Determination of Fracture Toughness of small ceramic discs and plate using the ball on three balls test.

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lrcal Organising Committee

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Intemational Advisory Board
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Deternination of fracture totrghngs ofsmall cenmic discs aDd platB Dsitrg
the ball-on-tbree-bslls tesa

Tdia Luber. Stefe R4chc1, TjototdacdeTirlaNindhia:, Srefd SFoblr
\n$itut ffir Shkrur lnd FunklionskeEnik. Monbuiversibel
3700 L€6b€n,

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bh, ler.Tunne.Sftn

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Depdnen orVRhdE. tn8leen & I dr)aM I r.teriry.l'nbrm. Ba i. lndone.is
Mr'e'ialsce re' Leoben l-o$lungCmbH, Ro*scebrmle l2,3 00 kokn,Ausma

Ketryods: ball{n-three-bails l€s! Facturc toueiDes, ninjatuied

d@h

ical testirs.

Abstmcl: Fmcnn€ bDghr6s m*wnals on cemic conpo!{ts d mt€rials e
sudly lqfomed on alatively ldge, b&-shap€d specinem (3 r 4 : 45 nm"l), whicb de
ofi€n mEh bissq the conlonents or the eomi ol naterial that is available fron lab scale
prcesing uits, Suitdble sDecinens thu have to be nelfactued spdtely md oflen with
a diff@nt prcc*sing route.Then nicrosb@tft dd theEfoe th€n mechdical b€havior cm
vrry lor tnis reaon. A new nactre ntruelness tesl h pEsenled. w[ich @ be applied to din
di$ or plateihaped sp€cinetr (0.5 m thickrcs). lt is bsd on the ballon-lnree-balls
(B3B) test, which is a bidial srrengd t$l n€ihod Rll-suited fof lhe stength nedwnot
of llin circule discs o! r€cllngdd plates. If the sp€cinec e pepd€d *ith a o@k of well
denned e€onetry, the B3B test @ be used for n&hre tougnness hebu€nenls too. In
dalog/ b tne surfm cmck in flexue (SCF) detho4 atificial semi€lliptical surfrc€ cEks
e inaoduced irlo the enler oflhe discs with a (n@p in.lenter ddre plalicolly dofomed
zone is rnoved by edndine or polishirg. Tnen the sp4ines @ loaded bidiallyin the B3B
t€st jie. The cnck is opeftd in node I duing loading. Ai6 $e tes! the @ck sizes re
n*uEd on the 6etw surfac6. The evalution of stes inlensiry f&tos is basd on finile
elmenl cahdatioN.lir sol$ioG for the Fet@ sEess ed tle seon€tric frclor calcdat€d
fo! pnctic.lly elevel mges of spdmem ed crok dimeNios e provided loeelbo silh
m eftr a&lysis. Tte higt ecmcy of the resdls is d€moNtaied Bine expenmotal dara
sained on vdious tuteials.

M0ilTAl{

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Determination of fracture toughness
of small ceramic discs and plates
using the ball-on-three-balls test
Tanja Lubel, Stefan Raschel, Tjokorda Gde
Stefan Strobll,

llrta Nindhiar,

qnsdtlt for s!!kb)r und Fuktlonslcdmib Mont nunisldt Lebe., Arstda
,DeparFmnt of Medrail€l Engln4dng, udat"M unlwEity, lhb€En, Ball, hdoaia
:t'4at!ials cent€r Lshen FlRhurc GmbH, L6ben, aLskl:
ECERS XN,

2l -

25, June 2015, Toledo

Motivation
stnndard KFspecimen

Material properties depend
on consolidation and
sintering conditions
available material & components

+

WfiNTED

+

test method for fracturc toughness
applicable to small material pieces

++

-

4rsFK

Principle
ball-on-three-balls test
B3B

test

Knoop

zone:
grind

off

support R"

-(t R- \ F
=,Ia,i,,
)e
K,.="","

yl:,i,;,,)ra
/-\

--xtp"F#
Goals

(1) Fit-formulae for geometric function f
easy evaluation of the tests

further calculations possible
(sub-critical crack groMh, btigue, ...)

(2) Error analysis

.
.
.

('

1olo, Poisson's ratio!!!)
errors from B3B test
errors from cmck position

errors from crack shape determination

(3) Experimental validation
-

4ISFK

Parametric FEM simulations
disc & f

full 3D FEM model

support radius

IdE 0.4

AE 0.05
EE 0,1
0.1

tl

Db

0.6

0.5
0.10
0.2
0.2

0.15

aa t

,']=

0.3

200GPa

F

\R'R' ) -T

6, F...

K, along the crack

result of FEl4 simulation

front

cc,

c*
4

t=

non-symmetric
poisition of maximum depends on
crack shape
Poisson's ratio

-

0.4

8mm

R \

"....Gi

a

0.8

D= 2R

f-(r
l
-.--e .v

K\

0.7
0.2

0,3

13.8s6mm 20mm

,,(

&

c

0.15 and 4R.= 0.2

-

Ya= Y(a=0o)

rc=maxr(85"