energy-based inelastic hardness of soda-lime silicate glassintrinsic strength of soda-lime glass: ~...

Energy-Based Inelastic Hardness ofSoda-Lime Silicate Glass

Satoshi YOSHIDASatoshi YOSHIDA 1, 21, 2, , Hiroshi SAWASATO Hiroshi SAWASATO 1, 21, 2,,

Masanori YOSHIKAWA Masanori YOSHIKAWA 11, , Jun MATSUOKA Jun MATSUOKA 1, 21, 2

1 Department of Materials Science,The University of Shiga Prefecture, Hikone, Shiga, JAPAN

2 Center for Glass Science and Technology, The University of Shiga Prefecture, Hikone, Shiga, JAPAN

The University of Shiga Prefecture

FFAG4, 2007, Shiga, JAPAN

Contents1. Background

Indentation impression of glass… What is a permanent deformation of glass ?… Densification and Shear flow of glass

2. Experimental procedure

3. Results and Discussion

4. Summary> Energy based hardness depends on a shape of indenter. > Energy required to create a unit volume of indentation

varies with contribution of densification.



1. Background

Permanent deformation of glass


3. Results and Discussion

4. Summary



1. Background Indentation impression of glass

Peter (1970)

Shear lines !

Ball indentation on soda-lime glass(radius = 80 µm, load = 1100 gf)

Plastic flow or Densification ?

Ball indentation on soda-lime glass(radius = 20 µm, load = 100 gf)

The contrast arises from an increase in refractive index.

Densification !



Silica glass : After unloading(Vickers indentation)

500 1000

Center of indentation

Outside

Wavenumber (cm–1)

Inte

nsity

(a.u

.)

Raman spectra of silica glass.(Indentation load = 1 N)

492 cm-1

430 cm-1

0.1 MPa

Quenched from ~ 30GPa

Hemley et al.(1986)

Raman spectra of silica glass under high hydrostatic pressures





Indentation profileAnnealing

Densified volumeTg ×0.9, 2 h

Relaxation time for viscous flow is long enough.

24

62

µm

4

6

0

-0 2

0 2µm

24

62

µm

4

6

0

-0 2

0 2µm

Discrimination of densified volume from total indentation volumeMackenzie(1969), Yoshida (2001, 2005)



after annealing (at Tg X 0.9)

500 1000


Outside

Wavenumber (cm–1)

Inte

nsity

(a.u

.)

Raman spectra of silica glass.(Indentation load = 1 N)

492 cm-1

430 cm-1

500 1000


Outside

Wavenumber (cm–1)

Inte

nsity

(a.u

.)

Silica glass : before annealing





The previous work Yoshida, Sangleboeuf, Rouxel (2005), J. Mater. Res. 20, p. 3404.

0.1 0.2 0.3 0.4 0.50

102030405060708090

100

Vol

ume

ratio

of r

ecov

ery,

VR (%

)

Poisson's ratio

Silica

BMG

YBC6

1. Various kinds of glasses, including silica, oxynitride(YBC6), metallic glass(BMG), undergo densification under an indenter.

2. Volume recovery (densifiedvolume) decreases with increasing Poisson’s ratio of glass.

3. The indentation volume provides important information on inelastic deformation of glass.

Soda-lime glass

Densification cannot be ignored for oxide glasses.



In order to get insight into inelastic deformation of glass

1. With different indenters, depth-sensing indentation experiments (Load-unload tests) are performed for soda-lime silicate glass.

2. Energy-based hardness, which is calculated from the inelastic work of indentation and the residual indentation volume by using an SPM, is obtained.

Objectives of this work



1. Background

2. Experimental procedure3. Results and Discussion

4. Summary




2-1. Depth-sensing indentation

Denpth-sensing indenter: Shimadzu DUH-201

Diamond indenter: Vickers, Berkovich, Cube-corner

Indentation load : 50 mN ~ 400 mN

Loading and unloading rates : 14 mN/s

Sample:Soda-lime glass(Matsunami S-0050)

Ur: Inelastic hysteresis loop energy, Ue: Elastic stored energy, Ut (=Ur+Ue): Total energy to create an indentation impression at Pmax

Ur Ue




2-2. Measurement of residual impression volume

Scanning probe microscope(SPM): Veeco Nanoscope E

Conditions of Image aquisition: Contact modeScan area 5 µm2 ~ 15 µm2

V +: Pile-up volume V ̶ : Indentation volume

24

62

µm

4

6

0

-0 2

0 2µm

V＋

V－




2-3. Energy-based inelastic hardness

V＋

V－

)(m area Projected(N)LoadhardnessMeyer 2=

Meyer hardness is an Elastoplastic workto create a unit volume of maximum indentation volume.

)(m volume,nIndentatio(J)energy,loop Inelastic hardness inelastic basedEnergy 3-

r

VU

=

Ur Ue

Energy based inelastic hardness is an Inelastic work to create a unit volume of residual indentation volume.

M. Sakai, Acta Metall. Mater., 41, 1751 (1993)N.A. Stilwell and D. Tabor, Proc. Phys. Soc. 78, 169 (1961)



1. Background


3.Results and Discussion4. Summary



3. Results and DiscussionLoad-depth curves of soda-lime glass using different indenters

0 1 20

100

200

300

400

Load

/mN

Depth /µm

Vickers Berkovich Cube-corner

Elastic recovery of Cube-corner indentation is small as compared with other indentations.Glass behaves like a metal under a Cube-corner, but has some cracks.

0 1 20

100

200

300

400

Depth /µm

Load

/mN

0 1 2 3 4 50

100

200

300

400

Load

/mN

Depth /µm



3. Results and DiscussionLoad-depth curves of soda-lime glass using different indenters

The indenter which has the larger face angle, β, shows deeper penetration.

0 1 2 3 4 50

100

200

300

400

Load

/mN

Depth /µm

Vickers

Berkovich

CubeCorner

βV = 22.0 º βB = 24.7 ºβC = 54.7 º

cf. Geometrical factors of indenter, g : Apro = g h2

gV= 24.5, gB= 24.5, gc= 2.6Apro : Projected area, h : depth

VickersBerkovich

Cube-corner



3. Results and DiscussionSPM image of residual impression

Using the maximum depth, hmax=0.54 µm, from load-depth curve and the contact depth , hc=0.44 µm, from the diagonal of impression, the surface geometrical factor, γ (= hmax /hc), is estimated to be 1.23.

Vickers 50 mN




The surface geometrical factor, γ (= hmax /hc), is 1.29.

Berkovich 50 mN




The surface geometrical factor: γ ~ 1No sinking-in

Cube-corner 50 mN



3. Results and DiscussionEnergy based inelastic hardness

Meyer hardness(from maximum depth @ 400 mN )

Vickers: 4.4 GPaBerkovich: 3.3 GPaCube-corner: 6.8 GPa

Inelastic hardness with a Cube-corner is larger than those with other indenters.

Inelastic hardness >> Meyer hardness

0 100 200 300 400 5008

10

12

14

16

Indentation load /mN

Inel

astic

har

dnes

s /G

Pa Cube-corner

Vickers

Berkovich



3. Results and DiscussionAnnealing recovery (Relaxation of densified volume)

Vickers 100 mN

Densified volume



3. Results and DiscussionAnnealing recovery (Relaxation of densified volume)

Sharp indenter:Less recoveryLess densification

Cube-corner 100 mN



3. Results and DiscussionEnergy based inelastic hardness

Pressure onset for hydrostatically densification of soda-lime glass:

~ 8 GPa

Inelastic hardness is an inelastic work to create a unit volume of residual impression.

Inelastic hardness: ~ 14GPa > Inelastic hardness: ~ 12GPa(Cube-corner) (Vickers, Berkovich)

Shear flow only Shear flow(20%) + Densification(80%)

Shear flow is a bond-breakage process.

Intrinsic strength of soda-lime glass:~ 10 GPa

(two-point bending of fiber)

The difference of inelastic hardness stems fromShear flow energy > Densification energy

S. Yoshida et al., J. Mater. Res., 20, 3404 (2005)

See Poster Presentation, M. Inoue et al. H. Ji et al., Scrip. Mater., 55, 1159 (2006)



4. Summary1. Hardness is an energy required to create a unit

volume of residual indentation impression.

2. Energy-based inelastic hardness depends on a shape of indenter.

Hardness (Cube-corner) > Hardness (Vickers or Berkovich)

3. Deformation mechanism changes with a shape of indenter.

Shear flow (Sharp indenter) Densification (Blunt indenter)

4. Energy-based inelastic hardness varies with contribution of densification beneath an indenter.

energy-based inelastic hardness of soda-lime silicate glassintrinsic strength of soda-lime glass: ~...

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