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1 Tanguy ROUXEL, Jean-Christophe SANGLEBOEUF, and Kwadwo KESE LARMAUR, Université de Rennes 1, France The temperature dependence of the Flaw Sensitivity The residual stress field Indentation Damage and Residual Strength of Glass PacRim 8, Vancouver 2009

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  • 1

    Tanguy ROUXEL, Jean-Christophe SANGLEBOEUF,

    and Kwadwo KESE

    LARMAUR, Universit de Rennes 1, France

    The temperature dependence of the Flaw Sensitivity

    The residual stress field

    Indentation Damage and Residual Strength of Glass

    PacRim 8, Vancouver 2009

  • 2

    I. Temperature Dependence of the Flaw sensitivity

    What Brittleness and Ductility mean?

    High temperature studies

    - To get insight into the nature of Brittlness

    - To understand the nature of process-derived contact flaws and

    simulate product handling damage

    - To study the strength-controlling sites at room temperature

  • 3

    !Comme elle a lclat du verre, elle en a la fragilit!Polyeucte, Corneille

    Low temperature or high rate

    !

    !

    Pre-existing flaw

    High temperature or low rate

    Ductile

    Brittle (Fragile)

  • 4

    Indented window glass specimens loaded in bending

    Brittle-Ductile transition

    P

    u

    DuctileBrittle

    Loa

    d,

    P

    Deflection, u (mm)

    J. Non-Cryst. Sol., 271 224-235 (2000)

  • 5

  • 6

    Mechanical analysis

    (Kt=E!Y! a)

    Crack tip stress intensity factor:

    Relaxation function:

    At fracture:

    !

    K = K1c

    !

    " ="decohesion

  • 7

  • 8

    10 hCopper at 20 C

    1 hCeramic composite Si3N4/SiC at 1600 C

    10 sBitumen at 5 C

    0,1 sWindow glass at 600 C

    1 msBitumen at 40 C

    1 msEpoxy resin at 20 C

    1 nsWater at 20 C

    1 dIce at 5 C

    1 dWindow glass at 500 C

    32 yWindow glass at 400 C

    120 yIce at 98 C106 yEarth mantle

    Relaxation timeconstant,

    "rel=#/Materials

  • 9

    Rela

    xation T

    ime C

    onsta

    nt (s

    )

    Reflets de la Physique (anc. Bull. de la SFP), n8 5-9 (2008).

  • 10

    II. The residual stress field

    What do we know about it?

  • 11

    Plastic deformation zone:

    Volume V $ b3 $ E1/2/H (b/a=(V/%V)3)

    Elastic

    deformation zone

    P

    a c

    P!r

    Lawn, Evans and Marshall (1979-81)

    2c

    ca

    Indentation volume: %V $ a3 $ H-3/2

    Unloading

    !r $ K %V/V

    K: bulk modulus

    2b

    "r # (E/H)1/2

  • 12

    Watanabe et al, J.Mater.Sci., 2001

    Michel et al, JNCS, 2004

    Shang Rouxel, JACS, 2005

    "r # (E/H)1/2

  • 13

    "r # (E/H)1/2

    Tg

    J. Non-Cryst. Sol., 271 224-235 (2000)

  • 14

    0

    5

    10

    15

    20

    25

    0 100 200 300 400 500

    Indentation temperature, C

    E/H

    Dwell time = 60 s, Michel et al

    Dwell time = 0 s, this study,

    Recall that the analysis of the indentation problem assuming pure elasto-plasticity leads to:

    "r # (E/H)1/2

    Residual stresses are expected to increase with

    temperature up to 450 C

  • 15

    !

    c = "P( )2

    3

    EH( )

    1

    3

    Kc

    2

    3

    Measured crack length gives $ = 0.020

    Sglavo Green, Acta Metall. Mater., 1995

    0.028

  • 16

    Window Glass : Planilux (Saint-Gobain)

    air sideT

    em

    pe

    ratu

    re

    Time

    2 h

    49 N Vickers

    0.1 mm/s no hold

    2C/min ->100C

  • 17K. Kese et al,, J. Phys. D, App. Phys., 41 [7] 074025 (2008)

  • 18

    Influence of Vickers residual stress

    field on indentation cracking

    cr

    ct

    co

    co

    2.94 N

    49 N

  • 19

    Calculate stresses from crack length

    !

    "T

    = Kc

    1# cocr

    $ % &

    ' ( ) 32

    *cr

    !

    "c

    = Kc

    1# coct

    $ % &

    ' ( ) 32

    *ct

    Zeng and Rowcliffe, Acta Metall. Mater., 1995

  • 20

    Estimation of the residual stresses

    RT

    K. Kese et al,, J. Phys. D, App. Phys., 41 [7] 074025 (2008)

  • 21

    Contact site transformation

    500C

  • 22

    Lateral crack dependence on radial crack

    600C

  • 23

    Crack length as a function of position

    C0

  • 24

    540 C

    600 C630 C

    20 C

  • 25

    Lateral crack dependence on radial crack

    600C

  • 26

    The nature of contact site can change from a fully crackedimprint at room temperature to a crack-free imprint athigher temperatures.

    The crack-free indent can transform into a fully crackedindent when the residual stress field is mechanicallydisturbed, as for example by another micro indent.

    The lateral cracks obtain their shape as a result of theircoupled growth with that of the radial cracks.

    Stresses are tensile in the tangential direction, andcompressive in the radial direction

    The spatial extent of the stress field decreases as afunction of temperature

    Conclusion