Corrosion fatigue strength of T-type welded connections of thick plates for high numbers of load cycles

CORROSION FATIGUE STRENGTH OF T-TYPE WELDED CONNECTIONS OF THICK PLATES FOR_{HIGH NUMBERS OF} LOAD CYCLES (MaTS-ST-IV-IO)

J.J.W. NIBBER'IÑG', B.C. BUISMAN, H. WILDSCHUT2 and E. VAN R-I'ETBERGEN1 Del'f.t University, Ship Structures Laboratory, Deift, The Netherlands

2

Metal Research Institute, Apeldoorn, The Netherlands

ABSTRACT

Corrosion fatigue experiments have been carried out in the. high cycle low stress domain. Several specimens were also subject-ed to incidentai high loads. They were either or not stress-relieved and a number of them were cathodically protected. The results

for-seawater were not alarming and cathodic pro-tection proved to be more than satisfactory.

1. INTRODUCTION

Up to now most of the corrosion-fatigue experiments at realistic frequencies

(0.1-0.5 Hz) have been carried out fo

life-times of

j5

to 106 cycles. The number of cycles due to wave loading is in

theorder-of _is

only about 1% of the service number. But this is too pessimistic for it ignors that the

timescale for fatigue is logarithmic. But the more the environment is agressive, the less that counts.

Another point is that short waves have smaller periods than long ones., which makes that the cyclic, frequency of the 90% smallest loads is in the order of magnitude of 0.5 Hz (wave length 6 m), while it is < 0.05 Hz for

the l.% highest ones (wave length 600 n). The smaller waves are of particular interest for chords and braces, the longer ones more for the complete structure.

There exist also very low frequency loads due to temperature differences (day-night), tide. streams and changes of wind/wave direction. Combined with wave loads., large low frequency peak to peak values may be the result (fig. J) In [41 it was shown that the

crack growth .per cycle may be increased 10-fold when the frequency diminishes 100-10-fold.

The foregoing. has led to the conviction

that apart from low-load, constant-amplitude testing, also a combination of that with incidental peak loads, should be. studied. This has the additional advantage that the effect of these on the welding stresses was included

in the investigation. A number of specimens were also stress-relieved by heating. 'In sea-water it may be more beneficient than over-stressing, because of the. smaller risk of

stress corrosion. On the other hand, both methods might be equally effective when cathodic protection is applied.

The investigation has the character of a tentative one in order to limit costs and time. When for-one or another aspect spec-tacular results might come forward,

additional tests will be considered.

2.

ÉXPERINTAL PART

2. 1 Test specimens and material

The number of specimens had to be limit-ed to 40. F.igure 2 shows the geometry and welding. The material was normalized Fe 510

with Nb- (Fe. E 355 KT).. (0.17 C; 1.45 Mn.;

0.015 P; 0.004 5; 0.31' Si'; 0.040 Al; 0.038

Nb')'.

0y = 414 N/mm2-; o = 562 N/mm2;' Charpy

160 J at -30°C

The intention was to weld the specimens in the same way as those, of the former

ECSC-investigations '[I] , [2] . But in order to

reduce the costs, only the top layers (6 tp Il in fig. 2) were made identical (vertical up). The rest has mainly been S.A.-welded. The idèa was that cracking always starts at

the undercut of the top layers and this indeed proved to b.e so.

2.-2 Test set-up and instrumentation

Special rigs have been designed in order

to be able to test seval_spc-imensatthe

SIMS- TS 43

I

Steel in Marine Structures,

edited by'C. Noordhoek and J-. de Back

5"SL°3O3

Elsevier Science Publishers B.V., Amsterdam, 1987- Printed in The Netherlands

774

same time in 4-point bending. In both labor-atories (Ship Structures Laboratory Deift and Metal Research Institute Apeldoorn), problems emerged due to the long testing time with the test rigs, the dynamometers and the

potentiostates. For a few specimens Zn-anodes had to be used. In most cases trouble could be traced by investigation of the fracture surfaces. A well cathodical]y protected sur-face was clean with some chalk deposit. Inefficient protection led to rust.

A particularly important point proved to be the isolation between protected and unprotected specimens. Of course, every group had its own testing tank and water-supply. Yet weak leak-currents could occur due to cables (strain gauges) and similar

well-isolated items. It proved to be more dif-ficult-to prevent cathodic protection than to applj, it. A conclusion was that even para-sitie currents can give, effective protection. Much time has been devoted to the study of

crack contours (growing lines). For air-specimens it was easy, but for seawater-ones not (figures 3).

2.3 Test programme

in I the various test parameters have

already been discussed. This has led to the programme shown in table I.

The pre- and intermediate high loads were always equal to 204 N/mm2. At this value some plastic deformation occurred close to the weld toes. The test frequency was 0.4 Hz as explained in the introduction.

3. RESULTS AND CONCLUSIONS 3.1 Tests in air

Table 2 gives the data. 4 Specimens (IO, 15, 39, 40) had obtained rather high loads in order to. be able to compare these results with those for the ECSC Ist and 2nd phase

ones.

Figure 4 shows that 10, 39 and 40 con form well to the. ECSC ist phase. line (A.W.). Only 15 is too well. But on the whole the

correspondence is satisfactory.

Specimens 26 and 34 confirm that for A.W.-specimens preloading at high level is beneficient. Intermediate high ipads are even better (27, 30, 28, 2). Stress relief by

heating has less effect (9., II).

Finally the unfavourable result of 27 is clearly due to the fact that a number of initiation points were present (fig. 3).

3.2 Tests in seawater without cathodic pro-tection (table 3)

In table 3 at several places the ex-pression appears. This value has to do

aeq.

with the fact that when the testIng took too much time, the load was increased. So P

i's a representative value for the whole't period. In fig. 5 the results are confronted with those of the ECSC ist and 2nd phase.

The A.W.-points 21 and 38 in fig.. 5 are situated slightly below the dotted ECSC 2nd phase line; 5 and 23 are above it and 8 and

22 on it. From the frac.ture surfaces of 5 and' 23 it can be concluded that perhaps some cathodic protection has occurred. If so it seems justified to conclude that the fatigue s.trength in seawater keeps descending linear-ly with N in a log S - log 'N diagram. Pre and incidental intermediate loading is clear-ly favourable but far less than in air. This is surprising, because for low cyc'lic loads one expects normally a large effect of the removal of residual welding stresses. Apparently stress-corrosion-type effects overshadow the stress relieving ones. For the intermediate high loads (I.P.L.) their ultra-low frequency might have given rise 'to an

'own' type of corrosion fatigue damage. For they constitute nearly 100 cycles of large magnitude [.4]., [7]

3.3 Tests,in eawater with cathodic pro-tection' (table 4)

The cathodic protection was so favour-able that the fatigue strengths concerned were' practically equal to those in air' (fig.

6). Also the benefits of stress relief by heat treatment have come back. The effect of

preloâding remained small,, but intermediate high loads were practically as useful as in air. Perhaps these intermediate loads indeed stopped the propagation of the cracks, so .that each time a new initiation stage was present. When cathodic protection has, its main, effect on the crack initiation period, thegood result for the intermediate loads could be explained in this way. Therefore a further analysis is made with the aid of fig.

7. This shows the crack propagation lifetime of the specimens. The results for seawater

are clearly below those for air,; the points for cathodic protection with intermediate loads (I.P.L.) are situated between those' for air and seawater. But the scatter is large Moreover there are no data for the. specimens'

that had nòt obtained pre-. or intermediate

loads.

The data of the ECSC 2nd phase programme, constant amplitude, seawater are below those of our points for seawater and intermediate loads. More insight has been obtained with the aid of da/dN - AK curves, (see 4).

4. CRACK GROWTH

For the air-specimens very accurate crack growth curves could be made. Figure 3,

(a, b) shows the crack contours at different numbers of cycles. The contour tines emerged after the alcohol used for estimating the crack lengths, had evaporated. The lines are formed by the residu of dust and dirt. The parameter for crack depth was the crack sur-face A. A/9 is more or less equal to.crack depth, because in general the cracks extend-ed quickly over the breadth (9,) of the.spec-imens.

tK

was takên equal to avnain which a was maximum crack depth. A more refined ex-pression in which the presence of the welded stiffener was accounted fór, for

tK

was not necessary for mutual comparisons of the re-sults. It is remarkable that all specimens but one only showed cracks on one side of the stiffener.

4.1 Air

From fig. 8 it follows that intermediate loads are more effective than preloads, as was expected.. It is remarkable that the co bination of stress relieving and intermediate loading (I.P..L.) is clearly better than -intermediate loading alone. This should probably be attributed to some improvement in the metal structure and perhaps the re-moval of rest-hydrogen. In thick plates hydrogen can stay longer than in thinner ones.

4.2 Experiments in seawater

Although the contour lines on the crack-ed surfaces were barely visible, a thorough study of the crack development has finally resulted in reliable crack growth diagrams. -The crack initiation moment could be es tab-lished-withthè aid of strain gauges.. The specimens 29, 33 and 35 show exactly the same behaviour (f 1g. 9). Yet 35 had obtained some cathodic protection for an unknown part of the lifetime. Apparently it has not worked during the crack propagation period, for com-parison of the S.R-specimens 3 and 4 sug-gests that there is a (slight) influence of cathodic protection on the crack growth be-haviour. A comparison, between A.W.- and S.R.-specimens in seawater with intermediate loads

(I.P.L.) confirms that stress relieving is less effective in seawater than in air.

The most realistic information comes from a comparison between the results of the I.P.L.-specimens for air, seawater and cathodic protection (fig. IO). The crack growth in seawater is some 50 times faster

than in air In seawater there seems to be no threshold value for K! Fortunately the cathodic protection eliminates this tendency. Looking to the f.racture surfaces (fig. 3),

.775

this is yet surprising. For while in air the cracks developed from several separate points, in seawater - either or not with cathodic protection - it occurred rather over the full breadth. But nevertheless the fatigue results for cathodically protected specimens lie, between those for seawater and air.. But how careful one must be in drawing .such conclusions is illustrated in fig. 11. Here the results are plotted in function of

(max.) crack depth (a) instead of crack sur-face (A) as in fig. IO (da/dN instead of dA/dN; K for both in terms of a ). Now al

- max

three curves do suggest to have threshold values, while in fig. IO the one for seawater did not.

Another difference. is that in this plot cathodic protection seems to have no effect Also the curves for air and seawater run parallel now. This is in fact in agreement with [4] where the effect of the environment appeared in the c-value and not in the' m-value of c.(tK)

5. COMPARISON. WITH OTHER 'INVESTIGATIONS Becaùse the present investigation has produced results for large lifetimes it is of interest to see, whether they are well in

line or not with results from other investig-ators for smaller lifetimes.

Of course there are large differences in specimen type, thickness, welding method, material nd test frequency.. For one of these: plate thickness, corrections have been made, derived from experiments of Berge [6] , BSC

[16] , ECSC2_[2L._A.l-l--reaìilis are given in the

_.-origi'fial form (figs.. l2a to 14a) and

correct-ed for thickness (figs. 12b - 14h), air, sea-water and cathodic protection. Specimens of

a very different character and those with thicknesses < 15 msi have not been considered.

The specimen geometry is a difficult item. In the ECSC-investigations T-types were worse than cross-types. But the weld angle had an important influence; 45 was clearly better than 60 As the cross-type ones

in [I] had only 20 , it is not sure what is

more important: ype or angle.. The UKO SRP specimens had 45 C. This is normal which per-haps allows the observation that their

(favourable.) position in figs. 1-IB is caused by their favoûrabié specimen geometry only.

The good results of .Solli for air must be attribüted tò both specimen ànd weld geo-metry. In seawater the rather high test

frequency (I Hz) will add to this. But the results of Berge, Solli and Haagensen for I Hz conform well.

Other observations are given in 6.

SIMS TS 43

776

6. CONCLUSIONS

Figure 12 shows that in air high pre-and intermediate loads are very beneficial in the high-cycle domain. They are clearly more effective than stress relieving by heat

treatment.

in seawater (fig. 13) a small but clear effect remains, especially for the case of the intermediate high loads.

Cathodic protection is always bene-ficial, and even very beneficial for the case of pre- and intermediate high, loads (fig.

14)

Yet the protection mainly works during the initiation period of the cracks (fig. 7). Some influence has also been observed for the propagation stage, especially in the high cycle domain when intermediate peak loads were applied. This may be explained by the

fact that when the cracks are still small and stop regularly, there are as many initiation periods.

The favourable effect of cathodic-pro-tection in connection to crack initiation allows the conclusion that weld-toe-improve-ments have much sense in those cases. Without

protection these techniques have less effect

[8], [15]

Without cathodic protection the classic measures of increasing lifetime by stress

relieving, either mechanical or by heat-treatment, have little or no effect. This has one advantage: fatigue calculations for structures in seawater can be reliably made with simple rules like the one of Paimgren-Miner or the one of Paris-Erdogan.. Adjust-ments for sequence effects, spectra shapes etc. are probably not practical. The cause may be that the "own' frequency of high

loads (distance of peaks) is very small and consequently unfavourable in seawater.

Cathodic protection is the best method for prolonging the life of structures.

Combining the ECSC 2nd phase results with the present ones led to the ('conser-vative) observation that in seawater the fatigue strength lowers linearly with

life-time in a log S - log N plot. For cathodic-ally protected structures a fatigue limit may ex-ist similarly to that in air.

-No attempt has been made to combine the results of the present study for programmed

loading to thOse of existing ones, because the latter apply to much shorter lifetimes.

The interested reader is referred to the literature survey in [19], (in Dutch).

of Offshore Steel Structures", Final RepOrt on ECSC Convention 7210-KB/6/602

(1.7. lf/7.6) , Delft/Apeldoorn (1981')

[2] Back, J. de and Vaessen, C.H.G.: "Effect

of Plate Thickness, Temperature and Weld Toe Profile on the Fatigue and Corrosion Fatigue Behaviour of Welded Offshore

-Structures-. Part I", Final Report n

ECSC Convention 7210-KG/601 (F7.418,1'),

De.lf.t/Apeldoorn (1984).

[31 Rietbergen, E. van: "Resultatenrapport

van het MaTS-ST-1O-Onderzoek naar het Corrosievermoeiingsgedrag van T-Verbin-dingen van Dikke Platen bi'j Grote Aan-tallen Wi'sselingen", Report No. 292, Ship Structures Laboratory, 'Delft Univ-ersity, Deift (1985). (In Dutch).

[41 Nibbering, J.J.W. : "Behaviour of Mild

Steel under Very Low Frequency'Loading in Seawater", Corrosion Science 23 (1983) 6, 645-662.

['5] Berge, S.: "Corrosion Fatigue Testing

of Welded Joints at Low Frequencies", Report SK/R40, Division of Ship

Struc-tures, Technical University Trondheim, Trondheim (1976).

[6] Berge, S.: "Effect of Plate Thickness

in Fatigue of Transverse Fillet Welds", Report SK/R54, Division of Ship

Struc-tures, Technical University Trondheiin,

Trondheim (1981')'.

[7.] Leeuwen, J.L. van and Back, J. de:

"Effect of Load History on the Fatigue Behaviour of a Low Alloy Steel in a Salt Water Environment", Report '6-74-13, 'Stevin Laboratory, Delft University, De-1 ft.

Berge, S.: "Fatigue Strength of K-Welds in Bending", Report SK/R39, Division of Ship Structures, Technical University Trondheim, Trondheim (1976).

Haagensen, P.J., d'Erasmo, P. and Pettersen, B.: "Fatigue Performance in Air and Sea Water and Fracture Toughness

of TIG-Dressed Steel Weidments", paper 8 presented at the European Offshore Steel's Seminar, The Welding Insitute,, Cambridge, November 27-29, 1978.

4 . - . SIMS TS

[IO] NRIM Fatigue Datasheet No. 5, National Research Institute for .Me tals, Tokyo

7. REFERENCES (1978).

[I] Back, J. de and Vaessen, G.H.G.: [11'] NRIM Fatigue Datasheet No. 1-8, National

"Fatigue and Corrosion Fatigue Behaviour Research Institute for Metals, Tokyo (1980).

[12] Soul, O.: "Corrosion Fatigue of

Weld-ments of C-Mn Steel and the Effect of

Cathodic Protetion, Stress Relieving

Treatment and Saline Atmosphere", paper

2.2. presented a-t the International-.

Con-ference- on Steel in Marine Structures,

Paris,. October 5-7,

1981.

['13]

Haagensen, P.J.

"Fatigue' Strength of'

TIG-Dressedi Welded Steel Joints", paper

9.4 pres'ented'

t the International

Con-ference on Steel in Marine Structures,

Paris, October 5-7.,

1981.

'[l4]

"Fatigue in' Offshore Structural Steel".,

Institution of Civil Engineers,

'Westminster', London (198I) .

-Olivier, 'R.

and Ritter., W'.:

"Improve-ments of Fatigue -Strength of 'Welded

Joins by Different Treatments;

StatiJa-ti'cal' Analysis of Literature Data",

paper 9-. 6 presented 'at the International

Conference on Steel -in Marine

Struc-tures,, Paris, 'October 5-7, 1981.

Webster,, S.E.,, Austen, L.-M

and Rudd,

W.J.: "Fatigue, Corrosion Fatigue and'

'Stress Corrosion of Steels for Offshore

Structures",. Report on ECSC -Convntiori

721O-KG/801,, BSC Ref. FR 103-6/-83-2,

British' Steel Corporation, London

('I984)

'[17]

N-ibb'ering, J.J.W., Buisman, B.C.,,

Wildschút, H. and R'ietbergen, E. van:

"Corròsievermoe.iing van T-Verbind'ingen

van Dikke Platen 'bi'j Grote Aanta'llen

Wisse'lingen", Lastéchniek 52,

9

(Sep-tember1.986)--187-I-9-5.'(Itj'Dutch).

[i8] Haagensen, P.J.: (see Li-an, B.: "An

Overview of the. Norwegian Research

Programme of Fatigue of Offshore Steel

Structure&', 'papei presented' at

Symposium in Ghent,

1986-).

[19] 'Overbeeke, J..L..: "I-nventarisatie en

Evaluatie van EGKS

CorEosievermoeiings-onderzoek. Deel II: Vermoeiing b±j

Variabel'e Amplitude BeFastin!', Report

MaTS-ST-5/-SMOZ. Project XVI,' THE-WH'

83-122, 'Ei:ndhoven (2983). (In Dutch).

77'7

© Seawater

with CR (Cpi,

Constant amplitude '(CA.) . 2.AW 2SR (MiLl

Pretoad (PL.) '- 2AW (Ml.)

Intermittent peak(oads (IP.L.) 2AW .2SR (S:SL.I

21 AW 13SR - - - 34 specimens

furthermore. 4 specimens load type 1' in air- for comparison with former tests

-.m.-.38specirnens

C.P. Cathodic Protection.

SR- Stress-Relieved. AW:As Walded.

I MJi Metal Institute.

(S.S!L.I Ship Structures Laboratory.

6. . . SIMS- 'TS 43

Table 3: Results in seawater without cathodic protection

Aii

Tnitirinn

Fracture

No. Lab. Category _{N/mis2 X 10° X 10°} Observat ions

38 MI CA SW' AW 60 3.92 2'l MI CA SW AW 60. 3.14 22 Ml CA SW AW 70 2.60 .1.7 Mi CA SW AW 70 4.91 probabiy

cathodically protected

23 Ml CA SW AW 60 >9.40

no fracture

'12 MI CA 'SW SR 60 3.57-8 MI CA SW SR 70 2;45 5 MI CA SW SR 60 >9. 40

no fracture

36 Ml PL SW AW 70 2.74 20 MI PL SW AW 60 8. 70 29 SSL IPL 'SW AW 8O 0.48 1.89 33 SSL IPL AW 70 1.06 3.60 probably

cathodically protected

3 SSL IPL SW SR 70 2.77 12.66 4 SSL IPL SW SR 80 0.88 2.25 778

Table 1: Test program Environment Loading program

Air

GJ JVtLflJtflflfb

Constint amplitude (CA) 2 AW 2SR (Ml)

(13 JÌJU1flJ'tTLflflP Pretoad (PL) 2AW lSS.L.)

® JlflJltLflJttLflul Intermittent peak loads(l.P.L.) 2AW 2SR .(SS.L.)

1O Cycles

Seawater Constant amplitude (C.A:F SAW 3SR

(il.I

without (P.

Preload (P.1.) 2AW - (Mi.)

]able 4: Results in seawater with 'cathodic protection

POT. electric potentiosate

'Zn. = zinc-anode

7,79

SIMS-TS43

' 7

AO Initiation 'Fracture

No. Lab. Category

N/nun2 x x 106 13' MI CA AIR AU (50)

_(20.80)

60 E8'.00 55.$I 38.8 16 MI 'CA AIR AU 50 >96 9 MI 'CA AIR SR 90 4.09 I! Ml CA'' AIR SR ('50)

(20.0)

(56)

(3.0)

75, 10.4 75'

ii

26 SSL 'PL AIR AU lOO

0.95

2.8

34 SSL PL AIR AW (80)

'(18.7)

(18.7)

90

0.8

3.4 84' 19.5 22.1 28 SSL IPL AIR AU (80)'

(20.0)

(20.0)

(90)

(6.6)

(6.6)

lOO

5.5

9.3

95 12.1 16 27 SSL IPL AIR AU 120 0.54 1.05 2 SSL'

IPL AIR

SR (80)

(20.0)

(20.0)

'(90)

(6.6)

(6.6)

(:100) '(12.6)'

(12.6)

(l'lO)

(18.2)

(18.2)

120

2.8

5.3

-

115:

2,1.0 ' 22.5 30 SSL IPL AIR SR '120

0.53

279

IO MI CA AIR AU 180

-0.23

'15 MI CA AIR AU 130 1.67 39 MI CA AIR AU 90 2.40 40 MI CA AIR AU 70 '

'822

Cath. Aa , Initiation Fracture

No. Lab. Category

prot. 106' 106 37 MI CA ,CP AU POT,.: 90

2.07

18 MI CA C? AU Zn. 70 7.10 7 MI CA CP SR POT. 90 l0' 6 MI CA CP SR 'Zn. (70)

(4.90)

80

> 9.40'

24 MI PL C? AU Zn. ' 80

4.14

25 MI PL CP AU Zn. 70'

9.14

31 SSL IPL C? AU POT.

(82 2)

(12.66') (1:2 .66') ('lOO)

(3.44)

'

(3.44)

120 ' I .08: 'I,. 34 1:10

4.52

4.78'

35 SSL I'PL CP AU 12O 0.29 0.6O

I SSL IPL CP SR POT.

(82.2)

(:1:2.66) ($12.66) (lOO)

(3.44)

(3.44)

120 2.34 ' 2.'89

l'lO 5.78 6,. 33

32 SSL IPL CP SR', POT'. ' l'2O

> 9.20

> 9. 20

Observations Aa increased' equivalent result no fracture Ao increased equivalent result Aa increased equivalent result Aa increased eqúiúalent result Aa' increased equivalent result Observations Aa increased no fracture Ao increased equivalent resült

cath. prat., 'failed"

Au increased

equivalent result no fracture

.780 200 150 AW SR AIR. I I S Pratoad Irilermittentpeakioads SRunrting out I i

I

I I 13

I'

I F I I I i I i i I I I

I II.

0i0 2 3 4 5, 6 7891O n

i

0,1Hz.

toad cycle of

very tow frequency

(105Hzj

Figure i: Low cycle - high stress loading

it

Figure 2 Specimen détails

Figure 4: Results in. air

8 SIMS TS 4

Laya,, W,Id..lhod Wald puaition

I -I 4-S , 6-II MltA-a.ldlflg Sbi.,6.d-.rc,oatding KttA-6.lding ho,i,00tal hal.anIal arIil,p-hill Day Night 3 4 5 678910? 2 5.

;

r;

ST 10-28 (AIR, IPL,AW)

ST 10-24 (CP, PL, AW)

ST 10-21 _{(SW, CA, AW)}

Figure 3: Fracture surfaces (27 and 28: air; 24: cathodic protection; 21: seawater)

781

782 200 i50 1001 E E

z

b

50' 10. E

z

c100

1200 150 'r, Preload' 'InI eroiittent peak loads S Running out '29's

'36 33

I I I .1 i''t II: I AW SR SEAWATER Il ' tn A C A 1' HOD IC PROTEC TIONI o .

o '

22%'17

2111 138".... 1lS;23 .12 ' '..20, . I I'

i. II

50 lOE5 50' 10 2 3 4'5 67691O n 3 I. '5 6 7.89107

Figure 5': Reuits' in seawater

AW SR SEAWATER z CATHODIC, PROTECTION '2 3 4 5 6 7 6 106

ii

2 3 4 5 6 78 '1Ó7

Figure, 6: ResüFts for cathodic protection

L ç 7_ - -26'

j

.

AIR AW SR 'UI

';

X SEAWATER'

rn:

£

La

'CATHODIC PROTEC1IO'

ci:

V,

o

_X i i I

i

I I I-I

i il

PreLoa'd Intermittent peak loads SRunning 'suE protection 33'..cSawater' '3 -. 2 3 t. 5 6789106

!(iJé

initiation 2 3' I. .5 6 789107

Figure 7:- Crack growth.periods

1 O. SIMS TS

D.-'X lñlermittent -.,17. 'ci I4 Q peak loads . 6 'S Running out - I I I' I I I I i i 'i i 'i i 200 150

z o 10_4 9, e'

z'

o o 0_5 SIMS:

TS 43

.10_4

' l I

i0 2 2 1 5 8 ! 9IÒ AK tOTO J o0. 2 1' 1 7,6-76910! AK o sp.J0...51 z16 ,0,PL,8WI Sp.i.8 7720-27 -'q Sp.o.o 57.20-76 (.0.PL. Awl S.i.o S7'lOiI no. IPL . 802

ri

58.,1..n.ST IO2 Jnl..!PL.58l .5p,,000. ST 77'00 l.i,JIPL', SRI PL'. Paiono'

.IPL .l0I.!iiIt.0l pal

AWl nr.410.4

59

Figure 10:. Summary of all results

(a crack depth) 'I ioT2 .7 .2 'ç3 'ç1 6, o I' z-o loT' 100 2 3 1 56 799l0 AK - Cathodic protecticn1 t0 -, so9 2' 9' I S 6 71,101 4K

i

Sp.,l..n ST I829 IS W !PL AWl -1 'Sp.,..oSl 70.22 ISV. IPL,AWt -

-o,r-

i

Spe,w,. ST-lo- IS lIP/SW. IPLAWI 5...57.07.6 I SW, IPL .' SA J

F

_{-Sp.JioIn.'Sl Io;2v}

i

ISW/CP.JPL.561 Sw.S_ (P (illodJ,p 40 IPL. l0Ii0.i1700tI,nA5 -0,0, 8W...10.4 SR .AtIe,IreIl...d

Figure 1-I :- Summary of all results

(A crack surface)

783

Figure 8: dA/.dN - AK curves for air Figure' 9:: dA/dÑ - AK curves-for seawater

784 150 150 50 AIR ASS SR AIR 'k-"44

'

'..

RISSE F. S Froissa

ifll.,mIlt.nt polk loads S-Rsooln9OUI

WTI Wald T,. Inpron.s.nll T -TIP MIsting

II -9d9

P -plasmo d,...g

I -Isprosod proOl.

5 -,hol p..lng F -sold fionS .ngl. slop.

38

Sp.ol.n WTI

11.0 0.omotry lhlokn.00 R PWIIT said Is.

n n 11 BERSI

I R I 1J

0030 0.1 AW HA000HSCN.O I 9 I ,:=sg=o 28 0 0W T 98111.. (10 I 60 0 ASS 11819.6 III I 20 0 AlA 0011.1

lIlI

35 O ASS

IIAMIEII500.b I Ill 01 0.1 ASS T

00059F.. 1141 35 0.1 AW TOS 011058Fb 1141 oun 38 0.1 LW - ECSC.l. II I 40 0.1 0W TOPIF RSC 1161 50 0.1 SR RCSC.lb II I 30 0.1 55 -- 8(55.0 I 2 I 40 0.1 SR 40 10 2 3 4 5 6 7 8 9 i.6 2 3 6 5 6 7 89io? n

Figure 12 a,b: Summary of all data for air

(on top: original; below: corrected for thickness)

.

u 3' I)

u

Sp.oimon VII

Rol 800mol,y lhlskna,s S PWIIT said lO

ç lm.l BERSI IS I L)4J 20-20 0.1 AW HAAGENSEN.1 I I I 28 0 ASS T 119111.1 1101 40 0 ASS I1R1H.b

lIlI

20 0 AV 50111 1101 25 0 ASS H0050IISEN.b 1131 33 01 AW T 0111058F., (lOI

0'

JR 0.1 AW TOS UKOSSP.b

1141 --

38 0.1 0W ((SC. 1. II I 40 0.1 0W TOPIF SSC 1161 50 0.1 SR ((SC. Ib 11 i 30 0.1 58

---(CSC.2

020 40 0.1 SR

Cala comidoS Vor dlfftr,ns,, la thickness. lu 50

l0 2 3 i. 5 6 7 8 9 io.6 2 3 4 5 6 7 8 9 107 2 3 4 5 6 7 8 9io

n

12 SIMS TS

WTI lW.ld To. lspros.,.nhl

T -TIR dr.ss.nq 6 -orisdinR p -plasma drusing 400 I - impooned pooTl.

S -Ihol p..oiln 350 P -..Id lIOnS OQI. slop.

300 250

+.,\

_... ASS SR 400 350 300 250 200

ç1 £ SJ SNIS 98L

(ssaupTq

103

poa1io

:ojdq

juitio

:do

uo)

UIp

I

11 30

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-

d650iIfl III i 80 0 ¿910 o I I IO Li ' i (II 9N3SN3955II I 0 10 I li I 11100 I 0 NL B I 6 I NOSN3001I6 SLIO 0 00-ti J I s I 939636 I IO 00-00 1101 odm loi tool II b.. pilo .o '"W'!ql 110 ELM o1o110dS 19MV351 600 6010009 S

L".._.''..0Z

16001 lUd .., IIlI.0lIW ..06 91 . PIOIUd S

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S E LOL6OL 9 S £ ¿ 90160L9 S E

i

Ido1, lilo. 9°i6 P11° 6op..d oq- S II!,Ud p.004.1- J J"i'"n' ..o.Id - d OoIPoiIN- il 60I"P DII- I 00d,l (1010 0j PPMI Ti ooz osz 00E OSE 00 D. cl

z

li E 001

786 400 35° o0 250 200 150

i

50 la5

WTI (Wild Te. i.p,.v.r,e(i

T -Till d,.iimi

ii -ylndleq P -plus. d.UII..Q i-l.pr,v.d p.eliii S -ibel piule) P -wild (link InRI. ilep.

..I,

'i9A

S (AWAT E R_PROTECTIONCATHODIC

i t i i

tilt

07! M

Q-tili

IROn

-o Die

₁

i i i

o-'I

i i i

liii

IO5 2 3 i. 5 6789106 n u-i.

tf ...;;...

AW SR SEAWATER

r

CATHODIC PROTECTION o

_r

WTi (Wild Tn. bepreni..nel):

T -Titi d,.UIrR G -R'1'1'H

P -pIne.. dnenelng i - lpnen.d nliI. O -tAnt punieR

P -wild theN IMII imp.

I Pr.lo.d let. ,.Ilt.nt pitH loads S Rr,nnlni net I I I

11111

ICATH0OIC PROTECTIOHI SI I 32

o O

O-liZn n

o-

_lt zn

D-Spucl.rt Hit S.nitey IWAkeusi R Pn.q.

i..i

lii.)

liti

25 0 t

UOOSRP

liii

0 ta o Old?

ECSC IT i trzerei 10 0.1 0.2 Data conectad lei dItt.r.nc.s In thIcknus..

2 3 4

56789106

n

2 3 4

S 678910

2 3 4

56789108

Figure 14 a,b: Summary of all data for cathodic protection

(on top: original; below: corrected for thickness)

14 SIMS IS 43

ICAT000IC PHOTECTIONI Spiclnul Rut il.oritny (birke...

it

R Pr.q.

(Hi.)

liti

20 0 i IIKOSRP

liii

OB O Old? ftSC

iii ..

70 0.1 0.2 AW SR

_r

E P,.I.id -. Inl.nnItt.nt p..0 leid. s snnmi net 00 350 300 250 200 150 .1100

z

b

so 2 3 4

5 6789lO

2 3 4

5 678910