JLO
Issued by the Council This report is not to be published
unless verbatim and unabridged
REPORT No. 82 S April 1966
(S 1/43)
NEDERLANDS SCHEEPS-STUDIECENTRUM TNO
NETHERLANDS SHIP RESEARCH CENTRESHIPBUILDING DEPARTMENT MEKELWEG 2, DELFT
LOW-CYCLE FATIGUE OF STEEL STRUCTURES
AN EXPERIMENTAL INVESTIGATION WITH FULL SCALE
SHIP STRUCTURAL COMPONENTS
(PLASTISCHE VERMOEIING VAN STALEN CONSTRUCTIES; EEN EXPERIMENTEEL
ONDERZOEK MET BEHULP VAN SCHEEPSCONSTRUCTIEDELEN OP WARE GROOTTE)
by
Jr. J. J. W. NIBBERING
(Chief Scientific Officer
Ship Structures Laboratory Delft Technological University)
and
J. VAN LINT
(Experimental Officer
Met het oog op de toenemende vraag naar meer
verant-woorde scheepsconstructies is ook meer kennis omtrent het verschijnsel plastische vermoeiing nodig.
In de loop van 1960 ondernam het Laboratorium voor
Scheepsconstructies van de Technische Hogeschool te Delft de eerste voorbereidingen voor een geeigend onderzoek, ge-steund door het Nederlands Scheeps-Studiecentrum TNO. Aangezien een 600 tons trek- en drukbank met te program-meren belasting aanwezig was, werd het mogelijk om
con-structies op ware grootte aan een vermoeiingsbelasting te
onderwerpen, waarmede schaalinvloed, lasinvloeden en
der-gelijke onzekerheden zijn uitgeschakeld. Een bijkomend
voor-decl van deze werkwijze was dat daardoor de proefstukken vervaardigd konden worden onder de gewone
werkplaats-omstandigheden op de werf, zodat de gewoonlijk
voorko-mende fabricage onvolkomenheden mede in het onderzoek zijn betrokken.
Om verschillende redenen werd een
vlak-langsspant-doorvoering door een dwarsschot als proefstuk verkozen en
wel van het onderbroken, het gemodificeerd onderbroken
en het doorgaand type. Het grootste deel van de proefstuk-ken was vervaardigd van gewoon scheepsbouwstaal, Lloyd's grade P 402, doch enige stukken van speciaal staal zijn ook in het onderzoek betrokken.
De proeven zijn verricht volgens een zorgvuldig opgesteld
en geprogrammeerd belastingschema. Registraties van
respectievelijk metingen met rekstrookjes, patroonmetingen en nauwkeurige waarnemingen werden aldus verkregen.
De resultaten zijn overzichtelijk gerangschikt in tabellen en diagrammen waaruit betrekkelijk eenvoudig kwalitatieve conclusies zijn af te leiden. Door de ingewikkelde aard van het gehele probleem is het nog niet mogelijk om voldoende betrouwbare numerieke waarden te geven. Een goede bena-derde schatting van de vermoeiingssterkte van gelaste con-structies ten behoeve van de vergelijking is echter zeer wel
mogelijk.
Een deel van de resultaten die in dit rapport zijn vermeld,
is uitgebracht voor de Royal Institution of Naval
Archi-tects".
HET NEDERLANDS SCHEEPS-STUDIECENTRUM TNO
With regard to the increasing demand for improved ship
structural components, also more knowledge of low-cycle fatigue strength is necessary.
Around the middle of 1960 the Ship Structures Laboratory
of the Delft Technological University undertook the first preparations for the proper investigation supported by the Netherlands Ship Research Centre. The availability of a 600 ton tension-compression machine with programmed
loading provided the possibility of fatigue testing full scale structures, thus eliminating scale influence, welding factors
and other similar uncertainties. An attendant advantage of
this procedure was that the test-pieces could be manufactured
under normal production conditions at the yard, so that
the construction deficiencies usually found were incorporated
in the investigation.
For several reasons interconnections of bottom
longitu-dinals at transverse bulkheads were chosen for testspecimens.
They were of the interrupted, the modified interrupted and
the continuous type. The majority of the specimens have
been made of mild shipbuilding steel, Lloyd's grade P 402, but also some made of a higher strength steel were included in the investigation.
The testing has been performed according to a carefully
scheduled and programmed fatigue loading scheme. Thus
records of straingauge measurements, pattern measurements and conscientious observations respectively were obtained. The results have been clearly compiled in tables and dia-grams by which qualitative conclusions could be relatively
easily derived. Because of the complex nature of the total
problem it has not yet been possible to present sufficiently
hard numerical figures. However, a good an approximate
estimation of the fatigue strength of welded structures is very
well possible.
Part of the information compiled in this report has been
delivered for the Royal Institution of Naval Architects.
CONTENTS 1 '2 3 4 5--6 Summary . eo Introduction. Test-specimens Test-procedures
Results of fatigue tests . Discussion of the fatigue tests.-. Conclusions - it i4 Acknowledgement References , , Appendix I . eg 0. P., , %4 page 5 5 -5 7' .9, 13 4 2,1 21 21 22' rtl
AN EXPERIMENTAL INVESTIGATION WITH FULL SCALE
SHIP STRUCTURAL COMPONENTS 1) by
Ir. J. J. W. NIBBERING and J. VAN LINT
Summary
Low-cycle fatigue-tests with full scale structural specimens have been carried out in the Ship Structures Laboratory at Delft on a 600-ton tension-compression machine.
The specimens represented the interconnection of longitudinal frames at transverse bulkheads. Most were of the interrupted type and were constructed in mild steel. A small number of specimens made of a higher-strength steel was also available.
Axial cyclic loading was applied (Prnin/Pinax= 1/2). The results are given for 0, 100 and 500 mm2 crack-area as a function of nominal, local and peak-stresses.
1
Introduction
The estimation of the risk of fatigue in welded
steel structures is often difficult because the loading is mostly only roughly known and the response of the structure to it is hard to foretell. This situation particularly applies to shipbuilding. This has been demonstrated in [1] where the loading of a modern fast dry cargo ship has been considered. For that ship the loading spectrum of the longitudinal wave
bending stresses was available but the determina-tion of the actual fatigue-loading of the longitudin-al structure necessitated laborious corrections for slamming, corrosion, changes in weight-distribu-tion, changes in temperature and local loads.
When this was done the result had to be "trans-lated" into equivalent loads of constant amplitude in order to be able to compare it with data on the constant-load fatigue-strength of welded details.
This procedure could not be avoided because
practically nothing was known about thefatigue-strength of welded structural details under
pro-grammed and random loading. Indeed, even for
constant-load cycling the situation was not much
better. The last fact has led to the
presentin-vestigation and explains why it only covers con-stant load cycling. It can already be said that the
results rather well substantiate the original
con-clusions given in [1]. As the present investigation has partly been based on these conclusions it will be useful to give them here briefly:
a. In the ship considered small fatigue cracks
might develop after a few years of service when
the structural
details are not carefully
de-signed.
1) Report no. 109 of the Ship Structures Laboratory Delft.
The formation of large cracks is unlikely thanks to the slow rate of propagation.
From a and b it can be concluded that
actual-ly, fatigue is not dangerous as such but only
as far as it favours the development of brittle fractures.
In view of the foregoing the investigations in the
Ship Structures Laboratory have covered both
low-cycle fatigue and brittle fracture of structures.
The specimens were first loaded cyclically and next statically tested to failure at low tempera-ture. The latter results will be published shortly
in Report 86 S of the Netherlands Ship Research Centre TNO.
2
Test-specimens
About 1950 IRwnv and CAMPBELL [2] statically
tested to rupture at low temperature various
types of full-scale interconnections of
bottom-longitudinals. A few years
later TAKAHASHI,AKITA and YOKOYAMA [3] measured the elastic and plastic strains in models (scale 1:2) of similar
specimens in which brackets of various
dimen-sions were used.
Both investigations, although being extremely
valuable, could not give a final answer to the
question how these types of structures would be-have in ships, because ships are largely subjected to cyclic loads. An investigation into the fatigue-strength is necessary. However, this will stillnot suffice as has been discussed in section 1, it is also necessary to know how the specimens behave at low temperature after being subjected to fatigue loading. These considerations led to the conviction that any investigation into the fatigue-strength of
ship structures should again be made with speci-mens representing the intersection
of a bottom
longitudinal at a transverse bulkhead. The choiceof the specimens has further been based on the
following considerations: They should represent
types of structures characteristic for ships; they
should also be of rather inferior design in order to
allow the estimation of a lower limit for the
fatigue- and brittle fracture-strengthof ship
structures in general; they should correspond wellto most of the specimens investigated
in the United States of America and Japan. Finally they should reflect opposite design trends, one typeto be rigid and another to be flexible , while
re-152 -S o 2000 14- SPECIMENS ( St.421 2000 ) 4,4,5 0 - SPECIMENS ( St. 42) de.65 17 2000 ,151 00... .22,1 so 300 o 0 o
Fig. 1. Test specimens
maining easily comparable. The specimens which
best suited these requirements were the original and modified connections of longitudinals used
in T2-tankers (figure
1). Next to these a few
continuous longitudinals have been tested. The
superior fatigue-strength of the latter necessitated
"spoiling" the design by adding a
"bulkhead-stiffener" in order to limit the testing time.The test-program comprised further
experi-ments with specimens of a slightly
different design made of a higher strength steel (St 52). Theresults will be compared with those of the main
investigation for St 42-specimens.
SPECIMENS -St.52
_152
Width of bottomplate 0- :1A- and 2A-specimens :457mm.
Width of bottom plate , 1B- and 28-specimens 1762mm.
L.44.1
56 50 Width of bottomplate 1575mm!
WELDING PARTICULARS (St 42) Electrodes
Frame-bottom one Layer Korneet " white 5mm.
at ends near bulkhead : one Layer
Korneet" white 6.3 mm. Bulkhea d- bottom : i de m
Bracket -f ramef Lange: two Layers Korneet" white 6.3 mm. one Layer Resistent " 5 mm,
Bracket- bulkhead tone Layer 0.K .48 " 3.25 mm ( vert.t ) Frame - bulkhead
Sequence 1 Bulkhead - bottom.
2 Frame - bottom.(from mid-span to ends.) 3 Bracket - frames,
4 Bracket - bulkhead.
WELDING PARTICULARS ( St.522
Electrodes O.K. 48" 3.25mm
Sequence , 1 Frame- bottom.-ii-First layer from mid-span
2 Bulkhead-bottom to end second-Layer
3 Bracket-frames from end to mid
4 Bracket-bulkhead 1472 2A-SPECIMENS ( St.42 ) SCALE: 1.10 o0 41,44 Tbr z1,6, 9 -: -1 2005 -25 SCALE: 11: -1 444.5
3
Test-procedures
All specimens have been tested in the 600-ton
tension-compression machine of the Ship Struc-tures Laboratory of the Technological University at Delft.
A bird's eye view of a specimen in the machine is given in figure 2.
The fatigue loading of the specimens represented more or less the loading of a bottom longitudinal
of a tanker due to longitudinal bending which is a combination of a sagging still water bending moment and wave-bending moments.
It results in a predominantly tensile fatigue
loading. Accordingly in most tests the tensile
component of the fatigue loading was taken two times as large as the compressive component.
(Pmin/P.a. =
The frequency of testing was between 2 and 6
cycles per minute depending on the magnitude of the applied load.
The end-connections of the specimens to the
Fig. 2. 1A-specimen in the 600-ton machine
testing machine could be pin-ended or fixed at
both ends. Originally the fixed condition was
chosen because it was more in conformity with the loading of longitudinals in tankers.However, it soon became evident that deviations
of this situation could not be avoided as will be seen in column 11 of table II. The end-connec-tions were not as rigid as was expected. In view
of this it was decided to avoid difficulties by
in-troducing a reference section fitted with strain gauges in all specimens. With these gauges the
amount of bending in the specimens was measured. Next the equivalent purely axial loading which would have the same effect at the crack-origins in
bracket or bottom as the applied loading was
estimated with the aid of strain gauge data for pure axial loading, pure bending and pure shear of the specimens given in figures 3 and 4 and
table I respectively. The result could be checked
with the aid of the data of gauges 6, 7 and 23
which were attached to practically all specimens (see table I).8
II
=1_,
600
Fig. 3. Stress distribution in 1A-type for 100 ton axial loading
-,3071i4
7.*/,', VIOL 121/-145
Fig. 4. Stress distribution in 2A-type for 100 ton axial loading
FIG.3
I
4
Results of fatigue tests
Fatigue damage, initiation and propagation of a
crack are three important phenomena in a fatigue process. Unfortunately the practical value of this distinction is small as the end of one stage and the beginning of the next one depends on the accuracy of the method of crack detection. Sharply defined are only the beginning of a test and the complete
failure of the specimen. But for investigations
with large structural components the latter is often
hardly more interesting than the former; for in-stance a ship can be flooded long before a com-plete failure is possible. Furthermore in practice a brittle fracture may develop when the fatigue
crack is still small in size.
Russian investigators [4] have found that in
welded plates low-stress brittle fractures are
possible after fatigue-cracks have grown to a
length of 3 to 4 mm. They conclude that fatigue
tests should end when that length is reached.
They apparently postulate that every structure may be used at temperatures low enough for the
development of low-stress fractures. This might be true for countries where extremely low tempera-tures frequently occur but for most cases this point of view does not lead to an economical optimum.
Although the authors do not entirely agree with the Russian proposals the results of the fatigue
tests are nevertheless given as numbers of cycles for an average crack-length of 4 mm in the bracket-plate, being 100 mm2 fracture area. Curves are also given for zero crack length. However, the position of these curves is dependent on the method used
for
estimating the corresponding numbers of
cycles. In the present case they were obtained by first plotting the various observations made duringa test with respect to crack growth as a function
of the logarithm of the number of cycles (log N). The intersection of a smooth curve through these points with the abscis gave the number of cycles
belonging to zero crack length (1= 0) . This of course,
is rather an arbitrary method because any axis
other than log N or 1 would have yielded a different number of cycles. But as will be seen in figures 5 to 8
the distance between the curves thus obtained
and curves for 100 mm2 and 500 mm2 crack area
give at least an idea of the large difference in
design-stresses valid for structures if either no
cracks or small cracks are permitted.
Curves for 500 mm2 crack area are also given
because they are thought to be the more
repre-sentative for what could be permitted in ship
structures. They can be sufficiently well detected during surveys but are yet small enough to permit
an eventual further growth until a next survey
without excessive risk.
In figures 5, 6, 7 and 8 the numbers of cycles for
various crack-areas are plotted as a function of
nominal and local strains for brackets and bottom-plates of the lA and 2A type specimens; in fact as
a function of the product of strain and Young's modulus. The strain values are obtained from
figures 3 and 4 as well as from measurements made
during the fatigue-tests. They are equal to the difference between the maximum strain during
tension and the maximum strain during
com-pression. For all specimens except no. 1A7, the
local strains of gauges 6, 7 and 23, measured during the fatigue tests proved to be practically
propor-tional to the range of fatigue loading applied.
This means that in these heavily loaded speci-mens, even in the immediate vicinity of severe stress raisers little or no cyclic plastic straining
occurred. For the specimen 1A7, which was sub-jected to high fatigue-loading, the plastic straining, i.e. width of hysteresis-loop, at gauge 23 was equal to 20% of the corresponding elastic value. It has
apparently not caused a distinct reduction in
fatigue strength. Specimen 2A2 has been loaded so heavily that cyclic plastic straining will certainlyhave occurred. Unfortunately the photographic
paper containing the records of that test has been
spoiled because of a defect in
the automaticdevelopping apparatus.
Before discussing and comparing the individual curves of the fatigue diagrams it is desirable to
consider the usefulness of all this information. Of course it gives the fatigue strength of the
longitud-inals tested, but the difficulty remains that in
practice the loading is likely to differ largely from what has been applied. All kinds of combinationsof axial loading, pure bending and shear
arepossible. In order to meet this difficulty table I
gives strain gauge data for three different loading
conditions :
Pure axial loading; Pure bending; Pure shear.
The last information is obtained from a test in
which the specimens were clamped at one side and
vertically pulled at the other side. That part of
the total stress which was due to pure bending was
eliminated. Due to this procedure the data for pure shear are less accurate than the other data.
10 27 TABLE I 12/13. 9 22,4*. 8 /7 -1/' 67 10/11. 14t151. 7' SPECIMENS 18 and 2 9 . 26 25 24 20 9
VALUES ARE STRAIN xYOUNG'S MODULUS (Kg/crri2)
Table I. Stresses in specimens 1A, 2A, 1B and 2B for axial loading, bending and shear
1A 2A 1 B 2B z ,,,T, ZV,D zo. El99.1 I
.
. 1213,33.-o_tr),, rc..6 z ,7 g ,,,, z eX,_,.Z...CCW,<.4x:'CtzCCW.I .---Os-'DW-,, 6 z z _,--a,co .2 ...-'752wEiEwaffi-'6°w6E.<u-',6211.15Ew<t.,-1,-90wEEw<Lu,,9 DMZ' cLcnul 6z d ---er Xo'DW-<t-,`" 6 z . atz:20-tn IZZ...,CCLU.,
2., L,-,,Z 2 DMr, Li 5 c ---,.."'CEZ X,"" -1--..
z OLLIgDIZ (L..= 'I ,,,,x. , (XL,. ci,n, 127 62o 575 IMMO 112:a NM IIM INIMEGINE3 245 -120miliganclillno -176 MINELEMILIEMI -9 MEI 1130M0 47 1537 -150 MEM CIEWEE1 -91 -220 -34mEg milmaim3 compamn Ing 48 -114 -360 16 -112
MI
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MCI MOO= 19 ECIIICIEI 205 ME WM NMMO857 215 759 257=3 155 1050 115110 874111E3.110 MEEll
_i MILIKIIIIIMIKEIKEIMEI1 1015 -459 -327MI
IMIIIIKIIIME 28 600 -25 625 205 -40 573 163 -123 608 -73 IMENCIEEmu=
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99 -173,11:01=11:0111111 MN ERI-365 4601=MM'
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ME111111=11M111111=1=1111 -111MEGE1111011111111111MI 17 37I
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-1270 4043 -213 -16 691 49 -9 -92 13 57 -2581 -292 960ll
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246 324 -18811M1 315 -7331
1312 -278I
1 -680 177WEINIMILEINEEI1031113:71 37 lEIDIMBINES -756 207 64 11111 1113711071111MIZE 11113211111E
HMO
372an
-243 -130MI
-156 -123NEENISEMM rs - so 294 -170 -120 363 -181 28 561 -36 -216MEI -363 III111111110 111111111111111M 310 185 NM 244=611=1111111 IIMIIIIII IMIIMIIIMI=I
al
-286ME 304 81 231 MN ME -26 4 7 -363 71 , -429 634 ,Ea
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-3325,1 331285 74 543 -281 41 IENIMICIEIMMIMIIIII 76 IMIIIIMIN-4"
IIIMIIIIIIIIIIIIIIIE oIIKIIMMIIM
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munitimmomoni
IRMIMMill 472-1 so -298 MN
=I
212 -565 2407 -360 10971 1287 53 975 64 bb/bb 5.11(59 k , 1 63 , ..."
27 61/62 74/75 SP,. WENS 1A and 18. 43/44 ;-. 32/33H 17371 41 / 38 13635 31 301 I 1 r. = . 24 2218 77-2O 28 21SPECIMENS 11 and 2A. 16/17.
28 21 6 1 2 12 1010 172 13 945 48 -80 794 368 5 693 4291 17 751 145 -32 760 -321 1165 601 44 644 59 16 901 198 748 357 47 17 861 50 -46 1149 -93 -85 -223 847 182 -231 -175 -10 597 122 0 -22 82 -18 191 1514- -693 -311 25 571 269 607 272 15 560 211 -35 26 600- 320 2 580 330 -6 594 190 -591 580 204 -56 27 600 254 18 658 18 591 160 -79 638 172 -83 290 118 34 35 -50 -17 38 36 77 -61 -251 -15 118 -88 9 305 -605 348 42 -167 137 -118 7 43 0 44 -83 188 85 47 -201 126 41 55 50 266 -338 330 -197 -45 297 -216 -17 314 -180 42 -171 -12 414 -270 -21 493 -334 -47 448 -270 -358 -74 -132 -77 376 -140 115 -80 573 -515 -284 197 160 -106 -70 220 -235 268 . 231 -165 -128 235 13 -502 192 -151 -32 255 -211 10 471 238 -215 -39 214 -314 90 201 -231 146 263 -335 174 126 -246 264 -576 55 601 597 -48 69 -185 -13 70 347 -679 72 73 5 325, I 1812/9133ri
TABLE 1"
Table II. Summary of tests and results for mild steel specimens
1 2 3 4 5 6 7 8
910
11 SPECIMEN: INS NUMBER OF CYCLESFATIGUE STRESS FRACTURE
LOAD ( TONS ) ( 1000 KG ) TEMP. °C AVERAGE STRESS (NET)
AREA OF FATIGUE FRACTURE (mm2 ) BENDING
DURING FATIGUE TEST (%) fFL-fexloci BRACKET BOTTOM OR .( LONGITUDINAL) kg/cm2 ts/o" kg/m2 ts/o" BROKEN PART INTACT PART BROKEN PART INTACT PART N.A.
141 ONLY STATICALLY TESTED 491 -34 2840 18.03
142 24000 +1095,/485, A +6.,9y 7 -3.0 32, -33 2010 12.76 230 20 900 40 -4.8 1A3 17620 +1020//-510 +8,47//-3.23 3 -23 2056 13.05 112 76 160 130 -10.5 1A4 5660 +1226//-613 +77,23
/
-3.89 465 0 2721 17.28 41 178 150 -12.1145 ONLY STATICALLY TESTED 516 +20 2984 1895
1A6 11250 +1236/ A618 +784/ A3.92 340 -10 2050 13.02 210 36 518 -6.6 1A7 4150 +1420/ A710+9 .0)/-4.5, 428 -6.5 2507 15.92 60 40 100 175 & 39 _10.4 1A8 31200 +780/ A555 +4.95//-3 .52 337 -40 1974 12.53 46 270 20 0
1B/22/00
+1046/ A523+6.64//-3.3ci 518 -36.5 2265 14.85 134 187 50 210241 ONLY STATICALLY TESTED 494 -35 2853 18.11
._ 2A2 4000 +16/ +101_4.92
/
386 -33 2295 14.57 306 & 136 160 _77, 345 2A3 14840 +110y -530 +6.9,"// -3.37 388 -21.5 2028 12.88 270 36 50 IN CIRC. EDGE 40 (168) -14.1 +905/ +5.75/ 105 2A4 17550 /-450 /-2.86 411 -8 2401 15.24 84 150 & 57 -17.5 +1250/ 24 2A6 7140 /- 618+797-3.92 384 -8 2234 14.18 79 84 & 75 -9.4 2A7 32000 +770//-555+4.8/8/ -3.52 389 -6.3 2255 14.32 96 100 IN CIRC. EDGE (474 ) -6.1 2A8 10000 +683/-683+4.37 -4.34 524 -10 2964 18.82 50 45 42 IN CIRC. EDGE 68 (160) -6.6 2B1 18500 +1172/_537+77
_341 514 -36 2272 14.43 432 375 30 02 37400 +149/- +g50/.57 -475 459 -34 2835 18.00 405 23 -2102'
31400 +1447 -725+9/
-4.60 240 -38 1754 11.14 629,//
2464 03 54770 +160 /0/ _800 +10y _5.08 439 -30 2990 18.89 80/1'840 72 -20.9 04 26810 +1770 855 /1, _5.43 +11.2,c/ 425 -13.5 2650 16.83 48 506 I -22.2 ) L 1 1/
12
With the information given in table I the stress
distribution for any desired combination of loads
can be obtained. Next the data for the gauges
situated close to the crack origins in bracket and bottom can be plotted in the diagrams by using the appropriate scale after which the number of cycles causing a certain crack-length is found.
The choice of scale is further discussed in section 5. Whichever of the values for bottom or bracket
is smallest is indicative: for the whole structure.
Attention should be paid to the fact that the width
of the bottomplate of the IA and 2A specimens
was not equal to one framespacing (762 mm) but
to 457 mm. In order to meet this difficulty the
stresses and strains, have also been measured on
ORDINATES ARE TOTAL RANGES OF CYCLIC STRAIN CRACK AREA IS ZERO (NUMBER OF CYCLES HAS BEEN ESTIMATED)
CRACK AREA IS 100mm2 CRACK AREA IS 500mm2
0 (NUMBER OF CYCLES MOSTLY ESTIMATED II
2.0 FOR BOTH PARTS OF SPECIMEN
A-TYPES 0 0 BREADTH OF BOTTOMPLATE IS 45720011,
B-TYPES; - 762mm.
INNERSCALE VALID FOR A-AND B-TYPE SPECIMENS., OTHER SCALES, ONLY VALID FOR A-TYPE SPECIMEN
lot
FG 5
two specimens with a bottomplate equal to 762 mm
in width; the results are given in table 1. Further
information on structures of similar design is to be
found in [2] and [3].
-Regarding the above mentioned proces ure it
should be realized that all results apply to fatigue loading of which the tension part is two iqimes as
large as the compression part. This has theaddi-tional advantage that the results are sufficiently close to a pure alternating load (Pnun/Pnia. = 1)
as well as to a pure repeated load (PMiniIPmax = 0)
With a -simple correction,
sufficiently-accurate-values for any type of loading between Pmin, - max =
=
1 -and 0 can certainly be obtained. 1.The authors often use a correction 34hich is
500 5000 .4000 4000 3000 000 0000 200 10 SOO 4000 00 COO I AL W K II 11, 0,
Fig. 5c Fatigue-lines for 1.A brackets
(mild steel)
Fig. 16!. Fatigue-lines for IA-bottoms (mild steel)
Fig. 7. Fatigue-lines for 2A-b ackets (mild steel)
Fig. 8. Fatigue-lines for 2A- ttoms. (Mild steep) 400000002000t 1A7 2. it 'NI
'gill
A4 l' * ....- .'11.1.1..1 1A2' I I' 1A3, .... 2000 1A8 0. ;,000_pawl '1
.... _All
... .er
, II It II $ I II11 1 11 0 1 IFIII 4000 ' H., .. NS, 7 ea .... T'" 10000 .1.11.\
q 1A6 0 3000 1A2 : -1-I ... 2000 No ...ilealk... IN 1A8c2.%. .ill
vo. ::....-4116ii2 I II II i'/1 IIII 1121 6000 500 10 500 .202 5000 7oa 4000 3000 200 2000 to Flak FfG 8 10 6000 2000- 50._1000.- 1000-''')I 247 .
I
0000- 3000- 2000-2\
2A6 0000-000 2 02 FIG.7 1000based on the supposition that the damage due to the tensile part of a fatigue load is two times as large as the damage from the compressive part. This factor two is certainly too high with regard
to the initiation of low cycle fatigue cracks at dis-continuous points in structures, but as the initiation time is relatively short in that case this deviation is not too serious.
If necessary, more accurate corrections may be made with the aid of information given by GUR-NEY [5] and by ROLFE and MUNSE [6]. But then also the considerations given at the end of section 5 will have to be taken into account.
For the specimens 2A7, 2A8 and 1A8 the tensile
part of the fatigue load was about equal to the
compressive part. The results were corrected in the above mentioned way. In figures 5 to 8 it can be seen that 2A7 and 1A8 conform well to the general tendency; 2A8 however is completely out of line,
which means that in this case the above given
factor two is too high. For this specimen it seems to be closer to 1. In connection to this it is probably
not without importance that 2A8 has been
sub-jected to the smallest tensile load of all specimens in which situation the residual tensile stresses will either be not or to a lesser degree relieved as in the case of the other specimens. This might explain the unfavourable behaviour of this specimen.
Another remarkable point is
that the two
specimens 1B1 and 2B1 with bottomplates 66%
wider than the other specimens were in every
respect better. This will be further discussed in
section 5. Here it is necessary to say that for these B-type specimens only the inner scale of figures 5 to 8 is valid because the stress distribution differs from that of the A-types.
5
Discussion of the fatigue tests
a. Interrupted longitudinals (mild steel)
Figures 5 to 8, giving all information from the
fatigue tests are not so well suited for a further
dis-cussion and mutual comparison of the results. Therefore the lines for 100 mm2 and 500 mm2 crack-area have been brought together in
dia-grams respectively for the five vertical scales used
in figures 5 to 8. The lines for 100 mm2
crack-area are the more accurate and will be discussed
in particular (figures 9 to 13). The thin lines for
St 52 included in these figures will be discussed under c of this section.
In figure 9 the results are given as a function of nominal stresses. The line for the bottomdetail of
the 1A-specimens is situated lower than the line
for the bracketdetail. This means that the fatigue strength of this type of specimen is governed by the bottomdetail. For the 2A-specimens it is the bracket-detail. This could be expected because the semi-circular cut-out must be more effective at the
bot-tom-side than at the bracket-side where much
material is left in the flange of the frame and the upper part of the web.
But it is surprising that the strength of the 2A-brackets should be worse than of the 1A-2A-brackets.
The cause is that in the 2A-brackets the local
(horizontal) bending at the end of the longitudinalframe is larger than for the IA-brackets.
Although this has not been measured directly
it can be derived from the data of other strain
gauges near this point; see figures 3 and 4. The change in the relative positions of the 1A- and
2A-lines for brackets in figures 12 and 13 illustrates the influence of the local bending well.
The bottomplate of the 2A-specimens behaved
only slightly better than the bottom of the
1A-specimens (see figure 9). The reason is that in case
of a semi-circular cut-out the bottomplate takes a relatively larger part of the whole load than in
case of a straight-ended frame. Accordingly when
the fatigue-data are plotted as a function of the
bottomload, 2A becomes better than IA (figure 10). When studying figures 9 to 13 it can be seen that the
fatigue-lines of the four different bracket- and bottomdetails correspond best to each other in figure 12. This might be taken as an indication
that the stress
(strain) parameter used in that
figure is the one which actually governs the fatigue
strength of each of the four details. This would
mean that the local bending is only of secondary importance which is not in conformity with what
has been said before for the bracket of type 2A.
Also the results for the two specimens with wide bottomplate (1B1 and 2B1) deviate. They fit best to the lines of figure 13 where the endurances are given as functions of strain data in which both the stress-concentration effect and the local bending are included.
It is disappointing that none of the five
strain-values used in figures 9 to 13 can be used as a
sufficiently reliable criterium for the estimation of
the fatigue strength of welded structures. This means that the procedure given in section 4 for cases in which combinations of axial loading,
bending and shear occur will not be very accurate.
Two different values for the fatigue life are
14 x 3000' 2000 6000 5000 4000 VP 3 3000 0 200a 71 1000 cr (11 Li"! 6000 5000 a4000 3000 2000 1000
almik
(A V G 2 .1BOTTOMPLAT65 (St 521 $.11111
ierd
\all--EE (AV G ) io3 _ .03 EE (21 I ...2110 128 EEIAV60/70--v-II N. TYPE 2ATYPE 10 4 FIG.9 IFIG.10 IFIG.11 105 1o5 0 rn 6000 5000 4000 300a-10000 2000 1000'-8000 7000 6000 4000 3000 2000 1000 1 0101=11
23 18 EE (874 1A I AL 1 II,I 011010 II
II 10 1 5ORDINATES ARE TOTAL /RANGES OF CYCLIC STRAIN.
CURVES APPLY TO 100mm2 CRACK AREA. 1B 29
SPECIMENS WITH VIDE BOTTOMPLATES (762mml
1--POINTING TO COMPARABLE /RESULTS FOR SA AND 2A SPECIMENS. (WIDTH OF .BOTTOMPLATE 4570m(
\
BOTTOMPLATES -St 52) 2k\. 6E023 I'1N
(2x); EEcAy 6/71 104 0 II 61 _aj 10 11 Fig. 9, 10, 11, 12, 13.Fatigue-strength of bracket- and
bot-tomdetails for 1100 mm2 crack-area shown as a function of nominal and local strains
\
I 80TTOM0-2A I (BOTTOMS - St.52 )i ...\
I( BRACKETS-1A )) 18 18 I I 1, 2B ( BOTTOMS-1A )-4`,.. BRACKETS-2A)--il.'\
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a.l gal EE IC 1 -'>----f--eal Ill 1 2A\ 11\
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rii 11 II A\
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, 11\
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1 e EE(6) 1\
. 1 1 I 1130TTOMPLATES)-0-\ , (St.52I, I .6.it 1 II ti Ill' 0 . I 1 11 1 01 $_ i I il alit 0 rd,
4000 -EE 141 I IA St.52 12, I IIII 9000 5000 -FIG 6/7 I 1 1 1 I
1000-6000 5000 4000 3000 2000 1000 6000 5000 4000 3000 2000 1000 (BOTTOMPLATES (St 52/ 1 1 1 1 111 105
.111
12E1
EE'M 1 1 1 1 1111 .104 F10.14 FIG.15 1 I I 1111 105 F10.16 6000 5000 000 3000 2000 1000 10000 9000 8000 7000 6000 5000 4000 3000 2000 1000ORDINATES ARE TOTAL RANGES OF CYCLIC STRAIN. CURVES APPLY TO500mm2CRACK AREA.
1B 2B
so SPECIMENS WITH WIDE BOTTOMPLATES (762mm)
Li--POINTING TO COMPARABLE RESULTS FOR IA AND 2A SPECIMENS. ( WIDTH OF BOTTOMPLATE 457mm)
IA TYPE
2A-TYPE
St.52
Fig. 14, 15, 16, 17, 18.
Fatigue-strength of bracket- and
bot-tomdetails for 500 mm= crack-area shown as a function of nominal and local strains SOTTO PLATE:-,S2t512) III . 2A EE (AVG 6/TI ,,,
III
iii
B2. 6/7\\
1
EE1AVG 6/7 ) I I 11111 1 1 1 1 1 1 11 I I 6/7 --930TTOMPLATES1 (St 521lli
li EEICI aIIIIM
\
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1
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,,-
,
\
\
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2. 18\
\ ,1
_ 6E16/ I 1 1 1 1 111 1 1 1 1 1111 1 1 1 1 1 1 4000 BOTTOMS St 52 (BOTTOMS-2, 3050-"Tx 2000 B2 BRACKETS A) 29 Ui ,Lxcn 1000 : (BRACKETS 17, 1001 OMS-1A1 04 os los FIG.17IMPORTANT THE INFORMATION GIVEN IN FIGURES 14 TO 18 WHICH RELATES TO
500mm2CRACK AREA IS OBTAINED BY EXTRAPOLATION
WITH THE AID OF DATA FOR SMALLER CRACK AREAS.
,04 io 10 FIB 19 EE N -1 \. -I I II II 9 IqII I lo
16
the time being the best thing to do is to take the
mean of the logarithm of these values.
In figure 13 an additional curve is given which
represents the low-cycle fatigue strength of
un-notched bars for axial alternating loading.
The cross-section of these pieces was 40 x 25 mm2 and they were loaded in a 100-ton Amsler pulsator. In all cases the mean load was a little higher than zero ton in order to avoid buckling. Due to this all bars had some permanent deformation after frac-ture; the highest value was 5%.
These results and the results of the tests with
bottom longitudinals might be compared although for the latter the mean load was generally appre-ciably larger than zero tons. This might be counter-balanced by the fact that only limited local plastic
straining could occur in these longitudinals
be-cause the nominal stresses were always below
yield point.
It is remarkable to see that in figure 13 the fatigue strength of the structures tested is approximately equal to the fatigue strength of the unnotched bars. A similar tendency has been found earlier [7].
This is not so natural. In fact the strain-values
used in figure 13 are not the highest strains
occur-ring at the particular structural detail because
they are obtained with the aid of strain gauges with a grid-length of 4 mm situated near theedge of thewelds. In figures 3 and 4 it can be seen that for
gauges situated at the welds of the bottomplate the strains are more than 1.5 times larger (in figure 3: 2600/1610; figure 4: 17/0//120) . Smaller gauges
would have resulted in still larger values. It seems that the development of low-cycle fatigue-cracks
in structures is not primarily governed by such very localized peak deformations but rather by the deformations in the immediate vicinity of a
potential crack-origin.
This conclusion, however, has only the merit
of possessing a certain practical value for it neglects the fact that the conditions for initiation
and propagation of a crack in an evenly stressed
bar are very different from those of a structure. In
an unnotched bar a crack once initiated,
prop-agates in highly damaged material. In a structure a crack initiates at a discontinuity but propagates in relatively sound material.
The observed correspondence in figure 13 is
perhaps mainly due to the fact that for the crack-length concerned the sum of the (short) initiation time and (long) propagation time for structures is by accident about equal to the sum of the (long)
initiation time and the (short) propagation time
for bars.
In figures 14 to 18 curves are given similar to
those of figures 9 to 13 for a different crack-area (500 mm2). Although being less accurate due to necessary extrapolations they permit the conclusion
that the fatigue-strength of the four structural
details of the specimens in relation to each other is similar to that for 100 mm2 crack-area. The ratioof the numbers of cycles for crack-areas of 500 and 100 mrn2, being about 1.5 or 2 for n < 104 becomes
smaller at larger number of cycles. It seems that
in low-cycle fatigue the initiation-time is relatively smaller and the propagation-time relatively larger
when compared with high-cycle fatigue. It is
however probable that this is only true for struc-tures containing severe discontinuities and not for structures in which the stresses do not differ
appre-ciably from one point to another. This will be
discussed under heading b. of this section.b. Comparisons between interrupted and continuous
longitudinals (mild steel)
In figures 19 and 20 a comparison is made be-tween fatigue data for the interrupted and three continuous longitudinals. Also some results of a
few interrupted and continuous specimens with a
symmetrical longitudinal frame (180 x 10) are
given. They are made of a higher strength steel
(St 52). They will be discussed under heading c. In drawing the curve for the flange of the three
continuous longitudinals of St 42 use has also been made of test results for the point where the
toe of the brackets of the lA and 2A specimensis
welded to the flange of the longitudinal frame.
This detail is rather well comparable to the welded
connection between the flange of a continuous longitudinal frame and a vertical stiffener. Both
figures 19 and 20 show that in spite of the presence
of such a stiffener the continuous specimens
re-main better than the interrupted ones. This is
not primarily a consequence of the existence of
large stress-concentrations in bracket and bottom
in the interrupted longitudinals. The main cause
is the inefficient use of the bracket material there.
The contribution of the bracket to the elastic
strength of the whole according to the strain
gauge data is only 28% for lA specimens and 12% for 2A specimens; it ought to be 50% in conformity with the sectional area of the bracket as a propor-tion of the whole.This means that near the bulkhead the total
effective material is not more than 70% and 60%respectively of the cross-section of bottomplate
plus frame. The trouble is mainly due to internal
4000
3000
2000
0 IE
103
FATIGUECURVES FOR '100mm2 CRACKAREA..
10 4
'ESTIMATED FROM RESULTS,OF A FEW "SPEC(MENS,
\
\
1 4\
\
\
\\
\
\
\
\ 1
\
\
NO CRACK AT END OF TEST.,COMPARISON BETWEEN INTERRUPTED AND CONTINUOUS SPECIMENS OF
ASYMMETRICAL CROSSSECTION St.421
AND
SYMMETRICAL CROSS SECTION (St.52 )--p-
I
-I- --cliI
II I105
Fig. 1-9. Summary of fatigue-results for 100 mm2 crack-area
II tI Ii JII .1 .
106
0
400
3000
2000
1000
103' o4 105
Fig. 20. Summary of fatigue-results, for 500 mm' crack-area
I!
106
ESTIMATED FROM RESULTS OF A FEW SPECIMENS
\
\
1 i il , ,\kk
\ \
\ \
LL1-5\
\
\
--\
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\
2 CRACK AT s-NO END OF TEST, 1ir....
T...\
,\
im
N\
1 1w.m.
SEMME
FATIGUE CURVES. FOR 500rnm2
COMPARISON BETWEEN INTERRUPTED AND CONTINUOUS SPECIMENS OF ASYMMETRICAL CROSS-SECTION CRACK-AREA. 1 St.4Z) i
-1
11 I 111 1 II Liill I I I ANDSYMMETRICAL CROSS- SECTION4St. 52
I-__ t _ IL I f II Ii L II 1 I II II II. II I I 1 18 (f) 0
A BRACKET
BRACKET.'gABRACKET "COS.
Fig. 21. Illustration of inefficient use of bracket material
by a shift of the neutral axis at the bracketed part of the specimens (see left part of figure 21).
The B-specimens had a wider bottomplate due
to which this shift was smaller. Accordingly the effective sectional material near the bulkhead
amounted to 85%.
From the foregoing it can be concluded that the
best structure is obtained (from the viewpoint of
pure axial loading!) if the height of the bracket is
reduced and the thickness of the bottomplate in that region increased until a practically constant
height of neutral axis is obtained. Where vertical loads due to cargo or waterpressure are present it is, however, necessary to
maintain a suitable
bracketheight in order to resist the shear forces.c. Comparisons between mild steel and higher strength
steel specimens
At first sight the results of the interrupted special
steel specimens in figures 19 and 20 seem to be
significantly better than of the mild steel ones. However, it must be kept in mind that the for-mer had a symmetrical bulb section and the latter an asymmetrical angle section. Considerable sec-ondary (horizontal) bending in the brackets of the
type of specimens last mentioned is responsible
for the difference in strength between these
brack-ets and the special-steel ones. For the
bottom-plates differences must be attributed largely to the relatively small cross-section of the longitudinal
frame of the St 52 specimens (180x 10). Due
to this the average load over the breadth of the
bottomplate at the interruption of that frame was only slightly larger than elsewhere and the stress concentration and local bending were small.
When these factors are taken into account no advantage remains for the higher-strength steel
over mild steel. This can be seen in figures 10 and
15 where fatigue data are given as a function of
the load in the bottomplate and more completely
in figures 12, 13, 17 and 18 where the differences
in stress concentration and local bending of the mild steel and special-steel specimens are taken into account. A comparison between the results
for the continuous St 42 and St 52 specimens
sub-stantiates that no important advantage for the
latter exists, provided that the differences in
de-sign of the specimens shown in figures 19 and 20 are again duly taken into account. This is the more remarkable because in all tests the fatigue-loading was predominantly tensile. For such cases it might
be expected that the higher strength steel would behave better than mild steel but probably this
advantage can manifest itself only at loads of
such magnitude that yielding is caused when mild steel is used and no yielding when steel of higher strength is used.d. Crack propagation in interrupted and continuous
specimens
One typical result from the tests with those con-tinuous St 52 specimens having no stiffener or bracket is worth mentioning. The rate of crack-propagation was surprisingly high. As soon as a
crack had initiated a complete fracture developed
within a very restricted number of cycles. In
comparison tothe interrupted specimens the
initiationtime was much larger but the number ofcycles between initiation and complete fracture
smaller. It seems that at the moment a crack
starts in the continuous specimens, very littleresistance to propagation is left in the remainder of the specimen.
For interrupted longitudinals the situation is different. They fit the so-called "fail-safe"
con-cept of fatigue strength better than the "safe-life" concept. When a crack starts at one of the points
of high stresses, the rest of the material outside
the stress concentration is still practically
un-damaged, and the crack can only propagate
slowly. The structure has a "failure" but is still
"safe". With continuous specimens it is less safe to
wait until a crack is found, because then little
reserve strength isleft. A "safe-life" has to be
prescribed after which the structure must be
replaced. When bending is present, either inherentin the structure or due to external loading, or
stiffeners are welded to the frame, the resulting
uneven stress distribution can also favour a quick
initiation of cracks and a slow propagation. In
such a case structures with continuous specimens might also regarded to be fail-safe". This applies fairly well to the continuous mild steel specimens with L-shaped longitudinals.
3000
2000
1000
Fig. 22,. Sketch of crack-growth in different specimen§
1 0
L467--1
I --E % St.52(in
\ \
..., r i St.52 labs. 5152 um, V. I II 'PS\
N \\\.._6° ''\
\,y'.\,'\\
\
\
\
\
11\
]\
1\
\
\.:\''
\ '
\
\
N.,Nk, 7:', Ni4 I II 0,\
\
\
S 1> N "t 0,
A1/4.\
\ \
-X,.,\
, St.42FATIGUE-CURVES FOR Omm2 ;100mm2,; 500mm2 CRACK-AREA
AND COMPLETE FATIGUE FRACTURE.
1
- 1
COMPARISON BETWEEN INTERRUPTED 5 Ornrn2
AND CONTINUOUS SPECIMENS OF
ASYMMETRICAL CROSS-SECTION (St.420
1
-- .
1 5mrn2, 0fflrn2.
AND ...7-4,2ti.IPLE2TE FRACTURE
SYMMETRICAL CROSS-SECTION 4,St.52)---*-- T I
{
0fron2 - Omm2 11 't 111_ 1 1 111 t t It r il 1 _II F III ii J._ 1 At ilt l' Ill
20 :,111 o3 iü 105 106 4000 0 0 I 1 1 1
The above given considerations are delineated in figure 22. The figure can only give a qualitative
impression because the number of continuous
specimens was very restricted.
Apart from what has been said before it should
be observed that in general the difference in
fatigue-strength between continuous and
inter-rupted longitudinals should not be fully taken into
account for structural design. The existing prac-tice of periodical surveys eliminates to a certain
degree the risks of using interrupted longitudinals.
6 Conclusions
The fatigue strength of interrupted longitudin-als is low as compared with continuous
spec-imens. The causes are large internal bending moments and the existence of local
stress-concentrations.
2A-specimens with semi-circular cut-outs do
not behave better than 1A-specimens mainly
because internal bending is comparatively lar-ger in the 2A-type.
B-type specimens with wide bottomplate are
better than A-type specimens. It is probable
that this conclusion is only valid for pure axial loading.
Asymmetrical longitudinal frames
are
un-favourable as compared with symmetrical T-or bulb-frames because of accompanying
horizontal bending.
Little advantage seems to be obtained by
using higher strength steels, except when the tensile component of the fatigueloading is so large that if mild steel is used, extensive yielding Occurs.Interrupted longitudinals fit a "fail-safe" con-cept because crack-propagation is slow.
Con-tinuous longitudinals better fit a "safe-life"
concept because whenever a crack is initiated it will propagate relatively fast.
g- It has not been possible to find one significant local stress or strain parameter which can be
used for all fatigue-results.
The influence of welding effects, complexity of stress state and gradient of stress are apparently considerable.
Acknowledgement
The authors express their sincere thanks to the
Head of the Ship Structures Laboratory Prof. Jr. H. E. JAEGER who made it possible to conduct this
investigation and stimulated it with his interest
and encouragement.
The comprehensive work of Mr. R. T. VAN
LEELTWEN in evaluating the results is deeply appreciated.
The assistence and suggestions of Messrs. H.
BOERSMA, P. P. Not, J. VERSCHOOR, A. KERSEN and A. PRINS are fully acknowledged.
Finally thanks are due for the financial and
material support of the Netherlands Ship
Re-search Centre TNO and the Dock- and Shipyard Company "Wilton-Fijenoord" at Schiedam.References
NIBBERING, J. J. W., Fatigue of Ship Structures; Neth.
Ship Research Centre TNO Report no. 55S,
Int. Shipb. Progress, Sept. 1963.
IRwiN, L. K. and W. R. CAMPBELL, Tensile tests of large
specimens representing the intersection of a
bottom-longitudinal with a transverse bulkhead; Report of
Ship Structure Committee S.S.C. 68, Jan. 1954.
TAKAHASHI, K., Y. AKITA and M. YOKOYAMA,
Experi-ments on the strength of the connection of bottom longitudinals and transverse bulkheads in tankers;
Int. Shipb. Progress no. 12 1955.
SERENSEN, S. V. and V. J. TROUFIAKOV, Propositions sur
la methode des essais a la fatigue sur les assemblages soudes; I.I.W. Document XIII-384-65, July 1965. GURNEY, T. R., The basis of the revised fatigue clause
for B.S. 153; Proc. Inst. C.E. 24, April 1963. ROLFE, S. T. and W. H. MUNSE, Crack propagation in
low-cycle fatigue of mild steel; Report of Ship Structure Committee S.S.C. 143, May 1963.
JAEGER, H. E. and J. J. W. NIBBERING, Beam knees and
other bracketed connections; Neth. Ship Research Centre TNO Report no. 38S, Int. Shipb. Progress Jan. 1961.
2..
5.
22
Mild steel specimens
Plate thicknessQuality (Lloyd's Reg.) Year of fabrication Condition Chemical composition
%C
% mn % Si % P%S
%A1 Chemical composition: Ferrite grain size: Yield point: U.T.S.: % elongation (dp5) : STEEL PROPERTIES 13 mm P 402 1960 Semi-killed 0.14 0.76 0.03 0.014 0.035 < 0.01 0.22% C; 0 7-9 bottomplate 36.6 kg/mm2 55.6 kg/mm2 27.2%Appendix I
19 mm 25 mm P402 P402 1960 1960 Semi-killed Al-killed 0.16 0.67 0.05 0.018 0.025 < 0.01 bulb frame 38.5 kg/mm2 60.2 kg/mm2 29.5% 0.15 0.70 0.06 0.023 0.023 0.03 .47% Si; 1.28%Mn; 0.014% P; 0.031% SFerrite grain size
(A.S.T.M.) 8 8 71/2 Mechanical properties Yield point 28.3 kg/mm2 27,6 kg/mm2 24 kg/mm2 U.T.S. 45 kg/mm2 44.3 kg/mm2 42.1 kg/mm2 % elongation (dp5) 34 30 34
Special-steel specimens
Reports
1 S The determination of the natural frequencies of ship
vibrations (Dutch). By prof. ir H. E. Jaeger. May
1950.
3 S Practical possibilities of constructional applications of aluminium alloys to ship construction. By prof. ir H. E. Jaeger. March 1951.
4 S Corrugation of bottom shell plating in ships with
all-welded or partially all-welded bottoms (Dutch). By
prof. ir H. E. Jaeger and ir H. A. Verbeek.
Novem-ber 1951.
5 S Standard-recommendations for measured mile and
endurance trials of sea-going ships (Dutch). By prof. ir J. W. Bonebakker, dr ir W. J. Muller and ir E. J. Diehl. February 1952.
6 S Some tests on stayed and unstayed masts and a com-parison of experimental results and calculated stresses
(Dutch). By ir A. Verduin and ir B. Burghgraef.
June 1952.
7 M Cylinder wear in marine diesel engines (Dutch). By
ir H. Visscr. December 1952.
8 M Analysis and testing of lubricating oils (Dutch). By
ir R. N. M. A. Malotaux and ir J. G. Smit. July 1953.
9 S Stability experiments on models of Dutch and French
standardized lifeboats. By prof. ir H. E. Jaeger, prof. ir J. W. Bonebakker and J. Pereboom, in collabora-tion with A. Audige. October 1952.
10 S On collecting ship service performance data and
their analysis. By prof. ir J. W. Bonebakker. January
1953.
11 M The use of three-phase current for auxiliary purposes (Dutch). By ir J. C. G. van Wijk. May 1953.
12 M Noise and noise abatement in marine enginerooms
(Dutch). By "Technisch-Physische Dienst T.N.0.-T.H.". April 1953.
13 M Investigation of cylinderwear in diesel engines by means of laboratory machines (Dutch). By ir H. Vis-ser. December 1954.
14 M The purification of heavy fuel oil for diesel engines
(Dutch). By A. Bremer. August 1953.
15 S Investigation of the stress distribution in corrugated
bulkheads with vertical troughs. By prof. ir H. E. Jaeger, ir B. Burghgraef and I. van der Ham.
Sep-tember 1954.
16 M Analysis and testing of lubricating oils II (Dutch). By ir R. N. M. A. Malotaux and drs J. B. Zabel.
March 1956.
17 M The application of new physical methods in the examination of lubricating oils. By ir R. N. M. A.
Malotaux and di F. van Zeggeren. March 1957.
18 M Considerations on the application of three phase
current on board ships for auxiliary purposes espe-cially with regard to fault protection, with asurvey
of winch drives recently applied on board of these
ships and their influence on the generating capacity (Dutch). By ir J. C. G. van Wijk. February 1957.
19 M Crankcase explosions (Dutch). By ir J. H.
Mink-horst. April 1957.
20 S An analysis of the application of aluminium alloys
in ships' structures. Suggestions about the riveting
between steel and aluminium alloy ships' structures. By prof. ir H. E. Jaeger. January 1955.
21 S On stress calculations in helicoidal shells and
propel-ler blades. By dr ir J. W. Cohen. July 1955.
22 S Some notes on the calculation of pitching and
heaving in longitudinal waves. By ir J. Gerritsma.
December 1955.
23 S Second series of stability experiments on models of
lifeboats. By ir B. Burghgraef. September 1956.
24 M Outside corrosion of and slagformation on tubes in oil-fired boilers (Dutch). By dr W. J. Taat. April
1957.
25 S Experimental determination of damping. added
mass and added mass moment of inertia of a ship-model. By ir J. Gerritsma. October 1957.
26 M Noise measurements and noise reduction in ships. By ir G. J. van Os and B. van Steen brugge. July.
1957.
27 S Initial metacentric height of small seagoing ships and
the inaccuracy and unreliability of calculatedcurves
of righting levers. By prof. ir J. W. Bonebakker.
December 1957.
28 M Influence of piston temperature on piston fouling and
piston-ring wear in diesel engines using residual fuels.
By ir H. Visser. June 1959.
29 M The influence of hysteresis on the value of the mod-ulus of rigidity of steel. By ir A. Hoppe and ir A. M. Hens. December 1959.
30 S An experimental analysis of shipmotions in
lon-gitudinal regular waves. By ir J. Gerritsma.
Decem-ber 1958.
31 M Model tests concerning damping coefficient and the
increase in the moment of inertia due to entrained water of ship's propellers. By N. J. Visser. April
1960.
32 S The effect of a keel on the rolling characteristics of a ship. By ir J. Gerritsma. July 1959.
33 M The application of new physical methods in the examination of lubricating oils (Continuation of
report 17 M). By ir R. N. M. A. Malotaux and dr F. van Zeggeren. April 1960.
34 S Acoustical principles in ship design. By ir J. H.
Jans-sen. October 1959.
35 S Shipmotions in longitudinal waves. By ir J.
Gerrits-ma. February 1960.
36 S Experimental determination of bending moments for
three models of different fullness in regularwaves.
By ir J. Ch. de Does. April 1960.
37 M Propeller excited vibratory forces in the shaft ofa
single screw tanker. By dr ir J. D. van Manen and
ir R. Wereldsma. June 1960.
38 S Beamknees and other bracketed connections. By
prof. ir H. E. Jaeger and ir J. J. W. Nibbering.
January 1961.
39 M Crankshaft coupled free torsional-axial vibrations of
a ship's propulsion system. By ir D. van Dort and
N. J. Visser. September 1963.
40 S On the longitudinal reduction factor for the added
mass of vibrating ships with rectangular cross-sec-tion. By ir W. P. A. Joosen and dr J. A. Sparenberg.
April 1961.
41 S Stresses in flat propeller blade models determined by the moire-method. By ir F. K. Ligtenberg. May 1962. 42 S Application of modern digital computers in
naval-architecture. By ir H. J. Zunderdorp. June 1962.
43 C Raft trials and ships' trials with some underwater
paint systems. By drs P. de Wolf and A. M.van
Londen. July 1962.
44 S Some acoustical properties of ships with respect to
noise control. Part I. By ir J. H. Janssen. August
1962.
45 S Some acoustical properties of ships with respect to
noise control. Part II. By ir J. H. Janssen. August
1962.
46 C An investigation into the influence of the method of application on the behaviour of anti-corrosive paint systems in seawater. By A. M. van Londen. August
1962.
47 C Results of an inquiry into the condition of ships' hulls
in relation to fouling and corrosion. By ir H. C.
Ekama, A. M. van Londen and drs P. de Wolf.
De-cember 1962.
48 C Investigations into the use of the wheel-abrator for removing rust and millscale from shipbuilding steel (Dutch). Interim report. By ir J. Remmelts and L. D. B. van den Burg. December 1962.
49 S Distribution of damping and added mass along the length of a shipmodel. By prof. ir J. Gerritsma and W. Betikelman. March 1963.
50 S The influence of a bulbous bow on the motions and
the propulsion in longitudinal waves. By prof. ir
J. Gerritsma and W. Bcukelman. April 1963. 51 M Stress measurements on a propeller blade of a 42,000
ton tanker on full scale. By ir R. Wereldsma. January
1964.
52 C Comparative investigations on the surface
prepara-tion of shipbuilding steel by using wheel-abrators and
the application of shop-coats. By ir H. C. Ekama, A. M. van Londen and ir J. Remmelts. July 1963.
53 S The braking of large vessels. By prof. ir H. E. Jaeger. August 1963.
54 C A study of ship bottom paints in particular pertaining
to the behaviour and action of anti-fouling paints.
By A. M. van Londen. September 1963.
55 S Fatigue of ship structures. By ir J. J. W. Nibbering. September 1963.
56 C The possibilities of exposure of anti-fouling paints in Curacao, Dutch Lesser Antilles. By drs P. de Wolf and Mrs M. Meuter-Schriel. November 1963.
57 M Determination of the dynamic properties and pro-peller excited vibrations of a special ship stern
ar-rangement. By ir R. Wereldsma. March 1964.
58 S Numerical calculation of vertical hull vibrations of
ships by discretizing the vibration system. By J. de Vries. April 1964.
59 M Controllable pitch propellers, their suitability and
economy for large sea-going shipspropelled by
con-ventional, directly-coupled engines. By ir C. Kap-senberg. June 1964.
60 S Natural frequencies of free vertical ship vibrations.
By ir C. B. Vreugdenhil. August 1964.
61 S The distribution of the hydrodynamic forces on a
heaving and pitching shipmodel in still water. By
prof. ir J. Gerritsma and W. Beukelman. September
1964.
62 C The mode of action of anti-fouling paints: Interac-tion between anti-fouling paints and sea water. By A. M. van Londen. October 1964.
63 M Corrosion in exhaust driven turbochargers on marine
diesel engines using heavy fuels. By prof. R. W. Stuart Mitchell and V. A. Ogale. March 1965.
64 C Barnacle fouling on aged anti-fouling paints; a sur-vey of pertinent literature and some recent
observa-tions. By drs P. de Wolf. November 1964.
65 S The lateral damping and added mass of a
horizon-tally oscillating shipmodel. By G. van Leeuwen. De-cember 1964.
66 S Investigations into the strength of ships' derricks.
Part I. By ir F. X. P. Soejadi. February 1965.
67 S Heat-transfer in cargotanks of a 50,000 DWT tanker.
By D. J. van der Heeden and ir L. L. Mulder. March
68 M Guide to the application of "Method for calculation
of cylinder liner temperatures in diesel engines". By
dr ir H. W. van Tijen. February 1965.
69 M Stress measurements on a propeller model for a 42,000 DWT tanker. By ir R. Wereldsma. March
1965.
70 M Experiments on vibrating propeller models. By ir
R. Wereldsrna. March 1965.
71 S Research on bulbous bow ships. Part II.A. Still water
performance of a 24,000 DWT bulkcarrier with a
large bulbous bow. By prof. dr ir W. P. A. van
Lam-meren and ir J. J. Muntjewerf. May 1965.
72 S Research on bulbous bow ships. Part II.B. Behaviour
of a 24,000 DWT bulkcarrier with a large bulbous
bow in a seaway. By prof. dr ir W. P. A. van Lam-meren and ir F. V. A. Pangalila. June 1965.
73 S Stress and strain distribution in a vertically
cor-rugated bulkhead. By prof. ir H. E. Jaeger and ir
P. A. van Katwijk. June 1965.
74 S Research on bulbous bow ships. Part I.A. Still water investigations into bulbous bow forms for a fast cargo
liner. By prof. dr ir W. P. A. van Lammeren and
ir R. Wahab. October 1965.
75 S Hull vibrations of the cargo-passenger motor ship
"Oranje Nassau". By ir W. van Hors.sen. August
1965.
76 S Research on bulbous bow ships. Part I.B. The
behav-iour of a fast cargo liner with a conventional and with
a bulbous bow in a seaway. By ir R. Wahab.
De-cember 1965.
77 M Comparative shipboard measurements of surface
temperatures and surface corrosion in air cooled and water cooled turbine outlet casings of exhaust driven marine diesel engine turbochargers. By prof. R. W. Stuart Mitchell and V. A. Ogale. December 1965.
78 M Stern tube vibration measurements of a cargoship
with special afterbody. By dr ir R. Wereldsma. De-cember 1965.
79 C The pre-treatment of ship plates : A comparative
investigation on some pre-treatment methods in use in the shipbuilding industry. By A. M. van Londen, ing. December 1965.
80 C The pre-treatment of ship plates: A practical inves-tigation into the influence of different working procedures in over-coating zinc rich epoxy-resin
based pre-construction primers. By A. M. van Lon-den, ing. and W. Mulder. December 1965. 81 S The performance of U-tanks as a passive anti-rolling
device. By ir. C. Stigter. February 1966.
89 S Low-cycle fatigue of steel structures. By ir J. J. W.
Nibbering and J. van Lint. April 1966.
1965.
Communications
1 M Report on the use of heavy fuel oil in the tanker
"Auricula" of the Anglo-Saxon Petroleum Company (Dutch). August 1950.
8 S Simply supported rectangular plates subjected to the
combined action of a uniformly distributed lateral load and compressive forces in the middle plane.
9 S Ship speeds over the measured mile (Dutch). By By ir B. Burghgraef. February 1958.
ir W. H. C. E. Rosingh. February 1951. 9 C Review of the investigations into the prevention of
3 S On voyage logs of sea-going ships and their analysis (Dutch). By prof. ir J. W. Bonebakker and ir j.
Ger-corrosion and fouling of ships' hulls (Dutch). By
ir H. C. Ekama. October 1962.
ritsma. November 1952. 10 S/M Condensed report of a design study for a 53,000 4 S Analysis of model experiments, trial and service
per-formance data of a single-screw tanker. By prof. ir
DWT-class nuclear powered tanker. By the Dutch International Team (D.I.T.), directed by ir A. M.
J. W. Bonebakker. October 1954. Fabery de Jonge. October 1963.
5 S Determination of the dimensions of panels subjected
to water pressure only or to a combinationof water
pressure and edge compression (Dutch). By prof. ir
11 C Investigations into the use of some shipbottom paints,
based on scarcely saponifiable vehicles (Dutch). By A. M. van Londen and drs P. de Wolf. October
H. E. Jaeger. November 1954. 1964.
6 S Approximative calculation of the effect of free
sur-faces on transverse stability (Dutch). By ir L. P.
Herfst. April 1956.
12 C The pre-treatment of ship plates : The treatment of
welded joints prior to painting (Dutch). By A. M. van Londen, ing. and W. Mulder. December 1965.
7 S On the calculation of stresses in a stayed mast. By
ir B. Burghgraef. August 1956.
