Fatigue Life Prediction of Cruciform Joints Falling at the Weld Toe WJ_1992_08_s269.PDF

7/22/2019 Fatigue Life Prediction of Cruciform Joints Falling at the Weld Toe WJ_1992_08_s269.PDF

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W E L D I N G R E S E A R C HSUPPLEMENT TO THE WELDING JOURNAL, AUGUST1992Sponsored by the American Welding Society and the Welding Research Council

Fatigue Life Prediction of Cruciform JointsFailing at the Weld Toe

A two-stage model appears to offerthe most accuracy in predicting fatigue lifeB Y M . SK O R U P A

a theore tical mo del to pre dict the w e l d . The experimental5 to 2 X 106 cycles for

s under constant amp li tude axialloadating at the w eld toe .

tal fatigue l i fe is spent in crack p ro p The local strain method was ap

s m easurem ents. The fatigue l ives

ge m od el results in life estimates an

Analytical procedures used for predict

= N p (la) = N (1b)SKORUPA is with the University of MiningdMetallurgy, Krakow, Poland.

and the two-stage models whereN f = N, + N p (2)

The approache s accord ing to Equations1a, 1b and 2 wil l be further termed as theP,Ian d l-Pmode ls, respec tively. In Equations 1 and 2, Nf is the total fatigue of life,N p is the crack pro pa ga tion life and N, isthe crack initiation life. For small metalcomponents, N, is defined as the numberof cyc les requi red to deve lop a dom inantcrack of a so-called initial size (ai), usuallyof the order of tenths of a mm. Themeaning of N pin Equations 1a and 2 is no tthe same. N p in Equation 2 is the num berof cycles spent in crack growth from a, tofinal fracture while N p in Equation 1aaccounts also for the earliest phase ofcrack gro wt h f ro m a f law or a microstructure de fect. Usually,low-cycle-fatiguetheory is ad op ted to estimate Nj, and frac turemechanics is employed to calculate N p .

Disagreement prevai ls on which of themod els define d by Equations 1 and 2 bestreflectsfatigue behavior of welds. A wide spread opin ion that de fects, usually crackl ike in shape, are unavoidable even inhigh-quali ty welds involves the predominant use of the P mo del (Refs. 1-3). Ho w ever, successful estimates of weld fatiguelife have also been made utilizing thetwo-stage approach (Ref. 4).Fatigue analysis of welds requires thatstrengtheffectsof the welding process be

K E Y W O R D SModel ingFatigue LifeCruciform JointsStructural SteelsWeld Toe CrackingCrack InitiationCrack PropagationLocal StrainFracture MechanicsHardness Measure

accounted for . The most important ofthese are: geometrical variabi l i ty, changeof material properties in the weld neighborhood and residual stresses.The objective of this paper was to select the theoretical model most adequatefor predicting the total fatigue l i fe of aw e l d . The study focused on a cruci formwe lde d joint in tw o structural steels underconstant ampli tude axial loading. The dimensions of the weldment were chosensuch that fai lure occurred at the weld toe.Fatigue lives calculated according to thetwo-stage and one-stage models for adefect less weld geometery and in thepresence of undercut were comparedwith the observed results.Exper imenta l TestsSpecimens

Cruci form welded specimens for fat igue test ing were fabr icated f rom structural steel plates. The steels were St3S(carbon mild steel) and 18C2A (low-al loysteel). The chemical composit ions andmechanical properties of these steels aregiven in Table 1. The w elding procedu rewas manual metal arc in the horizontalposi t ion.Based on Ref. 1, the ratios of theweld leg length Ito th e pla te thickness twere chosen such to promote fa i lure atthe weld toe under axial fatigue loading.The St3S plates were welded in longerpieces and then saw-cut into narrowspecimens. Each 18G2A specimen waswelded separately. The specimen sidesurfaces were mil led to discard weld startand stop areas, then ground. The specimen geometry is shown in Fig. 1 and thedimensions are given in Table 2.

Variable geom etry param eters (Fig. 2),kno wle dge of w hich is vital to analyticalfatigue l i fe prediction, namely, the weldcontact angle fi, the notch root radius atthe weld toe r, the depth of possible undercut at the weld toe d and misal ignment(eccentrici ty e and angular distort ion a),

W E L D I N G R E S E AR C H S U P P L E M E N T I 269 -s


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m

Fig.7Test specimengeometry.were measured. The measurements ofth e fi and r values were made in side surfaces of the specimens using an opticalmicroscope at a magnif ication of 10X.While only small variations in the


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15io5

39 41 43 45 47 49 51 53Weld Contact Angle /3,

5

0 ^

B

0.5 15 2.5 3.5 4.5 5.5 6.5 75 85Weld Toe Radius r. mm801

0 20 40 60 80 100Depth ot Undercut d^m JMeasured variations of geome try patest specimens: AW eld contact

fi, BRoot radius at the weld toe r;Depth of undercut d.

4Fatigue Test Results for 18G2A

Nomina lStressRatio Rangerial l/ t AS (MPa)TotalFatigueLifeN f l (cycles)

223 135 000180 000

1.5

200175171168

140

159 600363 700236 100324 900346 300371 500524 100821 300861 600

119 1 159 9001 291 100U n b r o k e n

300250200

Fatigue Data Points Regression Line

Q95Confidence Limits

N f Observed

Results

10 5 10u 2*10u,0 6 2*106N|, N f , cyclesFig.4Observed and predicted with two-stage approach fatigue lives for St3S l/t = 7.5 weldedspecimens.more favorable weld toe geometry ( lackof undercuts) in the former. The presentfatigue data fal l within the reported scatter bands obta ined w ith similar specimens(Ref. 1).Microscopic exam inat ion of the crackedspecimens revealed that fatigue cracksin i t iated and propagated wi th in the heat-affected zone (HAZ). Fatigue crack pathswere approximately straight l ines slopedto the direction transverse to the mainplate at an angle

8 deg for l / t = 1 (Fig. 2). An observation of the fracture surfaces indicated that the specimens fai led when thecrack dep th reached on an average abou t0.35LFatigue Life CalculationsGeometrical Variability

Based on the geometry measurements(Fig.3), the variations in the anglef i are ignore d and an average value of 8 = 45 degis assumed. In orde r to cop e w ith th evar iable nature of other geom etry param eters at the weld toe, i t is assumed, afterLawrence, ef al . (Ref. 4), that fatiguecracking starts at the location where thefat igue notch factor calculated throughPeterson's equation adopts i ts maximumvalue.

Peterson's equation readsK t - 1Kf 1 + (4)1 oc/t

w hereKtis the elastic stress co nce ntra tionfactor, r is the notch root radius anda isa ma terial co nstant given by 2.32 X1 0 4 S U -1 '8 (mm), S being the ult imatestrength of material in MPa.If the analytical Kt vs. r relationship isk n o w n , Equation 4 can be differentiatedwith respect to r to determine the cri t icalnotch root radiusrcforw hich Kf obtains amax imum.For the defectless weld toe geometry,the fo l lowingKt vs. r relationship was obtained f ro m finite e leme nt analysis (Ref. 6):K,= 1 + C f ( r / t p (5)

whe re the constantsCiandC2depend onthe ratio of 1/t.The Kf function given by Equation 4combined with Equation 5 passes througha maximum forC2-E 1rc= - ^ - - a (6)

In the presence of undercut (Fig. 2) thetheoretical stress concentration factor atthe weld toe was approximated by (Ref.7) Ktu=K,(1+2V(d7FT] (7)w h e r e Kt is g i v e n t h r o u g h Eq u a t i o n 5 .U s in g Eq u a t i o n s 4 a n d 7 , t h e f a t i g u e

Tab le 5Empirical Re la t ionsh ips be tween Mechan ica l Proper t ies and Hardness D PH of Steel

Proper tyUlt imate tensi le st rength, Su (MPa)Yie ld strength 0.2%, Sy (MPa)Fat igue strength coef f ic ient , o-j'(MPa)Fat igue strength exponent, b

Cycl ic y ie ld st rength,o-y'(MPa)Transit ion fatigue life, 2N tr (reversals)

Funct ion ofDPH3.45 DPH2.68DPH - 1383.3 DPH - I- 370

1-glog(2.1+266 /DPH)

2.1 DPH5.7 X 10s exp( - 0 . 0 1 7DPH)

SourceRef. 8Ref. 9Ref. 9Ref. 9

Ref. 8Ref. 9

W E L D I N G R E S EA R CH S U P P L E M E N T I 271-s


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o Fatigu e Data PointsRegress ion Line0.95 Conf ide nce Limi ts

N fObservedResul ts

10- 1Cfc 2 * 1 0 6Nf> Nj ,Np , cyc l esFig.5 Observedand predicted with two-stage approach fatigue lives for I8G2A welded spec-imens.

notch factor for a we ld wi th unde rcut wasobtained asKt(1 4- v w ) ) - 1

From Equation 8, theKfmaxcondi t ion fora weld with undercut exists i f1)2 4- 4Kt2V (a 2 (K,f a d ) - a

2K, a V ^ J (9)Based on the inspection of the w eld toeregions described earlier, the St3S specimens were assumed to be defectlesswhile for the 18G2A specimens the presence of undercuts was al lowed for. According to theKfmax concept, Equations 6and 9 define the values of the notch rootradius adopted in the crack init iat ion andcrack propagation analyses for the St3Sand 18G2A specimens, respectively. Asthe fatigue notch factor according toEquation 8 is a monotonic function of rand d, the minimum measured r valueequal to 0.5 mm and the maximum measured d value equal to 0.1 mm wereassumed for the 18G2A specimens.Est imat ing HAZ Mater ia l Propert iesth rough H ardness M easurements

The properties of the HAZ material thatare involved in the fatigue process of thetest specimens may be different fromthose of the base metal. As HAZ materialis difficult and expensive to test, all the required material parameters were eitherestimated from hardness measurementsat the weld toe using empirical relationships given in Table 5 or assumed.The fatigue d ucti l i tyexponent c = 0.6was assumed. The relationships of Syand


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A c c o r d i n g t o t h e m o d e l o f M a j u m d a ro r r o w ( R ef . 17 ) t h e m a t e r i a l a h e a d

n e is c o m p o s e d o f th e u n i a x ia l f a t i g u ee n t s o f a w i d t h o f 2P w h e r e p* is as t r u c t u r e s i z e . A s s u m i n g t h a t f a

d a r a n d M o r r o w d e d u c e th e f o l i n g e x p r e s s io nf or fa t i g u e c r a c k g r o w t h

iW~c

(17)

Tab le 6Mechanical Proper t ies of St3S HA Z and 18G2A HA Z M ater ia l

n')ey ]

h e r e AK is t h e s t re s s i n t e n s i t y f a c t o re , e / is t h e c y c l i c y i e l d s t r a i n , a n d t h en i n g o f t h e o t h e r s y m b o l s is e x p l a i n e d

T h e v a l i d i t y o f Eq u a t i o n 1 7 is l im i t e d b yRp 2 p* (18 )

Rp is t h e r e v e r s e d p l a s t i c z o n e s i z e .T h e p h y s i c a l i n t e r p r e t a t i o n o f p* g i v e nM a j u m d a r a n d M o r r o w ( R ef . 1 7) s u g

t h a t i t r e p r e s e n t s t h e m e a n d i s t a n c et w e e n t h e m a j o r m i c r o s t r u c t u r e d e f o r

This d i s t a n c e is t h o u g h t t o

( R e f. 1 9 ) . Ac c o r d i n g t o Usami (Ref. t h e d i a m e t e r (dpc ) o f suc h a c rack ina m a t e r i a l c o n s t a n td p c = 1 .633 X 10- 7 ( S y / E ) 2 ( m m ) ( 1 9 )T h e a b o v e m e n t i o n e d fi n d in g s f r o m

an d 19 a re the ra t io na le fo r d p c .Eq u a t i o n 1 7 wa s o n l y u t i l i z e d t o c a l c u

3 S s p e c i m e n s . T h e a p p r o a c h o f U s a m i8 ) w a s a p p l i e d t o d e r i v e t h e N p e s f o r t h e 1 8 G 2 A s p e c i m e n s s i nc e

t i o n 1 8 w a s n o t s a t i s fi e d f o r 1 8 G 2 Ac o n s i d e r e d . F r o m e x p e r i m e n t a l t e s t s

e , a e b e i n g t h el c r a c k i n a n i n f i n i t e b o d y ) a n d t h e

Aeeff = Ae / ( 1 - R ) , R < OAteff = Ae , R > O (20)h e r e Ae a n d R a r e t h e t o t a l l o c a l s t r a i n

a d i s t a n c e o f a f r o m t h e n o t c ht h e u n c r a c k e d b o d y .

U s a m i ' s e x p e r i m e n t a l d a t a p o i n t s c a ni n w i t h t h e f o l l o w i n g r e l a t i o n

Proper tyHardness, DPHUlt imate strength, Su (MPa)Yie ld strength 0.2%, Sy(MPa)Youn g m odulus, E (MPa)Cycl ic y ie ld st rength,ay '(MPa)Fatigue strength coef f ic ient , 07'(MPa)Fat igue strength exponent, bFatigue ductil i ty coefficient, tf'Fat igue duct i l i ty exponent, cCyc l ic ha rden ing exponen t , n 'Cycl ic st rength coef f ic ient , K' (MPa)Transit ion fatigue life, 2N tr (reversals)Peterson's mater ia l constant , a (mm)Cr i t ica l notch root radius,rc[ rc ' ] (mm)Max imum fa t igue no tch fac to r , Kfmax

St3S HAZ1705873182000003579300 .094

0.878- 0 . 60.157947316780.2420.167< a)

0.1571.995w

2.93

18G2A HAZ1535282722000003218750 .097

0.9370 . 6

0.162878422940.292[0 74]3.12

a) l/t = 1.5(b) l/t =1

( d a / d N ) / a e = 1 2 . 3 ( Aee f f )2

Aeeff


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2*10c

i/t=io* 18G2A

105 106 2*106Observed Fatigue Life N f l cyclesFig.7Comparison between observed and predicted fatigue lives for all test specim ens.

t i g u e t e s t d a t a f o r t h e w e l d e d s p e c i m e n s .T h e d i s c r e p a n c i e s b e t w e e n t h e p r e d i c t e dAS v s . N f d i a g r a m s a n d t h e r e g r e s s i o n l in e sa r e d e p i c t e d b y r a t i o s o f N f v a l u e s g i v e nf o r t h e t w o s tr e s s l e v e l s t h a t c o r r e s p o n dt o t h e h i g h e s t a n d t h e l o we s t s t r e s s r a n g ec o n s i d e r e d in t h e e x p e r i m e n t a l t e st s . F r o mF igs . 4 and 5 , it is seen tha t the p r ed ic te dAS v s . Nf c u r v e s f al l w i t h i n t h e s c a t t e rb a n d s o f t h e f a t i g u e d a t a . S i n c e t h e s l o p e s

o f t h e t h e o r e t i c a l AS v s . Nf d i a g r a m s i nF ig s . 4 a n d 5 a r e l o w e r t h a n t h e s e o f t h er e g r e s s i o n l i n e s , t h e m e a n f a t i g u e l iv e s( r e p r e s e n t e d b y t h e r e g r e s s i o n l i n e s ) a r eu n d e r e s t im a t e d a t h i g h e r s t re s s l e v e l s a n ds l i g h t l y o v e r e s t im a t e d a t l o we r s t r e s s l e v e ls.

T h e c o m p a r i s o n b e t w e e n t h e a c t u a la n d c a l c u l a t e d f a t i g u e l i v e s f o r a l l t h efa t ig ue sp ec i me ns is g iv en in F ig . 7 . Excep t

oo< 50 \M0DELW E L D \ .TOE ^ \

NO DEFECT(St3S)UNDERCUT(18G2A)

l-P P

1~lI I I l l E1 0 -

1.0

N.05,N0 DEFECT

y \ UNDERCUT

L i fe to Form Crack o f S ize O j , c y c l e sFig. 9 C omparison of estimates on life to form a crack of sizea,according to two-stage and one-stage model for sound weld and for weld with undercut.

Xf t f 210oN f , cycles.Fig. 8Predicted percentage of total life devoted to fatigue crack initiation as a function oftotal life for sound weld and for weld with undercut.

a s i n g l e d a t a p o i n t , t h e p r e d i c t i o n s a g r e ew i t h t h e e x p e r i m e n t a l r e s ul ts w i t h i n a f a c t o r o f 2 . T h e p r e d i c t i o n s a r e c o n s e r v a t i v ei n t h e s e n s e t h a t t h e a v e r a g e r a t i o o f t h eo b s e r v e d - t o - c a l c u l a t e d l i f e i s 1 . 1 5 . G e n e r a ll y l o w e r d i s c r e p a n c i e s b e t w e e n t h ea c t u a l a n d e s t im a t e d r e s u l t s o b s e r v e d i nFig.7 f o r t h e 1 8 G 2 A s p e c i m e n s c o m p a r e dt o t h o s e f o r t h e S t3 S s p e c im e n s a r ea p a r e n t l y d u e t o t h e h i g h e r s c a t t e r i n t h efa t igue da ta in the la t te r case .

I n F ig . 8 t h e p r e d i c t e d p e r c e n t a g e o ft o t a l l i f e s p e n t i n c r a c k i n i t i a t i o n is p l o t t e das afunct ion o f to ta l l i f e . For a sound w e l d ,t h e f i g u r e s h o w s t h a t w i t h i n t h e c o n s i d e r e d l i f e r a n g e c r a c k i n i t i a t i o n c o n s u m e s ap r e v a i l i n g f r a c t i o n o f l i f e wh i l e i n t h e p r e s e n c e o f u n d e r c u t , c r a c k i n i t ia t i o n l if e d o m ina tes on ly in the long l i fe reg ime (Nf >5 X 10 5 cyc les ) .One-Stage Approach

A s d i s c u s s e d p r e v i o u s l y , t h e d i f f e r e n c eb e t w e e n l if e e s t i m a t e s a c c o r d i n g t o t h etwo-stage a n d t h e o n e - s t a g e ( P m o d e l )a p p r o a c h e s a ri se s f r o m t h e d i f f e r e n t w a y so f p r e d i c t i n g t h e n u m b e r o f c y c l e s t o d e ve lo p a c ra ck o f s ize a ;.

I n F i g . 9 t h e e v a lu a t i o n s o f t h a t n u m b e ro f c yc l e s f o r t h e c o n s i d e r e d c r u c i f o r mw e l d b y u s i n g t h e l-P m o d e l a n d t h e Pm o d e l a r e c o m p a r e d , U sa m i 's c o n c e p t(Re f . 18 , see Equa t ion s 20 an d 21) be in ge m p l o y e d i n t h e l a t te r c a s e . I t c a n b e s e e nin F i g. 9 t h a t t h e P m o d e l g i v e s m o r e c o n s e r v a t i v e p r e d i c t i o n s o n t h e l if e t o f o r m acrack o f s ize aj t h a n t h e l-P m o d e l . T h ed i s c r e p a n c i e s b e t w e e n t h a t l i f e e s t i m a t ef r o m b o t h a p p r o a c h e s i n c re a s e w i t h d e c r e a s i n g s t r e s s l e v e l t o r e a c h t h e v a l u e o f9 . 1 f o r t h e s o u n d w e l d a n d 4 5 f o r t h e w e l dw i t h u n d e r c u t . C o n s i d e r i n g t h a t t h e l - Pm o d e l h as b e e n p r e v i o u s l y s h o w n t o y i e l ds l ig h t ly c o n s e r v a t i v e Nj es t ima tes (F igs . 4 ,5 an d 7 ) , f r o m F ig . 9 , i t i s c lea r tha t fo r l i vesg r e a t e r t h a n 1 0 5 c y c l e s t h e P m o d e l c a n n o t e n t i r e l y a c c o u n t f o r t h e t o t a l f a t i g u el if e e v e n f o r a w e l d c o n t a i n i n g u n d e r c u t .

Final RemarksA l t h o u g h b a s e d o n t h e m a t e r i a l p r o p e r t ie s e s t i m a t e d i n a r o u g h w a y , t h ef a t i g u e li v es p r e d i c t e d u s i n g t h e t w o - s t a g e

2 7 4 - s I A U G U S T 1 9 9 2


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are ing o o d a g r e e m e n t w i t hthe in f a t i g u e

of w e l d s the HAZm a t e r ia l p r o p via h a r d n e s s m e a s u r e

at thew e l d toe wasf ir s t p r o p o s e d ef al.(Ref. 4). The s u b s e

l y se s , h o w e v e r , w e r e c o n f i n e dth e p r e d i c t i o n s of the l o n g l i f e f a t i g u e

of w e l d s w i t h the use of theo n e - Im o d e l (Ref. 20).T h i s s t u d y i n c l u d

th e c r a c k p r o p a g a t i o n p e r i o d es t i to thec o n c e p t s in w h i c h is e x p r e s s e d

of the l o w - c y c l e - f a t i g u e m a t e r i a lr t i e s , e n a b l e d l if e p r e d i c t i o n s w i t h i n

of f r o m 105to 2 X 10 5c y c l e s .

T h e t w o - s t a g e a p p r o a c h , i n c lu d i n g b o t h and p r o p a g a

one to e s t im a t e t o t a l in the l i f e r e g im e of 105to

X 106c y c l e s , w h i c h a g r e e w i t h i n a f a c r o f 2 w i t h e x p e r i m e n t a l d a t a fo r c r u c i e l d e d s pe c im e n sfailingat th e w e l dT h e s t u d y s u p p o r t s th e a p p l i c a b i l i t y o f

t - a f f e c t e d z o n e m a t e r i a l p r o p e r t i e s viah a r d n e s s m e a s u r e m e n t st o

of w e l d s .T h e o n e - s t a g e a p p r o a c h , w h i c h ne

th e f a t i g u e c r a c k i n i t i a t i o n p h a s e , for the t o t a l fa

l i fe , e v e n fo r w e l d s c o n t a i n i n gu n

References1. Gurney ,T. R. 1979. Fatigue of Welded C a m b r i d g e ,U.K.2. Ya m a d a ,K.,and Hir t ,M.A.1982. Fatigue

/.of the ASCE 108, No. ST7, pp .3. Smith,I.F.C.,and Sm ith, R.A. 1983. Fatigue

in af i lle t we lde d jo int . Eng. Fract. 18 : 861-8 69 .4. Lawrence ,F.V.,Ho ,N.).,a n dMazumdar,981 . Predicting the fatigue resistanceof Annual Review of Materials Science5. Statistical analysis of l inear or l inearized

an d strainTife fat igue data. 1980.6. Skorupa,M Braam,H andPrij, J. 1987.

of approx imate K| solutions to rds cracks at we ld toes.Eng. Fract. Mech. 26:

7. Skorupa,M. 1989. Predicting the fatiguelifeofwe ld s . Scientific Bulletins of the StanislawStaszic Academ y of Mining and Metallurgy. N o .1257. Mechanics, Bull.18 (inPolish).8 . Mo r ro w , J. 1965 .Internal Friction, Damp ing and Cyclic Plasticity. AST MSTP 378, pp .4 5 - 8 7 .9. Mc Ma ho n, ) .C, and Law rence, F.V. 1984.Predict ing fat igue proper t ies through hardnessmeasurem ents. FCP Report No . 105, Universi tyof IllinoisatU rbana-Champa ign .10 . C h e n , W. 1980. A m o d e l for joiningcrack in i t ia t ion and pro paga t ion analyses. Ph.D.Thesis, University of Illinois at Urbana-Champaign.11 . C a m e r o n , A . D . , andSmith, R.A. 1982.Fatigue life prediction for no tched members .

nt J.of Pressure VesselsandPiping 10 : 205-217.12 . Burk, J.D.1978.Theef fect of residualstresses on weld fatigue life. Ph.D. Thesis, Un i versity of Illinoisat Urbana-Cham pa ign .13. Skorupa, M. 1990.Fatigue crack init iat ion l i fe predict ionforwe lde d jo in tsb y low cycle fat igue approach. Fat.Fract. Eng.Mater.Struct. 13:5 9 7 - 6 1 3 .14 . Do wl ing, N.E. , Brose, W.R., and Wilso n,W.K. 1977. Fat igue Under Complex LoadingAnalysis andExper iments. Advances in Engineering. SAE6: 5 5 - 8 4 .1 5 . M o r r o w , J. 1968.SAE Fatigue DesignHandbook, pp.2 1 - 3 0 .16. Jhansale,H.R. andT o p p e r , T.H. 1973.Cyclic Stress-Strain Behavior. Analysis, Experimentation, and Failure Prediction. ASTMSTP519 ,pp.2 4 6 - 2 7 0 .17 . M a ju m d a r , S and M o r r o w , |. 1974.Fracture Toughness andSlow Stable Cracking.ASTM STP 559,p p. 159-182 .18. Usami, S. 1986.Small Fatigue Cracks.The Metallurgical Society Inc.,pp.559-585 .19. Mi l ler , KJ.1987.Thebehav io r of short

fatigue cracks and their init iation. Fa t. Fract. Eng.Mater. Struct. 10:7 5 - 9 1and9 3 - 1 1 3 .20 . Yu n g , J.Y., and Lawrence , F.V. 1985.Analytical and graphical aidsfor thefat iguede sign of we ld m e n t s . Fat. Fract. Eng. Mater.St r u c t 8 : 2 2 3 - 2 4 1 .21 . Testin,R.A.,Yung , j.-Y., Lawrence ,F.V.,and Rice, R.C. 1987. Predicting the fatigueresistanceofs teel we ldm ents . Welding Journal66: 93-sto98-s.

Append ixaa e3fai

C r a c k s i z eEq u i v a l e n t c r a c k s i z eFinal crack s izeIn i t ia l crack s izeP e t e r s o n ' s m a t e r i a l c o n

s tan tF a t ig u e s t r e n g t h e x p o n e n t

cddpceEkKlKf (Kfmax)Ki (Ktu)

k'In 'NN fNiNPNtrr(rc)r' (rc')RRPSSuSyaPeP%f/p*

aC oCf'ffy


8/8

Nitrogen in Arc Welding A ReviewWRC Bulletin 369December 1991

ByIIW Commission IIIn1983, Commission II of the International Institute of Welding (IIW) initiated an effort to review and examine the roleof nitrogen in steel weld metals. The objective was to compile in one source, for future reference, the available information on how nitrogen enters weld metals produced by various arc welding processes, what forms it takes in these welds,and how it affects weld metal properties.This bulletin contains 13 reports and several hundred references related to Nitrogen in Weld Metals that has beenprepared as a review to show the importance nitrogen has in determining weld metal properties.Publication of this report was sponsored by the Welding Research Council, Inc. The price of WRC Bulletin 369 is85.00 per copy, plus $5 .00 for U.S. and $10 .00 for overseas, postage and handling. Orders should be sent with pay

ment to the Welding Research Council, Room 13 01 , 345 E. 47th St., New York, NY 1001 7.

Research on Modern High-Strength Low-Alloy Steel WeldingWRC Bulletin 373June 1992

(1) Influences of S teel Composition and Welding Procedu re on the HAZ Toughness of Thick-Section Structural SteelsBy P.L. Harrison and P. H. M. Hart(2) Heat-Affected Zone Properties of Thick-Section Microalloyed Steels A PerspectiveBy F. Heisterkamp, K. Hulka and A. D. Batte(3) Experience in Fabricating New Types of Offshore Plate and LinepipeBy P. Tuvnes and I. Harneshaug(4) Influence of Local Brittle Zone on HAZ Toughness of TMCP SteelsBy S. Aihara and K. Okamoto

The four papers contained in this Bulletin were presentedatthe Conference on Metallurgy, Welding and Qualificationof Microalloyed (HSLA) Steel Weldm ents, held at Houston, Tex., November 6 -8 , 199 0. The American Welding Societyholds the copyrights and is the source of these pa pers. Publication of this document was sponsored by the Welding Research Council, Inc. The price of WRC Bulletin 373 is $40.00 per copy, plus $5.00 for U.S. and $10.00 for overseas,postage and handling. Orders should be sent with payment to the Welding Research Council, Room 1301, 345 E. 47thSt., New York, NY 10017.

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