ML20117J451

Forwards Exhibit 13 Re Analysis of Inaccessible & Potentially Rejectable Defects in Plant for Insertion in Transcript

ML20117J451
Person / Time
Site:	Perry
Issue date:	05/02/1985
From:	Monick R ACE-FEDERAL REPORTERS, INC.
To:	NRC
References
CON-#285-032, CON-#285-32 OL, NUDOCS 8505150105
Download: ML20117J451 (1)

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- - - - . -

c ACE-FEDERAL $ss$n,aggsESI 2 REPORTERS, INC. (202> 347-3700

STENOTYPE REPORTERS t

-> May 2, 1985 I

TO: The Nuclear Regulatory Commission IN THE MATTER OF: The Cleveland Electric Illuminating Company, et al Perry Nuclear Power Plant Unites 1 & 2 Docket No.: NRC 50-440/50-441 April 30, 1985 Enclosed please find Exhibit 13 of the above referenced proceeding. Please insert the enclosed into your copy of the transcript.

We apologize for any inconvenience this may have caused.

Y

, Rob (rt J.~ Monick

s. Encl.

0+5 NRC:

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I (

1 8505150105 850502 PDR ADOCK 05000440 A PDR e . .. . - .

v

,, ~ .. f At3 641D52-1 Final Report b,209 OCCf ng /CfUTCC/,inC ENGINEERING CONSULTANTS

,. 795 SAN ANTONIO ROAD . PALO ALTO . CALIFORNIA 94303 (415)858 2863 .

k_.- s NUCLEAR RESilLAT98Y COMMiss10N

( Dr.chl No. W 0 i e- -

ja the matfor of 3 9,99 ICENTIFIED s App!!sant RECEIVED in!*rieser / REJICTED C

. t " ATC -

owr M Witnass P.gorter a

l ANALYSIS OF INACCESSIBLE AND P0TENTIALLY REJECTABLE

' f.

.u-DEFECTS IN PERRY NUCLEAR P0h'ER PLANT W ,O (G

l Prepared by Warren P. McNaughton Geoffrey R. Egan

• Jeffrey D. Byron Aptech Engineering Services, Inc 795 San Antonio Road Palo Alto, California 94303 Prepared for p Gilbert Associates, Inc.

L Q Post Office Box 1498 Reading, Pennsylvania 19603 Attention: Paul B. Gudikunst

.{^

g jfSE[ojjj July i n P

i S:rvices in Mechanicaland Meta!!urgical Engineering, Welding, Corrosion, Fracture Mechanics, Stress Analysis

r .- ,

QUA,LITY ASSURANCE VERIFICATION RECORD SHEET

+s'

Title:

Analysis of Inaccessible and Potentially Rejectable Defects in

, - Perry Nuclear Power Plant 1

Originated by: / 6-26-83 Warren P. McNaughton Y kD. ' 6-26-in Jeff' rey D. Byron ,0 ,

Verified by: [' .

YY\ d 6 3 n [effre , to

(

j, Approved by: 7-2.0-C l Geoffrey R. Egan -

l' Quality Assu~rance Approval: // [ h f ([B3

. bel 1C.Cipolla i

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i i

/

j TABLE OF CONTENTS

SECTION. TITLE PAGE SYNOPSIS ii 1 ' INTRODUCTION 1-1 References 1-4 2 LANALYSIS METHODS 2-1

.2.1 Fracture Mechanics Backoround. 2-1

-2.1.1 Linear Elastic Fracture Mechanics 2-3 2.1.2- Elastic-Plastic Fracture Mechanics 2-5 2.1.3- Limit Load Analysis 2-6 2.1.4 Summary .of Fracture Mechanics Background 2-7 2.2 Fatigue Loading _ _2-8 2.2.1. Analysis Method (2-8.

2.2.2 Crack Growth Rate Representation . . al-2-9

- References 2-10 3 ANALYSIS OF STRESSES 3-1 3.1 Secondary Stresses 3-1 O 3.2 Primary Stresses 3-4 f(V 3.3 Combined Stresses 3-7

-l " References -

3-14 4 FATIGUE CRACK GROWTH RATES 4-1 References 4-8

'S FRACTURE TOUGHNESS AND STRENGTH 5-1 5.1 , Introduction 5-1 5.2 Fracture Toughness: . Background .

5-1 5.3 Toughness Values for Containment Welds 5-4 5.4 CrackOpeningDisplacement(COD) Values 5-6 References 5-8 6 CHARACTERIZATION OF FLAWS 6-1 6.1 The Effect of Slag Inclusions on Structure Integrity 6-1 <

6.2- Defect Interaction and the Modelfng of Defects 6-8 6.3 . Digital Enhancement Methods Used in the Present Analysis' 6-12 6.4 Results of Flaw Characterization 6-13 O7 RESULTS OF ANALYSIS 7-1 V 7.1 Results.of the Linear Elastic Fracture Mechanics 7-1 I (LEFM) Analysis 7.1.1 Indications in Seams 1-1 and 2-1 7-1 L 7.1.2 Weld 1-4 7-3 1

.- .,(ak p.h .

' ~

) _ 11 9 TABLE OF CONTENTS y (Continued)

~

k SECTION TITLE' PAGE

'7.1.3 -Welds 1-7 and 1-9 7-3 7.2  : Limit load ' Analysis 7-3'

.7.3 Elastic-Plastic Fracture Mec'1anics (EP.FM) Results 7-6 References 7-19 8 CONCLUSION AND

SUMMARY

8-1 g APPENDIX A: Supplemental Toughness Data A-1 APPENDIX B: Background Inforrration About Digital Imaging B-1 Techniques _

APPENDIX C: Details of Flaw Characterization Work .-

C-1 APPENDIX D: Controlled Documents D-1

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X. SYNOPSIS

.QJ'

( yry

. ( /. This' report' summarizes the results of fracture mechanics and f atigue

. evaluations which were performed for the Perry Nuclear Power Plant Units 1 and 2. . These evaluations were perf ormed .f or several regions of the

' containment structures as. f oi lows:

s I" I" e inaccessible locations in weld Joints-1-1 and 2-1 which had weld Indications ' 1 r,

, .-- e Three inaccessible weld locations In Joints 1-4,1-7, and 1-9

- =

. 5-in these last three locations, incomplete radiographic information ex'Ists to esta'blish the existing def ect size (for example, whether or not f ul l repairs were made); however, suf ficient data do exist'to characterize the g ' maximum extent of Ja! defect that could remain in the structure and this O potential defect has been analyzed.

The evaluations that were perf ormed required three types of input data.

These_ data were stresses, both applled and weld res! dual stresses, fIaw gecmetries and material _ proper _tles. .

, Recently, reviseJ;Lsiress data were suppLled_by_G!lbert Assoclefes_f.or_the

,j' . containment. Bounding cyclleal and steady state stresses were incorporat'ed to provide an analysis that results in a conservative evaluation of the weld Indications. A conservative residual stress determination was also made by asseg g g e appropriate experimental data.

Flaw data were obtained frcm radiographic enhancement techniques perf ormed j - on supplied radlographs. The radiographs provided contain def ects which I ill . were deemed rejectable according to the criteria of ASME Boller and l Pressure Yessel Code Section lil, Subsection NE-5320. These techniques i

~

, ~ . were used .to provide accurate sizirg of the Indications. Such 1

,L

.' fii V: ~

.~

G determinations.rernove some of the conservatism which has traditionally been r used to assess structures with defects in the absence of actual flaw size

. da ta . .

,y-Material _ properties such as stmgth, fracture tqughness and crack g_rowth rates were determitieLusing_aya1Lable_Certi f led _Ma.terlaLJestJeports and by. comparison to generic data obtained f ecrn the open IIter_ature.

- The results. confirm that crack growth by fatigue is smal' over the design

~

plant ilfetime, even assuming conservative stress levelt, bounding initial

- ^ flaws and worst case crack propagation rates. Furthermore, it is' shown that the applied stress intensity values reached during and af ter such growth are less than the critical value to cause structural failure'. [The conservative result of the l_Inear elastic fracture mechanics methodof'oly

,, - used in this work is then conf irmed usinggh_elas1Lc-plattLc_and net section ' collapse (or llmit load) methods. It. is shown that relatively long f)

.;v and deep flaws can be tolerated even with the conservative assumptions L . which have been made.

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a V ,

1 .

3 I-l N

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Section 1

()

INTRODUCTION

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. A review of radiographs for the Perry' Nuclear' Power Plant Units 1 and 2,

..' has found-certain' containment welds that contain potentially rejectable

. Indications, when evaluated _per the requirements of ASME Boller and Pressure Yessel Code Section li t, Sub'section NE-5320 (1-1). This subsection provides accept / reject conditions based on workmanship

-standards. The radiographs can be grouped Into two logical regions of Interest. - -

5 The first group of weld indications are.found in radiographs associated with weld joints 1-1 and 2-1. These weld locations are !naccessible. They

/7. -are located in the containment wall (see Figure 1-1) In double sided butt

). welds and are covered on the Inside of the containment by a doubler plate.

Indications have been found that would be considered rejectable by ASME Boller and Pressure Vessel Code, Section 111 criteria. These radiographs, determined by Level 111 evaluation to contain rejectable indication's, include 21 radiographs of weld 1-1 and 43 radiographs f rom Inaccessile -

regions In weld joint-2-1.of Unit 2. The, weld imperfections on these radiographs were sized using enhancement techniques and conservative interaction criteria. The stresses in Units 1 and 2 are Identical, so that bounding defects'were developed considering both, Unit 1 and 2 indications.

The second group of Indications consists of three spectfIc weld IocatIons in joints 1-4, 1-7 and 1-9. Weld joint 1-4 has a defect at location (79-80) 11-12, which has been sized at 2.3/4" long and 1/16" in height. It O- an r= to be aiete eeiemiae+>oa (co-'39, ^++ c8 eat 4)-

In weld joint 1-7, at location (110-111) 25-26, the film shows a questionable Indication. If thls location were accessible the disposition

. would be to grind and retake. In addition, the film,Is in question because 1.

1-2 g:

Q) ll _., Elev.

575'-10"

, , ,,G I'd . /

/ -

Containment Shell Doubler Plate (Inside Surface)

(Inside Surface)

Containment Shell Doubler Plate (OutsideSurface)

(Outside Surface)

N Base liner Concrete S N jofnt 1 /\ Elev. f. Foundation Mat

, N 574'-10.187" *-

. T'T Cy

i s

N  ;

C) n l

l 1

L) uj Figure 1-1 Typical Horizontal Weld Joint (1-1shownhere)

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)l It does not cover the f ull Indication. At maximum, it would be a 9/16" g long slag l ine (CD-139, Attachment 3) .

I V 'In weld Joint 1-9, at location (134-135) 24-25, the f ilm has no y Indications, however, the adjacent flim did have repair which extended into this station. A slag incl _ slon may still be present, maximum length equal to -1 ~ 3/4" (CD-139, Attachment 3) . These locations are also inaccessible and the existing radiographic Information can be used to provide worst case estimates of defect size remaining in the structure, or of the possible incomplete repairs.

2 AlI welds have been fabr!cated us!_ng E7018 weld metal. The defects are *

.p , c go y contained in the weld metal . except In joint 1-4 where the .f.

Indication is in the base material-SA516 Grade 70. The concern in eAch case _ is that the indications if unrepair_ed,_may_l.ead_to_ ear _ly_structur_al fALLute This report addresses that concern and does so by evaluating the a potential for defect growth by a.f atigue mechanism and concurrent or subsequent failure by fracture.

I The remainder of this report consists of six sections. Section 2.0 routlines the analysis methods that have been used to evaluate the defects.

? The next four sections introduce and discuss input to the analytical model.

They are: the evaluation of stresses-both epp! led and residual (Section y 3.0), characterization of materla! properties (Sections 4.0 and 5.0), and results of the enhancement work performed (Section 6.'0). Section 7.0 provides the results of the analysis perf'ormed. Conclusions and summary are provided in.Section 8.0. Throughout the report, ref erence is made to

( documents which have been used to provide Input Information to the '

analysis. These documents which are considered controlled under the requirenents of the Aptech quality assurance system are designated

- 69 v Controlled Document (CD) and are ref erenced in Appendix D of this report.

I b

9

o.

,' 2-1 P

SectIon 2 L

ANALYSIS METHODS y, +

, .\s't -

k The foilowing sections discuss those aspects of fracture mechanics and

. f atigue theory which were used in the analysis of the present problem. A prerentation of general fracture mechanics background (2.1) is foi!cwed by a discussion of methods of analysis to assess _f atI_gue growth (2.2).

2.1 Fcac+nre Mechanics Backcrnond Thefa!!ure_b_ehaviorofstr_u_gtures_undermonotonic(slowlyincreasTngJ.

loadpg can be elassifled into three regimes In which_a_spect fIc_ type 'of failure' mode is appropriate. These three regimes cover brittle fracture, _

ductile fracture and plastic collapse. The disciplines required to assess e these' regimes are: -

b) -

e l'inear Elastic Fracture Mechanics (LEFM) - The structure f alls In a brittle manner and, on a macro scale, the load to f ailure occurs within nominally elastic loading.

e Elastic-Plastic Fracture Me'chanics (EPFM) - The structure falls In a duct!!e manner, and significant stable crack extension by tearing may precede ultimate fa!!ure.

o Fully Plastic Instability (Limit Load Theory) - The failure event is characterized by large deflection.s_and_plas_t,lc ,

,sttains-associated with ultimate strength coll _ apse.

tsjG A diagram that shows the relationship between critical or f ailure stress and flaw s'Ize for the three f ailure modes is given in Figure 2-1. The shape and position of the f ailure locus wl!! depend onithe fracture f

toughness (K Ic ) and strength properties (c/) of the material, as wel!

- e as the structural geomLtry and type of loading. .

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N ::Q ' 2.1.1' ' Linear Elastic. Fracture Mechanics (LEFM).

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37 .

y The principles of linear elastic fracture mechanics (LEFM) are n;

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Jappliedito _ assess . quantitatively the conditions for br.lt_tLe_ttactute_m 1 Brittle. fracture consists of two separate events: (1) the inff_lati_on of a

[~ , ', $ crack,iand (2)7 'the subsequent ' propagation of the crack to comp _lete f ailure.-

'4 Each.of'thesa~ events _, initiation and subse_que g ropagation, has different.

i characterist_lcs. ..For fe_rrltic structural steels'of the SA516 type and n

. car.-bon _ manganese _ke.Ld._mefal_of the E7018 class, the resistance to 'a 7propagatino fractur_e_J_5_usually_ lower than the resistance to fracture L initiation underr_ slowly _appj_ledloa.ds., This is tocause steels of this type

~

are . se ns i tge__to_l.oa din g._r_ ate ; the h_lgh loading rates associated with a~

running crack lead to hlgher,_yleid sttength and, hence, Low.er_y.alues,f fracture toughness. In constant load situations, therefore, continued' crackfpropa.gation_ is expected once the fracture has initlated. For th is

~

reason.; no' attempt is made to evaluate the characteristics of the

. propagating crack af ter it has initiated, and the cr_Iterion l of fracture

_InitIntf ort i s used_as_thepfinition of failure In' the fracture analyses.

. Fracture Initiation oc. curs at a_ dele.ct when the ctack_.dr!.yIng_for.ce exce_eds i

the materlalJs inherent resistance to crack initiat!_on, or frac._ture t touchness. The crack : driving force Is alyncil.on_of_fAe_ stresses _actina on

,. ~ the_def ectand_th_e_gecree_try _of the_de_f ect. . The stresses which act on the def ect. Incl ude .both prJ. mary, (appl ied) stresses and s.e.co_nidary (,lniernal)

I stresses. Examples of secondary _ stresses are residuaLsttesses and th.ermal .

' stresses that are in equ!!lbrium across the section.

The manter in which_a

. structure wIl l_f_all_w.LLLbe_de_termi.ned_by_the_1.nteract_lon_o.f the def ect

' gemetry.- loading, and mater tal toughness.

_in:IInear elestic fracture mechanies,-the most usef ul parmeter _for .

characterizingje_behav, lor _oLctacks ls the stress intensi,ty_f actor K ,

j which describes 'tha maenItu.de_of_ singular _ stres.ses__eh_e.ad_of. a_cc.ack _Ln a L :llne.ar elast!_c body loaded in tension. For loading _ttor;nal,lo_the crack p.l.an.e (Mode I), frac _t_ute_inItiatton occurs when the_ appiled stress h Intensity f actor, K , ~ equals _ot__ exceeds some critical. value, which is l 5 Qi

, .,o w ^.

2-4 -

t M g'; ~

. called the fracture toughr;e.ss of the material.

_ The applied stress

,' . Intensity facter can be_ written in the form:

g ,- - - -

,/ K = Cc/na~ (L 1 )

I where o Is'the acting stress, a is the characteristic flaw dimension, and C is a parameter which accounts for the flaw shape, structural gectnetry, and tie type of Icading. In general, C is a function of a and in many cases must'be evaluated numerically. Fracture wilI occur under cuasi-static

~_

. . loading when, K

i 2M Ic (2,2 )

(i.e. , when the appl,J,e_d_s.tr,ess_ t

,f,ntens_Ity f actor _ equal _s_or exc,eeds t,hej,'

static f racture toughness, K ). This means that the occurrence of

_ Ic ~

pa.cture_.lscontrolledby: _ (1) the stress level, (2) the _f_ law size, and_

b]

i i

'[ (3) the fracture toughness. For small fl'aws, low stresses and hfgh toughnessf the appiled K_w!!I not reach K i

Ic, and fract_ure wIII not occur.

These rel_ationsh t os are re_!__evant for_ material propertle_s_de_t_erm_l i.ed_ f unde.r plane strain, linear elastic conditions.

To determine the sign!'f f cance of the Inaccessible defects in. question, it is necessary' to know the material fracture toughness, acting stress level

• and. actual distributlen of defect sizes and shapes. Knowing any two of ,

these parrrneters, one can solve for the third. For example, the_crItIca,I flaw size to cause,fallure is calculat,ed fr_om:

2 1 (Kle \ l a = -2 (2.3 )

e nC \ cc /

if both the toughness (K ) and the stress level (c ) are~~known.

\o.

ic - - ~ ^ ~ ~

c

, v; Conversely, the critical appf led stress as a f unction of crack dep.tLcan_be computed from, y

r .

1

,, s p , a y J.

.U,. 2-5 ,

K n ic o' 8

d. c CG (2.4)

II.

1

,_ j _' A l th ough; th 'ese t co nd i t i on s most ap propr i ate l,y_de scr.lbe_t.h e_beh avlor_of_l ow

~

. toughness, hIgh strength materia _I s__where l LttLe_ duct.l.!_Lty _ptocedes

• fracture,'the use of K as_a__ toughness _. meas.ute__f.or_elther SA516 steel or i- '

Ic E7018 weld metal ensures a conservative estimate _of._qr_Itical flaw size for brittle fracture, since no account is taken of the increased toughjless

. which results from post-yield (transitional) behavior, ,1,,n.cor por_a_t_! n g .

, ' transiti_onal behavlor with more pre-fracture ductility gives increased

, toughness levels and decreases the susceptibility of the structure to fractur_e from_a_giv.ettsized flaw. The terspetature_ dependence of toughness properties means that at ambient or higher temperatures, both SA516_ st. eel En'd E7018 weld _ metal, are abob their lower shelf values on a fracturef, energy versus ternperature curye. .

This in turn Impiles that the use of standard elastic: fracture mechanics will be conservative. Elastic plastic p crack opening displacement (COD) concepts have been used as a check on L

structural Integrity. Elastic-plastic fracture mechanics concepts are discussed in the next section.

2.1.2 Elastic-Plastic Fracture Mechanics (EPFM)

The basic principles of EPFM have been developed over several years (2.L 2-2. 2-4) and one national standard exists for gr,achpening

. d,l_splacement (COD) testing _(2-5.) . This method.uses critical CCD values (as

. measures of the material toughness) wh'Ich are not available for the actual fleid materfal. A revlew of the iIterature (notably 2-5) was made to check the appropriate material characteristics. .

One of the best methodologies for EPFM evaluation, the British Standards a

n, Institution published document PD6493:1980 (2-1), ut!!!zes crack opening displacement (COD) concepts. Inprinciple,theer,l_tt, gal _conditionjs  ;

reached when the applled K or C00 (6) reaches the resistance !_evel_of toughness

~

necessary to cause fracture (K or 6 ). The COD method._f s Ic ~~

- completely

-~

compatible --

with the LEFM approach ( ) and can be used in place

, , c tt- ,

I . 2-6 ,

[:. ] of the K method. For appiled stresses well be_ low yiel_d, Ec a ( )

, 6

• f log,sec (2.5)

J where 6,Is 'the developed COD; e and o are the yleid, strain and yleid E-

' stress of the region in which the def ec is sited; o is the app!!ed

,[ stress; .and a is the half crack length of a center-cracked plate model.

It can' be seen from Equation 2.5 that as o approach'es c , the developed y

, 000 becomes InfInfte. This only occurs for the elestic-perfectly plastic material behavior that was assumed for the development of Equation 2.5.

For materials that work harden, the relationship between 000 and applied

, strain (for stresses above yleid) has been determined by arply_tl, cal, numerical, and e,xperimental methods (2-L. 2 .1.0). .

As in LE'FM, once the stresses and material . properties have been

- characterized, it is possible to determine the allowable flaw size to 3,e] prevent fracture inttlation. It is the4pos.sible_.to_ determine the exp_ected M margin of saf ety between the flaws that may be In the structure and .those necessary to cause fallur_e.

'2.1.3 Limit Load Analysis 8  %

As the size of,a_.cr Lt.lcal_ _ fl aw increases, a regime is entered in which

p. Incre,as!ng ma.terlaL. toughness ao longer can prevent initlation of a crack under monotonic load _Ing. The initiation criterlon_becomes Independent of tgughness_ and n_cw becomes a f unction of the strength properties of the ~

material and the rearning ligament of material. In this regime, a ,Ilm!t ,

load or plastic collapse analysis describes the governing f ailure mode.

For limit load analysis, the critical stress to cause fa!!ure is calculated from an Interaction relation common in the analysis of steel structures.

] This relationsh!p between the_ appl _I_ed membrahe l_ ca

~~

(M) at f ailure in a bem or plate with a rectangular cross-section ist m

F

+; ,

r. .

2-7 i s'- ,c ,

?Y 2~

- fP\

+;{ M \.=

. 1 Pg Mg (2.6) 3 >

where P and M are the applied loads, and P and M are the Ilmiting v

values 'of- P and ,M. The munitude of P _and M are functions of crack length ,a_, flaw gemetry and mater _laLpr_operties.

,. The limit load of P is " determined from the gecrnetry of the section and the material properlies. Af ter the_tedustion_in area due to the flaw is

'accounte'd, the iImit Ioad_can be expressed In terms _of a__lImit stress and.

the geometric variables.

The limit stress is normally_theataferl_aLypid

' strength ~when the material behavior is assumed to be Q

elastic perf ectly-plas. tic. However, for mater _ Leis _which_exhJbit ._

sIgnificant strain hardening, o couldbe_somewherebetweenyleidandjj ultimate. strength, and the appropriate value to _ use_sh_oul_d.,_begtermined by j', tests.

h . .

For -this analysis, we use-a flow stress which ,Js the average of the yleid

,and ultimate strengths, f.e.:

r

, o -= ' (a +o )/2 (2.7) 4 y uts '

a-where 4o - is the flow stress, o the specified minimum yleid stress and s' Y l o .the spect fled minimum uttImate strength.

uts 4.

Once the limit conditions have been calculated, Equation 2.6 and the expressions for a'pplied membrane stress as a function of pressure and j applled moment can be used to determine the failure condition.

, e a

A limit load evalua_tl,orLlles i beenJnade In conjunction with LEFM methods in i the present case.

2.1.4 Summary of Fracture Mechanics Background The failure behavlor of structures under monotonic loading can be

- ,- - - , . ,..--w.m..,.,,.,n_ , , , , , , . . .-...,---,nn.-.. . . , , , , _,.,n-n ,, ,,.,,-,_,,,,,.-.,_n,,..,, .n_w,,--_ , , , .

, 2-8 9

.; M cl assif ied into- three regimes. Of these, linear' elastic fracture mechanics M',. , -has r,

been determined to be most applicable to the" current material and

,  : service conditions. Boundj_ag_ studies based on elastic plastic and plastic

, {N.; _ limit load analys.es have also been perf ormed.

s .

' 2.2 Fa+1 gun t_nading 2.2.1 Analysis Method The preceding discussion addressed the case of monotonic loading. In the present case, there are a_smalI number of cyc!lc loads _which may occur on 2

the containment structure. This section discusses the way in which these '

loads can. be evaluated in the light of the previous discussion. ' 7-

..u-Fatigue evaluation,__ based on fracture mechanics, assumes that Initial flaws y e present of size a and I tAat._th.e_ll fetime of a_componen,t_ !s that required f or' a cr_ack to_ grow from the initial s_f ze,g a , to the critica G .sJ2e, ac. Cra.gLgtowth rate data may_be_cor. rela _ted._to_tAe_ crack tlp stress intensitylactor ran,ge_.(AK) for th_eJ ven I load cy_cle _Ln._the following form:

I da/dN = f(AK) (2.8) n- where da/dN is the crack growth per load cycle. By Integrating Equation 2.8 with the appropriate component stress field to calculate K, the number

p of cycles, N, (residual 'Ife) for a crack to grow frc~ma to a is I C computed from: e 9

i-

=

fc da.

.N (2.9) da/dN Ja Q

uj l

l The final _ flaw _ size _ expected _a_t_the_e.nd of the_ design _ life, a , can be f

de_te_rmined by integrati_nLEguati_on 2.8, using the appropriate stress distribution to calculate X, and the number of total design cycles N from o

9

ir *

,. 2-9 -

- r *. - a

-I > rf da 8 'k N -

=0 (2.10) da/dN O s i3 a where Equation 2.10 is a transcendental expression involving a and must

" ' ' ~

be solved by an iterative process.

2.2.2 ' Crack Growth Rate Representation

~

Many.agipirical relations _to_exptess_daldN behavfor have_been. proposed; the earliest and most well known is_the PaGJ.ule (.2 .U.) which takes the form,

=

da/dN CAK (2.11 )

5 where C and n are constants determined from the data, and AK is the.cange of applied stress intensity factor computed from the minimum and maximum stress in the cycle:

O l, . AK = AK - AK (2.12) min max The advantage of the Paris relation is that it is simple in form and it j 'ffts experimental data well In the middle range of AK. A di.salv_an_tage of

's the relation' ship is that It does not direcp_ account for mean stress-

' ) which can accelerate -

offacts (R-ratio offact where R = Kmin/K max

• ~ -

fatigue crack _propagallon. However, these ef fects are accounted for in the choice _off experimenta_I data used in the modelingJroced re. )

i

g

? -

2-10 Section 2

(! REFERENCES e

4 je\ ,

, 2- 1 ' Wells,.'A.A., " Notched Bar Tests, Fracture Mechanics and Brittle

. Strengths of Welded Structures," Houdremont Lecture 1964,

,, Br'+fth Ee.l. % Jeormaf, No. 1 (January 1965). ,

' '2-2 Sumpter,J.D.G.andC.E. Turner,"FractureAnalysisinAreasof High Nominal Strain," Erneaadingc Sacnnd In+arnn+f nna!

cnnfaranca en Peacen-a Vaccal Tachnnlogy, San Antonio, TX (October 1973).

- =

. . u. .

2-3 ,Egan, G.R.,'"The AppiIcation of Fracture Toughness Data to the

' Assessment of Pressure Vesel Integr ity," Pencandi ngs Sacnnd In+arnatfanai ranfaranca on Praccura Vaccaf Tachnalngy, D) - San Antonto, TX (October 1973).

Qf -

2 Burdekin, F.M. and M.G. Dawes,. " Practical Use of Linear Elastic and General Yleiding Fracture Mechanics With Particular Reference to Pressure Yessels," Ennfaranca an Prac+ feat Anniren+fnn of, Frac +nra Mach an t es fo Prne cera Vacca t Dactgn, Institution of Mechanical Engineers, London, UK (1971).

2-5 British Standards Institution, " Methods -for Crack Opening D!s-placem6nt (C00) Testing." (1.972).

2-6 Stuber, A., J.WelIman and S. Rolfe, "Elghth Progress Report '

! .- on AppiIcation of the C00 Test Method to the Fracture-Resistant Design of Pressure Yessels," far. Suheer++6a nn

' 3-F Hac+ f ve U+ t I f 7 n+f on af. Y f a f d S+ rang +h nf. fha E,yRC, (February 1980).

British Standards Institution, "Guldanco on Scrne Methods f or

^

7 L

4

c : n "I - ,

2 c: .

j .0 .the Derivation of Acceptance Levels for Def ects in Fusion T- -

. Welded Joints," Published Decument PD 6493:1980.

,/ \

4 ')

t l2-8 'Egan, G.R.,'"Compatability of Linear Elestic (K ) and C

General Yleiding (COD) Fracture Mechanics," Eng 'nnering Fracture Mechanics, Vol. 15, (1973).

2-9 Merkle, J. , " Analytical Applications of the J Integral," ASTM STP 53 6, Ama r t ca n Sec t e +v fcc Test i n g and Mn +ar I n ! *, (1972).

2-10 Hayes, D.J. and Torner, C.E., "An Application of Finite Element Techniques to Post-Yield Analysis of Proposed Standard Three-Point Bend Fracture Test Pieces," In+arnational Jnurna! ci.- !-

""~~

Frac +ere, Vol . 10, ( 1974) .

. 2-11 Paris, P.C. , M.P. Gomez and W.D. Anderson, "A Rational Analytic 7 J( ) Theory of Fatigue," Ihn Tennd in Encinaaring, Vol .13. No.

\' 1 (January 1961).

9

s. ,

l 4

r Om s ,

3-1

?.

Section 3 1 ANALYSIS OF STRESSES O

, The analytical model discussed in Section 2 requires as input the character!zation of the stress state present in the containment shel!

courses. This section discusses both the primary and secondary stresses.

The pr_lpary_s_ tresses are the appl ied stresses associated _wJ.th_ dead _f. cad and cyc!fc service stresses. The secondary _s_ tresses, in_tAls_. case, are the residual stresses due to welding.

3.1 SarnnM rv S+rassas ~h

..w-The welds under consideration are double sided butt welds. A literature review was performed to characterize the resulting distribution of residual stresses in this type of weld. The weld has stress ccmponents transverse to the weld and longitudinal or paral lel to' the weld, each with through-thickness distributions. A schanatic of these app!! cable distributions is shown in Figure 3-1. For this analysis the flaw location was assumed to.be at the centerline of the_pl.a.te_which is the location fer the maximum transverse _ stress. The ,f_l.aw location _was_a.l..so_ ass _umed_to_bo at y

the location of maximu_mpgl_t_ud!_naLstr.os.s.. The transverse distribution L through-the-thickness wil I vary as shown In Figure 3-1.

F Figure 3-2 shows single sided butt weld residual stress data transverse through the thickness. This figure is a-compos!,t_e of normalized experlmontaLdata . based _primarily on work done by Ncedel l and Hal l (2-1.) .

In their work, the base plate was ASTM A212 Grade B (precursor to SA516 Grade 70) with double-V butt welds of E7018 material. The applicable thicknesses tested were 1 inch and 1_5/8 Inches, requiring 12 and 30 weld

. pas se s._res pectlvol y. The two thicknesses demonstrated similar through I thickness transverse stress distributions. Also shown in Figure 3-2 are residual stresses measured by others (3-2, 3-3.) .

(

.I -

, 2

. . 3-2 hI

(" Compression Tension ll Tension ioS

?.

(a) .(b)

Compression Tension 1*

8 --

t (E) ,

m Figure 3-1 Schematic Standard Assumed Residual Stress Distributions in Plates Without Fixed Ends for a Double-Sided Butt Weld: (a) longitudinal, (b) Transverse, and (c) Transverse Through Thickness.

i  ; , ' i; ,  !

- hi 3

,,4

.~'~

)

n s w s .

o ) s h n e -

_. k < s wo k n

0 0 0 0 0 0 ) f h ) c -

_ 0 0 0 0 0 n l s n i 0 8 6 4 2 2 4 6 8 1 w a w h -_

1 - - - - - o h f o T

- ,. > - - - h l h T , - r

- - s t a s h g

m ' f r s h f u

_. x' l a w sr o t l o r

f a

- h ( h h s -

( o ( T .

s , d w(

e 1 e ) 2 e

_. n ' h n s e c d w e r k e c _ Y 0 c t e o c e o h h e v i

h T _

/

[' d_ 2 i n c s i P -

n ol f t P s

n a

h , l , U f l , r g / V a V V T u -

/ e V, V ( e e

, , h o - /

r s l 4 l l s h - s e b e 6 1V b a d T u l u n l

/ n o bE e o i e e .

4 k

c D u u l D S H s , o o b .

r ~

~ i " D D u " t e ' h 8 o "8 1 t

~

~

v s - T / " " D / u s 5 1 1 S , B

)

n / A l "

' 1 , 3 a l ,

,1 1 d r ' a ) ) - e W

- ,2 2 , , 3 d nm.(x)(

f T ) - - ) ) ( i -

- t 1 3 3 1 1 S

)

e 0 n - ( ( - - n d

6

• e c

3 3 3 o e

_ i / r ( h h ( ( t r

l g

t t S - ' e l. a a l l e n

w. / P m ml l l l i e N s a a a a a f

S l

g '

s

' 1 1 K K  !

! d n f n  % s -

d d d d d a o

, i S

s n n n n n

( 0 a a a a a l s -

a e d

1 - A 8

. l l

t t t t l l l l h

t s

s flI l

e e a a e e n er

.W ' ,. d g g d d e r g g r r s t o e e o o o

~, t t

u

'~ ' l f L L N  !

! R S

l B /' 's a

• A Y* e a u

d 0

0 0

0 0

0 0

r e4 0

/o 0 i

s e

. 0 8 6 4 2 2 4 6 g 0 R 1 - - - _ 1

' 2 3

g % 5 yo u" '*,u ymE e r

u g

i F

p,' s i ,

f "- '

l i

q4 .

i

.s, v. :c .

o, .

,. m v,-

• t iL .

34 i l ,

m

1. From these data a simplified through thickness transverse residual stress L distribution was developed. This is shown in Figure 3-3. The distribution r l%- assumes yleid level residual tensile stresses at the surf ace through 10% of

' h the thickness. The tenslie stresses then decrease to compressive residual

'v stresses. equal to one hal f yleid at the mid-thickness. This distribution e is then reflected about the centerline of the double s!ded butt weld to

,, achieve a symmetric and complete distribution. Since any residual stress t

, distribution musLbe_sel f-equilibrating, .the choice of values taken here  !

will be conservative. The sum of the tensile portions Is' larger than the l compressive portions and the maximum values have been assined uniform except in the through thickness direction.  !

.  ?-

3.2 .

Pe t u rv s+r =u= < '

The primary stresses for analysis have been obtained from unit stress - i

~ e calculations for. Joint 1 (CD-130) for welds 1-1 and 1-2; and from joint 5

.O (CD-139) for welds 1-4, 1-7, and 1-9. The stresses in welds 1-7 and 1-9 l

Q.> t

[

1.

are substantially less than in weld 1-4 (see CD-139 attachment 6). A bounding case has been formulated for welds 1-7 and 1-9 using ths stresses -

In joint 5 (elevation 592'-2"). These stresses are summarized by joint f

number and Load Combination for each joint and the applicable load f

combinations. S ince the 'f I avs_f ound._ ate _or,,len_tedyr_al,J.el ,_to_t,h el r wel ds,  !

I th e __str es se s I nde.,J,o ng l_tu d i na l d i rect i,o n_ap p l y . A schmatic diagre of flaw orientation and applicable stress component is shown In Figure 3-4. [

I The approach taken was to determine _the most_ hlghly_ stressed joint,and lead ,

. combination for.- th.e._ appropriate seam welds. These bounding _ ~- cases could

. l, then be applied to any

.s weld defect, regardless of location., to assure a [

. . . _ _ , , . . _ _ . . _ ~

conservative analysis. In f act, two primary stress distributions were ,

O

~

t obtained for each weld orientation; one for the f atigue analysis and the -

other for the fracture analysis..

y, in order to understand how these stresses were determined, it is necessary

( to review the tabular stress data as it was provided.. Table 3-1 ls the

{ -

I

" ' -~~-----._.__.- ,

r b

~ ~

m _ -

W t Assumed Double Sided Butt Weld Transverse Through Thickness a

% e

~

l 100 -

8

- 100 E

u g _ N .-

s Q..s-g

- \ l / f e I/ -

- /,,___-%

0 Y ~

a 0 0a5l .. n._ . j , ,- ~.l

• i j . ,

- ,, 0 0.1 1 .

,/ 0.9

• M l / .

m' . '

M'

\

f - -

,s'

,N~

} ,,,- -

-50 m e a - ,

s1C -

3 Percent Wall Thickness Figure 3-3 Assumed Double Sided Butt Weld TrEn@erse Through Thickness Residual Stress Distribution

..c ,

, 7 3-6 .

N.;

%)

ht; ,

Y3 p L C Vertical Double Sided Butt Peld -

L, .'

1

- .L t.ongitudinal Stress

),

. 1 y . . .:

i

. w '

f Horizontal x, Double

. Sided

(_O. .

. Butt Weld g

8th I . ,

t 0 '

Figure 3-4 Flaw Orientations and Applicable Service Stresses in Vertical and Horizontal Seam Welds 1 .

4.

aOM S ',

~ 3-7

,,e d y

s m

7' 7

, 1,. ' stress summary for Joint No. 5. From this table one can see that the it- longitudinal,-and circumferential stresses are broken doien into th!rteen t<3 Lload components and are then summarized at the bottom of the table into i'd ,four, load combinations.

These load combinat!ons represent maximum lcading

[ conditions. Some of ~ these load components act at al ! . times, some._act -

. . cyclleal Iv_ over _tha_1_1.f4-of-the plant, and'some may act eniy once. The

~

,, load components f alling into these three categories are summarizad In Table 3-2. For a f atigue analysis the cyclle loads are of primary significance, and are superimposed with the continuous or steady state loads. For a fracture analysis the mes,t_signif). cant loads are those p~roduel.ng the  !

. = l largesges.s, which gv_a,t_lon_of_,Iahle 3-2, 'are those load - ,

comtinations that include the single event loads. '

l ,

t-sl Table 3-3 is a summary of the cyclic stresses that govern the f atig'uI evaluation. There are other cyclic load components. However, the controlling load components in a given load combination are those listed in Tab l e '3-3. Thus, in order to simpilfy the analysis and provide conservative results, alI er!tical load combinat_f ons were evalua_ted for 4

1,6,800 cycy, regardless of which cyclic load components the load combinations include. Table 3-4 shows the appropriate load combination '

components. s For weld sesns 't-1 and 2-1, the stresses taken at joint 1-1 (elevation 575'-1") were used, es shown in Table 3-5. For welds 1-4, 1-7, and 1-9, weld seam 5 stresses were used to bound the appl. led stress conditicn.

-r m - - . _ _ . . .

' These primary stress f ields were combined with the assumed rostdual stress field for the analysis. -

p 3,3 &wh f nad Str a. tent *

()

The total stress considered for the evaluation of a defect consists of the j .. ' sum of theJrJJury and secondary components. ._ Both sets of stressos have been chosen to bound the expected stress state coMervatively. For

( ., , analytical purposes, they have been superimposed with elastic i',,_o._.__m-_m-___-- - - - - - - - - - - - - -

>: r h ~ ,. ,

3-8

h, .

)

b' Table 3-1 I C. .

m =

[r , @' .

=__j* ~. - ~

a.. . w.. i=. Pesa g y Nucun g ,

3 ,; ,3 f:__

c u ew u rio .. .... . . .. e t.x .v e v en. ,

l -

23 m / , u.<

,  ; , i . '

• i i >i '

i yorgf No .

l 'S 3 L Mb C94 M.Y,_b'." - - '

\' '-- Lowrvormt.- G l

$' rt s oi s n Ps e Ctu d ~ G

- - -l.cre GAst - '

> g o , s , 3,, ru s,ec curtis ) roer II 4_ ,

..._.335._.

___ DEA.o.ko.Ao .

i

. 54m:Nt'. 8Ai(L'4TWOOME 7d 1936. 0%.,, */ y_1R 10%. ,_ */. 654. %, 954.

, .___ Cu m _',. o1W.

- 41. 4 K... . .. . . . 1.4- Il.- ._ .'>.

-15 4 I62- ' - d Z- 50.

~QSt K[- 7!LTE[O 4e P00L.' '~M44iffic'$i,

+10f%~4t,

• H8,2c'is V4irgQ3, ,

Dit.SWUID0)NELRTg'JtKE %.._t7 ed . % 7. 7c4 *4 ,ll6c. .. 42,116o.,

.  % t stosu - az . ed. -ts zz.

._S.M . .7.LLT.D20cL : f s t.__ ' 475. .. - 17 6.: : I6

\

/7 1 ci - b + c ; 'l'18/317o #.3hfttJ$ ' llc

• if4 f4. ' l'4N_t

• • ig,4'.

vl .

.tntnus & sa:s,s,,e t o out ic . imws w.m. .a . 66 .

- 67. .

- -~

.46'6

- so '

. .~- ,5:06 Stoc.mv.ct Frnwn: 454. 1615. I 67o. IceA.

+

!?.OscmE. .6 WWcs.. '%. 443., ,. +4. 416_ *(. .. t.t 1. ../ A l..

l., W/Dmat. Mvect l".Pe?. i '/. . .  % .....  % 129. '/. 7.o. _,

M,V7. D ARGE.1,V [ feg$(QL*

• /. , 3bl.. toq . N .t.74 d69. */. I14. '/-. 33..

I' Wi.lJi f.CGSA1:cq 0$cittAT1oM '/ 11,

.  % . 7.7  % 13. W, s.

. 5tH C.WM!%. ... . . .M .4t. -

..  %.4.A  %.10 . . . .6 &_._

M.s3tfwKin-@r ar c- "TC--

,. . ' T o- ~ " "-u

_twoouwu. .... .- 6em . ....his4... . .7. h _ .. . )4=.C.

1 ou toci m m s u tss - u4is. em - toes. .-i_t tr i.

t> 1

-v .

%y sg 48 ', run.-

rog '. 'y, s ut. 'cu . sc01.

ntt s11,4 i . @ .

d t'5 s * *i.

". > s n.. 4rsr/ier.

1.tO@@@@@k t'. nV "'** .s ' os..'Ls-

.,3

.:. .. s .1 L.s__s'_T; in -*mM swnif.ic ed.?." u __e.t uafsa8tw/m u.

' )

+ 17,w.r.

to.. ..o.. .r io , . .

~ f.smfna.* *

.-}

k f

g .;i.i... _ - ir a r i

l l.

C:. 3'9 rs . -

T. J!.#

I r 7, r.

.L: i

') . , Table 3'-2 CLASSIFICATION OF LOAD COMPONENTS BY FREQUENCY OF OCCURRENCE I

(,,) ^" ' , l l Continuous or Steady State loads-l' Dead Load 4 External Hydrostatic Load Due to Annulus Concrete Pour E

Hydrostatic Pressure 18'-6" Cyclic Loads l

- g l OBE

. SS!! '

t SRV Discharge - 19 Valves SRV Discharge - One Valve,1st Pop oO N. SRV Discharge - One Valve, Subsequent -

, Mean Condensatfor Oscillation Mean Chugging i

s Sinole load Events

. LOCA Pool' Swell

^

DBA LOCA Thennal Stress

, 15 psig Static Internal Pressure s

4

,+

I.

1 . ,

r ,:, , .

3-10 9'

6-

Q l q, . -Table 3-3

1. SUKvARY OF CYCLIC STRESSES f .;

. NUMBER OF . NUMBER CYCLES TOTAL NUMBER l , SOURCES -- OCCURRENCES PER OCCURRENCE OF CYCLES

~

c5RV Actuation -1860 9 16,740

. OBE '5. 10 50 l l

SSE 1 10 10 I e -

l TOTAL 16,800

. ...u-

<Y g

i_.. -

, _1 - - -

I l c .

L: ,

.g.

I *

.a

(,

[I' e U' f % . .

Ii, -

's 3-11

~,

q.

m

'V Table 3-4 LOAD COMBINATIONS EVALUATED FOR ANALYSIS L)'

c Load Combination Number Load Comoonent's I DL + OBE + CONC + SRVy + HYDRO + PS

, , . II.

DL + SSE + CONC + SRV1 + HYDRO + PS' III:

DL + OBE + CONC + SIP + SRVyg + CHUG + HYDRO IV

-DL + OBE + CONC + SIP + SRV2 + CHUG + HYDR 0 + LOCATHERM

, 5-

.. S -

DL = Dead Load 0BE = Operating Basis Earthquake

.6 Qy SSE- = Safe Shutdown Earthquake CONC = External Hydrostatic Load Due to Annulus Concrete Pour

.. S I P

= 15 psig Static Internal Pressure SRV 19

= SRV Discharge - 19 Valves

- .SRV = 'SRV Discharge - One Valve, First Pop 1 , ,

t .

} SRV 2

= SRV Discharge - One Valve, Subsequent Pop CHUG ,= Mean Chugging HYDRO = Hydrostatic Pressure.18'-16" '

PS- = LOCA Pool Swell '

LOCATHERM = DBA LOCA Thermal Stresses f)V

,a 4

a .,

i

, 3-12 S

<35 Table 3-5 D B0UNDING SERVICE STRESSES FOR JOINT 1-1 it Stress (psi) i -

. Location Inside Outside Stress Comoonent H- Thermal ~ 633 -5857 Hydrostatic 421 -818 Design Pressure 2794 836

~

I Dea' d Load. -492 -659 ,

PSRV- 1085/-1847' -2078/3539 l- ,

t-

,l' CO- 146 279'

- SSE 1731 12194

,  %. OBE +555-

~

+1664

~

4 7()m Load Combination Stress Rance (osi)

I- -1569/-2473 -1891/498

• - II-~ C 1805/-2709 -1361/-32 l' '

III- 4509/175 '- 776/1055

, IV 5142/838 -

6633/-4802

l+ r

,73 (FromCD-130) Gilbert Ref. Letter PY-STR-1555 .

-V l.

8

-e < - - - - - - , e --, --

-.----- ,, , -.---w,, , e,-., ,, - . ,--..v --

k4

7. ...

, e e- . 3-13. .

1 .

?

h,\ '

perfectly-plastic material behavicr.

r

.e -

I The cyclic (primary or ' service)~ stresses are added to the residual stress

. . distributi_on_s.uch_tAatuthe_ h maximum stress does not exceed the assumed yield

[E _ess of .the material._. The yield stress used for developing this distribution.ls.78.6 ks! (see Section 5)..- .

y

> . 7 an ,

t 5-r 4

J;O.

r. ,

"I t _

' {i' L,

, m \ -

f

, +

r i

e ?I 1

-l i

4 4

(O. .

.e .

L--

U;- -

D

3-14 .

t

() Section 3 g, REFERENCES s_  !

.[ 3-1 Nordell, W.J. and W.J. Hall, "Two Stage Fracturing in Welded Mild

, . Steeli Pl ates," Wa f dt nn Pomaarch Snnn' ocan+, March 1955, Pp. 124-S to 134-S. -

.\.

2. Leggatt, R.H. and M.S. Kamath, "Res' dual Stresses in 25 mm Thick -

Weld metal C00 Specimens In the As-Helded and Locally Compressed States," The Welding institute, Report 145/1981, June 1981.

C 3

~

Rosenthal, D. and J.T. Norton, "A Method of Measuring Triaxle7-Residual Stresses in Plates," Welding Research Supplement,

May 1945, Pp. 295-S to 307-S.

() ~

4

• >4 I e b

l d

4 r

- r

• \

l X) '

7

• 4

• l

.w.

c.-

l 4-1 '

r" V Section 4 T

FATIGUE CRACK GROWTH RATES h.) .

in order to estimate the maximum extent of crack growth that could occur at an Indication over the design life of the plant, a f atigue evaluation was performed. This evaluation combined the cyclic stresses (Section 3)

+

with the appropriate crack propagation rates (Section 4) to obtain the expected creck growth (Section 7). ,

The purpose of this section is to assess propagation rates for defect s growth by a fatlgue mechanism. WLth the excep11on of_fAeJo_ssIbie; plate d,ef ect in wel djoj nt 1-4dh.e_def ects are located,ln weldnents, thus -

requiring an evaluation of carbon steel weld material crack growth data.

References have been drawn together to estimate a conservative (that is

~

fastest possible) bound on potential crack growth. Although no data are available for the exact condition in ef fect, significant studles have been perf ormed to permit boun' ding values to be estimated.

11 The following engineering unit conventions are in ef fect unless otherwise i stated:  !

s e AK (stress intensity factor' range), ks! /[7i e T (temperature). *F f

e da'dN

/ (crack growth rate), Inches / cycle S ' v) . i All weldments evaluated are composed of E7018 weld metal. Data available In the literature were collected for all types of carbon steel weld metal ,

e 9

with an emphasis on E7018. A study by Maddox (4-1), resulted in a .

substantial' amount of crack growth data for four dif ferent weld metals Including E7018. The four Wpes of test specimens frcm Maddox are b

,w 4.< 4-2

e. ,

.summarizedL in: Table 4-1 and the crack growth data for these specimens are m plotted in Figure 4-1. Crack growth data for the E7018 weld material (weld metal C) ara showr: separately In Figure 4-2. Also shown on Figure 4-1 is ffD .%.] .the bounding _ line from similar testing _ on plain steels performed by Gurney

. (A-2).-

. 10ther data. from similer weld metals (A .1) with and without' stress rollef, f alI 'wlthin the upper bound shown' in Figure 4-1 for-Gurney (3-2). The literature also_s_ tales _tAat_ weld metals for joining;. steel.s_such as A51.6

'. Grade 70 exhibit slower f atigue growth rates than the base metals (4-4).

~

3 -

Residual . stresses may increase crack growth rate (da/dN), but If theN '

stresses .are Included in estimating crack growth rates, the data 15dicate that the bounding IIne by Gurney- (A-2) wilI conservatively predict EIa^ck growth for E7018 wel dments.

Figure 4-3 shows Gurney's upper bou'nd which is represented by:

a /. '

N _to 3,44

, da/dN .= 2.63 x 10 AK (4.1) i The ' lam _Jaaflon41ke def 4ct in wel_d 1-4 may propagat.e ln .elther wel d .

material Lor SA516_Grv--70 base plate material depending on the exact defect

. location and orientation relative to the weld. Both cases were analyzed to bound the pos'sible of fects. The gr_owth_ rate- used for SA5I6 Gr. 70 material.

was derived In' previous work for Gilbert Associates (4-5), based on

- bounding curves developed from work by Bamford (A-d), and ASSE Code Section XI.(4-7). This work provides a three point curve depending on the relevant cyclle stress range.

-10 3.76 ' '

da/dN' = 3.8 x 10 AK AK < 4.9 .' -

(es), da/dN =

4.4 x 10

-13 AK

'8.0 11>AK)4.9 t

'6 1.4 da/dN. = 3.16 x 10 AK AK>11 C'

. . + .

'. 4-3 ,

p. Table 4-1

~

<--. ( TEST SPECIMENS FROM MADD0X*

'bu-]l .

~~._ "

. YIELD ULTIMATE

. WELD- - .AWS/ ASTM -STRESS STRESS

' METAL CLASSIFICATION (ksi)- (ksi)

. i

-A None 74.4 88.0 A MIG deposit using CO2 gas a

shielding and 1 mm diameter

, wire Type A-17 to BS 2901,

. Part 2, 1960.

s.

B . E7013 68.3 73.9 A manual metal' arc deposit of c medium strength using a BS 1719 Class E317.rutile coated electrode. !*

.u-C E7018.G 67.2 82.9 A manual arc deposit of medium strength using a BS 1719 Class

. E614 HJ low hydrogen electrode.

. ()r'

>- D E9018.G 89.6 105.3 A manual metal arc deposit of high strength made using a BS 1719 Class E614 HJ low ,

hydrogen electrode.

^

' *Ref.(4-1). T \

s ,

L

,!/

s t

[

( .

V

~

4-4 AK, kso /~h .

10 15 ' 20 3 -  ;

30 40 '50 *SO 70 80 SO

..f _, -

7 9

,, e i.,,. z-l x* *

I!qj  ;

I '

4 - KT'

, t. - .-

,e j 7**4 15

,, ly *,

Scatter band for y ,o, 1'a'l, ,

plain steels from + o a a

3 i Curney (h'l) f,# *** e s _i -i . . . . .

i a

' -. i '. .l7_.. . _ . _ _-. +, e n g+ A 6A 7

II !I

+4 . --

((8I.N#/

w,

+

• 4t"/

j ,  ;. g..,e..g' < -

/

- -/ ,,.* * *

• L' 6 -- 1: '- -

.

• l 7

l-5 es . *

• 1 -- - **

• .*k A0^0^ -- --- .

t% i '

.:.e. *' * ?J . 46 4 ~*

t** **6 .m e, s3 A ---.

N 8, 7c E .e +* . <

E- J i --

'p:'

,*.,g.f*.*w.4

,j a &

+ a a a ,--  %

g ' F s'

a t

s', s

, . t.

, ,g s .s g , ,

... . ga ___ .. gg E I (li; '.' \*k*$^

= t- - g 15 6 , u R l , * .ss **a -

g

' ([J e  ! n , ',,Mr -

4 R

~

, *u so.4 l

I +

+,

+isa /e S

~ 4.

o -

! .l -

l ,,, + . , .o= m t-3 , ,. ,, 4 g .--. --g..- ~.. ..._. .

j j v g

g a j; -- -

[f ,'o.h..

7 b

....'___, , I Q .c lll is * -- - . l Q

s , s, - - . . _ . . . . _ - . -_

4% ,

lh, l a HAZ mild steel

} *

• weld metal A 3  %,po% 1 o' *~ '

, 'x weld mefcl B Aeo ] o weld metcl C 2

ha e ,$. ',h ,, ;

, + weldmetcl D ' 79 6 A

e l \

35 ia a .

(~ i

'a4 4 /

a4 .

A 10 -5 ^> , , , , ,

9'*10 15 20 30 40 50 00 70 80 c0100 Range af stress intensity factor AK MNni 2

i. -

y; Figure 4-1.

Crack Growth data from Maddox (4-1)

' 4-5 I;- ,

< ,  : '.' 4 ksi/ik '

' Pc 624 - 4 .

n,-.

10 1S -20 30 40 50 x60 D 80 90 3

, p , j. , ',

,' 70 - 4 ,

1( "2 /  :

e x

.a. /

L/. g.s .- - -

1 x

,1

• z 10"3 y . . . ...

l l 7 7 18

.7. ..T I ~'A ,k'l

s. j 'J T j /l ,e f 7

0

~

ll * - -

r

/, , t/

o ln, *

.)

f x4y I

? o esy .4/

.N I c /

o E

E 3 1 e s d^/ _ .. t

~. 0A s.s . . b

~ 'g-5 ,\

ci

. %lf ' 1, '.

2

(

~.$ ( / %I%

'.4- 75 "

^ [%/3 ll r

g. / u k h l f b 10 b '8 l V lt. 51 6 $

e i /i i 6 m // i t i $

%  ; f; 3yj l g

-3 *

/ AV / ,

/ .

y l 4  %~

W l , . '

• ,/

a -I 15.7 ksi a j '

I o 17.9 ksi -

f , f . 20.2 ksi .

70-6

[ 31

~

3) x 31.4 ksi ,

,, -2 @appliedstress(ksi) -

15 h-g jW 15.7 # '

70-5 .

e r , , ,

. 9 10 15 20 30 40 50 60 70 80 90 l00 y

.g..

Range of stress it. vity factor 5,MNm' 2

~.

Figure 4-2 Crack gr th data for E7018 from M'ddox a (4-1)

l

.. i 4-6 Stress intensity factor range, oK (MN/m /2) ,

.p.

<l "e 4 6 10 20 40 60 80 100 ir 10-3 _, , , ,,, , , , , , , ,,

. ,m -

s 1 w/ _- ,

_ Bounding curve for SA516  :

Grade 70 -

o 10~ --

g ao  : -

r

~ e.;

s D - t

- -4 E 10 -

t _ -

g

.5 S

5 g - .-

zZ u 10

-5

.g a  : -

3

.r

> _ e l MIS 10-5 g

i 2- _ -

0 2 -

g en M a v .

V

' g

"  ! ~ u 10-6 __ Upper bound E7018 s Gurney (4-2)

(<,.

10-6 10-7 i ' l i I ' f 1 I II-1 4 6 8 10 20 40 60 80 100 g/

(, Stress -intensity factor range, AK (ksi /In)

Figure 4-3 Boundina Crack Growth Lines for E7018 weld metal and SA516 Grade 70 base material l ( .. .

e 4-7 .

t;~ , ,

-b .These values are shown in Figure 4-3.- It should be noted that this curve tr ' is very conservative relative to all experimental data reviewed and will

' provide =even-more conservative results than the weld metal curve also shown

, _ . -In Figure 4-3. *

>L m.

t 6

I*

• e

?-

. . . un -

LO .

I r*

m.

I

>+- ,

9 7

4 I*

7

,. O ,

.. j. . .:

4-8 cs ,

lI i..

Section 4

't-REFERENCES f~')s I\.- *

. '4-1 Maddox, S.J., " Fatigue Crack Propagation in Weld Metal and Heat j Af fected Zone Material," The Welding institute, Report No. E/29/69, Ab.ington,' Great Britain,1969. ,

4-2' Gurney, T.R. and S.J. Maddox. "A Roanalysis of Fatigue Data for Welded Joints in Steel," The Weldirg Institute, Walding Racaarch i n+arna +t enn t , Vol . 3, No. 4, 1973.

4-3 Seeley, R.R., L. Katz and J.R.M. Smith, " Fatigue Crack Growthi in Low Alloy Steel Submerged Arc Welds," Fa+f gua To=+f ng cl Etfd~en+n, Pp. 261-284

,C\

Ajy_/ 4-4 Gurney, T.R., "An investigation of the Rate of Propagation of Fatigue Cracks in a range of Steels," The Welding Institute ,

Members' Report No. E18/12/68.

_4-5_, Egan, G.R. , et.' al . , 'rThe Signi f icance of Sensitized Stainl ess Steel Material in Drywell Vent and Containment Structures in ,

.the Perry Nuclear Power Plant - Fracture and Fatigue Evaluations,"

~

-AES Report 81-11-88, November, 1981.

I. ,

4-6 Banford, W.H., " Application of Corrosion Fatigue Crack Growth 6 Rate Data to Integrity Analysis of Nuclear Reactor Vessels," ,

American Sne f etv ci h'nch an t en t Enginners, Paper No.

79-PVP-116, 1979.

y V("%. .

4-7 American Society of MechanicalI Engineers, Boiler and Pressure Vessel Code,Section XI.

y r .

6 m - , . - _ _ _ _ _ . - . . - ,_ _ , _ _ , , _ - - , _ , , - - -

N1 .

5-1 ,

,n v

<~

Section 5 7.m w FRACTURE TOUGHNESS AND STRENGTH

<- lv) ,

5.1 in+rnduc+fnn e

Two additional model inputs to be discussed are the material properties; fracture toughness and strength. As discussed in Section 2, the applied stress Intensity !s compared to a critical value which is defined as the

. . fracture toughness. Thus, to determine allowable flaw sizes, the fracture '

-toughness must be characterized. Although no direct measurments of

,f racture touchness wereJetf.orredin the course of th is werk, inference about the level of fracture resistance Inherent in the material can be made

g. _,

by__teference to the-Chacpy 11npa_ct values _which are avge. The . .

background is presented in Section 5.2. The data are discussed in Section 5.3[ for the containment welds and base plates (for p,ossible plate delamination of weld 1-4). Section 5.4 analyzes typical crack opening

[("v

- _displacement values to be used in the elastic plastic fracture mechanics evaluation. Section 5.5 addresses the yleld and ultimate strength values

to be used in the Iimit load assessment. C yedJatettal.Jes_t__Reper_ts t n

(CMTR's) (CD-4~, CD-7, and CD-127), were alta_l_yzed to determine Charpy (CVN),

- yleid strengtA_and tenslie strengt._h_ data. - Control led docment 127 was provided.speelfically to confim the CMTR's for E7018 used in Weld Joint 1-1 behreen sens 21-22 where the largest defects occurred. CD-4 ~nd a CD-7 ~

were obtained in previous work for Gilbert and list data for many heats of -

E7018 used In containmen_t_ welds. These data hav.e_al.so_.been_f.ncluded_(see Tabl e 5-1) to Indicate the _ variation _in_matettaj_pr_opertie.s. .

, (~3 - 5.2 Frme +nra Tnochnnu - B ec k cenon ef V

E To.use the analyses described in Section 2.0, it is necessary to have the appropriate value of material fracture toughness in terms of the critical plane strain stress intensity factcr (K ). Because of the excellent b Ic ~-

toughness in this material, these data are not ncrmally available fcr weld metals such as E7018 at-%tmperatures around 70'F. YalId K data for lC 4 .

r .

5-2 ,

Table 5-1

SUMMARY

OF WELD PROPERTIES BY HEAT

.  ::s (AS-WELDED) i (fs f.

. WELD WIRE YIELD STR NGTH LIMIT STRESS AVERAGE TEMP.

QC# CMTR# (XSI)

[ (KSI) CVN (FT/LBS) ( F) 77NNI518 456 66.3 72.3 77.3 -30 77NNI540 472 - 78.1 83.2 69.8 -30 77NNI563 493 --63.4 70.3 45.0 -30 78NNI004 552 - 68.8 75.7 . 82.6 -20 78NNI013 557 - 65.8 72.0 95.2 -20 78NNIO14 557 -68.4 74.3 109.6 -20' 78NNIO15 557 65.3 69.9 24.0 -20 e

.- 78NNI016 557 - 65.5 71.4 85.0 -20 78NNIO24 625 -65.3 69.9 24.0

• /LNNIl00

- {, -20 596 s 78.1 80.7 62.0 .t- -20 78NNI163 630 - 68.2 73.1 76.0 -20 78NNI164 630 - 63.8 69.0 115.3 -20 18NNI202 646 - 66.9 71.5 120.2 -20

'h8NNI221 . 653 -68.1 73.9 86.8 -40

• 78NNI224 655 - 66.3 72.6 101.0- -20 E 78NNI255 663 -70.2 73.6 118.4 -20 I 79NNI016 694 ,- 84.9 89.8 66.7 -20 79NNIO17 694 __78.6 83.3 92.7 -20 h 79NNIO18 694 67.2 72.7 114t0 -20 79NNIO99 710 - 64.5 71.3 84.6 -20 795 nil 00 710 70.9 76.4 102.4 -20 79NNI131 716 - 72.7 79.2 80.3 -20 79NNI161 729 - 65.3 71.5 56.8 -20 79NNI172 737 - 65.3 71.5 56.8

-20

['

80NNI017 746 74.8 79.5 81.0 -20 j NNIO50 752 70.0 77.0 69.0 -20 t ,oNNI182 224 ~ 68.9 74.9 i 42.3 ,30 076NNI218 256 - 68.5 74.3 85.7 -30 o77NNIO58 398 70.0 73.8 138.0 -30

• 77NNI519 . 69.0 73.8 113.3 -30

} G77NNI589 520 - 69.7 73.7 109.7 -30 Taken from CD-4 and CD-7

• Included in CD-127

t

• 7 w.

5-3 ,

t p*m

• J 1.5". thick material are generally only available at temperatures such as 9 --100*F. However. ,Lt_i_s_possibl_e_to_lAf er__lnf_ormation about the relati_ve Ltoughness' of the present mater _l.aL_from available CMTR's. There are several

[," ~ correlations that have been proposed to relate Charpy energy to K Ic

values. These include two empirical relationsh!ps proposed and verf f led by Barscm and Rol fe (1-1.). The relationship for the transition temperature regime'is: .

~

• 2 3 K = .2 (CVN) /2 Ic (5.1)

E 4

where

.  ?'

=

K Plane strain fracture toughness (psi /T70

=

E Young's modulus (psi)

'p CVN =

Charpy V-notch energy (ft-lbs)

W The ' corresponding relationship for the upper shel f regime is:

1 fKIc) =

5 f a y)

CYN -

s .i 'a i o i 20 (5.2) .

(y/ y

\

where '

o y

=

Material yield strength (ksi)

=

K Plane strain fracture toughness (ksi /T6)

Ic Barsom and Rol fe found that at 80'F. the upper shel f correlation was appropriate for all material they tested. All their tests were with -

(A) .

material of yield strength greater than 100 ksi, although they claim that Equation 5.2 is val!d for materials with yleid strength less than 100 ks!

If dynamic yleid strength _f.s_used_instead n of static yield strength.

,( Another common correlation, due to Sallors and Corten, wh!'ch was developed for A5338 and A517F (1-2), is

[

• 5-4 ,

0.5

, K =

15.5 (CVN) (5.3) i rr where i?("~ '

K = ks! /Tii

+

CYk ~=--ft-lb Piserski- (1-3.) who reviewed and verf f led by experiment ten correlations including those listed above, found that good predictions can be obtained e-for high strength steels (o > 113 ksi).- For lower strength steels, the Y

' correlations tend to be generally conservative with the degree of conservatism Increasing with decreasing yield strength. Thus, either

' Equation 5.1 or 5.3 should provide conservative estimates of critical fracture toughness. As a check, relations between critical crack opening e ' displacement value and K IC arealsoavailablefromRolfeandBarsom-(554) and Egan (1-5.), and take the form: "'

E 6

C- =, (KIc)' (5.4)

,- 0c 4 o

'y Vy) i -

t where o

c

=

Critical crack opening displacement (In.)

c y

=

Yield strain (in/in) = c /E Y

K ic

-=

Critical fracture toughness -(ks! /In)'

o =

Yield Strength (ksi)

Y A further evaluation of typical crack opening displacement (COD) values is

, found in Section 5.4 T

5.3. Tn"P ra u Va!"as

• ConStrrant_ Wefds r

. #(l 5 Specific certified material test reports (CMTR's) were reviewed only for weId _1-1 between vertical Joints 21-22 (CD-127). Furthermore. CMTR's f or Parry containment stif fener wolds f abricated using E7018 were evaluated in serl ier work by AFTECH (1-5) . These weld data are considered 4

m 5-5

,m. '

=

b representative of those that would be found elsewhere in the containment.

~

if There Is_a_Lar_Se scatter of Charpy_V-notch (CVN) data as shown in Table 5-1. The range of test values represented there is 24.0 to 138.0 f t-lbs.

The values given for CVN in the table are the " average." This is the average the 5 data points listed in the CMTR or 3 data points If 3 data points are given. In order to be conservative, the f.cwest CVN value was

~ - ~ -

used

- to determine fracttq.ughness (K, ) of the weld material. Thus, the 24 f t-lbs.

corresponds to a Barscrn c-Rolfe toughness value of 82.6 ks!

/Tii. With the exception of this one heat, all other heats have calculated K values greater than 132.3 ks!/Tn.

These values reptesent

~ ~ .tough

_ . welds, particularly since the CYN tests Yere

. perf ormed at. a maximum tmperature of -20*F. wel l below the operatinf

' temperature. This fracture toughness value of 82.6 ks t/Tn wil I be

, conservative since:

~

e The Barscrn-Rol fe correlation used to arrive at these values has been shown to be conservative for materials with these

, strength levels.

e Most calculated K values using this correlation are substantial ly abov6 th is level.

e The test tm perature used to evaluate K is -20'F, whereas a higher tmperature during oper3t'lon will result in correspondingly higher toughness.

A. lower bound-determination of SA516 Gr. 70.. toughness expected in the containment structu.ie_was_perf ormed in _ previous work for Gilbert Associates a

(1-2). This value was found to be 73.2 ksi / In. The derivation of this

}

, - resut t Involves const derable conservatt sm.

..- i l

e '.

5-6 Q-

- (.J - Other values determined from Table 5-I to complete the analysis are yield

. stfength and limit stress. The yleld stress Is u.s.ed_In_determina.t!.on_of .

5- residual stres_se_su _s.

a they are a f unction of_yJ,e_ILstrength level . The b- higher the yleid strength of th_e_ male.r_Lal, the high.e_r the residual stresses. Therefore, the upper bound yield strength Is used to determine

, the maximum possible residual stresses present. The ligt_s_tgength is used

'In evaluating the !Imit load capa. city _of the structure. The limit strength '"'

g (ol ) is defined as o = (c +o ) (5.5)

J y uts /2 where.yo is the yleid strength and o uts is the ultimate strength. . For-conservatism in the limit load analy_ sis, lower _ bound _ values _for_yleldiend ultimate strength _ar_e_use.d_inde_ determination of the limit strengtfi.'

For yleid stressntvalue_2&6 ksLttes_been used and f or !!mit stress, 66.0

%(~); ksi.

'(See Section 7.2) The_ conservatism is apparent in that the prescribed yleid stress is 12 ks! creater than the limit stres_s_used _In the analysis.

5.4 Crack Onaning Drentaca-ant (COD ) Valua=

Crack opening displacement testing is used as a direct measure of fracture reststance. Literature data are avalIabie to provide typ! cal C00 yalues for E7018.- These are presented l_n Appendix A. These data were used in two ways. First, as a check in the derivation of X and second, as direct input to the EPFM analysis. t

. A check on derivation of the K value used can be provided by Equatlon 5.4. From the data in Appendix Ic A, the lowest COD value data at 32*F is b) .023". For this value of COD, and for c = 0.2%, o = 63.4 ks! (the

. Y y lowest strength material given in Table 5-1), the resulting K value is calculated as: -

Ic

,y 3

c; .

5-7

' E

-- 6 c_ , {KIc\ 1

'y \y/

'O x m

- 2i4.9 usi ein Thus, the value of 82.6 ksI/TR taken in Section 5.3 corresponding to a CVN value = 24 ft-lbs., is very conservative.

I e i.

- O e

l.

,; , O s

{ _

1 3

I i

o

% f l

e e

- - - - -- , . - - , - _ m _

r

r-y -

5-8 r-Section 5 u

REFERENCES

.;-s

)

' 5,

.. 5-1 Barsm, J.M. end S.T. Rol fe, " Correlations Between K and Charpy Y-Notch Test Results in the Transition Temperature Range," ASTM STP 466, (1970), Pp. 281-302. .

5-2 Sailors, R.H. and H.T. Corten, " Relationship Between Material Fracture Toughness Using Fracture Mechanics and Trar.sition Temperature Tests," ASTM STP 514, (1973), Pp. 164-191.

5-3 -  :

Plsarski, H.G. , "A Review of Correlations Relating Charpy

~ Energy to K , " Tha Ec.Ld i ng i n st f +erta Racer _tch ButIa+ra- (December 1978), Pp. 362-367.

( 5-4 Rol fe, S.T. and J.M. Barscrn, Frac +tira and Fa+f c"a Co n +r n i .l.a Struc+uram- Annt f eat!nns af, Frar+nra Vachanics, Prentice-Hal1 (1977).

1 5-5 Egan, G.R., " Compatibility of Linear Elastic (K i

) and General Yle! ding (C00) Fracture Mechanics," Fnc!raarf nc Frac +ura vach an ics, (1973), Vol . 5, Pp. 167-185.

Egan, G.R. , W.P. McNaughton and J.D. Byron, "A Fracture Mechanics 5-6)hAal1 n

ysis of Containment Stif fener Flange Welds in the Perry  ;

g Nuclear Plant," AFTECH Report, AES-82-01-92 (Apr!! 1982).

II i

5-7 Egan, G.R., et. al., "The Significance of Sensitized Stainless s-l )

.a Steel Material in Drywell Vent and Containment Strtctures in f

the Perry Nuclear Power Plant - Fracture and Fatigue Evaluations,"

AES Report No. 81-11-88, November, 1981, t

e i.

{ --

. = .

W ',

o f. , 6-1 -

.y N

y Section 6 CHARACTERIZATION OF FLAWS h.R -.

. The final inpu.t-__required

_ ___ for-the,fractur_e_ mechanics evaluation is.fIaw s'I ze. The applied stress Intensity f actor calculated by 1:near elastic S

fracture mechanics methods and the net section stress of the limit load

- method will both require en accurate description of flaw thmensions. This wilI include both depth and length information. Length Iniormation is generally easier to obtal.1 as the projection of length onto f!!m is obtained by standard radiographic methods. Depth data have been less o-easily obtained without _re_so.rt

_ __ _ _ _ _ to_vo_l_u._me_tri_c_e.xamination by ultrasoni,E.

techniques or d.e_s_t_ruct_lve testing techniques. . Eor _structuraMntegr4ty evaluntiens an assump_t_i_on has been, general _ty_ Imposed _that_ conf ines-the flaw

• depth to one weld pass in multipass welds for certain defect types. This

. assumption wilI be conservative for porosity and sia Dioh defect types. However, in many -Instances It may be overly conservative. Such an

~ assumption confInino'the_expe.cied_def_ect depth _t,o,one_wel.d pass will not ,

.however cuarantee_ conservatism for "IInear" defects like cracks, Ia'ck of

~

. fusion and lack of penetration. To more fully characterize both types of

. defects. In the weld-joints of Interest, a radiographic enhancement

~

' technique.has been used. This !s discussed in Section 6.3 below. The enhancement procedure also allows accurate length sizing of defects. When combined w!th equations of. interaction (discussed below), this allows the analyst to determine l.f_two adjacent defects or a series of defects should be'most accurately. represented as single Imperfections or treated as c.. . -.

y continuous. Thedetailsofdefectinteractionare-discussedinSection . . . . . . .

6.2. , The following section discusses the ef fect on structural Integrity of the rounded defect types, particularly slag inclusions.

6.1. .T.b.e F Hae of. S. Lag inc!"a f ma on S+rnr+ ora fn+arr'+v

- Work'.by Harrison-(6.l.) has Indicated thatpg inclusions have little f ,

effect -onJJ1e__ tensile-strength of butt welds-up to considerable percontages

,k.

I*

6-2 4

~

[

of cross-sectional area, infsupport, he shows results of' work by Ish!!

i ( M ) and by K!hara ( M ). These results are.shown in Figure 6-1. '

. Harrison further points out that by their nature slag inclusions are e unilkely to occupy a large proportion of the cross-sectional area of a

. given weld and the weld metal will usually overmatch'the base metal in strength. The. concl uslon to be drawn from these f actors _is th.at_the..ef feet of slag inclusions on static _ tensile strength in materlaJs like E7018 is

. negligible. - Harrison conf irms that size-for-size, slag __!negrons wil l be less detrimental than crack's because of their roundness and limitations on their through-thickness size. ,

A sim!!!ar conclusion is reached considering 'loit cycle f atigue. Work _by Ish t ! and lida (M) is shown in Figure 6-2 and indicates that slag l'

<~2-

., Incl _usions_have_L!dtge_ef_fect on load-cofttrolled low-cy_cle f atigue and up to lives. of about_10_ cycles The design can thus be based on the static n

tensile behavior. For 'the analysis of these inaccessible defects, the

().

structure may: be subjected to as many as 18,600 cycles., This !s stil!

considered . low-cycle fatigue for the purposes of our analysis, and the of feet of . slag inclusions wilI .be welI characterized by the static loading case, particularly in light of the relatively low magnitude of the'cyc!!c l stresses (relative to the ful'ly reversed limit level stresses used to generate the S-N curves of Figure 6-2). Additional results given in

.f Igures' 6-3 though 6-5 Indicate the of fects on f attgue ' strength for hIgh cycle ~ fatigue. The number of cycles required to enter a regime-characterizsd by substantial of fects on life Is shown to be at least an l-l:

- order of ~ magnitude greater than the design I!fe in the present case.

I l-p' In summary, Harrison . (M) ' states that there seems to be suf ficient I

v . .. evidence to Indicate that under load-controlled conditions, low-cycle yO fatigueif s--not

- ~- a protilem~which wil Lbe Influenced-by..the presence of slag inclusions. _ _ _ _

-Thh tens!!e strength, o , of a defective butt weld will be either u

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>=- -

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1 p Figure 6-1 Effect of Slag Inclusions on Tensile Strength

. t . s) .

(taken fro. 6-1)

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,, , v i e> ce o Fig 0re 6-2 Results of 1. cad-Controlled Repeated Stress Fatigue Tests on Butt Welds Containing' Slag Inclusions (taken frcm 6-1) .

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Figure 6 'Results of Tests on Low-Hydrogen Welds Containing p Slag Inclusions up to 5m long "

(taken from'6-1) t 64

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t Figure 6-4Results of Tests on Low-Hydrogen Welds Containing-g; Containing (taken Slag) Inclusions up to 25m Long from 6-1 -

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~ 6-5 7- .

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Figure 6-5 Results of Tests on Low-Hydrogen Weids Containing i Slag Inclusions up to Continuous Slag 1.ines

, - (taken from 6-1) ,

)ll "

e k

eQ. 1

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g

-, J

. 4 .

I r- *

. 6-6 i

• l y

l' F o

u,w (1 - LA/A) it or C

(

c:

u,p

't T U whichever is least. Where:

o = the tensile strength of the weld metal

. u.w c = the tensile strength of the parent ma'terial u,p LA/A = ratio of The loss of area due to porosity or slag inclusion to the total area Th geet_of_ porosity _on structural _Ifitegr_i_t.y__Is simil ler to that fer slag Inclusions. Figure 6-6 shows the of fect on tensile strength of a wellas a function of volume of pores. This figure is from work by Harrison .(f-5.).

Figure 6-7 shows- the ef fect on fatigue life for porosity defects fo;- the flx_) case of low cycle fatigue. The behavior is similiar to that for slag Inclusions. Harrison concludes for porosity (fc5.) that, "There_s_eerns _

o be suf ficient evidence to Indicate that, under load controlled _conditJons, low cycleJtigue is no_t_ajroblem which wilI be intluenced_by_ practical

[ porosi ty_l,evels. " Furth ermore: .

i I '

"In view of the probabie necessity to limit poros!ty to scrne

_ percentage probably well below 10% because higher levels would obscure other defects, there is no need to give further consideration to the offeet of porosity on static duct!!e strength. This is because weld metals normally_ overmatch patent matettal_sttength_and even where this__!.s_not_t,he_ case the percentage 2 eductI_on in sitength_due_to_porosit.y_Is_cqual to ihe_ percentage-by-vol ume-of_pocosLty_and_at_a maximum of _

10% this would not in any normal circumstances be signifi_ cant."

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_ . _ . _ _ . . . _ _