Issue 3

M. Zakeri et

al., Frattura

trutturale, 3

(2008) 2 - 10

ed Integrità S

Figure

4. Applied th

ermal cycle t

o remove resi

dual stresses f

rom test spec

imens.

3 E

XPERIME

NTAL PRO

CEDURE

form ess. sam spe test Tes unlo was isoc the cen

ed to deter For this pu e material w cimens. This under diago t was condu ading, and obtained as hromatic fri two fringes tre of disk.

mine the fri rpose, a disk as put in th disk was th nal compre cted in two considering f =6.9 [N/(m nge patterns of order N=

nge value af of diamete e furnace alo en employed ssive load a steps inclu both cases, m·fringe)] in the calib 8 are joinin

ter thermal r 50mm from ng with the for a calibr ccording to ding loading the fringe . Fig. 5 show ration disk g together i

proc- the main ation [16]. and value s the when n the

3.1 For e elasti utiliz of th first jet te gen o come by ap crack with tal cr the s R=66 2), re in th ness, speci Since all re ting p accor heati 145° ture in th check the d 3.2 As a fring [N/(m to he

Specimen Pr xperimental c stress fie ed. The disk ickness t =1 an initial sm chnology. T f -196°C tem completely plying a me obtained in sharp tips (F ack lengths heet was cu .5mm (spec spectively. I is way are n and there is ally in the ca the specim sidual stress rocess were ding to Fig ng rate is C, which is for polycarb e furnace ed in the po isks are almo Determinati n optical p e value for m·fringe)] at treatmen

eparation investigatio ld, two Bra s were made 0mm. For cr all notch w he notched s perature fo brittle, and chanical sho this way is ig. 3-a). For were 2a=58 t in the fo imen N-1) t is notable ot perfectly a curvature se of thick s ens should b es induced d removed b . 4. It is se decreased in the minimu onate [15]. for 59 hour lariscope m st stress-fre on of Materi roperty of an intact p [11]. Since t t, a materia

n of T-stres zilian disk from a poly eation of th as made by heet was pu r 15 minute then the cr ck on the no very close to the perform .8mm and 2 rm of two and R=60mm that the crac straight thr which may heets (Fig. 3 e stress-free uring the cr y using a th en from the temperatu m glass tran The specim s and then achine. It w e. al Fringe Va photoelastic olycarbonate he specimen l calibratio

s effects on specimens w carbonate s e central cra using the w t in liquid n s in order to ack was cre tched zone. a natural c ed tests, the a=60mm. T disks of ra (specimen k tips gener ough the th affect the res .b). before load acking and ermal treatm figure that res higher sition temp ens were pla , stresses w as observed lue materials, is about f s were expo n test was

the ere

heet cks, ater itro- be ated The rack to hen dius N ated ick ults ing, cut ent the than era ced ere that

Figure 5. I

sochromatic f

ringes in cali

bration disk.

3.3 The fram plie forc P=3 sho [4], tion pos for

Photoelast cracked B e as shown d by using t e amount. T 67.5N for s uld be ment the angle α (see Fig. 6) ed to mode N-1 (a/R=0.

ic Tests razilian disk in Fig. 6. he loading s he loads w pecimens N ioned that u between the was such s II condition 44), and α=2

s were site Compressiv crew and th ere selected -1 and N-2 sing the ea crack line a elected that . These ang 3.2° for N-2

d in the lo e loads wer e gage show as P=525N , respective rlier FEM r nd loading d the crack wa les were α= (a/R=0.5). F

ading e ap s the and ly. It esults irec s ex 24.5° ig. 7

the =7 sed

per

5