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} 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

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