Interim report on low cycle fatigue investigations with ship structural components made of higher strength steel

TECHNISCHE HOGESCHOOL - DELFT

RAPPORT Nr.

BETREFFENDE:

Interim-report on low cycle fatigue inve st igat ions with ship structural

components madeof higher strength steel.

Prof.Ir. J.J.W.. Nibbering Ir. H.G. Scholte

INTERIJI-REPORT ON LOW CYCLE FATIGUE INVESTIGATIONS WITH.

SHIP STRUCTURAL COMPONENTS MADE OF HIGI-R STRENGTH -STEEL

/

By Prof.Ir. J.J.W. Nibbering and Ire E.G. Scho]te.

EGKS program 6210-55/2/162 of ihe Committee "Fatigue etCoIstructionsT7pes'.

Prepared or the meeting at Rome in April 1974.

Ship Structures Laboratory

-Deift University of Technology Mekeiweg 2

DELFT - The Netherlands.

Report - no.

Section 2. Observations concerning the fatigue experiments with small structural specimens carried out in

France 3

Section 3. The experiments carried out in Belgium 10

Section 5. Final observations

Literature

Appendix I.

Appendix II.

Section t. Analysis of the experimental results obtained with

the full-scale specimens tested in Deift 26

t0

Secti.on 1. IntrodUction.

This report serves two purposes.

First of ail it makes available to. the members of the committee 't!Fatigue

et Constructions Types" the more important experimental data from the reports

of the Belgian and French participants. (See extracts - appendix I and II).

The second intention of this report is to give the actual state of progress

of the work of analysing and synthesising of all experimental results, which is

done in the Delf't Ship Structures Laboratcryo This ,ork is time-consuming

be-cause, as always, the results are sometimes incomplete and inaçcurate dueto

experimental difficulties', A large part of the work consists of careful studies

of .orck growth.

The greatest difficulties were;

a) Many cracks developed from the surface: in the.width- and

thickness-direc-tion, while only the extension in the width-direction has been recorded

during the tests. - . .

In various specimens of one type, cracks have developed in different way's.

('See section 4).

c) Many cracks have not been detected in the initial stage but only fter they

had developed to significant lengths. This handicaped greatly extrapolations. to .zero-cack--iength,.

For the smaller specimens the data for relatively large cracklengths have

to be corrected' in order to allow comparisons with the data of the, large

specimen s.. '

e). Specimens of one type shed appreciable' differences.. n_we.ld f.orms

f) Some of .the Deift specìîn,ens tave been tested at +20°C, while' others at -37°C'. The influence of this difference had' to be studied' in order to. be

able to present reliable data. ('See also /2/).

Altogether the analysis of the experimental results as presnted in this

report is thought to be sufficiently advanced to permit the committee to make critical observations and constructive suggestions. These will be of help for' the preparation of the -forthcoming first overall synthetical-report, which will.

be ready in August.

-it is hoped that eventual observations Wi 11 be' given in a written form

-From the original French report the most characteristic and interesting

pages have been copied. They can be found in the appendix I of this booklet

under the name "Extrait du compte-rendu d'essais de fatigue

In. Deift the results of the French experiments are now plotted in diagrams

for crack-growth as a function of numbers of cycles. (Figs. 2-land 2-2 show some examples). From the tables shown f.i. on page 27 and 32 of appendix I i.t

will be understood that it was not easy to obtain reliable crack growth

in-format ion..

The nextstep being plotting thecrack growth data as a function of the

local streSss (strains) df tables I and II of the "Extrait", (see also figs.

:13 and 38), has also been started. Similar.work is done for the'est results obtained from the full-scale experiments cartied out in Deift.

Together wit1ì the results for the elementary specimens tested in Belgium and

Germany, all these results will allow a study cf the iifiuence of

macro-stress-concentration factor, local bending and weld shape (micro-stress

con-centration) on fatigue strength. (For information about the progress of work

in connection t-o the Belgian experiments, see section 3).

in the Extrait some-results othe .experiJpents have already been given

as numbers of cycles to incomplete fracture in function of amplitude of nominal

stress.. They confirm the tendency of the German test results that there is

hardly any difference ini fatigue-performance for St,. 37 and St. 52-specimens.

(Fig. 17 page 22; fig. 26 page 31, fig. 51 page 57; fig. 61 page 67)..

This becomes especially clear from fig. 62 page 70, where all results have

been brought together. On the average St. 37 and St. 52 behaved similar.

In section of this report itwillbe seen that for the full-scale

welded specimens a distinct advantage for St. 52 has been observed. It amounts

to some 10% on. the average in terms of stresses.

It has been trie to present the French results in the form of rate of crack growth (da/dn) as a function of stress intensity '(AK,), fig. 2-3. The main difficulty was that the cracks start at points of. structural (macro)

stress concentrations of inaccurately known magnitude. Therefore for the.

stress-factor in AK the nominal stresshas been taken. In the formula

. (AK) this will only influence the magnitude of C and not the more impprtant rn, (provided the cracks are relatively small). The result in fig.

2-3 of course Is not very satisfactory, but it may be used carefully.

The value m for the French specimens proved to be equal to 2,8 for St. 52

which corresponded satisfactorily with the value 2,35 found for the same

mate-rial with axially loaded elementary specimens. (See section 3).

Figures 2-ii and 2-5 give a presentation of the results in a final form.

The curves are W3hler crves for various crack lengths. The dotted curve "End

of testtl. has not any practical significance because aftèr 500 mm2 crack area

the specimen section had been redüced too much, resulting in very high nominal

stresses. One of the actual tasks is to translate figures 2-'4 and 2-5 into.

diagrams valid for infinitely wide specimens. Only these diagrams shoùld be

700-600 500 A 400

E 200

I

- 100 t-(J o I

measured

values.

\

_Crack.2

300

ii

Crack.3

10

; 1

j

pCrack.2 (mm2)

¡ ci ¡ E

/

/

/

,'

Crack.3 (mrn)

E

_i

j

I

//

////

Ii'

i

O I

i

.1

t

I I 0

500000

1000000

1500000

2000000

Number of cycles

FiG 2-1

FATIGUE CRACK PROPAGATION TYPE A, St 52, N2 13 REPEATED LpADING, 7= 0,5/4 kg/mm2

.45-40

30

O

Number of cycles

FIG. 2-2. FATIGUE CRACK PROPAGATION TYPE.B;St.37; N9.4

REPEATED LOADING ; G

05/16 kg/mm2.

measured

-values.

i

1L.o-

I

I

1H

20000 40000 60000

80000

100000 120000 Crack.1 tpCrack.2 Crack.3 Crack.1 Crack.2 (mm2) Crack. 3 (mm2) (estÍmatd)

15-3- '7'

20

400

--

200

E E -C .4-, w L-D) C w

-j

-X C) C) L..

L

(j

C-) o I

9

8

7

9 101

,,

24G

25

Fig. 2-3.

Fatigue crack growth rata.

J I I 1_ F i

5

6 7

9lO

20 18

4-3 i i 2 3 4 5

6 7 8

Number of cycles.

lo

E.

E8

6

16 5(R.L.)

1

4-3 i o? o 100mm2 500mm2 End o test

Numbér of cycles.

26 (R.L.)

_{; 36(R.L.)}

t . t.. .Ì t I

5 6789

'16 (R.L.) Or ¿t 15 (R.L.) I I. I I

6 7 89i6.

FIG. 2-5

FATIGUE CURVES OF DIFFERENT CRACK AREAS FOR

REPEATED LOADING; TYPE.A ; St.42.

15-3

lo

-Section 3 The experiments carried out in Belgium.

In Belgium two kinds of experiments have been carried out.

Fatigue-experiments, with elementary axially loaded or, bent , specimens.

(Report Lab.

y.

1eerstand van Materialen Ghent, no.

153/"4,585).

A.'few pages of thisreporthave been copied forin'formation (see appendix

II)'. The, results havé been presénted as on page

2.

On page 3 the method of measuring crack length i's. de!nönstrated. Page shows the spècimens and gives a summary of the test program.

The second type of éxperiments carried put in Ghent consisted of

fatigue-bending of sull

scale specimens. (Report Lab.

y.

Weerstand van Materialen

no.

153/14706).

T'he iesults in the form of tables giving crack lengths as fUnction of

numbers of cycles are actually transformed to diagrams. Furtherniore the

specimens have all been broken in order to make the fatigue-cracks visible

This makes it' possible to trânsf,orm the beforementioned diagrams for. crack

lengths

into diagrams for 'crack surfaces. A picture of the testset-up and of some characteristic fractures are given i appendix II,, (page

5,

6, 7).

Returning to the' fatigue-tests with elementary specimens under a), f igures

3-1, 3-2, 3-3, 3-14

and

3-5

show the crack growth for

fatigue-bending.

From these diagrams the rate of crack growth da/'dn has been determined as a

function of crack length,, an this transferred to da/dn - K curves. The latter

diagrams have not been included in this report, but the next table summarizes

the results.

*

'three plate thicknesses tested.

Both for bending and axial loading a significant' diffeçence has been found

for m for St. 52 and St.

42, (2,3 -t-'

14,1 as an' average).

m _r C

da/dN C.(AK)m

St. 52

St.

.142 St.

52

. St. '42

bending

2,22,32,O*

4,5-3,5 9,3-5,14-7,2X109 1,02xi01,3,X10'

both types of steel,(grade D

ures are given for axial alternating and repeated loading o

From figures 3-8, 3-11 and 3-i4 it can be concluded that on the average,

and especially in the regidnof lower stresses, St. 52 did not behave better

II

I'

4,

2o

1/

ié

4/

1,

tr>

I

o

a n27A

g

Oaz2éa/

we

9e/,lgez7

Results of fatigue-bending with 25 mm thick

St. 52-specimens.

__L_IJJ I I I

ILLiI

'

B V s

8-f-»

15-3-'7'4

42

A. 9..

£aX.r

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.&L.

&':

£

3 967899

Oa,z/a/

-t

J + 5

7Ic

1;r f28cô'

f9.

3-2.

Results of fatigue-bending with 1g mm thick

40-, g-

O, =

2t'4fg/4z2S

i 2&/t 2á'j

./b:

25 I3,%222fl2

il '5o

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/?/ 519

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2y £2, D o 4s. 9 I 3 . 3

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3-3.

Results of fatigue-bending with 13 'mm thick

.92

f'

fo

/6

-

2544/rnm2

£e':

!5J7 53' 4

-

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¿

-.& 7'29/46494

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£-a?/e,' .75/iJ'z7

c9: £Xi.

f54/nm22

-.

e( i25c4/JqIA

CÍ0:

2oy/?rn21'

&Z;

3

'

5 67

8g/4

ï

4 5 67

a,/d we&79e17

F&. 3-4.

Results of fatigue-bending wjth 19 mm thick

St..

42-specimens..

¿t'

'4,

22

I,

f'

.4,

jD

4

i

li9: cT,25kg/rz??d

...Se!: t/6o?

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ill:

L

1a5 .2

Oaz7éa/ cthsSene2z

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-.11

D.9

J

.3

4' 56789/

ff9.

3-5.

Results of fatiguebendirig with 13 mrì thiôk

St. 42-specimens.

lito

5

30Specimen. C.12

25 c.11

20 cia

c.

- Bending repeated loading.

Specimens: C.9-C.12 (75mm xlgmm) Steel: grade. D

s I I -

LI ---.1

I I

.11_j

I

2 3 4 5

6 7894.2

:3

4

5 6789i5

NUmber of cycles

:

FIG.3-6 FATIGUE CURVES FOR Omm,lmm AND 5mm CRACK LENGTH.

I t t I

.5

6 7B9iS

35 30

- 'is

c4 E E tY)

X

10 E X E

b

sending repeated Lnading.

Spe&rnen:E.9-E.12 (75mmxl9mrn) SteeL grade. DH 36 Nb.

5 1 i i i

ti

2 4 5

6 7 8 9 io.4

Number of cycles

FG.3-7 FATIGUE CURVES FOR Omrn,imrn AND 5mm CRACK LENGTH.

Specimen. E.12 E.0 E.g ElO 14-3!-'74 6

7 8 9

5

6.7 8906

(I E

b

30 10 .5

Number of cycles

FIG.3-8 FATIGUE CURVES FOR.lmm CRACK LENGTH AND FOR COMPLETE FRACTURE.

1t-. 3'74

N

.. . O

\

\

. . .

\

N

H

-- Bend ng repe3ted Lod'ng

steeL:grde.D steeL:grade.DH

i.[

I 36Nb. .

1

I. I I

I;

.

I

. .

I.

t Specirnen:C.9 -C.12 (75mrnxi9mm) Specimens: E.9-E.12 (75mm xl9mm) - t I I 25

t

20 15 E 5

6 7 89i6

S

6 789ib5

.2 3.

6 7 8iO4

o

E.

b

10

-

_{AxL aLternated Loading.}

I. _{Specimens : C.5-C.8 (WOrnm} 19 mm) Steel: grde.D

.1

1

.lt

io

2 3 4 5

6 7 8 9j4

Number of ôycles

.

FIG.3-9

FATIGUE CURVES FQR 1mm AND 5mm CRACK LENGTH.

I I I

6 7 8 9

₀ Specimen. C-7 c.a, C.5 c.5

7896

14-3-.74

30 25 20 E

b10

X E

b

5 c%J E E '10:

AxiaL a1trnated Loading.

Specimens: E.$ -E.S (100mm xl9mm) Steel: grade. DH36Nb.

J i I I i

II

2

13

4

5.6 78 94

Number of cycles

FIG.3-10

AÎJGUE CURVES FOR 1mm AND 5mm CRACK LENGTH.

I I I L

I-5 6

7 8

E. 8 E.6 14-3-'74 I I I

6 7 8906

E

.110

AxiaL alternated Loading.

Specimens: C.S C.8 (100mm x 19mm.) stéeL: grde.D.

Specimenc: E.6 - E.8 (10.0mm xl9mm) steeL: grade. D1 3ENb

5.

T.

. I .2

Number of cycles

I 1 I I

I

-56 7 8 9

5

_{6 7 8.g.S}

j .-.

i.

j.

i:

i I

1.11

.

34 5.6 7.8 9io6

E

ç

Axi;L repeated Lodin.

Specimens: C.1C.4 (100mm xl9mm) SteeL : grde.D 25 20 13

110

E X E

b

O I I I I

II

ia3

2 3 4 5

Number of

yc1es 2 Specimen. Ci C-1 C.4

FIG.3-12 FAflGUE CURVES FOR Omm,lmm AND 5mm CRACK LENGTH.

14 3'74

0.6

t

30-25 20 15 13

4i:L

AiaL repeated Loading.

Specimens: Ei - E.4 (100 mm 19 mm) Ste: grade.DH 36 Nb. o 2 -

Number of cycLes

5

6. 7

5 6 7

FÍG.3--13

FATIGUE CURVES FOR Omrn,lmm ÂNb 5mm ÇRACK LENGTk

8

_i

678

25 2 15 13 E E X E

b

o

i

AxiaL repeated Loading.

Specimens: Ci-C.4 (lOOmrnxl9mm) steCl:grade.D

Speclmen5: Ei-E.4 (1OOmrn,13mm) ste2l:gradê.DH 36 Nb.

I I i I t I - I I I_ I I I I

2 3 4 5

6 7 8 94

2 3 4 5 6

7 8 9

Number of cyces.

FIG3-14

FATIGUE CURVES FOR 1mm CRACK LENGTH AND FOR COMPLETE FRACTURE

t I I I

5

_89i06

a.

.Cracjrowth.

The difficulties mentioned in the introduction concerning the analysis

of the eÑperimentai data have also been met hen studying th' behaviour of

the full-scale specimens. The greatest problem was that in specimens of one

type the cracks could, propagate in essentially different ways. This especially

applied to the bottom details. The influence of this complication on thé

pre-sentatio of the result is still studied,. But 'it may be taken that eventual'

corrections will not

òhange

the figures in this report significantly.

Therefore they have 'been included' in the present report. They replace figures

i to 8 of /2! on 'account of new test data and improved' analysis of results.'

Figures 'i-1 a, b, e show the results for the bracketparts of the

spec-imen,s for 20°C, -37°C and

combined. Figures 4-2 a, b,

c apply to' the

bottom-parts.

From figures 4-i-c and 14-2-c, it remains clear that the fatigue-strength

is better the lower th

temperature, as already observed in /2/.

.

In figures '-l-a and Li-2-a the dotted lines indicate the fatiguelives of

the formerly tested specimens made of St '42, /3/ A distinct adartage for

St. 52 can be observed for 100

and

500 mm2 crack area. (The dotted lines' for

O min2 crack area should not be compared with the full ones (St. 52) because

it is certain that the first have not, been determined as carefully as the

second).

'In fig. '4-i-b is demonstrated how a miflor wéld detail may. influence the

results.. The points on the line 703-03 ar.e s{tuated more 'favourable, than the

ot'her ònes. This :may be attriluted to the f act that in the specimen ccnerned

thè connecting weld between bracket and. longitudinal frame had been

interrupt-.ed (did not exist,) at the end of the; longitudinal frame.

In the'. 'brackets. the cracks generally propagated

n the direction

hown

in fig,. '4-3-ib-c. Only in one case the .crack propagated parallel to the

fusion

line, (see fig. 4-LI-c).

l'ri 'the bottom 3 types of crack propagation have been

26.

-Section

'i.

Analysis of the experimental results obtainethw±th the

fuji-scale specimens tested in Deift.

observed: see fig. '4-6.

crack

a. (See fig. 4-LI-a). b. (See fig. 4-'4-d). C. (See fig. '4-5-d

FIG. '4-6.

Mixed forms of fig. L!-5-a and b were quite common,, (fig.

l4-lI-a)..

The peculiarities in crack path are often reflected in curves, representing

crack growth as function of numbers of cycles. Figures '4-7, 'I-8 and 'i-9 may

give some idea of this

In order to make possible comparisons between the behaviour of the present

spcimensand those of St. 142 formerly tested, the numbers of cycles connected

to the horizontal part of the crack paths may be elmiìated. As said before,

3000-2500

2000

1500 i coo

Q

'i

100 mmL 500mm

H'

N

N

ot

N

N

N

N

Ñ 10w. 1O iO

FiG.4-1-a FATIGUE-LIÑES FOR iABRACKETS AT ROOM TEMPERATURE.

CRACK-AREA OF 0,1ÙO AND 500mm1.

ResuLts of the now tested specimen5

of HSsteet; grade DH 36 Nb. ResuLts of earLier tests with

miLd steeL specimens.

2500-2000 1500 1000

o

z

u

II

-o

z

u)

w

O

GD

I t I I_ 1I I-N

io

io5

FIG.4-l-b FATIGUE-LINES FOR lA-BRACKETS AT TEMPERATURE OF -37°C.

1.

3000r

2500F

s'

2000

1500 1000

o

o

w

w

2

10 _N I I I 10 s' s. s. s. s. s. s' s. s. s. s' s. s. s. s. s' 'I s. s' s. s. s. s' s' s' s' s. s. s' s' _s. s' 5%. s. 5%. V s' 'I L) s. s. 10

---Results at -.37°C.

FIG.4-1-c

COMPARISON ÓF FATIGUE-LINES FOR iA-BRACKETS AT

DIFFÈRENT TEMPERATURES.

CRACK-AREA OF 0,100 AND

.500mm2. (.HS-STEEL;GRADE.,Dft36Nb!).

ResuLts at ruorntemperature (abt. +20°C).

2500

2Q30 1500 1000

i

o

o

w

w

N I I i I I - I I i i

I.

WO mm2 10

D

FIG.4-2-a

FATIGUE-LINES FOR -lA-BOTTOMS: AT ROOM TEMPERATURE.

14 3'74

3000

2500

2000

1500 1000

z

o

z

b

li

z

o

z.

w

N

FG.4-2b

I . . I 5

10

FATIGUE-LINES FOR lA-BOTTOMS AT TEMPERATURE OF -7°C;

2500

2000

1500 1000

z

o

z

b

n

I

.0

_z

w

w

io2

N s. s. s. . s. s. s.

..

_s. s. 's. s. s. s. . s. 'I s. s. s.

,'

s. s. . _s. s.. s. s. s. s. s.

ll..III.. ...I_I

- . . .

,05

ResuLts at -37°C.

FIG 4-2-c

COMPARISON OF FATIGUE-LINES FOR lA-BOTTOMS AT DIFFERENT TEMPERATURES

CRACK-AREA OF 0,100 AND 500 mm2 (HS-STEEL, GRADE DH 36 Nb)

143.!74 L.J:

a-'

/

SC-703-' 9'

SC-703- g'

B. _{Bracket right (backside).}

C. Bracket left (backside),

Fig.4-3

Fatigue cracks of specimen _{nr. 9.}

.-I

SC-703- 9

f A. General view of fatigue cracks.

/

O 3RAcy

B. Bracket right (backside).

r

SC-703- Ø'

i.

j?t

1 ' F;

I). 13o ttom

j.'.f t

-BOTTOM

q 3!

A. General view of fatigue cracks.

j

rig. 4-4 ¡it:igue crrìcks

of specïmeri nr. 8.

C. Bracket left (backside).

:1 _{Bottom right.}

SC-703-e

o

o

SC-703- 9

SC-703- g

Bottom: left. E. Bottom

right..

36

F. Bottom right lower side..

/

Fig.4-5

Fatigue cracs of specimen nr.9.

-

-zÇ'

;,0/ç_ :_ca-a/q

,s

-jo/Q

tzc7 6.-/z°m1'

:5Q-fc4

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uí-/o,zsz

(7-fl)

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O9 Vo

oQ9

X'% 09/ 081 0o.

11V

I

'I

/

/

/

/

/

/

/

'5Oc'

_5côco

tz'in6er

c/ych/e

-

38

_-

de!

-fradeé

left

&--

J

oéécm

le/E

(e-l)

Ioaa

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zz1,re:

_-37''.

I

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nc

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ac-5op/e

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om

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2' 346789 3

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F5. 4'-9 Crr

4-6'

-

qrz'JmLc ßCa/.

14'-fÇ-3 -7v 1 I i i I i' - _/78..c25

Seòtion 5. Final observations.

't is hoped that the committee has obtaiìed a satisfactory idea about

.the experimental wbrk carried out in the various countries, the scope and

progress of the analyzing and synthesizing work, and the form which the final

report will get..

One intriguing problem, which emerged from the German part /6/ of the,

nvestigations is worth mentioning in view of possible extra work. A

signif-icant difference has been observed between the results of the prograiiìmed

fatigue tests with elementary specimens for St.. 42 and St. 52. It would be

interesting to know whether that tendency' also will appear for welded

struc-tural specimens. A number, of these specimens are still available in France.

They will be transported to Dift,. It wouldbe. ,weiòome When some financial.

support for program testing with these spec:imens could be obtained,

prefer-ably from the CECA,. .

The main conclusión from. all results remains. that for constant amplitude.

loading, as well in axial repeated and alternating loading, as in repeafed

bending, the advantage of St. 52 over St. L1.2 .is small. In the high-cycle r,gion

there is virtually no advantage. In the low-cycle region a fair differencçbe-»

tween St. 52 arid 2 is obvious. . .

Literature.

/1/ H.G. Schoite.

"Low cyc'ie.fatigue investigations with ship structural. components

¿ade f higher strength steel".

Report no. 175, S.S.L. De]ift, April1973.

/2/ .H.G.. :Schoite,. . . .

"interim-report on. low cycle fatigue investigations with ship' structiral

components 'made of higher strength steel'!.

/3/ J.J.W.. Nibbering g J. van Lint.

"Low cycle fatigue of steel.structures".

Report N:SS-TNO no.. 82 S, 1966.

/4/ "Compte-rendu d'essais de fatigue en traction ondule et

traction-compression.d'lments souds eu acier ordinaire et acier a haute

resistance".

Par Lopard - 10-5-1973.

Ministre d.'tat chargé de la dfene .nationale,.dlgation ministie1le

pöur. l'armement, direction technique des constructions navales.

/5/ Report no. 153/4585, Lan. y. Weèrstand van Materialen Ghent.

/6/ Report no. 153/4706, Lab. y. Weerstand van Materialen Ghent.

/7/ H.. Paetzold.

"Vergleichende Untersuchungen an gekerbten Proben ais Schiffbaustahl

Cütegrad A und Höherfestem Schiffbaustahl DH 36".

CO1PTE-RENDU DtESSAIS DE FATIGUE EN TRACTION ONDULEE

ET TRACTION-COMPRESSION DtELEMENTS SOUDES EN ACIER

ORDINAIRE ET ACIER A HAUTE RESISTANCE

L:APPENDIXI

e

1,1. - Dans le cadre d'un programme général d'essais réalisé en _coopération avec l'Italie, la Belgique, la Hollande1 l'Allemagne, sous l'égide de l'Insjt de Recherches de la Construction Navale, cet organisme a demandé, par lettre EdER N° 19832 du 12/10/70, au Groupe F4ATERIAUX et STRUCTURES NAVALS du Service Technique des Constructions et Armes Navales, des essais do fatigue

sur deux types d'éléments soudés, confectionnés à partir de t8les d'acier de deux nuances différentes, afin dc comparer les comportements en fatigue de ces assamblae

1,2.

-résùltats.

2,1. - Eléments d'essais

2,11 - ... Les éléments d'essai ont été réalisés en tales d'acier ST37 (acier

ordinaire) et 5152 (acier HR).

2,12 - Deux types d'éprouvettes ont été testées : type A (figure 1), type B

(figure 2) -. Elles sont au nombre de 13 par typa et par nuance d'acier.

2,2. - Définition des essais

2,21 - Les éléments d'essais étaient soumis à un essai de fatigue suivant deux modes de sollicitation (traction ondulée : P min _{- o}

Pinax

-. ou

- traction-compression :

"'

-

I

)

Pmax

2

pour deux niveaux d'endurance (environ 50 000 cycles et i million de cycles), suivi pour la presque totalité, d'un essai de rupture statique à température ambiante et à 0°C pour une éprouvette de chaque type.

2,22 - Le critère de fin d'essai était l'apparition d'une fissure de fatigue

de 'ordre de 25 mm de longueur, la controle de la propagation de cette fissure se faisant visuellement.

2,23 - Les essais de fatigue ont été effectués sur la machine verticale Aoslc

de 100 tonnes, les essais de rupture statique sur la machine NAN de 500-1 000 tor-ines

2,24 - Pour chaque type d'éprouvette, la répartition des contraintes a'été déterminée à l'aide de jauges de déformation. Le nombre, le type et la position des jauges sont définis sur les figures 13 et 38, les résultats obtenus sont

consignés dans les--tableaux I et II.

Le présent compte-rendu relate ces essais et en présenta les

II. - EXECUTION DES ESSAIS

I II?(' UJU U ?,?.I,... t t i i1 t ritt cu iu II t %i

I11t.tt(.

I O

A A I QQ 850

Eprou7cttc typo A

A

Cout,c B3

-5--III. - RESULTATS OBTENU5

3,1 - Les tableaux Iii et IV récapitulent les résultats obtenus _{sur les}

éprouvettes testés.

3,2 - La figure 62 montre les positions relatives des courbes _{de l/oehler} pour chaque type d'éprouvette, par nuance d'acier et suivant le mode de sollicitat!

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Récanitumatif des résultats obtenus sur les éproLJv.etts so'Il1cj'ts

en traction ondulée ST 37 N0 26 N° 36 N° 16

N°15

N°8

.!. ST 52 ST 37 I, t. I' -1.Repère MSN de éprouvettt N" 25 N° 1.2 N° 14 N° 13

N°2

N° 3 N° 4 N° 7 N° 6 N" 9 N°1'0

f

N° 37 't Miri i. 0,5 0,5 0., 5 '0,5 0,5 0,5 0,5 0,5 0,5. 0,5 0,5 0,5 0,5 .0, 5 0,5. 0,5 .0,,,5. Taux de travail k o/mm 2

L

Maxi 10 10 6 'I .5 Nombre de supportés obtention fissure. 72 809:. 89 700 182600 cycles j'usquI:à de là .5

t.

4,5 '790 200 16 _{14 700} 1 0': _{58 500} 6 _{266 800} 5 _{395 400} 4 _{1 515 000} .20 _{4.2 000} 1.6 _{82 200} 16- _{103 000} 12,.5 _{?00 .000} 7- ---i--069 -ODD 20. _{41 800} 18 _{'54 non} 11, _{305 100} 9 _{271 900} i .889 5

Eprouvettes sollicitées eri traction ondulée

N° -5 0, 5 1.6 _{11 400}

i

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ST 52

I t I I

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j1áprouvetth de de

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;5T37

en trar.tioncompression

-Eprouvettes sollicitées en traction-compression

Tcìux de trivail _!IJombre

de cycles

ko/mm2

tsupportés

jusqu'à

Mini

Maxi

obtention de la _t

;fissure. N° 20 - 5 24 000 91 500 t t I t N° 28 463 000 t I t I I

I

N 29 , - 1,8 + 3,6 350 000

TypeA

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t I I t i N° 19 - 5

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;sT52

N° 24 ! - 2 i + i 210 000 I t I

I.

t t N° 30

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--2

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!6T37

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i 110500 I I t t I I i N° 22 i - 3 + 6 583 200 t I t t I I I W° 32 - 2,5 + 5 841 600

!Tvpe

B ! t - ! I t I I t I t N° 34 - 6 + 12 i 81 000 t I t . I I ST 52 t N° 18 i -i + 10 69 600 I t t I t I N° 21 - 3 + 6 530 000 I I I I t - t N° 31 - 2,5 + 5 1 077 400 .1 t -+ 6 N° 23 3

Ap1it,.c, ou aux de trv

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19 '18 .17 ST 37.0 CT 52.TC 16 15 14 13 12 11 10 9 8

.7

6 4 ii

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ST 52.TO ST 37,TC TYPi B i) Qn _'-o J. lu'., 3T 520TC ST 52.T0

F1062

Courbes de Wch1or pour 1e pronettc typo A et type B o1licite3

en traction or.du1e et trcticncoprc$ion

N

i4

-I

Au vu des résultats obtenus au cours des essais précédemment exposés,

il apparaît

4,1 -

que les éprouvttes type B donnent de bien meilleurs résultats que les

éprouvettes type A, ce qui était prévisible eu égard à la conception nìme des

éprouvettes.

4,2 -

que l'utilisation d'un acier HR 51 52 en remplacement de l'acier

ordinaire 51 37 n'améliore pas sensiblement l'endurance.(elle est rnme prfois

inférieure)..

4,3 -

que le mode de sollicitation est sans grande influence sur le comporten

à la fatigue de l'élément soudé.

Paris, Le 30 tiars 1913,

LOPARD,-g

Laboratorhum voo Wecrsthrd va; t1toraen

St.-Pietesnieuwstrczcit 41 -

OOO Gent. s

Directeur: TeL 2S.?.71

Pxof. ir. V/. SOETE P.C. 4S94.1

APP

VERSLAG Nr 153p..5

Aangevraagd door:

De heer ir. J.J.L. Vk !WNEN, Direkteur

Lnlzenweversctraat 21

1050

Ï:ULL

Ten koste van:

idem.

Betreft:

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mm ir*et een dikte van I

mi en

II. Vcrmoeiinsproeven.

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eri Pmin. werden op de net10 sektie berekend.

1. VerrnoeiinEsroeven in trek.

?roefr;achine

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Al

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LABORATORIUM VOOR WEERSTAND VAN MATERIALEN - Dir.: Prof. ir. W. SOETE

F

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r-t is plar-te r-thickness(mm)

TABLE.rr

TEST PROGRAM OF STANDARD FATIGUE TESTS.

!i

.75

P 2 350 700

Notch

350 4

Ç

(kg/mm2)

Steel Gr. D

Steel Gr. DH 36 Nb.

t13 tl9

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Repeated Loading O

i

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10

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