design considerations for aluminum hull structures - Ship Structure ...

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-28-AllOyS 5083 and 54.56(~ contents 4.5 and 5.1 per cent respectively)are somewhat susceptible to SCC, particularly at elevated temperatures. Inthe O temper, thermal treatment for 4 hours at b50 degrees F is suggestedto relieve residual stresses. H321 temper has no tendency toward SCC ifcold formed to a sufficiently large radius. For smaller radii (less thanSt)j hot forming Q.rstress relief in way of cold forming is recommendedfor L hours at 450 degrees F. This method of stress relief is,not recommendedfor welded assemblies inasmuch as it can lead to susceptibility toScc . Temper H311 is only recommended for alloy 5456, subject to the for~iwlimits and stress relieval practices noted for5456-H321. Tempers H32 andH34 are susceptible to SCC with either alloy and are not recommended.Microbiological Corrosion. Corrosion has been observed in aluminumaircraft fuel tanks due to accumulations of microbes found in the fuelresidue at the bottom of the tank. These problems occurred with 7000series alloys, and have been solved with fuel additives. Experience todate indicates no comparable problem with S000 series alloys exposed tomarine grade fuels.Combustion Products. If soot is allowed to stand on the decks of analuminum ship, the soot deposit will act as a cathodic metal and producepittiqg of the aluminum. Experience to date with S000 series alloys indicatesthat the intensity of pitti~ from combustion products is notsevere, though frequent washdown of deck surfaces is recommended.Bfoliation or intergranular corrosion results from excess magnesiumprecipitating into the grain boundaries causing separation of the materialalong grain boundaries. This form of corrosion is most pronounced in highmagnesium alloys, primarily 5M6, and appears to affect plates (temperH321) more than extrusions (temper Hill). The problem was brought to lightrecently due to plating exfoliation in bilges and wet areas of U. S. Navypartrol boat hulls operating in Southeast Asia. The aluminum industwundertook a program to investigate the causes of exfoliation and means ofpreventing or inhibiting it, including the test program discussed inReference (44). This program led to the development of the H116 and H117temper, now available with alloys 5086 and54.~6. These tempering processesare expected to eliminate the exfoliation problem, though service experiencewith the new tempers is very limited at this time.!2WWZZ” In summary, it may be concluded that S000 series alloys havesatisfactory corrosion characteristics in a salt water environment when conventionalprecautions are taken to avoid conditions promoting corrosion. Thelower magnesium content alloys such as 5052, 5454, 5154 and g086 are somewhatless susceptible to stress corrosion and exfoliation than the high magnesiumcontent alloys.Tables 6, 7 and 8, derived from Reference “(45) indicate that exposure ofwelded and non-welded samples of ~083 and 5086 alloys to sea water immersionfor five years produced a maximum depth of attack of only .008 (8 roils) withno significant loss in tensile strength, yield strength or elongation. OtherS000 series alloys would yield results in this same range. Fora ship’s hull,assuming a 20 year life, the average loss in thickness would be between 10and 12 roils,which is considered negligible.
-29-TABLE 6 Sea Water Immersion Tests ~5086.H34)Eiposure Average Depth of Per Cent ChangeTime Attack Inches in Strength2 Years5 Years.001 0.003 0TABLE 7 Corrosion Resistance of Aluroinum Alloys to Tide Range Sea WaterAlloy &Location Tensile= Samples5083-0 Totally ImmersedWater LineSplash Zone5083-H34 Totally ImmersedWater LineSplash Zone5086-0 Totally ImmersedWaker LineSplash Zone~~e~slon - SeYen ~e~~s~ ExposurePer Cent Change in Strength++Tensile Strength Yield Tensile-2 0-3 -2-6 -20 00-? o-2-200-3 05086-H34 Totally Immersed o 0Water Line o 0Splash Zone -1 0(++Percentchange negative (-) indicates apparent loss)TABLE 8 Resistance of Aluminum Alloy Weldmen’cs to CorrosionIn Sea Water - Five Years’ ExposureAlloy &TestPer Cent Change in Strength ++Temper Condition X- Ultimate Tensile Yield Tensile5083-HI13 Beads Intact. -6 0Beads Removed o -2Non-Welded -2 -145086-H32 Beads Intact -2 0Beads Removed -8 0Non-Welded -2 0~154-H34 Beads Intact oBeads Removed -2 -;Non-Welded -2 0S3S6-HI12 Beads Intact -2 0Beads Removed -1 0Non-Welded -2 -1++ MIG Welded vrithS3S6 filler alloy.Y&c Per cent change negative (-) indicates apparent loss.
Page 5: CONTENTSI.. II.III.Iv.v.VI ●VII.I
Page 9 and 10: LIST OF FIGURES(Cent’d)FIGURE NO.
Page 11 and 12: I. INTRODUCTIONThis report summariz
Page 13: art in fabricating and maintaining
Page 16 and 17: MONTEROSSO GRANA /17VALGRANA / CARA
Page 18 and 19: -8-Numerous references have been re
Page 20 and 21: .10.TABLE 2. Mechanical Properties
Page 22 and 23: TABLE 2 Mechanical Properties of Al
Page 24 and 25: TABLE 3 Mechanical Property Limits
Page 26 and 27: -16-l?igures5, 6, 7 ati 8 present f
Page 28 and 29: -18-ti-’”’-”-””””-L
Page 30 and 31: -20-60 .r---.— ..,.— -——,L-
Page 32 and 33: .22-each stress level, rate of load
Page 34 and 35: -24-!Z456-H321 = 0.485083-H321 = 0.
Page 36 and 37: -26-(c)Members with partial or cont
Page 40 and 41: -30-The previous paragraphs have de
Page 42 and 43: -32-The problem of cargo hold abras
Page 44 and 45: -34-The question of residual stress
Page 46 and 47: .36-Each alloy was given a relative
Page 48 and 49: -38-GENERAL OBSERVATIONSFYior to a
Page 50 and 51: -40-The question of comparative imp
Page 52 and 53: -42-(d)(e)Poor quality welds due to
Page 54 and 55: -44-The ABS criteria noted above we
Page 56 and 57: -46-DNV would consider fatigue in e
Page 58 and 59: -48-is less, for the exposed side s
Page 60 and 61: Equation (2):-50-Hu1l SMa~um = Hull
Page 62 and 63: -52-Another aspect of vibrations wh
Page 64 and 65: -54-000000000Bottom Shell PlateSide
Page 66 and 67: -56-at the deck and keel. This stre
Page 68 and 69: -58-AT is the change inUT= Thermal
Page 70 and 71: -60-SUl@!ARYAll parties contacted f
Page 72 and 73: -62-(c)(d)(e)(f)T~e exterior side o
Page 74 and 75: TABLE 12 Aluminum Bulk Carrier - Su
Page 76 and 77: .66-INSUT.ATION AND SHEATHINGShell8
Page 78 and 79: -68-(b)(c)(d)(e)(f)(g)(h)(i)(j)At l
Page 80 and 81: -70-IIF.INSTALLATION OF SYSTEMS AND
Page 82 and 83: Rudder Assembly -carrier should be
Page 84 and 85: -74-(b)MechanicalTensile Strength 6
Page 86 and 87: -76-(e)The steel piping must be of
Page 88 and 89:
-78-Other Piping Systems and Valves
Page 90 and 91:
-80-struetion for the aluminum hull
Page 92 and 93:
-82-Large heavy type machine~ must
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suffers attack in an alkaline envir
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-86-REPAIRSObtaining proper repairs
Page 98 and 99:
-88-The design of the midship s~cti
Page 100 and 101:
-90-assuming the increase is applic
Page 102 and 103:
LIGHT SHIP WEIGHT ESTIMATE-92-In or
Page 104 and 105:
-94-TABLE 20 Aluminum Bulk Carrier
Page 106 and 107:
TABLE 22 Trim and StabilityFull Loa
Page 108 and 109:
-98-TABLE 24 Price of Steel Bulk Ca
Page 110 and 111:
GaseNumber. . . -.,- .TABLE 27 Comp
Page 112 and 113:
-1o2-TABLE 28CarriersComparison of
Page 114 and 115:
12 ---n..T.[T7%l,=LEGS IU ORF=ErY
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-106-such as iron ore, on two of th
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-108-7)is,zg~ gg~5e mzz~E’4E!~K2j
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-11o-(a)(b)(c)(d)Inerting system fo
Page 122 and 123:
-112-fatigue, particularly in the p
Page 124 and 125:
-114-2k* Installation of Systems an
Page 126 and 127:
-116-LIST OF REFERENCES(7)Fatigue P
Page 128 and 129:
-11.8-LLST OF REFERENCES(Cent’d)(
Page 130 and 131:
-120-ADDITIONAL SOURCES OF INFORMAT
Page 132 and 133:
-122-redistribution of the still wa
Page 134 and 135:
-124-APPENDIX BEXCERPTS FROMRULES A
Page 136 and 137:
-126-92.07-10(d)(~) Interior stairs
Page 138 and 139:
-128-~gE1+0102030- .. ..—405060
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ectintyclassification4KEYWORDSROLEL
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SHIP STRUCTURE COMMITTEE PUBLICATIO
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