Session V. Material Characteristics

Transcription

1 Sssin V Matrial Charactristics

2 V- l Effct f Rvrs Cyclic Lading n Fractur Rsistanc Curvs in CT Spcimns C. S. Sk, Sung Kyun Kwan Univrsity, Dpt. f Mchanical Enginring, Kra Y. J. Kim, Sung Kyun Kwan Univrsity, Dpt. f Mchanical Dsign, Kra J. I. Wn, Sung Kyun Kwan Univrsity, Graduat Schl Dpt. f Mchanical Dsign, Kra

3 Effct f Rvrs Cyclic Lading n th Fractur Rsistanc Curv in C(T) Spcimn C.S.Ska, Y.J.Kima, J.1.Wna 'Schl f Mchanical Enginring, Sung Kyun Kwan Univ., Suwn, Kra Fractur rsistanc (J-R) curvs, which ar usd fr lastic-plastic fractur mchanics analyss, ar knwn t b dpndnt n th cyclic lading histry. Th bjctiv f this papr is t invstigat th ffct f rvrs cyclic lading n th J-R curvs in C(T) spcimns. Tw paramtrs wr bsrvd t b ffctiv n th J-R curvs during th rvrs cyclic lading. n was th minimum-t-maximum lad rati (R) and th thr was th incrmntal plastic displacmnt ((5;.y.1/:i), which is rlatd t th amunt f crack grwth that ccurs in a cycl. Fractur rsistanc tst n C(T) spcimns with varying th lad rati and th incrmntal plastic displacmnt wr prfrmd, and th tst rsults shwd that th J-R curvs wr dcrasd with dcrasing th lad rati and dcrasing th incrmntal plastic displacmnt. Dirct Currnt Ptntial Drp (DCPD) mthd was usd fr th dtctin f crack initiatin and crack grwih in typical labratry J-R tsts. Th valus f J, and (5;, wr als btaind by using th DCPD mthd. 1. INTRDUCTIN This papr prsnts xprimntal rsults frm cyclic displacmnt-cntrlld C(T) fractur tsts. Sismic lading cnsists f dynamic lading and cyclic lading. Accrding t a study by th Intrnatinal Piping Intgrity Rsarch Grup (IPIRG) prgram[1], which pinrd th wrk n cyclic lading with C(T) and pip spcimns, th rvrs cyclic lading was infiuncd by th paramtrs f lad vlcity, Iad rati, and incrmntal plastic displacmnt. Th rvrs cyclic lading culd cntribut t th rductin f matrial's fractur tughnss, i.., J-R curv. This wrk is applicabl t flawd-structur valuatins undr sismic lading cnditins, i.. Lak-Bfr-Brak (LBB) and in-srvic flaw valuatin critria whr sismic lading is addrssd. In LBB and flaw valuatin critria such as th ASME Sctin XI, th cyclic natur f th sismic lading is nt implicitly accuntd fr n th ptntial ffcts n fractur tughnss. Th bjctiv f this papr is t study th ffcts f rvrs cyclic lading n th nuclar piping intgrity. In rdr t assss th ffct f cyclic lading n fractur bhavir, th xprimnts cnsidring tw diffrnt paramtrs wr prfrmd. n paramtr is lad rati (R) and th thr is. incrmntal plastic displacmnt ((5i,y.11;i), which can b just as imprtant as th lad rati paramtr n th lad-carrying capacity. 2. EXPERIMENTS Th tst was prfrmd at quasi-static lading rats. Th dtaild tst prcdur will b fllwd

4 2. I Matrial and spcimn. Matrial usd in th tst was SA Gr. 70 carbn stl, which is usd fr nuclar piping. Th chmical cmpsitin f th stl in wight prcnt is givn by Tabl I. Th spcimns fr tnsil and fractw tsts wr cut frm a rctangular plats. As spcifid in th ASTM E8[2] and E21L3], th tnsil spcimns wr dsignd with 50.8-mm gaug lngth and mm diamtr. Th spcimns fr th fractur tughnss tst wr st t I -in.- thick cmpact tnsin spcimns in accrdanc with th ASTM E813. Th crack plan f th cmpact tnsin spcimns was st t th T-L rintatin. Tabl I Chmical cmpsitin ftst matrial (Wt. /) 2.2 Tnsil and fractur tst A srv-hydraulic cmputr cntrlld matrial tsting systm was usd. Th tst tmpratur was st t 288. Tabl 2 summarizs tnsil prprtis fr SA Gr. 70 carbn stl. Fig. I shws th schmatic diagram f th fractur tughnss tst systm. In rdr t masur lad-lin displacmnt, a high tmpratur capacitanc typ CD gaug was usd. Th DCPD mthd was usd fr masuring crack lngth and crack prpagatin. This systm cnsists f a DC-pwr supply (30Amp.), pr-amplifir ( x l04), and filtr (lhz Iw pass filtr). Th fractur tughnss tst prcdur n cyclic lading is nt clarly dfind yt. Thrfr, th fractur tughnss tst n cyclic lading was prfrmd n th basis f th singl spcimn mthd spcifid in th ASTM E8 1 3 [4] and E I 1 52[5] fr static fractur tsting. Th fatigu pr-cracking was prcdd fr a cmpact tnsin spcimn in th sam maunr. Accrding t th ASTM E813, th maximum lad fr pr-cracking was limitd t prvnt th infiunc f plastic dfrmatin in cas f th static fractur tst. Undr this lad limit, th crack was xtndd t a/w=0.55. T prduc th plan-strain cnditin, th pr-crackd C(T) spcimns wr I / sid grvd n ach sid with an dg angl f 45 '. Th fractur rsistanc tsts wr prfrmd by changing th lad rati f R frm I t - I. Fig. 2 shws th variatin f lad vs. Iad-lin displacmnt fr R=-1. T bsrv th variatin f J-R urvs with varying th incrmntal plastic displacmnt, (5;.y.//6i, th DCPD mthd was usd. Fig. 3 shws th lad vs. Iad-Iin displacmnt fr 6.y.//6,=1 and R=0. Firstl)r; th crack initiatin displacmnt ((5:i) was btaind frm th lad-lin displacmnt vs. ptntial drp (vltag) curv as shwn in Fig. 4. This crack initiatin displacmnt was usd fr a critrin in dtrmining th numbr f rvrs cyclic lading fr th fractur rsistanc tsts

5 Fig. l Schmatic diagram f th J-R tst systm q 3 R = -l 5cvcl / = ' l 2 Z :X 10-1:(!' S : Dis placmnt., 3.0 (m m ) Fig. 2 Lad vs. Iad-lin displacmnt curv fr cyclic lad tst (R=-1 (5; /:..=01) '.yct, ' 2.3 Crack initiatin[6-8] DCPD mthd is n f th mst accurat and snsitiv tchniqus fr dtcting crack initiatin. Th Crack initiatin during th tsts was dtrmind by pltting a linar lin, scalld an E.P. blunting lin, n th lad-lin displacmnt vs. ptntial drp curv, as illustratd in Fig. 4. In th bginning f th tst, th crack tip ara was cntrlld undr

6 1'11' Mntnic intt iaan ta s 8c8i = 0.1 R=0 8= 8i Displacmn 8 Fig. 3 11lustratin fcyclic lad tst (R=0 (5; 1:, = I ) '.yct i ' 20 l l 14 E 4J c E aj u (l9 a! (1) b / E.P. blunting lin.2 1, Vitag, (V) Fig. 4 Lad-lin displacmnt vs. EP data fr SA Gr. 70 stl linar-lastic md, and thus n chang in th ptntial drp was bsrvd. As th crack tip bluntd with incrasing lad, a linar rlatin btwn th lad-iin displacmnt and th ptntial drp was bsrvd up t th pint f crack initiatin. Thrfr, th E.P. blunting lin can b usd t dtrmin th crack initiatin displacmnt ((5:i). At th sam tim th valu f J-intgral crrspnding t (5:, was prpsd as J,. In th prsnt papr, th avrag valu f crack initiatin displacmnt dtrmind with th mntnic lading was 0.92mm

7 3. RESULTS A summary fth fractur tughnss tst rsults prfrmd at 288 was listd in Tabl 3. Th J-R curvs wr fittd t a pwr-law quatin, which is givn by JR = C] (A a)c2 Th C1 and C2 Valus wr btaind frm th tst and ar als listd in Tabl 3. In rdr t valuat th ffct f cyclic lading, th xprimnts wr als cnductd at quasi-static lading rats with a lad rati (R) ranging frm - I t I. Th ffct f incrmntal plastic displacmnt was invstigatd by changing 6,y,/1;, frm I /40 t I /10 with a fixd lad rati f - I cnsidring th rvrs cyclic lading cnditin. Tabl 3 Summary f fractur tughnss tst rsults at 288 ) Mats. s.c ' Ratc f* t::ip;:::.4ip '.>' (s:: ), **=* ;;;;;-'"1/1"''i/';"i://' :;;:(:;": ;/;; '///:t:;:;i:i;...;;i=;/;;/:_=':': '; ; ' ' ';l'f!';t '':"'/i..,s;;':""#i! '.*'f''/ti.:"i'"": 'i7;(;; ;;,,/i:" +:+ ';':'*;." + " 'i':;t"';...j' ;:/,j.t;; '"'?' _ r ' 1;c */"' "+= + ; l / l l SA 516 Gr. 70 Quasi - Static =1. l /20 l/ l /40 77 l I Eff_ct f lad rati n C(T) spcimns Th xprimntal rsults wr prsntd in Fig. 5 in trms fj-intgral with incrasing crack xtnsin. In ths tsts, nly th lad rati was varid fr 7 diffrnt valus cvring mntnic lading (R=1), R=0.5, R=0, R=-.3, R=-.6, R=-.8, and R=1 with a fixd incrmntal plastic displacmnt f (5i,y,/16:i = 0.1. Th rsulting J-R curvs shw that th J valus ar significantly rducd with dcrasing th lad rati in th rang f R=0.5 was nt vidnt. This rsult prvs' th validity f ASTM E1152 rquirmnt 253

8 which rstricts th amunt unlading up t 500/0 f th currnt lad. Fig. 6 shws th J, valus bsrvd frm th tsts with 7 diffrnt lad ratis. Th crrspnding Ji Valu, th J-intgral at crack initiatin, was nprmalizd by th Ji,valu undr mntnic lpading cnditin. Th nrmalizd Ji Valu was dcrasd with dcrasing th lad rati. Th J, valu was abut 60 prcnt f n fr mntnic lading cnditin whn th lad rati rachd Whn th lad rati rachd - I, th Ji valu was abut 40 prcnt f n fr mntnic lading cnditin. f IE: t ' 15L* ', = J:b 10Cl] 900 8CID 7Cx) 5Cx] ICx3 K 1) A v R= 1 c R=0.5 R=0.0 A R= -0.3 R= -.6 v R= -0.8 R= -1 : (F.- ( $ AAAAA AJLA l C'(F. c A4+ AA + A + A A A AA A A () ')q) QP c c (blcia$aa+aa A A (_t i +2:Aa q, A/A,) IP V Vy vvvv vvv ((^:. :Vvvvy V -i:q, r: 8dirlbVlv 1 ;Vv : IQ ; ID ID IE! IDI Dl riv : Crack Extnsin, (mm) Fig. 5 Cyclic J-R curvs fr SA 5 16 Gr. 70 stl at 288 ) (6.y.11;, =0.1) 1,..8, i) 5 07 c: '5 c E ' : c.6 Z 0.4 t JD: I. - I.2 Lad Rati Fig. 6 Effct f lad rati fr J at crack initiatin (6.yctl:, =0. I ) - 254

9 3.2 Effct f incrmntal plastic displacmnt n C(T) spcimns Th rsulting J-intgral vs. crack xtnsin bhavir was prsntd in Fig. 7. Th xprimnts wr als cnductd at quasi-static lading rats, and th incrmntal plastic displacmnt, (5:.y.//(5:i, was st t 4 diffrnt valus f l/l, l/20, l/30, and l/40 with a fixd lad rati f - I. Th rsulting J-R curvs shwd a dcrasing tndncy f J- th J-R curvs wr cnsidrably dcrasd whn th 6.y.1/6/ Valu was changd frm l/l t 1/20. Fig. 8 shws th variatin f th J, valu with dcrasing th incrmntal plastic displacmnt. In this Fig., th crrspnding J, valu was nrmalizd by th J, valu fr (5;.y.1/;,= I /l. Th nrmalizd J, valu was apparntly dcrasd with a dcras in th incrmntal plastic displacmnt as shwn in Fig Discussin It was bsrvd frm th tsts that th J-R curvs and th Ji Valus wr dcrasd with dcrasing th lad rati and th incrmntal plastic displacmnt as shwn in Figurs 5 t 8. In gnral, th valu fj-intgral is masurd frm th lad vs. Iad-lin displacmnt curv. Fr th mntnic lading, th ara dfind as A(BCD) m Fig. 9 is usd fr th J-intgral calculatin. Hwvr, th phnmnn f crack pning and crack clsur bsrvd frm th rvrs cyclic lading tst is quit diffrnt frm th mntnic lading tst as illustratd in Fig. 9. Whil th crack pning is ccurrd at pint B fr th mntnic lading, it ccurrd at pint A fr th rvrs cyclic lading cnditin. Thrfr, th valu fj-intgral which is th actual nrgy cnsumd with E Ca _s 200 L, _0= 150!:, , V:1r.V V V' : vv 7VVVV'V l I ll le]ialal ala I D I D D a y Dll i( 1(CF. cc ca AAAJdL c c c _JF AAAJLAA VV al IILA:A:AALA A AAAA;AA':L AA AJ2AA A A A ;Ii!lZf.! ' I:::AAA : 6cycJq= I / 5 : v v 60yd/q=1/10 I D c,lq= ' c 6cyd/q=1/ G I Crack Extn8in, (mm) Fig. 7 Cyclic J-R curvs fr SA 5 16Gr. 70 stl at 288C (R=-1)

10 I F 1.1 lp CD c (1) =a). E 5 c Z Smallr Plastc displacmnt incrmnts (, 1) 1' Il30 1/40 s / s. yd.. Fig. 8 Effct f incrmntal plastic displacmnt fr J at crack initiatin (R=- I ) crack grwih must b masurd frm th ara spcifid as A(ABCDE) cvring th pint P rathr than A(BCD). In thr wrds, calculating th J-intgral fr th rvrs cyclic lading basd n th ara A(BCD) will undrstimat th J-intgral which shuld cnsidr th ara A(ABDE) t accunt fr th ffct f rvrs cyclic lading. It will b n f rasns f dcrasing th J-R curvs undr th rvrs cyclic lading. Thrfr, th way f J-intgral calculatin fr th rvrs cyclic lading shuld b studid furthr rgarding bth tnsil and cmprssiv lading cnditin. "p'" l:,c:f A B.l / r/f/ ' ll. /// ' '/ "' ll l" / //' ;' ' ;' '! "*" '/'\\>7'\' ' /*. " _/ ' P pn / ll / //'./i ll / / / *. t..ll.*,.'* I I J $ ) t C D i sp I acmn t E Fig. 9 Dfinitin f ara fr th J calculatin undr rvrs cyclic lading

11 4. CNCLUSINS This papr prsntd th fractur rsistanc tst rsults rgarding th ffct f rvrs cyclic lading in C(T) spcimns. Th cnclusins ar summarizd as fllws: (1) Fr th SA Gr. 70 carbn stl, th J-R curvs and th Ji Valu wr dcrasd with dcrasing th lad rati and th incrmntal plastic displacmnt, rspctivly. (2) Whn th lad rati was st t - I, th rsulting J-R curvs and th J, valu wr abut prcnt f ths fr th mntnic lading cnditin. (3) In calculating J-intgral undr th rvrs cyclic lading, bth tnsil and cmprssiv lading shuld b cnsidrd. A furthr study n th tst prcdur rgarding th rvrs cyclic lading is rcmmndd. 5. REFERENCE [ I J P. Sctt, G. Kramr, P. Vith, R. Francini, and Gry M. Wilkwski, Th Effct f Dynamic and Cyclic Lading During Ductil Taring n Circumfrntially Crackd Pip: Exprimntal Rsults, ASME PVP Vl. 280 (1994) [2] Standard Tst Mthds f Tnsin Tsting f Mtallic Matrials, ASTM E8. [3] Standard Tst Mthds fr Elvatd Tmpratur Tnsin Tsts f Mtallic Matrials, ASTM E2 1. [4] Standard Tst Mthd fr JIC, A Masur f Fractur Tughnss, ASTM E [5] Standard Tst Mthd fr Dtrmining J-R Curvs, ASTM El [6] G. M. Wilkski, J.. Wambaugh, and K. Prabhat, Singl Spcimn J Rsistanc Curv Evaluatin Using th Dirct-Currnt Ptntial Drp Mthd and Cmputrizd Data Acquisitin Systm, Fractur Mchanics : 1 5th Sympsium, ASTM STP 833 (1984) [7] M. G. Vassilars, and E. M. Hacktt, J-Intgral R-Curv Tsting f High Strngth Stls Utilizing th Dirct-Currnt Ptntial Drp Mthd", Fractur Mchanics : 1 5th Sympsium, ASTM STP 833 (1984) [8] Ad. Bakkr, A DC Ptntial Drp Prcdur fr Crack Initiatin and R-Curv Masurmnts During Ductil Fractur Tsts, Elastic-Plastic Fractur Tst Mthd, ASTM STP 856 (1985)

12 V-2 Th Frquncy Effct n th Fatigu Crack Grwth Rat f 304 Stainlss Stl Jin-Jng Chn & Yan-Shin Shih, Institut f Nuclar Enrgy Rsarch Atmic Enrgy Cuncil, Taiwan, Rpublic f China

13 Th frquncy ffct n th fatigu crack grwth rat f 304 stainlss stl Jin-Jng Chn"'b and Yan-Shin Shihb "Nuclar Divisin f Institut f Nuclar Enrgy Rsarch, Bx 3-3, Lung-Tan, Tayuan Taiwan, Rpublic f China b Mchanical Enginring, Chung-Yuan Christian Univrsity,Chung-Li 32023,Taiwan,Rpublic f China ABSTRACT Undr cyclic lading cnditin, th fatigu crack grwth (FCG) rat gvrnd by strss intnsity factr and strss rati is wll knwn. Walkr's quatin, Frman's quatin and Elbr's quatin ar th typical frmula f th FCG rat. Hwvr, th lading frquncy ffct n th FCG rat is still nd t xplr. Th bhavir f lading frquncy ffct has bn studid n sm f th visc-lastic matrial rcntly, and givs a mr clar aspct f th frquncy ffct n th FCG rat. In physical sns, Th knwldg is still lacking n fr th lading frquncy ffct n th FCG rat fr th 304 stainlss stl. Jams had prvidd a lt f xprimnts, thrugh th data analysis, h suggstd an valuatin quatin which is mrly basd upn th xprimntal illustratin. In this study, th altrnatin f physical prprtis f th matrial undr varius lading frquncy is usd t illustrat th mdificatin f FCG rat, and a nw frmula basd upn mdifid Frman's quatin has bn prvidd. 1. Intrductin Th mdifid Frman's quatin(frman t. al.., 1992) which accunts th strss

14 intnsity factr rang, th man strss lvl and thr imprtant paramtrs is n f th bst frmula fr all th fatigu crack grwth analysis. This quatin is shwn as fllwing: da C" [AK -,h JP dn [(1 -R)Kc C]q (1) whr C, n, p, q ar matnal cnstants R rs strss ratr rs th cntical strss intnsity factr, and AKth is thrshld f strss intnsity factr. Thrfr, th mdrn cds f FCG analysis, such as NASA/FLAGR(EMT,1995), NASCRACK(F, 1994), tc., hav alrady incrpratd this mdl t valuat FCG rat f structural cmpnnts. Hwvr, th FCG is a vry cmplicatd subjct which can b affctd by matrial prprtis, Iading histry, glbal structur with lcal crack gmtry and nvirnmntal cnditin, tc. Hnc, in th fatrgu llf analysrs f machm cmpnnts, thr ar still smwhat diffrnc btwn prdictins and xprimntal data. Fr xprimntal rsult, a grat munt f ths dviatins may b causd by diffrnt tsting cnditins. Hnc. cnsidring as many as th imprtant paramtrs int valuatin frmula is sti]] as a majr tpic fr fatigu lif assssmnt. Many f th mdrn structurs may b pratd fr a wid rang f lading frquncy, and fatigu failur ccurs during thir srvic lif. Thrfr, th ffct f cyclic lading frquncy n th FCG rat is as an imprtant rsarch subjct. In th rviw by Jams(Jams, 1985), bsid f th strss intnsity factr, th FCG rats ar prcisly affctd by sm thr paramtrs, and th cyclic lading frquncy is a significant n f all th imprtant paramtrs. Hwvr, du t th cmplicatd intractin btwn matrial and lading, th bhavir f th lading frquncy ffcts n th FCG rat is still nt clar

15 In th analysis f FCG rat with lading frquncy ffct, thr ar tw apprachs hav bn publishd in th litratur. n cnstructs th mdl f FCG rat with th frquncy ffct by analyzing xprimntal data, th thr xplains th undrlying rasn f cyclic lading frquncy. Frm xprimntal data, th incrasing th lading frquncy gnrally dcrass th FCG rat fr varius matrials. In arly 70's, a pwr law f lading frquncy was addd t th mdl by Muknrj (Mukhrj, 1971) da dn = Cf () (2) whrf is lading frquncy, C ' ;L and n ar cnstants fr a givn cmbinatin f th matrial, tmpratur and nvirnmnts. This mdl has als bn adptd by Slmn and Cffm ( Slmn t. al., 1973), Jams (Jams 1979), Plumtr and Schafr (Plumtr t. al., 1984), and Ykbri and Sat (Ykbri t. al., 1976). Altrnativly, Jams (Jams 1985) prfrms a curv fitting f xprimntal data, and suggstd a frmula as fllw, da dn = C F(C) (3) lg(f) = B + BIX + B2X2 + B3X3 (4) whr F is frquncy crrctin factr, B ' Bl 'B2 and B* ar fitting cnstants, and X is lgarithm f th frquncy in cycl/min. This apprach givs a clsly frtting with xprimntal data. Rcntly, sm xprimntal datum shw that a prtin f FCG rat curv is indpndnt f cyclic lading frquncy. Hnc, a nw cncpt n critical frquncy was prsntd by Makhluf and Jns (Makhluf, 1993) Thy accmplishd a sris f xprimnts n Cr. frritic stainlss stl with varius

16 frquncy at lvatd tmpratur, a stp functin f rlatinship was prsntd as fllws [ da f da dn = C(AK) fr f > f (6) whr f. (T) is a critical lading frquncy n ach tmpratur, such as f. (655 "C) is clsd t 60 cpm and f.(500 "C) is nar by 3 cpm. Fr th undrlying rasn f lading frquncy ffct can b spculatd by Ykbri and Kami (Ykbri t. al., 1975) wh us dislcatin dynamic thry t analyz th bhavir f strain rat snsitivity f matrial and driv th rlatinship as fllw, da = C +1 f +1 '2()'2 (7) dn whr m is th xpnnt in th dislcatin vlcity quatinv=v(t / T;)",T. is applid shar strss, T; is a cnstant which rprsnts th strss rquird t giv v = l cm/sc. This quatin rachs th sam frm as q.(2), and can b rgardd as physical basis f th pwr law quatin, but th xpnnts f frquncy and strss intnsity factr in Ykbri's frmula hav th sam valu with ngativ sign is hard t cnfirm with xprimnts data. Th bjct f th prsnt invstigatin is t study th ffct f frquncy n FCG rat f 304 stainlss stl. A nw FCG rat mdl is dvlpd basd n Mdifid Frman quatin fr bttr prscribing th lading frquncy ffct n FCG rat, it can nt nly ffr clsr prdictin n FCG rat but als with physical in sns

17 2. Data acquisitin and analysis Th xprimntal FCG rat analysis f 304 stainlss stl has bn carrid ut by svral authrs (Jams t al 1971, hta t. al. 1978, Hudsn t. al. 1978,1982,1989,1991) fr invstigating th ffct fth varius paramtrs. All fth xprimntal data usd in this analysis is btaind frm th pn litratur. T avid th lading hld tim ffct, mst f th adptd data was gnratd by sawith lading wavfrm with a lading/unlading rati f Th ttal FCG rat with diffrnt lading frquncy vrsus strss intnsity factr rang is shwn in Figur I. Th datum appard n varius articls wr shwn with svral typical frms and units. Ths basic raw datum ar tratd by using Frman's quatin, firstly. Fr minimizing th ffct f strss rati, critical strss intnsity factr and thrshld f strss intnsity factr, th crack grwth rat can b xprssd int th similar frm with Paris quatin and shwn as fllwing, 3. Lading Frquncy Analysis da [(1 - R)Kc ]* CAK (8) dn [AK -,, J' Frm th cnstructd raw data, th cfficints C and n in q. (8) fr diffrnt lading frquncy can b calculatd and shwn in Tabl I. Th pwr cfficint, n, fr diffrnt lading frquncis in Tabl I is vry similar. Thrfr, n may assum th pwr cfficint b nt affctd by lading frquncy. A man pwr cfficint has bn dtrmind using th fllwing rlatin: n^,.. - = n ' M (9) M whr n and M ar th pwr cfficint and numbr f data with this pwr cfficint. * 263 -

18 By th curv fitting f q. (8) fr all xprimntal datum, C and n ar btaind, and th rsult shwn in Fig. 2, n can fmd that th n valu is th sam as q(9). T rduc th rrr f simulatin, n cnsidrs that C dpnds n lading frquncy, Th nw frtting matrial cnstant C ' basd n th pwr xpnnt f valu can b btaind and shwn in Tabl 2. In th analysis f FCG rat with frquncy ffct, incrasing th lading frquncy incrass dislcatin dnsity and dcrass FCG rat. Frm mntin abv, th FCG rat can b xprssd as a frm f pwr xpnnt. Hnc, a mdifid pwr law has bn prpsd as, ) r " da CC"[AK- AK,h]P L f dn = [(1- R)Kc K]q f..f (l) whr frf is a rfrnc stat lading frquncy, and 2 cpm is usd in this study. 4. Rsult and Discussin Th matrial cnstant rati ( C' / Cf ) with rspct t ladmg frquncy ratr rs shwn as Figur 3, whr C:.f is th matrial cnstant f th rfrnc stat. n may fins that incrasing th lading frquncy rati dcrass th matrial cnstant rati, and th matrial cnstant apprachs t a lw bund valu 0.5 whil f >3000 cpm. This fatur rach th sam cnclusin with Makhluf (Makhluf, 1995). Th curv frtting quatin.fth matrial cnstant rati is shwn as, C' f ) f f.,f.0802 Substituting int quatin (l), n btains

19 da C:,f"[AK- AK,h]P L r f.2 ) dn = [(1-R)Kc AK]q f..f (12) Th fatigu crack grwth rats fr diffrnt lading frquncy by Jams, q. (12) and xprimntal data ar shwn in Figur 4-6. A clsr fitting has achivd by th prsnt mdl. 5. Cnclusin Th wid-rang lading frquncy ffct n 304 stainlss stl at rm tmpratur has bn studid, and a nw mdificatin basd n mdifid Frman's quatin is als prvidd. Sm cnclusin ar mad as fllws. l. A nw quatin is prpsd t rplac th mdifid Frman's quatin fr cunting th lading frquncy ffct n FCG rat. Th dviatin btwn Jams and nw quatin ar vry small. 2. Blw th critical lading frquncy, th FCG rat incrasd slightly with dcrasing lading frquncy at rm tmpratur, this is causd by th highr strngth fatur f 304 stainlss stl at rm tmpratur. 3. Th lwr bund ffcg rat xists whil f > f.. Acknwldgmnt This wrk was supprtd by Natinal Scinc Cuncil, Taiwan, Rpublic f China undr grant numbr NSC E Rfrnc Enginring Mchanics Tchnlgy, Inc., NASA/FLAGR- Fatigu Crack Grwth Cmputr Prgram Vrsin 2.0, publishd by Enginring Mchanics Tchnlgy, Inc. Failur Analysis Assciats, Inc., NASCRAC-NASA Crack - 2,65 -

20 Analysis Cd. Vrsin 3.0, publishd by Enginring Mchanics Tchnlgy. Inc. Frman, R. G., Mttu.S. R., Bhavir i' Surfac and crnr cracks subjctd t tnsil and bnding lads in a Ti-6Al-4V ally, Fractur Mchanics 22'th Sympsium(Vlum l).astp STP I 131, Ernst. H. A., Saxna, A.. McDwll, D.L., Eds.. Amrican Scity fr Tsting and Matrials, Philadalphia, pp Hudsn C. M., "Fractur Tughnss and Fatigu Crack Grwth fr Mtallic Allys-Part I" Intrnatinal Jurnal f Fractur, Vl. 14, pp. R15 l-r184. Hudsn C. M., "Fractur Tughnss and Fatigu Crack Grwth fr Mtallic Allys-Part ll" Intrnatinal Jurnal f Fractur, Vl. 20, pp. R59-RI 17. Hudsn C. M., "Fractur Tughnss and Fatigu Crack Grwth fr Mtallic Allys-Part lll" Intrnatinal Jurnal f Fractur, Vl. 39, pp. R43 R63 Hudsn C. M., "Fractur Tughnss and Fatigu Crack Grwth fr Mtallic Allys-Part IV" Intrnatinal Jurnal f Fractur, Vl. 48, pp. R19-R43. Jams L.A., Frquncy ffcts in th lvatd tmpratur crack grwth bhavir f austnitic stainlss stl -A dsign apprach, Jurnal f Prssur Vssl Tchnlgy-Transactins f th ASME, Vl. 101, pp Jams L A., Jns D. P., "Fatigu Crack Grwth Crrlatins fr Austnitic Stainlss Stls in Air", in Cnfrnc n "Prdictiv Capabilitis in Envirnmntally Assistd Cracking. (Prsntd at th Wintr Annual Mting f th Amrican Scity f Mchanical Enginrs.), ASME PVP Vl. 99, pp Jams L.A., Schwnk E. B.,1971. Fatigu-crack prpagatin bhavir

21 f Typ_ 304 stainlss stl at- lvatd tmpratur" Mtallurgical Transactins f ASME, Vl. 2, pp Makhluf K. & Jns J.W., "Effct f Tmpratur and Frquncy n Fatigu Crack Grwth in 180/0 Cr. Frritic Stain]ss Stl" Intrnatlnal Jurnal f Fatlgu Vl 15 N 3 pp Mukhrj B., & Burns D. J., Fatigu-crack grwth in plymhylmthacrylat, Exprimntal Mchanics, Vl I l, pp hta A., Ksug M. and Sasaki E., "Fatigu Crack Clsur vr Th Rang f Strss Ratis frm -1 t 0.8 Dwn t Th Strss Intnsity Thrshld Lvl in HT80 stl and SUS 304 Stainlss Stl" Intrnatlnal Jurnal f Fractur Vl. 14, pp Plumtr A. & Schafr S., Wavfrm and frquncy ffcts n th high tmpratur fatigu crack prpagatin rat f stainlss stl" in Advancs in Fractur Rsarch (Fractur 84), VL. 3. Pub]ishd by Prgamn Prss, xfrd, England Nw Yrk, USA, pp Slmn H.D. & Cffin L.F, Effct f frquncy and nvirnmnt n fatigu crack grwth in A286 at I 100 F, in Fatigu at Elvatd Tmpratur, Editd by Cardn A.E. t. al., ASTM- STP 520, Philadlphia, pp. I Ykbri T. & Sat K., " Th ffct f frquncy n fatigu crack prpagatin rat and striatin spacing in 2024-T3 Aluminum ally and SM-50 st]", Enginring Fractur Mchanics, Vl. 8, N. l, pp Ykbri T., Ykbri A. T., Jr. and Kami A., "Dislcatin Dynamics Thry fr Fatigu Crack Grwth", Intrnatinal Jurnal f Fractur, Vl. I l, N. 5, pp

22 Tabl I : Th matrial cnstant f FCG f varius lading frquncy Tabl 2 Th matrial cnstant C ' 268 -

23 1 E-3 ' 1 E-4 >.\ _ = I E-5 Z.\ CU 1 E-6 l ; ; > 1 E AK (ksi in), Figur I : Th ttal FCG rat data fr 304 stainlss stl f varius lading frquncy and

24 1.E-3 '\ :L, d) 1.0E-5 C - -Z. CU 1.0E 6 Y = pw(x, ) * I.74928E-I > > > ; :x_ ; > 1.E-7 10,00 1. AK (ksi in), Figur 2 : Th man slp f th ttal FCG rat data fr 304 stainlss stl

25 1 E-3 1 E-4 Exprimntal data Jams [1985] q (12) /.A / / / / Z._ CU 1: 1 E-5 / / / / / / / 1 E-6 1 E-7 AK Figur 4 : Th fatigu crack grwth rat fr SS 304 n 2 cpm 1 E-3 f lading frquncy and 75 F Z '\ cu U 1 E-4 1 E-5 1 E-6 Exprimntal data Jams [1 985] q (1 2) / / /> '), / / /, / 1 E-7 AK Figur 5 : Th fatigu crack grwl:h rat fr SS 304 n 180 cpm f lading frquncy and 75 F

26 1 E-3 1 E-4 Exprimntal data Jams [1 985] Eq(12) d' Z D CD \ I E-5 1 E-6 l c 1 E-7 AK Figur 6 : Th fatigu crack grwth rat fr SS 304 n 400 cpm f lading frquncy and 75 F

27 V-3 Invstigatin n Fractur Tughnss Evaluatin Mthd fr Ractr Prssur Vssl Survillanc Kuni nizawa, Thru Tbitz & Masahid Suzuki, Ractr Cmpnnt Rliability Labratry, Japan Atmic Enrgy Rsarch Institut, Japan

28 Invstigatin n Fractur Tughnss Evaluatin Mthd fr Ractr Prssur Vssl Survillanc Kuni NIZAWA', Thru TBITA and Masahid SUZUKI Ractr Cmpnnt Rliabilty Labratry, Japan A tmic Enrgy Rsarch Institut, Tkai-mura, Naka-gun, Ibaraki-kn, 319- I 195, Japan Abstract T valuat clavag fractur tughnss in th ductil-brittl transitin rang f RPV stls, th applicability f prcrackd Charpy-v (PCCv) spcimns has bn invstigatd. An apprach basd n th wakst link thry was applid t analyz th spcimn siz ffct and th scattr f fractur tughnss valus. Fur kinds f ASTM A533B class I stls mad by Japans stl makrs wr usd. Th spcimn siz ffct n clavag fractur tughnss was clarly sn amng PCCv, l T-CT and 4T-CT spcimns. T btain th quivalnt data frm PCCv spcimns t I T-CT spcimns, th siz crrctin schm basd n th wakst link thry was applid t th PCCv data. Th scattr f fractur tughnss valus was cnsidrd t hav a Wibull typ distributin. lrradiatin ffct n th scattr was shwn t b insignificant. Th fractur tughnss transitin curvs wr dtrmind by PCCv data accrding t th drafi ASTM and th JEAC. Th shifi f th mastr curv by irradiatin was smwhat gratr than th Charpy 4 1 J shifi. Th schm fr th stimatin f lwr bund fractur tughnss was als studid. 1. INTRDUCTIN Th brittl fractur f an RPV must b prvntd, bcaus it may lad t a catastrphic fractur f th vssl fllwd by svr accidnt. Thrfr, th RPV is pratd at highr tmpratur than th ductil-t-brittl transitin tmpratur f th RPV stl. Hwvr, fast nutrns frm th ractr cr during pratin can caus th incras f th transitin tmpratur, i.., th irradiatin mbrittlmnt. T assur th structural intgrity f an RPV thrughut th pratinal lif, th fractur tughnss aftr nutrn irradiatin ar ndd. T d this, th survillanc prgram fr th RPV is prfrmd accrding t a crtain cd and rgulatin. Th rsults btaind frm th Charpy impact tsts accrding t th cds ar usd fr th stimatin f fractur tughnss aftr irradiatin(1, 2). Mst f th cds assum that th dgr f irradiatin mbrittlmnt btaind frm Charpy impact tsts ar quivalnt t that f fractur tughnss fr th matrial cncrnd. Rcnt rsarch, hwvr, has indicatd that th crrlatin is nt always cnsrvativ in prdicting th dgr f irradiatin mbrittlmnt in trms f fractur tughnss(3'4). Fractur mchanics mthdlgy is, thrfr, ncssary fr th prcis valuatin f irradiatin mbrittlmnt t assur th structural intgrity f an RPV. A mthdlgy t valuat fractur tughnss f RPV stls has nt bn stablishd ' Crrspnding authr. Tl: ; Fax: ; -mail : knizawa@ppsvr.tkai j ari.g jp

29 cmpltly, particularly in th transitin rang. As th fractur tughnss valus frm tst spcimns f th RPV stl shw a larg scattr in th ductil-t-brittl transitin rang, th fractur tughnss shuld b valuatd with th statistical natur. This mans that a crtain statistical apprach is ncssary fr th valuatin f th fractur tughnss. Fractur tughnss valus frm small siz spcimns, such as survillanc spcimns, als shw larg ffcts n spcimn siz. Althugh intnsiv rsarch("g' 5) has bn cnductd t stablish th statistical tratmnt and th valuatin mthd f siz ffcts in th past, th mthds nd a larg numbr f spcimns and/r rlativly larg siz spcimns(6). Th numbr and th siz f survillanc spcimns ar limitd by th small vlum f a survillanc capsul. Thrfr, furthr rsarch is dsird t rslv th limitatin and t stablish an imprvd survillanc tst mthd that is applicabl fr th small nulnbr and th small sizs f spcimns. This papr dscribs th rsults f fractur tughnss tsts using fur kinds f prssur vssl stls including an IAEA rfrnc matrial JRQ. Basd n th rsults f th fractur tughnss tsts by prcrackd Charpy spcimns and standard siz I T-CT and 4T-CT spcimns, a statistical analysis was prfrmd t valuat th scattr and th lwr bund f fractur tughnss in th transitin tmpratur rang. A part f this rprt was prfrmd at JAERI in th framwrk f th IAEA Crdinatd Rsarch Prgram Phas-3(7). 2. EXPERIMENTS 2.1 Matrials Matrials usd in this study wr fur kinds f prssur vssl stls f ASTM A533B class I. Th n is dsignatd JRQ, which was usd as a crrlatin mnitr matrial in th IAEA CRP-3(8). Th anthr matrial ws chsn t hav a larg numbr f databas fr clavag fractur tughnss frm small siz spcimns t larg ns. Th matrial is dsignatd as JSPS A533B-1 which was usd in th rund rbin study rganizd by Th Japan Scity fr Prmting f Scinc (JSPS)(9). Th thr matrials wr mad as A533B-1 stls which wr calld as Stl A and Stl B that crrspndd t th ld ag RPV stl and th mdm stl, rspctivly. Chmical cmpsitins f th matrials ar summarizd in Tabl I. Mchanical prprtis at rm tmpratur fr th matrials ar listd in Tabl Fractur Tughnss Tsts Fur typs f spcimns wr usd in this study, namly prcrackd Charpy (PCCv), 0.5T-DCT, I T-CT and 4T-CT. In sm cass th spcimns wr sid-grvd by I / n ach sid f th spcimn aftr prcracking. Fr JSPS A533B-1 stl, n f th authrs prfrmd fractur tughnss tsts using PCCv spcimns machind frm halvs f brkn 2T-CT spcimns at SCK/CEN(r). Th ntch rintatin f th spcimns is T-L dirctin fr all spcimns. All spcimns wr machind frm th apprximatly quartr thicknss psitin f th matrial. Fractur tughnss tsts wr prfrmd at mainly lwr transitin tmpratur rang which a clavag fractur was ccurrd bfr th limit lad f th spcimn. Sm spcimns wr als tstd at an uppr shlf tmpratur rang t btain J-R curvs. Tsting and valuatin fr fractur tughnss wr prfrmd accrding t ASTM standards(ll,12) and JSME mthd(13). A valid plan-strain fractur tughnss, Klc, culd nt b

30 btaind frm th spcimns xcpt fr 4T-CT spcimns. Th fllwing mthd, thrfr, was applid t btain lastic-plastic fractur tughnss. Fractur tughnss valus at clavag fractur, Jc, wr calculatd basd n th ara undr lad-displacmnt curv up t th suddn lad drp and th clavag fractur lad (s q. I ). Fractur tughnss KJC Valus wr thn cnvrtd frm Jc by th fllwing quatin (2). Elastic mdulus E and Pissn's rati v wr fixd t 206 GPa and 0.3 in this study, rspctivly. J - Jcl + Jpl C K 2 na - C + P! E' BN b (1) whr Kc: Strss intnsity factr at th clavag fractur, n = *(a/W) fr cmpact spcimns, n =2 fr PCCv spcimns, Apl: Plastic part f th ara undr lad-displacmnt curv, BN: Nt thicknss, b: Initial ligamnt (=W-a), a: Initial crack lngth, W: Spcimn width, E'=E fr ASTM, E'=E/(1- v 2) fr JSME. In th ASTM draft mthd(14), n factr has bn changd frm 2 t 1 9 basd n th 3-D dtaild analysis fr PCCv spcimn(15). This maks th fractur tughnss valu lwr by maximum 50/0 in trms f J-intgral. Whn sm quatins in th ASTM draft mthd ar applid t th data, th nw 7? factr is usd. At uppr shlf tmpratur rang, Jlc Valus and J-R curvs fr th matrials xcpt fr th JSPS A533B-1 wr btaind accrding t th JSME mthd. Ductil crack grwih in a spcimn during a tst was masurd by unlading lastic cmplianc mthd. 2.3 Irradiatin PCCv and 0.5T-DCT spcimns f JRQ wr irradiatd in Japan Matrials Tsting Ractr (JMTR, thrmal utput 50MW). Fast nutrn flunc fr ach spcimn was calculatd t b within th rang frm I.9 t 2.5 x I 019 n/cm2 (E> I MV). Th displacmnt pr atm (dpa) fr irn by th irradiatin t 2 x I 019 n/cm2 (E> I MV) was abut 3 x I 0-2. Fast nutrn flux was abut I.2 x I 013 n/cm2s (E> I MV). Tmpratur fr th spcimns during irradiatin was cntrlld in th rang frm 280 t 300 C. Th shifts f Charpy transitin tmpraturs and th hardning by nutrn irradiatin ar summarizd in Tabl 3(7) Many spcimns f Stl A and Stl B wr als irradiatd at JMTR. Sixtn PCCv spcimns f th stls wr ncapsuld with tn Charpy-V spcimns fr th JMTR irradiatin. Pst irradiatin tsts fr ths spcimns ar nw undrway. 3. RESULTS AND DISCUSSIN 3.1 Fractur Tughnss Databas Figurs I t 5 shw clavag fractur tughnss data btaind in this studyl 1 6). Th

31 validity limit fr th PCCv data basd n quatin (3) is indicatd. This critrin has bn stipulatd in th JSPS mthd. b ' B > JcaY 25 (3) Th quatin (3) usd in th JSPS mthd is th sam as th validity critrin n th dtrminatin f a Jlc in th ASTM E813. Fr th PCCv spcimn, th ligamnt siz, b, is smallr than th spcimn thicknss, B. Thrfr, b is cnsidrd as a ky paramtr fr th validity f PCCv data. Figur I shws KJC valus f unirradiatd JRQ spcimns tstd in th transitin rang. At rm tmpratur, clavag fractur was nt bsrvd frm any PCCv spcimns, but frm all 0.5TDCT and ITCT spcimns. Whn PCCv and IT-CT data ar cmpard at -80 C, it is sn that I T-CT data ar situatd within th scattr rang f PCCv data. Th Jlc Valu at I C btaind frm IT-CT and 0.5T-DCT spcimns by mans f th JSME mthd is als indicatd in th figur. Sm data pints f PCCv and cmpact spcimns tstd at uppr transitin tmpratur rang xcdd th Jlc Valu. Figur 2 shws all clavag fractur tughnss data f irradiatd JRQ spcimns. Tst tmpraturs fr fiv PCCv and six 0.5TDCT spcimns, prfrmd in th fram wrk f IAEA CRP-3, wr spars frm t I C. W tstd additinal irradiatd PCCv spcimns; twlv spcimns arund 1 7 C and tn at 35 C s that a statistical analysis culd b dn. Figur 3 shws fractur tughnss valus frm PCCv spcimns f JSPS A533B-1 stl with a larg numbr f databas by mans f cmpact spcimns frm 0.5T t 4T (13). Th databas includs -25, and 25 C data whil PCCv wr tstd at C. bviusly PCCv data shw highr fractur tughnss valus than th thr cmpact spcimn data. Th clavag fractur tughnss data f Stl A ar shwn in Figur 4. Th data includ sm valid Klc data frm 4T-CT. Th Klc data lcats narly th lwst bund f th thr data. Th PCCv data shw highr KJC Valus than KJC f I T-CT and Klc f 4T-CT data. Th uppr shlf fractur tughnss, Jlc, btaind by I T-CT at 20 C is indicatd in th figur. Mr than halffpccv data at -50 C xcdd th Jlc Valu. Figur 5 indicats th rsults f fractur tughnss tsts by spcimns f Stl B. Valid Klc data pints frm 4T-CT ar als shwn in this figur. Th Klc data li narly lwst bund f th thr data. Similarly t Stl A, PCCv data indicat highr tughnss valus than th thr CT data. Th uppr shlf fractur tughnss, Jlc, btaind frm I T-CT at 20 C is indicatd in th figur. Svral PCCv data at -80 C xcdd th Jlc Valu. 3.2 Spcimn Siz Effct n Clavag Fractur Tughnss As is knwn wll, a fractur tughnss valu frm a small spcimn can b highr than that frm a larg spcimn. In additin t this, in th transitin rang, a statistical ffct n clavag fractur is apparnt. This has bn xplaind by th wakst link thryll7,18) that is basd n th lcal inhmgnity in th matrial. Th thry trats th prbability t find a particl that is lcatd randmly in th matrial and that lads t th fractur f th spcimn. Anthr rasn is that th small spcimn has insufficint lngth in thicknss t kp small scal yilding and maintain a crtain lvl f cnstraint at a crack tip, as cmpard with a larg siz spcimn r a ral havy-sctin structur(19)

32 Figur 6 shws th ffct f spcimn thicknss n fractur tughnss valu. Each valu was nrmalizd by Klc Valus fr ach tsting cnditin. This figur clarly shws th siz dpndnc n th man valu. Th highst PCCv data was largr than fur tims f Klc Valu. Th man valus f PCCv data xcpt fr invalid data wr I.5 t 2.2 cmpard t Klc Valu. n th thr hand, th lwst valu f PCCv data was apprximatly th sam as th Klc Valu. T btain a rliabl fractur tughnss valu frm a small siz spcimn, svral crrctin schms hav bn prpsd. Wallin(20) has prpsd th fllwing quatin fr crrcting spcimn siz applicabl t prssur vssl stls; + (KJC _' KJC =K i* y K, )(B. / By)1/ (4) whr KJc_.., y: KJC fr spcimns f thicknss, B.., y Kj. = 20 MPal/ m=4 Figur 6 includs th siz ffct crrctin curv basd n th quatin (4). Th uppr curv is crrspnding t Stl B, th lwr curv is fr Stl A. Th crrctin curv fr Stl B vrstimatd 300/0 f Klc Valu by 4T-CT spcimn. Unfrtunatly Klc Valu f JRQ was nt availabl. Hwvr, th siz crrctin was cmpard btwn PCCv and I T-CT data. As a rsult, th crrctin prvidd th I T-CT quivalnt valus frm PCCv data. T vrify th crrctin quatin, w nd mr databas including sufficint numbr f PCCv data. 3.3 Scattr f Fractur Tughnss Th quatin (4) is basd n th wakst link thry. Th thry assums that th distributin f th fractur tughnss valus f a matrial can b dscribd as a Wibull typ statistics. Using thr paramtrs, Ki., m and K, th fractur prbability basd n Wibull statistics can b xprssd by th fllwing quatin(20). f =1-xp Jc_lT Ki =1-xp K KJc_rr 20 " K Kj. K 20 (5) whr Pf: Mdian ranking( = (i-0.3)/(n + 0.4) ) m, K: Fitting paramtrs All data btaind by th sam-typ spcimns at a crtain tmpratur can b analyzd by ths quatins (4) and (5). This quatin (5) has als bn incrpratd int th ASTM draft mthd t dscrib th statistics f clavag fractur tughnss. Figurs 7 t 9 cmpar Wibull plts f PCCv data and I T-CT data. PCCv data wr crrctd by quatin (4) t I T-CT thicknss fr cmparisn. Ths figurs als includ th fitting curv by quatin (5). Figur 7 indicats that th crrctd PCCv data and I T-CT data f unirradiatd JRQ ar in gd agrmnt. Th paramtr m in quatin (5) wr 2.3 and 2.5 fr PCCv adjustd data and I T-CT data, rspctivly. Ths valus wr much lss than th thrtical valu f fur. Figur 8 shws th Wibull plts f PCCv data f irradiatd JRQ. Th m valus wr 2.8 and 3. I fr th data tstd at 1 7 C and 35 C, rspctivly. Th slps wr again smallr than th thrtical valus. Hwvr, it is ntd that th m valu bcam a bit larg

33 aftr irradiatin.' In thr wrds, nutrn irradiatin culd 'mak th data scattr smallr. This mans that th scattr aftr irradiatin may b stimatd cnsrvativly by applying th scattr bfr irradiatin. Figur 9 shws Wibull plt f stls A. In this cas, I T-CT data wr wll fittd by mans f a thrtical m valu. Th man valu f crrctd PCCv data was highr than that f l T-CT data. Fr th data scattr, th crrctd PCCv data shwd th sam tndncy as PCCv f JRQ, that is, th m valu was smallr than th thrtical valu f fur. Fr th lwr bund data, hwvr, apprximatly th sam trnd was sn btwn bth data blw 50/0 fractur prbability. If th thrtical m valu was usd fr data fitting, th lwr tail f PCCv data is much highr than that f I T-CT data. Figur I summarizs th Wibull paramtr m btaind frm this study. Althugh a larg scattr f m valus was sn, th m valu tnds t dcras as spcimn thicknss dcras. T stimat th lwr bund frm a limitd numbr f PCCv data, it may b hlpful t us th xprimntal m valu instad f th thrtical valu. 3.4 Tmpratur Dpndnc f Fractur Tughnss Th mdian valu f th data can b btaind by K fllwing quatin as a fractur prbability Pf=0.5. KJC IT(md) = (K020)[ In(2) I / frm quatin (5) and th (6) Using this mdian valu, th tmpratur dpndnc f clavag within th transitin rang is xprssd by th fllwing quatin(14.20). fractur tughnss Jc IT(md) { xp (T - T)} (7) This quatin has bn stablishd by statistical analyss using a hug databas (20) including unirradiatd and irradiatd RPV stls. This quatin, which is calld a mastr curv, uniquly dfins th clavag fractur tughnss transitin curv. A rfrnc tmpratur, T' can b calculatd by T = T I. In{(KJc IT(md) 30)170} Tabl 4 Iists th T Valus btaind frm matrials usd in this study. Figur I I shws th valus f T basd n th mthd abv as a functin f spcimn thicknss. Th valus f T frm unirradiatd JRQ and JSPS A533B-1 shwd littl ffct n spcimn thicknss, whil ths f stls A and B shwd a siz ffct t sm xtnt. Th T Valus frm PCCv data wr abut 20 C Iwr than ths valus frm I T-CT data fr bth stls A and B. Th dviatin f 20 C is largr than th dviatin f 5-l C rprtd fr sm RPV stls in rfrnc (21). Th rasn f th dviatin is nt clar fr th mmnt. Additinal tsts might hlp t undrstand th rasn bcaus th numbr f valid data frm PCCv spcimn f Stls A and B Figur 1 2 shws all data as a functin f th diffrnc btwn tst tmpratur and T dtrmind by PCCv data. Th fractur tughnss valus wr siz-crrctd t I T thicknss by quatin (4). Blw 30 C f T-T, th mastr curv agrs wll with th data. At th highr -278-

34 transitin rang th mastr curv tnds t vrstimat th data. f curs, th us f th mastr curv t highr tmpratur shuld b rstrictd bcaus th PCCv data is n lngr valid abv -200 MPalrm. Cmparing th T bfr and aftr irradiatin, w btain th shifi f fractur tughnss. Figur 1 3 shws th mastr curv fr JRQ stl bfr and aftr irradiatin. Bfr irradiatin, th T valu was dtrmind by PCCv data tstd at -80 C and -50 C. Th T Valu aftr irradiatin was th avrag ftw T Valus frm tw PCCv data sts tstd at 1 7C and 35C. Th shift f T by irradiatin t JRQ was thn calculatd as I 08 C. This shift is largr than th Charpy shifi listd in Tabl 3 by abut 20 C. Basd n Wibull statistics, tlranc bunds fr th mastr curv can b drawn. Assuming th Wibull slp m=4, th third paramtr Kj.=20 and an mfinrt samplmg slz a lwr bund curv in th sam frm as quatin (7) can b dfind. Figurs 1 2 and 1 3 indicat th lwr tlranc bund curvs. As mntind bfr, th xprimntal data indicatd largr scattr thn th thry. Th 50/0 Iwr bund curv is nt nugh t bund th xprimntal valus. Instad f 50/0 bund curv, th I / bund curv is in gd agrmnt. Th Japans cd n th mthd fr th fractur tughnss tst and valuatin, JEAC 4206(22) stipulats th mthd t btain th lwr bund tughnss curv fr th intgrity assssmnt f RPV during a PTS transint. Th curv can b dfind as th lwst nvlp f all th fractur tughnss data pints frm th survillanc tsts. Th frm f th curv is xprssd by th fllwing: Figur 1 4 shws th JEAC Klc curv tgthr with I / tlranc bund curv basd n th wakst link thry. T cmpar all data with ths curvs, th data pints withut sizcrrctin wr plttd as a functin f T-T' Th shap f JEAC Klc curv cincids wll with th lwst data pints. Th I / tlranc bund curv agrs with th JEAC Klc curv in th lwr transitin rang but tnds t bcm highr at highr tmpratur. Althugh this cmparisn is limitd t nly fur matrial, th JEAC mthd culd giv th cnsrvativ stimatin f th lwr bund curv. Applying quatin (8) t th data f JRQ stl, w btain th lwr bund curvs bfr and aftr irradiatin, and hnc th shift f th lwr bund curvs. Figur 1 5 indicats th JEAC Klc curvs bfr and aftr irradiatin tgthr with all tst data. Th curv aftr irradiatin was dtrmind by shifting th Klc curv bfr irradiatin by th amunt f Charpy shift. Th lwr bund curvs agrd wll with th data up t uppr transitin rang, Iading t a cnsrvativ valuatin. Whn w cmpar th tst data bfr and aftr irradiatin, w btain th shift f TJ valu by irradiatin f -80 C. This valus was slightly lss than th Charpy shift. Thrfr, th Klc curv aftr irradiatin bcam cnsrvativ. This may dpnd n th statistical tratmnt f th data. If w had mr data frm irradiatd spcimns r lss data frm unirradiatd spcimns, w might hav gt lss cnsrvativ Klc curv aftr irradiatin. Th fllwing quatin (9) is th Klc curv in th ASME Sc. XI(1) t dscrib th lwr bund fractur tughnss f RPV stls. RTN/)7' ) f In this cas, w nd an RTNDT f th stl t dfm th Klc curv. Th RTNDT is

35 dtrmind by th cmbinatin f th rsults frm drp wight tst and Charpy impact tst. Th drp wight tst can nt b dn afir irradiatin bcaus th tst rquirs rlativly larg siz spcimns. Thrfr, Charpy impact rsults ar usd instad f th rsults f drp wight tst t dtrmin th irradiatin ffcts. Th adjustd RTNDT Valu aftr nutrn irradiatin is thn calculatd with th Charpy shift addd t th initial RTNDT. Th Klc curv afir irradiatin is dfind by an quatin (9) using th adjustd valu. This mans that th irradiatin ffct n Charpy prprty and fractur tughnss shuld b quivalnt. Figur 1 6 shws th cmparisn f th xprimntal data and th ASME Klc curvs. This figur clarly shws that all data ar bundd by th ASME Klc Curv basd n RTNDT. Fr th mmnt, th ASME mthd givs a gd apprximatin fr th lwr bund curv. Hwvr, th shift f fractur tughnss can b largr than Charpy shift as btaind frm JRQ rsults. Th lwr bund curv fr highly irradiatd matrial shuld b carfully chckd by fractur tughnss tsts. 4. SUMMARY AND CNCLUSINS T stablish th mthd t valuat fractur tughnss valus in th transitin rgin, fractur tughnss tsts using PCCv t 4T-CT spcimns wr prfnnd. Althugh pst irradiatin tsts hav finishd nly fr JRQ, th fllwing cnclusin wr drawn frm th tsts f fur typs f Japans RPV stls and thir analysis; ( I ) Th siz ffct crrctin basd n th wakst link thry was nt always nugh t btain an quivalnt valu frm a PCCv spcimn t a larg spcimn. (2) Fr data scattr, xprimantal valu f th Wibull slp was nt much affctd and slightly dcrasd by nutrn irradiatin. (3) Accrding t th mastr curv, th shift f th curv by irradiatin was valuatd t b smwhat gratr than th Charpy 4 1 J shift. (4) JEAC Klc curvs fr JRQ data bfr and aftr irradiatin culd b cnsrvativ. Hwvr, larg numbr f data bfr irradiatin wuld b ncssary. ACKNWLEDGMENTS A part f this wrk was carrid ut undr th cntract btwn JAERI and Scinc and Tchnlgy Agncy f Japan undr th auspics f th spcial accunt law fr lctric pwr dvlpmnt prmtin. Th authrs wuld lik t thank Dr. K. Shibata and Mr. Y. Nishiyama, Japan Atmic Enrgy Rsarch Institut fr thir ncuragmnt and hlpful discussin, and many staffs at Ht Labratry f JAERI fr thir carful tsting f irradiatd spcimns. Thy ar als gratful t Dr. T. Iwadat and Dr. Y. Tanaka f th Japan Stl Wrks, Ltd. fr prviding th JSPS A533B-1 matrial. Th tsts f PCCv spcimns f JSPS A533B-1 wr dn at SCK/CEN during th prid that n fth authrs had stayd thr. REFERENCES (1) ASME Bilr and Prssur Vssl Cd, Sctin XI, "Insrvic Inspctin Pwr Plant," Amrican Scity fr Mchanical Enginrs, f Nuclar

36 (2) (3) (4) (5) (6) (7) (8) (9) ( I ) (ll) ( 1 2) (13) ( 1 4) (15) ( 1 6) ( 1 7) Japans Elctric Assciatin, "Mthds f survillanc tsts fr structural matrials f nuclar ractrs," JEAC (in Japans) R. Nanstad t al., "Irradiatin Effcts n Fractur Tughnss f Tw High-Cppr Submrgd-arc Wlds, HSSI Sris 5," NUREG/CR-5913 Vl.1, ctbr 1992, U.S.NRC. K Wallm t al "Bynd th Charpy - Imprvd tughnss prdictins and advancd survillanc," prsntd at Radiatin Damag and Embrittlmnt in Prssur Vssl Stls - IGRDM pn Wrkshp. Santa Barbara. May 6, M.T. Miglin, t al., "Analysis f Rsults frm th MPC/JSPS Rund Rbin Tsting Prgram in th Ductil-t-Brittl Transitin Rgin," Fractur Mchanics: Twnty-furth Vlum, ASTM STP 1207, J.D. Lands, D. E. McCab and J. A. M. Bult, Eds., Amrical Scity fr Tsting and Matrials, Philadlphia, 1995, pp T. Iwadat t al., "An Analysis f Elastic-Plastic Fractur Tughnss Bhavir fr JIC Masurmnt in th Transitin Rgin," Elastic-Plastic Fractur: Scnd Sympsium, Vlum II-Fractur Rsistanc Curvs and Enginring Applicatins, ASTM STP 803, Amrican Scity fr Tsting and Matrials, 1 983, pp. II II-561. K. nizawa t al., "JAERI cntributin fr th IAEA crdinatd rsarch prgram phas III n ptimizing f ractr prssur vssl survillanc prgramms and thir analysis," JAEFLl-M , Japan Atmic Enrgy Rsarch Institut (ctbr 1 993). CRP Sub-Cmmitt, "Manufacturing Histry and Mchanical Prprtis f Japans Matrials Prvidd fr Th Intrnatinal Atmic Enrgy Agncy " Japan Wldmg Enginring Scity, ct JSPS 1 29 Cmmitt, "Standard Tst Mthd fr Fractur Tughnss within Ductil- Brittl Transitin Rang," Japan Scity fr Prmting Scinc, R. Chauadi, "Fractur Tughnss Masurmnts in th Transitin Rgim Using Small Siz Sampls," Small Spcimn Tst Tchniqus, ASTM STP 1329, W. R. Crwin, S. T. Rsinski, and E. van Wall, Eds., Amrican Scity fr Tsting and Matrials, Philadlphia, 1 998, t b publishd. ASTM E399-83, "Standard Tst Mthd fr Plan-Strain Fractur Tughnss f Mtallic Matrials," Annual Bk f ASTM Standards, Vl.03.01, Amrican Standard fr Tsting and Matrials, ASTM E "Standard Tst Mthd fr Jlc, A Masur f Fractur Tughnss " Annual Bk f ASTM Standards, Vl.03.01, Amrican Standard fr Tsting and Matrials, JSME Sl-1992, "Standard Mthd f Tst fr Elastic-Plastic Fractur Tughnss Jlc (Supplmnt, I st Editin)," Th Japan Scity f Mchanical Enginrs, Fb., ASTM Draft 1 5, "Tst Mthd fr Th Dtrminatin f Rfrnc Tmpratur, T, fr Frritic Stls in th Transitin Rang," Rv , ASTM. M. Nvalainn and R Ddds "Numncal Invstrgatrn f 3 D Cnstramt Effcts n Brittl Fractur in SE(B) and C(T) Spcimns," NUREG/CR-63 17, UILU-ENG , July K. nizawa, t al., "Invstigatin n th Evaluatin f Clavag Fractur Tughnss Using PCCv Spcimns in th Ductil-Brittl Transitin Rang f Ractr Prssur Vssl Stls," JAERI-Rsarch , Nv J.D. Lands and D.H. Shaffr, "Statistical Charactrizatin f Fractur in th Transitin

37 (18) ( 1 9) (20) (2 1 ) (22) rgin," Fractur Mchanics: Twlfth Cnfrnc, ASTM STP 700, Amrican Scity fr Tsting and Matrials, 1980, pp K. Wallin, "Th Scattr in KlcRsults," Enginring Fractur Mchanics, Vl. 19, N0.6, pp.l085-l093, T. Andrsn and R. Ddds, "Spcimn Siz rquirmnts fr Fractur Tughnss Tsting in th Ductil-Brittl Transitin Rgin," Jumal f Tsting and Evaluatin, Vl. 1 9, 1 991, pp K. Wallin, "Irradiatin Damag Effcts n th Fractur Tughnss Transitin Curv Shap fr Ractr Prssur Vssl Stls," Intmatinal Jurnal f Prssur Vssl and Piping, 55(1993) pp K Wallm "Validity f Small Spcimn Fractur Tughnss Estimats Nglcting Cnstraint Crrctins," Cnstraint Effcts in Fractur Thry and Applicatins: Scnd Vlum, ASTM STP 1 244, M. Kirk and Ad Bakkr, Eds. Amrican Scity fr Tsting and Matrials, Philadlphia, Japans Elctric Assciatin, "Fractur Tughnss Tst Mthds fr Nuclar Pwr Plant Cmpnnts," JEAC (in Japans) Tabl I Chmical cmpsitins f matrials usd in this study. (Wt.l) Tabl 2 Matrial prprtis at rm tmpratur fmatrials usd in this study. Tabl 3 Nutrn irradiatin ffct n matrial prprtis fjrq