} NTERNATI ONAL STAN DARD I SO 7539- 6 Second edi t i on 2003- 02-15 Cor r osi on of met al s and al l oys一 St r ess c or r osi on t es t i ng一 Par t 6: Pr epar a t i on and us e of pr e- cr ack ed speci mens f or t est s under const ant l oad or const ant di spl acement Cor r osi on des met aux et al l i ages一 Essai s de cor r osi on sous cont r ai nt e一 Par t i e 6: Pr epar at i on et ut i l i sat i on des印r ou v et t es pr ef i s s u r ee s po ur d印l acement const ant e s s a i s s o u s c h a r g e c o n s _ t a _ } n t - e o ' } u , } Y s o u s Ref er ence number 奎 近幸 _ 奎 I SO 7539- 6: 2003( E) = ISO- 回I SO 2003 I SO 7539- 6: 2003( E) PDF di scl ai mer cor dance wi t h Adobe' s l i censi ng pol i c y, t hi s f i l e may be pr i nt ed or vi ewed but ypef aces. I nac Thi s PDF f i l e may cont ai n embeddedt ch ar e embedded ar e P i censed t o and i nst al l ed on t hec o mpu t er p er f om} i n g t h e e d i t i ng . ! n shal l not be edi t ed unl ess t he ypef t aces wh' i ol i c y . The I SO Cen t r al Se c r e t ar i a t h e r es p on s i b i l i t y o f n o t i n f r i n g i n g Ad ob e' s l i c en s i n gp downl oadi ng t hi s f i l e, par t i es accept t her ei nt accept s no l i abi l i y t i n t hi s ar ea. Adobe i s a t r ademar k of Adobe Syst ems I ncor por at ed. Det ai l s of t he sof t war e pr oduct s used t o cr eat e t hi s PDF f i l e can be f ound i n t he Gener al I nf o r el at i ve t o t he f i l e; t he PDF- cr eat i on pa r a me t e r s we r e op t i mi z ed f o r p r i nt i n g. Ev e y r c ar e ha s b ee n t ak e n t o e ns u r e t h a t t he f i l e i s s u i t ab l e f o r us e b y I SO me mb e r b o di e s. I n t h e u nl i k el y e ve n t t h at a pr ob l e m r e l a t i n g t o i t i s f ou n d, pl e a se i n f o rm t h e Cen t r al Se c r e t a r i at at t h e a d dr es s gi v en be l o w. 自 I SO 2003 Al l r i gh t s r e s er ved. Un l e s s ot he r wi s e s pe c i f i e d, no pa to r f t hi s pu bl i c a t i on ma y be r e pr o duc e d or u t i l i ze d i n a n y f o r m or by any means, e l e c t r o ni c o r mec h an i c a l , i n c l u di n g p h o t o co p y mg ' an d mi c r o f i l m, wi t ho u t pe r mi s s i on i n wr i t i ng f r o m e i t he r I SO a t t headdress bel ow or I SO' s member body i n t he count y r of t he r equest er I SO copyr i ght of f i ce Case post al e 56.CH- 1211 Geneva 20 T el .+41 22 749 01 11 Fax +41 22 749 09 47 E- ma i l c op yr i g ht @i s o. or g Web www. i so. or g Publ i shed i n Swi t zer l and 刀 t Q I SO 2003一 Al l r i ght s r eser ved I SO 7539- 6: 2003( E) Cont ent s Page For ew or d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v r 1 Scope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 2 Nor ma t i ve r e f er e nc e s. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ……。 . . . . . . . . . . ・ . . . . . . . . . ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ……1 3 Te r ms and d ef i ni t i ons二, . . …, . ‘ . , . …, . , 二, , . , 二 。 . . …, …, . …。 , . , . . . . . . . ……。 . . . . . . ……, . . . . . . . ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ……2 4 Pr i nci pl e. . …。 . . . . . . . . . . . . . . . . . . . ……。 . . . . . . . . . . . ・ ……。 . ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ , ・ ・ ・ ・ . . . ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ . ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ……4 5 Sp eci men s. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ , ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ……5 6 I ni t i at i on and pr opa ga t i on of f at i gue cr a ck s……, . . . . . . . ・ ……。 . . . . . . . . . . . . ・ . . . . ……, ・ . . ・ . . . . . . ・ . ……, . . . . . ・ ・ ・ . ・ ・ ・ . ……2 3 7 Pr ocedur e. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 8 Tes t r epor t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Ann ex A ( n or mat i ve) Us e of not che d spec i mens f or s t r e ss cor r os i on t e s t s. . . : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Annex B ( nor mat i ve) Det er mi nat i on of cr ack gr owt h vel oci t y. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - . . . - - - - . . - - - - - - - - . - - - - - - - - - -38 ) I SO 2003一 Al l r i ght s r eser ved 1 1 1 I SO 7539- 6: 2003( E) For ewor d I SO ( t he I nt er nat i onal Or gani zat i on f or St andar di zat i on) i s a wor l dwi de f eder at i on of nat i onal s t andar ds bodi es ( I SO memb er b odi e s ) . The wor k o f pr e par i n g I n t e r na t i ona l St an da r d s i s n or ma l l y c ar r i ed o u t t h r ou gh I SO t echni cal commi tees. Each member body i nt er est ed i n a subj ect f or whi ch a t echni cal commi tee has been e s t ab l i sh ed h as t h e r i g h t t o be r e pr es e n t e d on t ha t c ommi tee. l n t er na t s ' ona l or gan i z a t i o ns , go v er n me n t a l an d non- gover nment al , i n l i ai son wi t h I SO, al so t ake par t i n t he wor k. I SO col l abor at es cl osel y wi t h t he I nt er nat i onal El ect r ot echni cal Commi ssi on ( I EC) on al l mat t er s of el ect r ot echni cal st andar di zat i on. I nt er nat i onal St andar ds ar e dr af ted i n accor dance wi t h t he r ul es gi ven i n t he I SO/ I EC Di r ec t i ves, Par t2 . The mai n t ask of t echni cal commi tees i s t o pr epar e I nt er nat i onal St andar ds. Dr af t I nt er nat i onal St andar ds a do pt e d by t h e t e ch ni c al c ommi tee s a r e c i r c u l a t e d t o t he me mb er b o di es f o r v o t i n g. Pu bl i c a t i o n as a n I n t e r n at i o nal St an da r d r equ i r e s ap pr ov a l by a t l e as t 75%of t he me mber b odi e s c a s t i n g a v o t e. Aten t i on i s dr a wn t o t h e po s si b i l i t y t ha t s ome o f t he e l emen t s of t h i s d oc umen t ma y b e t h e s u b j e c t o f p a t en t r i gh t s. I SO s h al l n o t be he l d r es p on s i b l e f o r i de nt i f y i n g an y or a l l su c h p a t en t r i g ht s. I SO 75 39 - 6 wa s p r e pa r ed b y Te ch ni c a l Commi te e I SO/ TC 1 56, Co r r os i o n of met al s a nd a l l o y s, i n c ol l ab or a t i o n wi t h t he Nat i o na l Phy si c a l L ab or a t or y ( Uni t e d Ki ng do m) Thi s second edi t i on cancel s and r epl aces t he f i r s t edi t i on ( I SO 7539- 6: 1989) , Cl auses 1,2, 3, 4 and 7; subcl ause 5. 2. 5 d) ; Fi gur es 1,2 d) , 5 b) , 8, 9, and 10; Annexs A and B of whi ch have been t echni cal l y r evi sed. I SO 7539 consi st s of t he f ol l owi ng par ts, under t he gener al t i t l e Cor r osi on of met al s and cor r osi on t est i ng: 一 Par t 1 : Gener al gui dance on t est i ng pr ocedur es 一 尸ar t 2: Pr epar at i on and use of bent - beam s peci mens 一 Par t 3:尸r epar at i on and use of U- bend s peci mens 一 Par t 4: Pr epar at i on and use of uni axi al l y l oaded t ensi on speci mens 尸ar t5 :尸r epar at i on and use of C- r i ng speci mens 一 Par t 6: Pr e par at i on and use of pr e- cr acked s peci mens f or t est s under const ant l oad or const ant di spl ac ement 一 Par t 7: Sl ow st r ai n r at e t est i ng 一 Par t 8:尸r epar at i on and use of speci mens t o eval uat e wel dment s 一 Par t 9: Pr epar at i on and use of pr e- cr acked s pec i mens f or t est s under r i si ng l oad or r i si ng di spl ac ement I V ) I SO 2003一 Al l r i ght s r eser ved I NTERNATI ONAL STANDARD I SO 7539- 6: 2003( E) Cor r osi on of me t al s and al l oys一 St r ess c or r osi on t es t i ng一 Par t 6: Pr epar at i on and use of pr e- cr acked speci mens f or t est s under const ant l oad or const ant di spl acement 1 Scope 1. 1 Th i s pa r t o f I SO 75 39 c o ve r s p r oc e du r es f o r de s i g ni n g, p r e pa r i n g an d u s i n g pr e - c r a ck e d s p ec i me ns f o r i nvest i gat i ng suscept i bi l i t y t o st r ess cor r osi on. I t gi ves r ecommendat i ons f or t he desi gn, pr epar at i on and use o f p r e - c r a c k e d s p ec i men s f or i n v es t i ga t i n g s us c ep t i b i l i t y t o s t r es s c or r os i on. Re c ommen da t i ons c on c er ni n g n ot c h e d s p e c i men s a r e gi v e n i n An ne x A. The t er m " met al " as used i n t hi s par t of I SO 7539 i ncl udes al l oys. 1. 2 Because of t he need t o conf i ne pl ast i ci t y at t he cr ack t i p, pr e- cr acked speci mens ar e not sui t abl e f or t he eval uat i on of t hi n pr oduct s such as sheet or wi r e and ar e gener al l y used f or t hi cker pr oduct s i ncl udi ng pl at e bar and f or gi ngs. They can al so be used f or par t s j oi ned by wel di ng. 1. 3 Pr e- c r ac k e d s p ec i men s ma y b e l o a de d wi t h equ i pmen t f or app l i c at i o n o f a c o ns t a nt l o ad or c an i nc or po r a t e a d ev i c e t o p r od uc e a c o ns t an t di s pl ac eme n t a t t he l oa di n g p oi n t s. Te s t s c on duc t e d un de r i nc r e as i n g di s pl a c emen t or i n c r e as i n g l o ad ar e d eal tw i t h i n I SO 7 539 - 9 1. 4 A p a ti r c u l ar a dv an t a ge of p r e- c r ac k e d s p ec i men s i s t h at t he y a l l o w d a t a t o b e ac qu i r ed f r om wh i c h cr i t i cal def ect si zes, above whi ch s t r ess cor r osi on cr acki ng may occur , can be est i mat ed f or component s of known geomet y r subj ect ed t o known st r esses. They al so enabl e r at es of st r es s cor r osi on cr ack pr opagat i on t o b e d e t e r mi n e d. Th e l a te r da t a ma y be t ak e n i n t o ac c o un t whe n mon i t or i ng pa ts r c on t a i ni ng de f ec t s d ur i ng ser vi ce. 2 Normati ve r ef er ences I SO 7 53 9 - 1, Co r r o s i o n of me t a l s a nd a l l o ys一 St r e s s c or r os i o n t e s t i ng一 Pa r t 1 : Ge ne r al gu i d a nc e o n t e s t i n g pr ocedur es I SO 11 7 8 2- 2, Co r r o s i on of me t al s an d a l l o y s一 Co r r os i o n f a t i gu e t e s t i ng一 Par t2 : Cr ac k pr o pag at i o n t e st i n g us i ng pr ecr acked spec i mens ) I SO 2003一 Al l r i ght s r eser ved 1 I SO 7539- 6: 2003( E) 3 Terms and defi ni ti ons For t he pur poses of t hi s par to f I SO 7539, t he def i ni t i ons gi ven i n I SO 7539-1 and t he f ol l owi ng appl y. 3. 1 cr ack l engt h 口 efec t i ve cr ack l engt h measur ed f r om t he cr ack t i p t o ei t her t he mout h of t he not ch or t he l oadi ng poi nt axi s dependi ng on t he speci men geomet y r 3. 2 speci men wi dt h W efect i ve wi dt h of t he speci men measur ed f r om t he back f ace t o ei t her t he f ace cont ai ni ng t he not ch or t he l oadi ng pl ane dependi ng on t he speci men geomet y r 3. 3 speci men t hi ckness B si de- t o- si de di mensi on of t he speci men bei ng t est ed 3. 4 r educed t hi ckness at si de gr ooves B} mi ni mum si de- t o- si de di mensi on bet ween t he not ches i n si de- gr ooved speci mens 3. 5 speci men hal f - hei ght H 50%o f t h e s p ec i men h e i gh t me as u r e d p a r a l l e l t o t h e d i r e c t i on o f l oad ap pl i c a t i on f or c ompa c t t en s i on , do ub l e c an t i l ev er b ea m an d mod i f i ed wed ge op en i n g l oa de d t es t p i ec e s 3. 6 l oad 尸 t hat l oad whi ch, when appl i edt o t he speci men, i s consi der ed posi t i ve i f i t s di r ec t i on i s such as t o c ause t he cr ack f aces t o move apar t 3. 7 def l ect i on at l oadi ng poi nt axi s YL L cr ack openi ng di spl acement pr oduced at t he l oadi ng l i ne dur i ng t he appl i cat i on of l oad t o a const ant di spl acement speci men 3. 8 def l ect i on away f r om t he l oadi ng l i ne Yp cr a ck o pe ni n g d i s p l ac eme n t p r odu c e d a t a l o c a t i o n r emo t e f r om t h e l o a di ng pl an e, e. g. a t k n i f e e d ge s l o c a t e d at t he no t c h mo ut h , d ur i n g t h e a pp l i c a t i on o f l o ad t o a c on s t an t d i s pl ac e me n t s p ec i me n 3. 9 modul us of el ast i ci t y E el as t i c modul us ( i . e. st r ess / st r ai n) i n t ensi on 2 @I SO 2003一 闪恤r i ght s r eser ved I SO 7539- 6: 2003( E) 3. 10 st r ess i nt ensi t y怕ct or KI ch f unct i on of appl i ed l oad, cr ack l engt h and speci men geomet y r havi ng di mensi ons of s t r ess x l eng t hwhi u n i q u el y d e in f e t he e l a s t i c s t r es s f i el d i n t en si f i c a t i on a t t h e t i p o f acr ack subj ect ed t o openi ng mode di s pl a c eme nt s ( mo de I ) NOTE I th as b een f ound t hat s t r e ss i nt en si yf t ac t or s, cal c ul at ed as sumi ng t h at s peci mens r es pond pur el y el ast i cal l y, cor r el at e t he b eha vi our of r eal cr ac ke d b odi es pr ovi ded t ha t t h e si zeo f t he z one of p l as t i ci t y at t he c r ack t i p i s smal l compar ed t o tl n g t h and t he l en gt h of t he un cr ac k ed l i gament .I n t hi s p ar t of I SO 7539, mode Ii s assumed and e cr ackl en g t he sub sc r i pt Ii s i mpl i ed ev er y wher e 3. 11 i ni t i al st r ess i nt ensi t y怕ct or Kl i s t r ess i nt ensi t y appl i ed at t he commencement of t he st r ess cor r osi on t est 3. 12 pl ane st r ai n f r act ur e t oughness K 己‘! c cr i t i cal val ue of K at whi ch t he f i r st si c T ni t l cant envi r onment al l y i ndependent ext ensi on or t he cr ack occur s u nd er t h e i n lu f en c e o f r i s i n g s t r e s s i n t en s i t y un d er c o nd i t i on s o f hi gh r es i s t a nc e t o p l a s t i c oe t or ma t l o n 3. 13 ar ovi si onal val ue of凡。. Kn … 巴 兮 坪. . , . 。 . . 。 二 , K。 二K . , , when t he vaudi t y cnt ena f or pl ane str a旧 pr eaom m ance ar e sansnea 毛 d I 七 ‘ 3. 14 thr eshol ds t r ess i nt ensi t y f act or f or suscept i bi l i t y t o st r ess cor r osi on cr acki ng 与scc gr ow f or t he speci f i ed t est t hat st r essi nt ensi t y f ac t or above whi ch st r ess cor r osi on cr acki ng wi l l i ni t i at eand r ai n pr edomi nant condi t i ons un der condi t i ons of hi gh r esi st ance t o pl ast i c def or mat i on, i . e. under pl anest condi t i ons 3. 15 pr o vi s i onal v al u e o f Kl sc c} 今s c c t r ai n pr edomi nance ar e sat i sf i ed ar t y cr l t er l a f or pl anes KQ S C C二Kl s c c wh e n t h e v a l i 3. 16 m axi m um st ressi nt ensi t y怕ct or Kma x i n f at i gue a l u e o f t he s t r e s s i n t en s i t y f a c t or i n a c y c l e, c or r es p ond i ng t o t h e ma x i mu m l oa d hi ghest al gebr ai cv 3. 17 0, 2% pr oof st r ess 0. 2 ress whi ch must be appl i ed t o pr oduc e a pl ast i c s t r ai n of 0, 2%dur i ng a t ensi l e t est 3. 18 appl i ed st r ess ’ O i cat i on of l oad t o t he speci men st r ess r esul t i ng f r om t heappl 3. 19 st r ess i nt ensi t y怕ct or coe伟ci ent Y f ac t or d er i v ed f r om t he s t r e s s an al y s i s f o r a p a r t i c u l ar s p ec i men ge ome t y r whi c h r el a t es t he s t r e ss i n t e ns i t y f ac t or f or a gi ven cr ack l engt h t o t he l oad and speci men di mensi ons ) I SO 2003一 Al l r i ght s r eser ved 3 I SO 7539- 6: 2003( E) 3. 20 l oad r ati o R i n怕t i gue l oadi ng al gebr ai c r at i o of mi ni mum t o maxi mum l oad i n a cycl e: R 二 pmi n Kmi n Ama x Kmax 3. 21 cr ack vel oci t y i nst ant aneous r at e of st r ess cor r osi on cr ack pr opagat i on measur ed by a cont i nuous cr ack moni t or i ng t echni que 3. 22 aver age cr ack vel oci t y aver age r at e of cr ack pr opagat i on cal cul at ed by di vi di ng t he change i n cr ack l engt h due t o st r es s cor r osi on by t he t est dur at i on 3. 23 speci men or i ent at i on f r a c t ur e p l an e o f t he s pe c i men i de n t i f i e d i n t e r ms o f f i r s t l y t h e d i r e c t i on o f s t r es s i n g an d s e c on dl y t he di r e c t i on of cr ack gr owt h expr essed wi t h r espect t o t hr ee r ef er ence axes i dent i f i ed by t he l eter s X, Y and Z w her e Z i s coi nci dent wi t h t he mai n wor ki ng f or ce used dur i ng manuf act ur e of t he mat er i al ( shor t - t r ans ver se axi s) ; X i s coi nci dent wi t h t he di r ect i on of gr ai n low f ( l ongi t udi nal axi s) ; 丫 i s nor mal t o t he X and Z axes 4 Pr i nci pl e 4. 1 The u s e o f pr e - cr a c k ed s pe c i me ns ac k n o wl e dg es t he di f f i c ul t y o f en s ur i n g t ha t c r a c k - l i k e de f e c t s i nt r oduced dur i ng ei t her manuf ac t ur e or subsequent ser vi ce ar e t ot al l y absent rom f st r uct ur es. Fur ther mor e, t he pr e s enc e of s uc h de f e c t s c an c a us e a s u s c ep t i bi l i t y t o s t r e s s c or r o s i on c r ac k i n g whi c h i n s o me ma t er i al s ( e. g. t i t an i um) may n o t b e e vi d en t f r o m t es t s un d er c on s t a n t l o ad on s moo t h s pe c i men s. Th e p r i nc i p l es o f l i near el ast i c f r act ur e mechani cs can be used t o quant i f y t he st r ess si t uat i on exi st i ng at t he cr ack t i p i n a pr e- cr acked speci men or s t r uct ur e i n t er ms of t he pl ane st r ai n- st r ess i nt ensi t y. 4. 2 The t es t i nvol ves sub j ect i ng a speci men i n whi ch a cr ack has been devel oped by f at i gue, f r om a machi ned not ch, t o ei t her a const ant l oad or di spl acement at t he l oadi ng poi nt s dur i ng exposur e t o a c h emi c al l y a gg r e s s i v e en v i r o nmen t . Th e ob j e c t i v e i s t o qu an t i f y t h e c on di t i on s un de r whi c h e nv i r o nme n t al l y - assi st ed cr ack ext ensi on can oc cur i n t er ms of t he t hr eshol d s t r ess i nt ensi t y f or st r ess cor r osi on cr acki ng, Ki sca an d t h e k i n e t i c s o f c r ac k p r o pa g at i on. 4. 3 The emp i r i c a l d a t a c an b e us e d f o r d es i gn o r l i f e p r edi c t i o n p ur po s es i n or der t o e ns u r e ei t he r t ha t t h e s t r e s s es wi t hi n l a r ge s t r uc t u r es ar e i n su f f i c i en t t o p r omot e t h e i n i t i at i on o f en v i r on men t a l l y - a ss i s t e d c r a c k i ng a t wh at e v er pr e - e xi s t i n g de f ec t s ma y be pr e s en t or t h a t t h e a mou nt o f c r ac k gr owt h wh i c h wo ul d o c c ur wi t h i n t he desi gn l i f e or i nspect i on per i ods can be t ol er at ed wi t hout t he r i sk of unst abl e f ai l ur e. 4. 4 St r ess cor r osi on cr acki ng i s i nf luenced by bot h mechani cal and el ect r ochemi cal dr i vi ng f or ces. The l at er c an va y r wi t h c r ac k d ep t h, o pe ni ng o r s h ap e be c au s e o f v ar i at i on s i n c r ac k - t i p c h emi s t y r a nd e l e c t r od e pot ent i al and may not be uni quel y descr i bed by t he f r act ur e mechani cs st r ess i nt ensi t y f act or . 4. 5 The mec h ani ca l dr i v i n g f or c e i nc l u de s bo t h a pp l i e d a nd r e s i du al s t r es s e s. Th e p os si b l e i n l f ue n ce o f t h e l a te r s ha l l b e c o ns i d er e d i n b o t h l a b or at o y r t es t i n g a n d t h e a pp l i c a t i on t o mor e c ompl e x g eo me t r i e s . Gr adi ent s i n r esi dual st r ess i n a speci men may r esul t i n non- uni f or m cr ac k gr owt h al ong t he cr ack f r ont . 4 ) I SO 2003一 Al l r i ght s r eser ved I SO 7539- 6: 2003( E) 5 Speci mens 5. 1 Gener al 5. 1. 1 A wi de r an ge o f s t an da r d s p ec i men g eo me t r i es o f t h e t y pe u s ed i n f r a c t ur et oughness t est s may be a pp l i ed . Th e pa ti r c ul ar t yp e o f s p e ci men u s ed wi l l be d ep en de n t up on t hef or m, t he st r engt h and t he suscept i bi l i t y t o st r ess cor r osi on cr acki ng of t he mat er i al t o be t est ed and al so ont he ob j ect i ve of t he t es t . 5 . 1 . 2 A b as i c r equ i r emen t i s t h a t t h e d i me ns i o ns b e s u f f i c i e n t t o mai n t ai n p r ed omi na n t l y t r i a xi al ( pl an e s t r ai n ) c on di t i on s i n wh i c h p l a s t i c d e f o r ma t i on i s l i mi t e d i n t h e v i c i ni t y o f t h e c r a c k t i p. Ex pe r i e nc e wi t h f r a c t ur e t ou gh n es s t es t i n g h as s h own t h a t f or a va l i dK I D mea s ur eme nt , b o t h t h e c r ac k l en gt h , a, an d t h e t h i ck n es s , B, shal l not be l ess t han 2, 5 and t hat possi bl e, l ar ger speci mens wher e bot h a and B ar e at l east 2 、、 lesesesJ了 2 - C - 、八 n 卜 - 0 2、 - P 4 矛 2 lessell、 shal l be used t o ensur e adequat e const r ai nt . F r om t h e vi e w o f f r a c t u r e me c h an i c s, a mi ni mum t h i c k ne s s f r o m wh i ch an i n v ar i an t v al u e o f Kl sc c i s ob t ai ne d c an n o t b e s p ec i f i ed at t h i s t i me. Th e p r e s en c e o f a n a g gr es s i v e en v i r o nmen t dur i n g s t r es s c or r os i on may r ed uc e t h e ex t e n t o f pl a s t i c i t y a s s oc i a t ed wi t h f r a c t ur e an d hen c e t he s pe ci men di men s i on s ne ede d t o l i mi t pl a s t i c de f or mat i o n. Ho we v er , i n o r d er t o mi ni mi z e t he r i s k o f i na de qu at e c on s t r ai n t , i t i s r e c omme nd ed t ha t s i mi l a r c r i t e r i a t o t h os e us e d d ur i n g f r ac t u r e t o ug hn es s t es t i n g s h ou l d al s o b e u s ed r e ga r d i n g s pe c i men di mensi ons, i . e. bot h a and B shal l be not l ess t han 2 十 、 2 2 - I L  ̄ n〕 圣n - P 5 厂 .lesl ,1.、、 2 and pr ef er abl y shoul d be not l ess t han 4 wher e st r es s i nt ensi t y t o be appl i ed dur i ng t est i ng. The t h r es h ol d s t r es s i n t en s i t y v al u e e v en t ual l y d et e r mi n ed sh ou l d b e s ub s t i t u t ed f or KI i n t h e f i r s t o f t he s e e x pr e s s i on s a s a t es t f o r i t s v a l i d i t y . 5 . 1. 3 I f t he s p ec i men s ar e t o b e us e d f o r t he de t e r mi n at i on o f Kl s cc} t h e i n i t i al s p ec i me n s i z e s h oul d be b a s e d on a n e s t i ma t e o f t he Kl s cc o f t he ma t er i al ( i n t he f i r s t i ns t an ce , i t b ei ng b ete r t o o ve r - e s t i ma t e t h e 价sc c v al u e an d t h er e f or e u s e a l ar g er sp e ci men t h an ma y e ve n t ua l l y b e f oun d n e c es s a y) r . Whe r e t h e s e vi r c e a pp l i c a t i on i n v ol v e s t h e u s e of ma t e r i a l o f i ns u f f i c i en t t h i c k ne s s t o s a t i s f y t he c on di t i o ns f o r v a l i di t y, i t i s per mi ssi bl e t o t est speci mens of si mi l ar t hi ckness, pr ovi ded t hat i t i s cl ear l y st at ed t hat t he t hr eshol d i nt ensi t y v a l u e o bt ai ne d, KQS CC} i s o f r e l e va n c e o nl y t o t h at sp e ci f i c ap pl i c a t i o n. Whe r e d et er mi n i n g s t r e s s c or r o s i on cr ack gr owt h behavi our as a f unct i on of st r ess i nt ensi t y i s r equi r ed, t he speci men si ze shal l be based on an est i mat e of t he hi ghest st r ess i nt ensi t y at whi ch cr ack gr owt h r at es ar e t o be measur ed. 。I SO 2003一 Al l r i ght s r eser ved 4 } I SO 7539- 6: 2003( E) 5. 1 . 4 Two ba s i c t y p es o f s pe c i me n c an be u s ed a) t h os e i n t en de d f or t e s t i n g un de r c on s t a n t d i s p l ac e me n t , whi c h a r e i n v ar i ab l y s e l f - l o ad ed b y mea ns o f bui l t - i n l oadi ng bol t s; b) t h os e i n t e nd ed f o r t es t i n g u nd er c on s t a nt l oa d, f or whi c h an ex t er nal me ans o f l oa d a pp l i c a t i on i s r eq ui r e d. 5. 1 . 5 Con s t a nt di s pl a c emen t s p ec i me ns , be i n g s e l f - l oad ed, ha v e t he ad v an t ag e o f e c on o my i n u s e s i n c e n o ex t er n a l s t r e s s i n g equ i pmen t i s r e qu i r e d. Th ei r c omp ac t d i men s i on s a l s o f a c i l i t at e ex p os u r e t o op er a t i n g s er vi c e en v i r onmen t s . Th e y c an b e u s ed f or t h e de t er mi n a t i on o f Kl S CC b y t he i ni t i a t i on of s t r e s s c or r os i on cr a c k s f r om t h e f at i g ue p r e - c r ac k , i n whi c h c as e a s er i e s of s p ec i men s mu s t b e u s e d t o p i n - po i n t t he t h r e s ho l d val ue, or by t he ar r est of a pr opagat i ng cr ack si nce under cons t ant di spl acement t es t i ng condi t i ons t he st r ess i nt ensi t y decr eases pr ogr essi vel y as cr ack pr opagat i on occur s. I n t hi s case a si ngl e speci men wi l l suf f i ce i n pr i nci pl e, but i n pr act i ce t he use of sever al speci mens ( not l ess t han 3) i s of ten r ecommended, t aki ng i nt o account t he di sadvant ages descr i bed i n 5. 1. 6. 5. 1. 6 The di sadvant ages of const ant di spl acement speci mens ar e 、、 a 尹 appl i ed l oads can onl y be measur ed i ndi r ec t l y by di spl acement changes; ‘飞.J JLJ oxi de f or mat i on or cor r osi on pr oduct s can ei t her wedge open t he cr ack sur faces, t hus changi ng t he appl i ed di spl acement and l oad, or can bl ock t he cr ack mout h, t hus pr event i ng t he i ngr ess of cor r odent and i mpai r i ng t he accur ac y of cr ack l engt h measur ement s by el ect r i cal r esi st ance met hods; c) cr ack br anchi ng, bl unt i ng or gr owt h out of pl ane can i nval i dat e cr ack ar r est dat a; d) cr ack ar r est mus t be def i ned by cr ack gr owt h bel ow some ar bi t r ar y r at e whi ch can be di f f i cul t t o measur e accur at el y; e) el as t i c r el axat i on of t he l oadi ng syst em dur i ng cr ack gr owt h can cause i ncr eased di spl acement and hi gher l oads t han expect ed; f) pl as t i c r el axat i on due t o t i me- dependent pr ocesses wi t hi n t he speci men can cause l ower l oads t han expect ed; g) i t i s somet i mes i mpossi bl e t o i nt r oduce t he t est envi r onment pr i or t o appl i cat i on of t he l oad, whi ch can r et ar d cr ack i ni t i at i on dur i ng subsequent t est i ng. 5. 7了 const ant l oad speci mens have t he advant age t hat st r ess par amet er s can be quant i f i ed wi t h conf i dence. Si nce cr ack gr owt h r esul t s i n i ncr easi ng cr ack openi ng, t her e i s l ess l i kel i hood t hat oxi de f i l ms wi l l ei t her bl ock t he cr ack or wedge i t open. Cr ack l engt h measur ement s can be r eadi l y made vi a an umber of cont i nuous moni t or i ng met hods. A wi de choi ce of const ant l oad speci men geomet r i es i s avai l abl e t o sui t t he f or m of t he t es t mat er i al , t he exper i ment al f aci l i t i es avai l abl e and t he obj ect i ves of t he t est . Thi s means t hat cr ack gr owt h can be st udi ed under ei t her bend or t ensi on l oadi ng condi t i ons. The speci mens can be used f or ei t he r t he d et e r mi n at i on o f Ki sC C b y t h e i n i t i a t i on o f a s t r e ss c or r os i on c r a c k f r om ap r e - ex i s t i n g f a t i gu e c r ac k us i n g as er i e s o f s p e ci men s , or f or mea s ur e me n t s o f cr a ck gr o wt h r a t es . Con s t a nt l o ad s pe c i me ns c a n b e l oaded dur i ng exposur e t o t he t es t envi r onment i n or der t o avoi d t he r i sk of unneces sar y i ncubat i on per i ods. 5. 1. 8 The pr i nci pal di sadvant age of cons t ant l oad speci mens i s t he expense and bul k associ at ed wi t h t he ne ed f or a n ex t er n al l oa di ng s y s t em. Be nd s p ec i men s c an be t e s t e d i n r el a t i v el y si mpl e c a n t i l e v er b ea m equ i pmen t , bu t s pe c i me ns s ub j ec t ed t o t en s i on l oa di n g r equ i r e c o ns t a n t l oa d c r ee p r up t ur e o r s i mi l ar t e s t i n g mac h i n e s. I n t h i s c a s e, t he e xp e ns e c a n b e mi ni mi z ed b y t e s t i ng c h ai ns o f s p ec i men s c on ne c t e d b y l o a di n g l i nk s whi c h a r e de s i gn ed t o pr e v en t un l oa di ng on t h e f ai l u r e of s pe c i men s . Th e s i z e o f t h e s e l oa di n g s y s t e ms means t hat i t i s di f f i cul t t o t est const ant l oad speci mens under oper at i ng condi t i ons, but t hey can be t es t ed i n envi r onment s bl ed off r om oper at i ng syst ems. 5. 2 Speci men de si gn 5. 2. 1 Fi gur e 1 shows some of t he pr e- cr acked speci men geomet r i es whi ch ar e used f or st r es s cor r osi on t est i ng. 6 。I SO 2003一 Al l r i ght s r eser ved I SO 7539- 6: 2003( E) a) Bend t est pi ece b) Ten si l e t e s t pi e ce c) Bend or t ensi l e t est pi ece Edge of t es t pi ec e Loadi ng l i ne of t es t pi ece Fi gur e 16一 Envel ope l i mi t i ng si ze and f or m of not ch and f at i gue cr ack } }: 回I SO 2003一 Ai l r i ght s r eser ved I SO 7539- 6: 2003( E) 7. 3 Envi r onment al chamber 7. 3. 1 The envi r onment al chamber shal l compl et el y encl ose t he t est sec t i on of t he speci men. Wher ever p o s s i b l e , t he g r i p pe d p or ti on s s h al l b e e x c l u d ed f r o m c on t a c t wi t h t he s ol u t i on en v i r o nmen t i n or d er t o p r e v en t g a l v an i c ef f ec t s a n d c r ev i c e c or r os i on . Th es e pr ob l ems c an b e ov er c o me b y t he u s e o f a l oc a l en v i r on men t al c el l o f t h e t y pe s ho wn i n Fi gur e 1 7 i n wh i c h t he en vi r on me n t i s c i r c u l at e d a r ou nd t he v i ci n i t y o f t he no t c h, pr e- c r a c k a n d a n t i c i p a t ed c r ac k gr owt h r eg i on o f t h e s p ec i me n. Cr ev i c e pr ob l ems may a l s o a r i s e wh er e t he s p e c i men e mer ge s f r o m t he t es t c el l a nd t h es e s h af t be a v oi d ed by a pp r op r i a t e de s i gn o f t he c e l l or b y t h e u se o f p r ot e c t i v e c oa t i ng s a t s u c h l o c a t i o n s. I f t ot a l i mmer s i on i n t h e c o r r o de n t i s c o nt e mp l a t e d, t h e l oa di n g po i n t s shal l be pr ot ect ed agai nst cor r osi on. I f t hi s i s not possi bl e, appr opr i at e measur es shal l be t aken t hr ough, e. g. , t he use of si mi l ar met al s, el ect r i cal i nsul at i on or coat i ngs. 7 . 3 . 2 An a de qu a t e v o l ume o f s o l u t i on t o me t a l a r e a r a t i o i s r e qu i r ed ( de p end en t on r e a c t i on r at e s an d e x p o su r e t i me) a nd a ci r c ul a t i on s y s t em i s us u al l y n ec e s s ar y. F or c o ndi t i on s of a pp l i e d po t en t i al or ap pl i e d c u r r en t , a s e p ar a t e c ompa tmen r t f or t he c ou n t er e l ec t r o de may b e n e c es s a r y i n or d er t o l i mi t an y e fec t s c a u s ed b y r e a c t i on pr o du c t s f r o m t hi s el e c t r o de. I t sh ou l d be no t e d t ha t p o t en t i os t a t i c c o n t r o l a t t h e t i p o f a s t r e s s c o r r o s i on c r a c k ma y b e s ub j ec t t o l ar ge va r i a t i on s as t h e c r ac k l en g t h i nc r ea s es , wh i c h mu s t b e t a ke n i nt o account when consi der i ng mechani sms of st r ess c or r osi on cr acki ng. 7. 3. 3 Non- met al l i c mat er i al s ar e r ecommended f or t he envi r onment al chamberan d ci r cul at i on syst em as t i cs ar e not i ner t at wher e t hi s i s pr ac t i cabl e. These mat er i al s shal l be i ner t. Not e t hat gl ass and cer tai npl el evat ed t emper at ur es. Wher e met al l i c chamber s ar e necessar y, t hese shal l be el ect r i cal l y i nsul at ed f r om t he speci men i n or der t o pr event gal vani c i nt er act i on. 4 7 .3. Fo r t e s t s i n a ga s eo us en v i r o nmen t , an al l - me t a l - c h amb er i s p r ef e r r e d. y Ke ,. 2 Di s pl ac emen t t r ans duc er Sol uton out l et 3 Sol ut i on i nl et 自 Load b Sol ut ion low f Fi gur e 1 7一 Pos i t i on of a ypi t ca l en vi r onme nt a l cel l on a f r ac t u r e mecha ni c s s peci men ) I SO 2003一 Al l r i ght s r eser ved 27 I SO 7539- 6: 2003( E) 7. 4 Envi r onment s! cont r ol and moni t or i ng 7. 4. 1 t he pH Th e en vi r on me n t s h al l b e mon i t or ed an d co n t r ol l e d du r i n g t he t es t as r e qui r ed. I n u nbu fe r e d s y s t ems , c a n be ma i n t a i n ed c o ns t a n t us i ng a n au t oma t i c pH c on t r ol s y s t em; o t he r wi s e t h e e fe c t of a n y var i at i ons i n pH on cr ack gr owt h shal l be assessed. 7 . 4. 2 I n s y s t e ms op en t o t he at mos ph er e, a er at i o n c an be ma i n t ai n ed b y bu bb l i n g ai r t hr ou gh t he s ol u t i on. I n c l o s ed s y s t ems , mon i t or i n g i s r equ i r ed. Th e lo f wr a t es us e d i n t e s t i n g s h oul d s i mu l a t e t he r an ge o f c on di t i o ns i n s er vi c e be c au s e lo f w c an a fec t t he el ec t r o de po t en t i al , e. g. by i n lu f en c i ng t h e l f u x o f ox y g en , a nd ma s s t r ans f er be t we en t h e c r ac k e nc l av e and t h e bu l k s o l u t i on. The o r i en t a t i on of f l o w wi t h r e s pe c t t o t h e cr a ck c a n b e i mpo tan r t i n t he l a ter c as e. Se al i ng of t he c r a ck s i de s t o l i mi t ar ti f i c i a曰h r o u gh - t hi c k n es s t r anspor ts houl d be consi der ed but may i nt r oduce l ocal cr evi ce pr obl ems. 7. 4. 3 I t i s s t r on gl y r ec o mmen de d t ha t t he e l ec t r od e p ot en t i al be meas u r e d wi t h a r e f er e nc e el e c t r o de a ppr o pr i at e f o r t h e a p pl i c at i on. Ca r e s ha l l be t ak e n t o l i mi t I R d r op i n t he meas u r eme n t o f p o t en t i a l . Th e t emper at ur e of t he sol ut i on shoul d be cont r ol l ed t o 1 2 0 C. 一 f t  ̄ -.片 . -十下 戈 . - } Z. ` J }t 一 、、 1 少 , 一 尸 -a 产 - 艺‘ 护0 c -打 勺从 J又 一, L 一 - 几 Load Cr ac k t i p Fi gur e 1 8一 Me asur emen t l oc a t i on an d r el at i on bet ween肠an d吮L val ue s 28 回I SO 2003一 Al l r i ght s r eser ved I SO 7539- 6: 2003( E) 7. 5 7. 5. 1 De t er mi nat i on of与scc by cr ack ar r est Const ant di spl acement speci mens can be used f or t he d e t er mi na t i on o f拍s cc b y c r a c k ar r es t . I n p r i n c i p l e, a si n gl e s pe c i men wi l l s u f f i c e f or t hi s pu r p o s e, al t hough i t i s r ecommended t hat addi t i onal speci mens be t est ed t o reduce t he l i kel i hood of an er r oneous r esul t. 7. 5. 2 F or t h e de t e r mi na t i on o f凡s cc b y c r a c k a r r e s t , t h e pr e- c r a c k e d s p ec i men s h al l b e f i x ed i n a ho l d i n g devi ce a n d, i f pr ac t i c al , t he en v i r o nme nt al c o n di t i o ns s ha l l b e ap pl i ed t o t he r egi on of t he n o t c h r o ot 7. 5. 3 Th e a r ms o f t he s p e ci men s h al l t h en b e de l f e c t ed by t ur n i n g a b ol t t o g i v e a p r e - d et e r mi n ed与} v a l u e i n ex c es s o f t he a n t i c i p a t e d Ki sc c v al ue. Ove r - de f l e c t i on s ha l l be a v oi de d. The de l f ec t i o n, V} } , a t t he l o ad i n g l i n e c a n b e r e l at e d t o t h e de l f ec t i on,介,mea s ur e d b y di sp l ac e me n t gau ge at k ni f e e dg e s l o c a t ed a t t h e n ot c h mo u t h, b y mea ns o f t he p r o c e dur e i l l u s t r a t e d i n Fi gur e 1 8. Th e s en s i t i vi t y o f t h e di s p l a c e me n t g au g e s hal l b e not l ess t han 20 mV/ mm i n or der t o mi ni mi ze er r or s due t o over - ampl i f i cat i on of a weak si gnal . The l i near i t y of t he gauge shal l be such t hat t he devi at i on f r om t r ue di spl acement i s not mor e t han 0, 003 mm f or d i s p l a c e men t s o f u p t o 0 , 5 mm a n d n o t mor e t h an 1%o f t h e r e c or de d v al u e f or l ar g er d i s pl a c emen t s. L oa di ng c a n b e ap pl i e d t o t he s p ec i men a te f r c a r yi r n g ou t a l o ad / d i sp l ac eme nt c al i br a t i on c on d uc t ed u p t o a l o adi n g l evel whi ch does not exceed t hat ai med at f or t he st r ess cor r osi on cr acki ng t est . F or t h e ( W- a) i nd i fer e n t DCB sp e c i me n, t he d e l f ec t i o n r eq ui r ed t o gi v e t h e de si r e d s t r es s i n t e ns i t y , K} } , f o r a g i v e n v al ue o f a / H c an be c a l cu l a t ed f r o m t h e r e l at i o ns h i p be t ween K} and V } } gi v en i n F i g ur e 1 0. I n t he case of t he (W- a) domi nat ed modi f i ed WOL speci men, a knowl edge of t he uni que compl i ance c a l i br a t i on i s n ec e s s ar y i n o r d e r t o c a l c ul a t e t h e d e le f c t i o n r e qu i r e d t o pr o du c e a g i v en s t r es s i n t e ns i t y v al ue f o r a p ar ti c u l ar c r ac k l e ng t h r a t i o, a / W, u s i n g t he r el a t i on sh i p gi v en i n Fi gu r e 11 . Ty pi c a l c ompl i an c e ca l i b r at i on c u ve r s f o r t h e s moo t h an d s i de - gr o ov e d mod i f i ed WOL s p ec i mens ar e s h o wn i n Fi gu r e 1 9. Af t er l oa di ng , t he di spl acement gauge shal l be r emoved. 7. 5. 4 Once t he envi r onment al condi t i ons ar e appl i ed t o t he speci men, t he cr ack l engt h i s moni t or ed as a f u n c t i o n of e l ap s ed t i me. Th i s c an be a c hi e v ed by ei t h er di r e c t op t i c al mea s ur eme n t or i nd i r e c t l y by t he u s e of back f ace s t r ai n measur ement s, et c. As cr ack ex t ensi on occur s, t he s t r ess i nt ensi t y f act or decr eases. The s l o p e of t h e r el at i on s hi p be t we en c r a c k l en g t h a n d t i me de f i n es t h e c r ac k g r owt h r a t e, whi c h i s u s ua l l y d e t e r mi n ed by gr ap hi c a l d i fer e n t i a t i o n o f t he c r ac k l e ng t h v e r s u s t i me c ur v e. The c r ac k ma y e ve n t ua l l y a r r e s t , t h u s i n di c a t i ng Ki s ca Gen e r a l l y , h owe v er , t h e c r a c k e x t e nd s at an e xt r eme l y s l ow r a t e a nd Ki s cc i s d e s i gn a t ed a t an ar bi t r a r i l y s e l ec t ed c r ac k gr o wt h r at e. Th e mos t ap pr op r i a t e v al u e o f t h e ar r es t gr o wt h r a t e depends on t he met al / envi r onment sy st em under c onsi der at i on and shal l be agr eed bet ween t he par ti es. For h i gh s t r en gt h al l oy s, v e l oc i t i es o f ab ou t 1 0 - } mm/ s h a ve b ee n s u gg es t e d b u t pr a c t i c al e x p er i en c e ha s i n di c a t ed t h at s t r es s c o r r o s i o n c r a ck s c a n p r opa g at e a t gr o wt h r a t e s d own t o b el o w 1 0 _ 9 mm/ s . Th e t i me f or c r a c k ar r e s t c a n b e d ec r e as e d c o ns i d er a bl y by t h e a pp l i c a t i o n o f K} } l e v el s c l os e t o K} sc c i f a n a p pr ox i mat i on of t hi s i s known. 7 . 5 . 5 Whe n c r a c k a r r es t i s de eme d t o ha v e o c cu r r ed, t h e f i na l l oa d a n d f i n al cr a c k l en g t h s hal l b e d e t er mi ne d, f r om whi ch t h e s t r e s s i n t e ns i t y at cr a c k ar r e s t c an b e c a l cu l a t ed, t o gi v e a pr ov i s i on al v a l u e of Kl sc c } KQS CC) } Th e f i na l l o ad c a n b e de t e r mi n ed b y r e pl a ci n g t h e di s p l ac emen t g au g e an d no t i ng t h e d e l f ec t i on. Th e s p ec i men c an t h en b e u nl o a de d an d s ub s e qu en t l y r e l oa de d i n a t ens i on mac h i ne t o mea s ur e t he c o r r e s pon d i n g l oad. Th e s p e c i men s h a l l t he n b e b r o k e n o pe n an d t he f i n al ma x i mum a nd mi n i mu m l en g t h s o f t h e s t r e s s c o r r o s i on c r a ck mea s ur e d o n t h e f r a c t u r e s u r f ac e t o t h e n ea r e s t 0, 5%W The f i n al l en g t h o f t h e s t r e s s c or r os i on c r ac k s h al l al s o b e mea s ur e d wi t h t he s ame de gr e e o f p r e c i s i on at t h e f o l l o wi n g t h r e e pos i t i ons f r om one edge: 0, 25 B, 0, 50 B and 0, 75 B. The aver age of t hese l ast t hr ee measur ement s shal l be used as t he efect i ve cr ack l engt h i n t he cal cul at i on of与scc} 。I SO 2003一 Al l r i ght s r eser ved 29 I SO 7539- 6: 2003( E) 13 } U 八U J 哎 . 好 d ̄ -J -J Am山 12 八U ” 八 Ijl 10 n甘 9 n甘 5 n. 了 n. 6 n. 5 . U ‘ 八U 3 魔 11. 2 八 U 1 0. 3 0. 35 0. 4 0. 45 0. 5 0. 55 0. 6 0. 65 0了 a/ W Smoo t h, t heor et i cal 5% f ac e, not ch ed, exper i ment al Smoot h, e xper i men t al Fi gur e 1 9一 Compa r i s on of wedge op eni ng l oa ded spe ci men c ompl i ance a t c ent r al l oa dl i ne 30 。I SO 2003一 Al l r i ght s r eser ved I SO 7539- 6: 2003( E) The t est i s i nval i d i f : a) t he di fer ence bet ween any t wo of t hese l ast t hr ee measur ement s exceeds 2, 5% W' , b) t he di fer ence bet ween t he maxi mum and mi ni mum cr ack l engt hs exceeds 5% 叱 c) any par t of t hecr ack sur face l i es i n a pl ane t he sl ope of whi ch exceeds an angl e of 100 f r om t he pl ane of t he not ch; ' S { K R i s c c d ) t h e f a c t o r 2 i s gr eat er t han t he t hi ckness of t he speci men andl or t he cr ack l engt h. \‘ “ao, z } Ot her wi se, KQS CC=Ki sc a 7. 6 Det er mi na t i on of KI SCC by cr ack i ni t i at i on 7. 6. 1 Ei t h er c on s t an t t o ad or c on s t an t d i s pl a c eme n t s p ec i men s c an be u s e d f or t h e de t e r mi n at i on o f Ki s cC by cr ack i ni t i at i on. 7. 6. 2 A s e r i e s o f s p ec i me ns i sr e qu i r e d t o a l l ow t h e v al u e o f Ki s cC t o be d et e r mi n ed by cr a c k i ni t i a t i on. Two appr oaches may be adopt ed, as descr i bed i n a) and b). a ) I n c a s es wh er e t i me i s at a p r emi um b ut t he av ai l ab i l i t y o f s p ec i men s an d t es t i n g a pp ar a t us i s pl en t i f u l , i t i s mo s t a pp r opr i at e t o s i mul t a ne ou s l y e xp os e as er i e s o f s p e c i men s s t r e s s ed t o di fer en t Ki ; l ev el s e nc o mp a s s i n g t he r an ge wi t h i n whi c h i t i s an t i c i p at e d t ha t K} sC C wi l l l i e. b ) I n c i r c ums t a nc e s whe r e t i me p er mi t s, t h e va l ue o f K} s cc c an be d et e r mi n ed wi t h g r e a t er c er tai n t y an d economy of speci mens and t est i ng appar at us by means of t he bi nar y sear ch pr ocedur e. Thi s r equi r es t h a t an i ni t i al s p ec i men b e u s ed t o d e t er mi n e t h e f r ac t ur e t ou gh n es s o f t h e mat e r i al , K} } ( or KQ i f i n v al i d) , u s i n g r e c ommen de d pr o ce du r es . Th i s va l ue e s t ab l i s h es t h e u pp er b oun d t o Ki s cc} The f i r s t s t r es s c o r r o s i on t es t s h al l t he n b e c o nd u c t ed at a n i ni t i a l s t r es s i n t en s i t y o f h al f K} } wi t h su b s equ en t t e s t s at o t he r f r a c t i on s o f K}i n ac c o r da nc e, e . g. , wi t h t h e s c h ed ul e gi v e n i n I SO 7 53 9- 1 ,d ep en di ng on wh e t he r or n o t f a i l u r e ( or c r a c k ex t en s i on ) oc c u r r e d i n t h e p r e c ed i n g t e s t s . 7. 6 . 3 Whe r e c on s t a n t d i s pl a c emen t s p e ci men s ar e u s ed, t h e d ef l e c t i on s h al l b e a pp l i ed i n ac c o r d an c e wi t h t he r ecommendat i ons made i n 7. 5. 2 and 7. 5. 3. For cons t ant l oad speci mens, t he l oad r equi r ed t o pr oduce t he d e s i r e d s t r es s i n t en s i t y c an b e c a l c ul a t e d b y mea ns o f r el a t i on s hi p s s uc h a s t h o s e g i ve n i n Fi g ur es 1 2 and 1 3. Th e t es t i n g ma ch i ne u s ed t o a ppl yt h e l o ad s h al l pe r mi t t h e a ppl i e d l o a d t o b e me as u r ed t o an a c c ur ac y of 土1% an d l o ad i n g f i x t ur es s ha l l al l o w t he l oa d t o be ap pl i e d s mo ot hl y f o l l owi ng e xp o su r e t o t h e t es t envi r onment . di spl acement i s appl i ed. An ar bi t r ar y t est 7. 6. 4 Th e t e s t pe r i od c o mme n c es a s s o on a s t h e r equ i r e d l o ador dur at i on shal l be chosen f or t he det er mi nat i on of a pr el i mi nar y Ki sc c v a l ue ab ov e whi c h s t r e s s c or r os i on and envi r onment i n quest i on and shal l be cr ac ki ng wi l l i ni t i at e. Thi s dur at i on wi l l depend upon t he mat er i aI ag r e ed up on b et we en t he pa r t i es c on c er ne d. Howev e r , f or pr e l i mi n ar y t e s t i n g, t i me s o f 1 0 h f o r t i t ani u m al l oy s 1 00 h f or ul t r a h i gh s t r e n gt h l ow al l oy s t ee l s a nd 10 00 h f o r l o wer s t r en g t h s t eel s , h i gh al l o y s t e el s of t h e mar agi ng t ype and al umi ni um al l oys may be appr opr i at e mi ni ma. 7. 6. 5 Dur i n g t e s t i n g, c r ac k l e n gt h may b e mon i t or e d op t i c a l l y at i n t e val r s o r c on t i nu ou sl y b y mean s o f el ec t r i cal r esi s t ance, back f ace st r ai n, di spl acement gauge or al t er nat i ve t echni ques, dependi ng on t he exper i ment al ci r cumst ances. These measur ement s may f aci l i t at e t he det ect i on of cr ack i ni t i at i on and enabl e cr ack gr owt h r at es t o be det er mi ned as a f unct i on of st r ess i nt ensi t y. 7. 6. 6 On c ompl e t i on o f t h e t e s t p er i od, t he sp e ci men sh a l l b e i ns p e c t e d f o r s i gn s of f a i l u r e. I f i n t ac t , i t s h al l b e b r ok e n o pe n an d t h e mi ni mu m a nd ma x i mu m f at i g ue pr e - c r a c k l en gt hs mea su r ed, i f po s si b l e t o t h e n e ar es t 0, 5%W. Th e l en g t h o f t h e f a t i gu e p r e - cr ac k s h al l al s o be mea s ur e d a t bo t h e dge s an d a t t h e f o l l owi n g t hr e e p os i t i on s f r om o ne e d ge: 0, 25 B, 0 , 50 B an d 0, 75 B. Th e a v er a ge o f t he s e l as t f i v e mea su r emen t s s ha l l be u s ed a s t h e e fe c t i v e i n i t i al cr a c k l e ng t h, a p , i n t h e c a l c ul a t i on o f KQSC a 31 ) I SO 2003一 Al l r i ght s r eser ved I SO 7539- 6: 2003( E) The t est i s i nval i d i f : a) t h e di fer en c e be t wee n a ny t wo o f t he s e l a s t t h r ee me as u r emen t s ex c ee ds 2, 5% W' , b) t he di fer en c e b e t we en t h e ma x i mu m an d mi n i mum c r a c k l en gt h s ex c ee ds 5% W; c) an y p ar to f t h e f a t i gue c r ac k s ur fac e l i e s i n a p l an e t he s l o pe o f whi c h e x ce ed s a n an gl e of 1 0 0 f r om t he pl ane of t he not ch; dl t he f at i oue cr ack i s not i n one pl ane, i . e. efect s of mul t i - nucl eat i on ar e pr esent ; 、2 e ) t h e f a c t o r 2 . 5 } Kd s c C}i s g r e a t e r t h a n t h e t h i c k n e s s o f t h e s p e c i me n a n d / o r t h e c r a c k l e n g t h ; I R , I \ J、 pU, }2 f ) t her e i s uncer tai nt y over t he f at i gue cr ack l engt h. Ot he r wi s e, KQS Cc=Kl sc c} Any e v i den c e o f s t r e s s c or r os i on c r ac k ex t en si o n i s i n di ca t i v e t ha t t h e Kl l v al ue was i n e x c es s of Kl s cc} On c o mp l e t i on o f t he s er i es o f t e s t s, t he Ki s cc v al u e i s t h e hi gh es t Ki lv a l ue f or whi c h no s t r e s s c o r r o s i on cr a c k ext ensi on occur r ed. NOTE A 3 - p o i n t a v er a g e, n o t i n c l u d i n g t h e e d g e s o f t h e c r a c k , wa s s p e c i f i e d i n t h e c a l c u l a t i o n o f凡s c c b y c r a c k ar r es t ( s ee 7. 5. 5) . Thi s i s bec ause t he st r ess i nt ensi y t f act or i s domi na t ed by t he deep est par ts of t he cr ac k whi c h, f or st r ess c or r osi on cr ac ks gr o wn under cons t ant di s pl ac emen t , ar e us ual l y l ocat ed i n t he c ent r al r egi ons of t he s peci men 7. 6. 7 St r e s s c or r os i on c r ac k i ng i s a t i me - d ep en d en t pr oc e s s. For t h i s r e as on Ki s cc i s n o t an a bs ol ut e mat er i al pr o per t y b u t d ep end s on t he t e s t d ur a t i on ( as wel l as on t h e en v i r o nmen t a nd t e s t me t h od u s ed ) . I f t i me pe r mi t s , t h e r el i ab i l i t y o f t he p r el i mi na yv r al ue o f Kl s cc c a n be ch e ck ed by a f u th r e r s t r e ss c or r os i o n t e s t at a st r ess i nt ensi t y equal t o t hat val ue but f or whi ch t he t est endur ance i s i ncr eased by one or der of magn i t u de. I n gen er al , f u the r r t es t i n g wi l l o nl y b e n ec e s s ar y i f t h i s t es t s ho ws e v i den c e of cr a c k ex t en s i on. Ot h er wi s e, s o me i n di c a t i on of t he t i me- d epe n den c e of Kl s cc ca n b e gl ea ne d by pl o t t i n g t h e t i mes t o f ai l ur e o f t h os e s p ec i me ns i n wh i c h f ai l ur e oc c u r r ed wi t hi n t he e x po s ur e t i me, a s a f un c t i o n o f Ki ; t o es t a b l i s h wh e t h er t h e c u r v e ap p ear s t o b e a s y mpt o t i c t o t he Kl s cc v al u e, a s i l l us t r a t ed i n Fi gur e 20. 7. 7 Measur ement of cr ack vel oci t y 7 . 7. 1 Tes t s p er for med i n 7. 5 or 7. 6 t o d et e r mi ne Kl s cc c an al s o be u s ed f o r d et er mi ni n g t h e v e l oc i t y o f t h e env i r onmen t a l c r a c k gr o wt h e i t he r as a v er a ge da t a or a s a f un c t i on of t he s t r es s i n t en s i t y f a c t or K f o l l o wi n g t h e pr o c edu r e gi v en i n Ann ex B. To d et e r mi ne t he s e d at a t he s p ec i me ns s ha l l b e br ok e n a nd t he f r ac t u r e sur faces exami ned by mi cr oscopy. 7. 7. 2 The f i nal cr ack f r ont shal l be measur ed, i f possi bl e, t o t he near est 0, 5% W at bot h edges and at t he f ol l owi ng t hr ee posi t i ons: 0, 25 B, 0, 50 B and 0, 75 B. Th e a v er ag e o f t hes e f i v e me as u r e men t s s h al l b e u s ed as t he e fec t i v e f i nal cr a ck l e ng t h, o f NOTE A 5 - poi nt a ver age i s s peci f i ed i n con nec t i on wi t h c r ack vel oci t y measur emen t bec ause on- l i ne cr ac k l engt h measur ement met hods based on el ec t r i c al r esi s t anc e ar e s t r ongl y i n luenc f ed by t h e pr esenc e o f unsev er ed l i gamen t s a t t he edges of t he speci men. 7. 7 . 3 Th e av er a ge c r ac k v e l oc i t y , oa / Dr , i s ob t a i n e d b y di vi di n g t he di f f er en c e be t ween t he f i n al a n d i n i t i al c r ac k l en gt h s, o f一a o , by t he t i me el ap s ed b et we en c r ac k i ni t i a t i on and t e s t t er mi nat i o n. 32 。I SO 2003一 AU r i ght s r eser ved ! SO 7539- 6: 2003( E) ‘ ! ! !!卜卜r.Ilwe ee . = 狱. 者su。妇 ujs的 巴祠 51 .一 祠 一 ul B Ki s c } 可 |1 || 1 一-卫 一一一一一一一分 Logar i t hm of t i me t o f ai l ur e Ar bi t r ar y t i mes f or end of t est s Fi gur e 20一 Schemat i c r epr esent at i on of st r ess cor r osi on dat a pr oduced by t est met hod based on t i m e to fai l ure 8 Test r epor t The t es t r epor ts hal l cont ai n t he f ol l owi ng i nf or mat i on: a ) f ul l de s cr i p t i on of t he t es t ma t er i al , i nc l u di n g c omp os i t i o n, s t r u c t ur al c on di t i on a nd mec h an i c al pr o per ti e s, t ype of pr oduct and sect i on t hi cknes s f r om whi ch t he speci mens wer e t aken; b) wh er e mo ni t o r ed, i n i t i a l s o l u t i on c omp os i t i o n, pH, de gr e e o f ae r a t i on ( or c o nc e n t r a t i o n o f o t h er r e l e v an t g as e s) , l f ow c o nd i t i on s , t empe r a t ur e a n d e l e c t r o de p o t en t i al ; s p ec i f i c a t i on o f lo f w r at e s h al l be i n t e r ms o f appr oxi mat e l i near r at e past speci men i f det er mi ned by t he r eci r cul at i on r at e; c) f or each speci men: 1) speci men t ype and l oadi ng met hod; 2 ) t hi c k n es s , B, i n mi N i me t r e s ( an d Bi f s i d e- g r o o ve d) ; 3) wi dt h,城 i n mi l l i met r es; 4) ha l f h ei gh t , H, i n mi l l i me t r es [ ( W- a) i n di f er en t s pe c i me ns o nl y ] ; ) I SO 2003一 Al l r i ght s r eser ved 33 I SO 7539- 6: 2003( E) 5) f at i gue cr acki ng: i ) t he v al ue o f Kma x dur i n g t he p r o pa ga t i on o f t he f i na l por ti o n o f t h e c r ac k ; i i ) t he f at i gue l oad r at i o, R; i i i ) t h e t emper a t ur e an d e n vi r onme n t dur i n g p r e c r a c ki n g; 、 ..夕 6 l en g t h o f t h e f at i gu e p r e- c r ac k, a; 、 ! 1 ‘ 1 了 i ni t i al s t r ess i nt ensi t y, Kl i 8) i n i t i al t i mes o f e xp os u r e t o t h e en v i r o nmen t a nd o f l oad i n g an d t h e t ot al t i me o f e xp o s ur e; 9) wh e t he r cr ac k e x t en s i on o cc u r r e d ( o r cr a c k ar r es t i n t h e c as e of c on s t a n t di s pl a c emen t sp e c i me n s) ; 10) whet her f ai l ur e occur r ed and, i f so, t i me t o f ai l ur e; 11)cr ack pl ane and pr opagat i on di r ec t i on, i dent i f i ed as shown i n Fi gur e 15 d) KI D ( or KQ i f t h e va l i di t y c r i t er i a a r e n ot obe y e d) i f d et er mi ne d; e) l i di t y c r i t er i a ar e n ot ob ey e d) , s t a t i n g wh e t h er ob t ai n ed b y c r ac k i ni t i a t i on o r Ki s cc ( or Kascc i f t heva crack ar r est and cr i t er i aus ed ( t est dur at i on or ar r es t gr owt h r at e, r espect i vel y) ; o 34 cr ack vel oci t y dat a ( aver age val ues or as a f unc t i on of s t r ess i nt ensi t y) wher e avai l abl e. 回I SO 2003一 Al l r i ght s r eser ved I SO 753 9- 6: 2003( E) Annex A ( nor mat i ve) Use of not ched speci mens f or st r ess cor r osi on t est s A. 1 Scope A. 1. 1 Fr a c t ur e me c h an i c s sp ec i men s c an be t e s t e d i n t he b l un t n ot c he d c o nd i t i on wi t h ou t a f at i gu e pr e-c r a c k u n de r c i r c ums t a nc e s wher e i t i s de s i r ed t o ev a l ua t e t h e c o ndi t i on s u n de r wh i ch en v i r onme nt a l l y - assi s t ed cr acki ng can i ni t i at e at bl unt not ches i n st r uct ur es and component s A. 1. 2 Si mi l ar basi c geomet r i es and met hods of l oadi ng t o t hose out l i ned i n 1. 2 and 1. 3 can be used wi t h bl unt not ched speci mens. A. 2 Symbol s I n a dd i t i on t o t h os e d e f i n i t i on s gi v e n f o r pr e - c r ac k e d s pe ci me ns ( Cl a u s e 3 ) , t h e f o l l o wi n g s y mb o l s ap pl y . 一 ! Di st ance f r om not ch r oot t o not ch mout h or l oadi ng poi nt axi s, dependi ng on t he speci men geomet y r 一 a} No mi n al s t r es s 一 ar , . , e Ma x i mu m no t c h s t r es s b a s ed on el a s t i c i t y 一 6mk Ma xi mu m no t c h s t r es s b as e d on f r a c t u r e mec h an i c s met h od s 一 u r n Thr e sh o l d v al ue o f no t c h su fac r e s t r a i n a b ov e wh i ch e nv i r on me n t a l l y - a s s i s t e d c r ac k i ng wi l l i ni t i at e and gr ow f or t he speci f i ed t es t condi t i ons 一 6T n Thr es h o l d v a l u e of n ot c h s t r es s a b ov e whi c h e n v i r on me n t al l y - as s i s t ed c r ac k i ng wi l l i n i t i a t e a nd g r o w f o r t h e s p ec i f i e d t es t c on di t i on s 一 r Not ch root r adi us 一 Kt The or e t i c al e l as t i c s t r es s c on c en t r a t i on f ac t or 一 Ki ' Ap pa r e n t c r a ck t i p s t r e s s i nt en s i t y f a c t or c al c ul at e d on t h e ba s i s o f t h e n o t c h de pt h a nd a pp l i e d l oad M Bendi ng moment 声 Poi sson' s r at i o A. 3 Pr i nci pl e A. 3 . 1 Th e t es t i n v ol v e s s u b j e c t i ng as pe ci men c on t a i ni n g am ac hi ne d n o t c h, t o e i t h er a c on s t an t l oa d o r di s p l ac e me n t a t t h e l oa di n g p oi n t s o r t o am o no t o ni c al l y i n c r ea s i n g l oa d du r i n g e x po s ur e t o ac he mi c al l y aggr essi ve envi r onment . The ob j ect i ve i s t o quant i f y t he condi t i ons under whi ch envi r onment al l y assi st ed c r ac k ex t e n si o n ca n o c cu r i n t er ms of t h e t h r e s h ol d s ur f a c e s t r ai n, e T h , e s t i ma t e d f r om t h e ma xi mum el ast i cal l y cal cul at ed not ch s t r ess, amen 回! S0 2003一 Al l r i ght s r eser ved 35 I SO 7539- 6: 2003( E) A. 3. 2 The empi r i cal dat a can be used f or desi gn pur poses i n or der t o ensur e t hat t he s t r ess wi t hi n s t r u c t ur es i s i n s u f f i c i e n t t o p r omot e e n vi r on men t al l y - as s i s t e d c r ac k i n g pr ov i de d t ha t t h e v al i d i t y of t h e cor r el at i on bet ween t he maxi mum st r ai n, based on t he el ast i cal l y cal cul at ed maxi mum st r ess i n t he bl unt not ched speci men, and t he maxi mum st r ai n i n t he st r uc t ur e or component i n quest i on has been exami ned. A. 4 Speci mens A. 4. 1 Gener al Bl un t no t c h ed s pe ci men s of o t h er wi s e s i mi l ar de s i gn t o t h os e o u t l i n ed i n Cl au s e 5 f or pr e- c r ac k e d s p e c i men s may be ut i l i zed apar tf r om t he absence of a f at i gue pr e- cr ack. A. 4. 2 Speci men desi gn As i n t h e c a s e o f pr e - c r ac k e d s p ec i me ns , t he di men s i on s s ho ul d b e s u f f i c i e nt t o ma i nt a i n pr e do mi n an t l y p l an e st r ai n condi t i ons at t he not ch base si nce, under condi t i ons when t he pl as t i c zone at t he not ch base i s c o ns t r ai n ed, t he t ot al n o t ch s t r ai n ( el a s t i c p l us p l a s t i c ) wi l l b e, t o a r e as o nab l e app r o xi ma t i o n, a u ni qu e f unct i on of t he el as t i cal l y cal cul at ed maxi mum not ch s t r ess f or a par ti cul ar mat er i al . Thi s shoul d be so pr ovi ded t hat bot h t he pl ast i c zone si ze and t he r oot r adi us of t he not ch ar e smal l compar ed t o t he not ch dept h. Ther ef or e i t i s r ecommended t hat : , \2 a) bot h t he not ch dept h, l , and t hi ckness. B. shoul d be not l ess than 2. 5}一--' 一. f IR , 】 \J、 pU, }夕 wh er e K} ' i s t h e ap par e n t s t r es s i n t en si t y c al c ul a t e d o n t he ba s i s o f t h e a ppl i e d l oa d and t he n ot c h d ep t h ; b) t he not ch r oot r adi us, r , i s such t hat t he r at i o r= does not exceed a val ue of 0, 2 ( W一l } A. 4. 3 St r ess consi der at i ons A. 4. 3. 1 The maxi m um not ch st r ess can be c al cul at ed el ast i cal l y f r om t he pr oduc t of t he nomi nal st r ess, v n , an d t h e el as t i c s t r es s c on c en t r a t i on f ac t or , Kt A. 4. 3 . 2 Th e el a s t i c s t r es s c o nc en t r a t i on f a c t or ,从,c a n b e de t er mi ned b y el a s t i c f i ni t e el eme n t a na l y s i s f r om publ i shed t abl es, or can be es t i mat ed f r om t he r el at i onshi p Fmk Kt= 口n wher e } m 、 一 2 K e r } ' I t shoul d be not ed t hat t he accur acy of t he l ater met hod decr eases wi t h i ncr easi ng r oot r adi us. A. 4. 3. 3 Th e no mi n al s t r es s , } } , dep en ds u p on t he s p ec i me n ge omet y. r F or be nd s pe ci men s : 6M 叮n =下二丁-认代二 L w 一l ) 万 wher e M i s t he bendi ng moment . K }; } ) I SO 2003一 Al l r i ght s r eser ved I SO 7539- 6: 2003( E) For compac t t ensi on speci mens 「 P 1 ( 3 ( W+ 1 }飞 6 } = i— ii— 十 .i L b w一I } a1 L w一1 A. 4. 4 Speci men pr epar at i on A. 4 . 4. 1 Not ch i ng o f sp e ci men s s ha l l be c on du c t e d a ter f t h e c o mp l e t i o n of a ny he at t r ea t men t , us i n g ma ch i n i n g c on di t i on s wh i c h si mul a t e t h os e u s ed du r i n g t he ma nu f ac t ur e of t he c omp on en t of i n t er e s t . I n vi e w o f t he g r e a t er l o ad s a s s oc i a t e d wi t h c r ac k i ni t i a t i on i n n o t c he d s p ec i men s c omp a r ed wi t h A. 4. 4. 2 speci mens, i t may be necessar y t o use a somewhat gr eat er not ch dept h such t hat t he t h o s e f o 一 p r e c 一 a c k e l d i s of t he or der 0, 6. val ue or m e rauo — W Degr ease speci mens t hor oughl y bef or e t es t i ng. A. 4. 4. 3 A. 5 Pr ocedur e A. 5. 1 The t h r es h ol d s u fac r e s t r es s , 6 T h , ab ov e whi c h t h e mat e r i a l i s su s c e pt i b l e t o en v i r onme nt al l y - a s s i s t e d c r a c k i n g, c an be de t er mi n e d u s i n g ei t h er c on s t an t di s p l ac e men t or c on s t an t l oa d s p e ci men s b y met h o ds an a l o gou s t o t ho se o u t l i n ed i n 7. 6 f or t h e de t er mi n a t i on o f Ki sc c b y c r ac k i n i t i at i on . A. 5. 2 Th e c or r es p on di n g v al u e o f t h e t h r es h ol d s u fac r e s t r ai n , e T h , ab o ve wh i c h t he ma t e r i a l i s su s c ep t i b l e t o envi r onmen t al l y- assi s t ed cr acki ng, can be es t i mat ed f r om t he f ol l owi ng appr oxi mat i on: E下h = ( , 一 。 ’ ) 。 下 n E A. 6 Test r epor t I n addi t i on t o t he r el evant dat a l i st ed i n Cl ause 8, t he f ol l owi ng i nf or mat i on shal l be r ecor ded f or each speci men: 、..产 a not ch r adi us, r; 』、..户 卜LJ not ch dept h, l ; 、 , C 户 ni ng par amet er s used ( si nce t hese may i nf luence t he sur face met hod of machi ni ng of t he not ch andmachi condi t i on of t he not ch and hence t he condi t i ons r eq ui r ed f o r t he i ni t i a t i on o f en vi r on men t al l y - as s i s t e d c r ac k i n g) . ) I SO 2003一 Ai l r i ght s r eser ved 37 I SO 7539- 6: 2003( E) Annex B ( nor mat i ve) Det er mi nat i on of cr ack gr owt h vel oci t y The cr ack gr owt h vel oci t y, da/ dt , i s cal cul at ed f r om t he cr ack l engt h ver sus el apsed t i me dat a ( a ver sus t ) . I f t h e d at a a r e n oi s y or t he r e ar e un r e al i s t i c o u t l i e r s, i t ma y be ad vi s a bl e t o f i t t he a v s r c ur ve wi t h a p ol y n omi al p r i o r t o c al c u l a t i on o f c r ac k gr o wt h r at e s, o t he r wi s e ap p ar e n t os c i l l at i on s i n c r ac k gr owt h may ar i s e. Ca r e sh aA be t aken t o ensur e t hat r eal var i at i ons i n a vs t ar e not obscur ed by t he f i ti ng pr ocedur e. One r ecommended met hod i s t he I ncr ement al Pol ynomi al Met hod as descr i bed i n I SO 11782- 2: 1 997 f or t he e v al ua t i on o f f a t i gu e cr a ck gr o wt h r a t es ( d a / d 劝.Th i s me t h od i n vo l ve s f i ti n g a s e c on d- or d er p ol y n omi a l ( par abol a) t o set s of ( 2;+1)successi ve dat a poi nt s, wher e n i s usual l y 1,2, 3 or 4. The f or m of t he equat i on f or t he l ocal f i t i s as f ol l ows: _ _ /_ _ 、2 I - }一 }. } 1 . I Li一 L} 、 。=b。十如 ̄ 一二一二+62卜- 气厂一 } c . 2 、 L2 ) where T 一C, 一,5 -二一 一二5 +1; C2 不 i s t he t i me e l aps e d; 如,b } , an d b 2 a r e t h e r e gr es s i on pa r a met e r s t ha t ar e de t er mi n ed b y t h e l ea s t s qu ar es met h o d ov er t he r ange a; } , ,(a毛a} +n. Th e v a l u e a i i s t h e f i ted v al u e o f c r a c k l en g t h a t不・ Th e pa r amet e r s C}二0, 5 x ( T } _+T+) an d CZ二0 , 5/( T,一T} , ) ar e u s ed t o s c a l e t h e i np u t da t a. Th e cr a c k gr owt h v el oc i t y at不i s ob t a i n ed f r o m t he d er i v a t i ve o f t h e ab ov e pa r a bol a , whi c h i s g i v en by : T; 一C} ( d a l d t ) Q ; 一 母・ 2 6 2 。 2 L2 The v a l u e of Kl a s s o ci a t e d wi t h t h e d a / dt v al u e i s c omp u t ed us i n g t h e f i ted c r ac k l e ng t h, 6 ; , c or r es p o nd i ng t o不. 38 。I SO 2003一 Al l r i ght s r eser ved I SO 7539- 6: 2003( E) ! CS 77. 060 Pr i ce based on 38 pages ) I SO 2003一 Al l r i ght s r eser ved