heat transfer model of assembly




                                     8/36
Coupled 3D fluid flow / thermal analysis




                                       Surface temperatures
               N2 flow rates

       Fluid flow analysis (CFD)   Thermal analysis (FEA)
       Required parameters:        Required parameters:
        Material properties        Material properties
                                    Surface conductance values



               Surface heat
                   fluxes               Boundary conditions




                                                                  9/36
Temperature profile

• Gradient of 10oC through the lens
• This validates the axisymmetric assumption




                                               10/36
Heat fluxes
• Can visualize heat fluxes
• Heat is drawn to the center of the assembly (inlet of cooling
  channels)




                                                                  1/25
 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
         Creep test



         Constant force



 Glass
sample




                          13/25
   Experimental Characterization of Stress
           Relaxation Properties

Three issues
• Separate shear and hydrostatic behavior
• Manufacture samples
• Numerical treatment to extract stress relaxation properties




                                                                14/36
        A considerable experimental effort is required
           to define visco-elastic behavior of glass

                                     1
                         Separate stress into shear and hydrostatic parts
                           ij  sij   ij
                                         3
                                             t
                                                           eij (t )
 Shear constitutive law          sij (t )   G1 (t  t )            dt 
                                            0
                                                             t 

                                                                    (t )
                                                        t

Hydrostatic constitutive law                (t )   G2 (t  t )          dt 
                                                    0
                                                                    t 

     G1( t )  2 G0  1( t )        G2 (t )  3K   3( K   K 0 ) 2 (t )

                                                 n
                                i (t )   wij e
                                                             t /  ij
Relaxation functions:                                                    (Prony Series)
                                                 j 1
                      Stress Relaxation Basics

                 Strain produced by
                 viscous flow. The
                 viscosity is related       Instantaneous
                 to the slope.              Elastic Strain


                                               Delayed
                                               Elastic Strain
Delayed
Elastic Strain
                                                       Strain due to
                                                       viscous flow
                                CREEP   RECOVERY


Instantaneous
Elastic Strain



                                                                 16/36
    Shear and Hydrostatic Deformations

         Shear or deviatoric               Hydrostatic or dilatation




         Shape change                        Volume change




 Comparatively easy to conduct          Experiments involving pure
experiments involving pure shear   hydrostatic component is complicated

                                                                          17/36
Shear and Uni-axial Tests
         Shear test                    Uni-axial test




Shear deformation only
    (pure shear)         Shear deformation   +     Hydrostatic deformation
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
Overview of Characterization Process
                                         Viscoelastic Characterization


     Shear Creep-Recovery experiments                                          Uni-axial creep-recovery experiments


          Displacement-Time curve                                                     Displacement-Time curve


           Shear strain-Time curve                                                       Strain-Time curve
                                                  Shear / Uni-axial
                                          relaxation moments & constants
            Isolate delayed part                                                         Isolate delayed part


       Retardation function-Time curve                                             Retardation function-Time curve
                                                  Shear / Uni-axial
                                         retardation moments & constants
  Normalized Retardation function-Time(log)                                   Normalized Retardation function-Time(log)



                  Curve fit
                                         Hydrostatic relaxation/retardation
                                              moments & constants
         Shear retardation parameters                                    Curve fit for hydrostatic retardation parameters


 Shear retardation to relaxation conversion                            Hydrostatic retardation to relaxation conversion
                              Creep tests on Helical Spring sample
                             (At different loads and temperatures)
                   2.5




                    2


                                                                                   Series1
                                                                                   Series2
                   1.5                                                             Series3
Displacement(mm)




                                                                                   Series4
                                                                                   Series6
                                                                                   Series7
                    1                                                              Series8
                                                                                   Series9
                                                                                   Series10


                   0.5




                    0
                         0   50   100   150          200   250   300   350   400        450
                                                                                              21/36
                                        Time (sec)
                              Curve Fitting
                        1

                       0.9

                       0.8

                       0.7
Retardation Function




                       0.6

                       0.5

                       0.4

                       0.3

                       0.2

                       0.1

                        0
                          0    1         2       3    4
                        10    10      10        10   10
                                   Time (sec)
 Stress Relaxation Module



 Create dog-bone specimen           Create spring specimen


Conduct creep relaxation test      Conduct creep relaxation
   at various temperatures          test at diff. temperatures


     Strain vs time data           Displacement vs time data                            n
                                                                   i (t )   wij e
                                                                                                         t /  ij

                   Data processing based on                                             j 1
                   Mathematical formulations
                                                                         563oC                       588oC
                                                                   w1j           τ 1j          w1j            τ 1j
                                                                 3.06E-03        5.96    2.91E-02            5.05

                                                                  0.970          97.4       0.918            23.92

                                                                 0.0260      253.2          0.051            75.3
                      Alternative Geometries
  Helical spring
  (pure shear)
                                          Tension/compression
                                          uniaxial test
                                          (shear + hydrostatic)




                                               3-point bending
                                               (shear + hydrostatic)
Shaft under torsion
(pure shear)




                                                                  24/36
              Equipment
Creep frame          Parallel-plates viscometer (PPV)




                                                        25
  Manufacturing Samples




Pyrex      BK7       LBAL35
Glass Manufacturing




                      27/36
          Manufacturing Samples of Low Tg Glass


Manufacturing process


  Short thick rod




                                                              Wrap long rod
                        Create ball     Stretch into
                                                            around metal rod
                                         long rod
                                                             to create spring



    • Heat treatment and large deformations may alter optical
      and thermo-mechanical properties

    • BK7 was successful with some defects
      L-BAL35 was not successful




                                                                       BK7
Glass Manufacturing




                      29/36
Glass Manufacturing




                      30/36
Glass Manufacturing
Glass Manufacturing
Glass Manufacturing
Glass Manufacturing
                 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
              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

				
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