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/I

ALCOA 7 1475 SHEET AND PLATE

by

Stanley J. CieslakPaul L. Mehr

Aluminum Company of AmericaApplication Engineering DivisionAlcoa Center, Pennsylvania 15069

4th Revised Edition1985 December

(Supersedes 1978 February Edition)

ALCOA 7475 SHEET AND PLATE

INTRODUCTION

Alcoa 7475 was developed by theAlcoa Laboratories for sheet and plateapplications that require high strengthand a high level of guaranteed fracturetoughness. The Alcoa patented alloy wasregistered with the Aluminum Associationin 1969. Since then, Alcoa has producedmillions of pounds of 7475 sheet andplate for fatigue and fracture-criticalcomponents in high-performance aircraft.Alloy 7475 has the highest toughness fora given strength of the current commer-cially available high strength aircraftalloys. Alloy 7475 sheet and plateproducts are currently being used forfuselage skins, upper and lower wingskins, wing spars, center wing struc-ture, and fuselage bulkheads for commer-cial, transport and fighter aircraft.

7475 SHEET

Alloy 7475 is available as bare andalclad sheet in the T61 and T761tempers. The T61 temper is a variationof the T6 temper and utilizes specialthermal practices to produce hightoughness. In this condition, 7475sheet has tensile properties approachingthose of 7075-T6, with significantlyhigher toughness than 7075-T6. Similar-ly, T761 is a variation of the T76temper that provides good resistance toexfoliation corrosion and high tough-ness. In the T761 temper, alloy 7475will have strength and exfoliationcorrosion resistance comparable to7075-T76 and toughness approaching thatof 2024-T3.

Corrosion protection for the higherstrength 7475-T61 sheet products isprovided by one or two sides being cladwith 7072 alloy. One side clad 7475-T61sheet is currently being supplied byAlcoa for a transport aircraft applica-tion requiring a combination of highstrength, good fracture toughness andcorrosion resistance. Property levelsof one-side clad 7475-T61 sheet fall

between those of bare and two-side clad7475-T61 sheet.

BARE AND ALCLAD 7475 PLATE

Alloy 7475 is available as bare andalclad plate in T651, T7651 and T7351tempers. All three tempers are heattreated, aged and then stress relievedby stretching to achieve the high tough-ness properties. The T651 temper hasbeen aged to the highest strength level,T7651 is aged past the peak strengthlevel for higher resistance to exfolia-tion corrosion and T7351 is further agedfor high resistance to both exfoliationcorrosion and stress-corrosion cracking.

The tensile and yield strengths of7475-T651 and T7651 plate are equal toor 1 ksi (7 MPa) higher than 7075 on atemper-for-temper basis while thefracture toughness greatly exceeds thatof the established aluminum alloys ofcomparable strengths. Alloy 7475-T7351tensile and yield strengths are 1 to 7ksi (7 to 48 MPa) higher than 7075-T7351plate depending on plate thickness, andexhibit fracture toughness superior to2024-T351. Superior tensile propertiescombined with a high level of resistanceto exfoliation and stress-corrosioncracking give 7475-T7351 additionaladvantages over 2024-T351.

CHEMICAL COMPOSITION

Composition limits for alloy 7475are compared with those of 7075 in TableI.

Alclad 7475 sheet and plate areclad with alloy 7072. The claddingthicknesses are the same as alloy 7075.One-side clad or two-side clad sheet andplate are available.

PHYSICAL PROPERTIES

Typical physical properties of 7475are shown in Table II.

1

ROOM TEMPERATUREMECHANICAL PROPERTIES

Tables III and IV list designMechanical properties for bare andalclad 7475-T61 and T761 sheet. TablesV and VI show Alcoa's proposed newdesign allowables for 7475-T651, T7651and T7351 plate. Data is based onanalysis of recent production data.These new values will be proposed forinclusion in MIL-HDBK-5D.

Typical tensile and compressivestress strain curves and compressivetangent modulus curves for bare 7475-T61and T761 sheet are shown in Figures 1through 4. Similar curves for alclad7475-T61 sheet, 7475-T651, T7651 andT7351 plate are contained in MIL-HDBK-5D.

MECHANICAL PROPERTIES AT CRYOGENICAND ELEVATED TEMPERATURES

Refer to Tables VII and VIII fortypical mechanical properties at varioustemperatures for bare 7475-T61 and T761sheet.

PROCUREMENT SPECIFICATIONS

The Aerospace Material Specifica-tions (AMS) for bare and two-side alclad7475-T61 and T761 sheet and 7475-T651,T7651 and T7351 plate are shown in TableIX. One-side alclad 7475-T61 sheet iscurrently being used for a fuselage skinapplication and is purchased to a custo-mer's in-house specification. Currently,there are no AMS specifications forone-side alclad 7475-T61 and T761 sheet,and material availability is subject tospecial inquiry.

The Aerospace Materials Specifica-tions (AMS) are usuall y the primaryspecifications for the procurement of7475 sheet and plate. These AMS speci-fications require a guaranteed level offracture toughness (K or K

i

) with lotacceptance based on minimumnotch-yieldratios. In the case of 7475-T7351 and7475-T7651 plate, short rod fracturetoughness indicator values or notchyield ratios may be used as lot releasecriteria.

However, there may be design con-siderations where the fracture toughnessrequirements need a modification ofthese acceptance criteria (i.e; K or

). Alcoa can provide correlative cdatato insure that specifications reflectthe true fracture toughness character-istics, lot release criteria andmechanical properties.

FATIGUE PROPERTIES

Modified Goodman Diagrams, whichwere developed from axial-stress fatiguetests of notched and unnotched specimensof bare and alclad 7475-T61 and T761sheet, are illustrated in Figures 5 and6. Figures 7 and 8 show smooth andnotched axial stress fatigue data gener-ated from tests conducted on bare 7475-T7351 plate.

FATIGUE CRACK PROPAGATION

Alcoa has conducted extensive,constant amplitude fatigue-crack growthrate (FCGR) tests on 7475 sheet andplate products in various environment:;including air with different degrees ofhumidity, salt fog and simulated sumptank water. Full range constant ampli-tude FCGR plots are shown in Figures 9,10 and 11 for 7475-T651, T7651 and T7351plate. Figure 12 shows FCGR data for7475-T7351 plate in two differentenvironments for two plate thicknesses.

At near threshold regime, 7475-T651has a lower rate of fatigue crack propa-gation than 7475-T7351. At stressintensities above 10 ksi in. (11 MPaF), the lower rate of fatigue crackpropagation of 7475-T7351 compared with7475-T651 is probably associated withthe higher fracture toughness.

The fatigue crack propagation ratesof 7475-T7351 and 2024-T351 plate aresimilar based on constant amplitude FCGRdata.

Bare and alclad 7475-T61 and T761sheet FCGR data are shown in Figures 13and 14 for various test environments,specimen orientations and sheet thick-nesses. These data show that thefatigue crack growth rates of 7475-T61

and 1761 sheet are aimilar. Other dataindicate that the fatigue crackpropagation rates are similar for bareand alclad 7475 sheet. At higher stressintensities, the fatigue crack propaga-tion of 7475-T61 and T761 is slower than7075-T6 sheet and comparable to 2024-T3.

Fatigue crack growth behavior underspectrum loading is becoming increas-ingly important in the selection ofalloys for fatigue critical aircraftstructures. Two recent Naval AirSystems Command contracts (Reference 13and 14) studied this behavior for anumber of high strength 2XXX and 7XXXaluminum alloys for a fighter aircraftload spectra. Some results from thesereports are shown in Figure 15. Thesedata show that 7475 has superior fatiguecrack growth characteristics for theseparticular spectra in comparison with7050 and 7075 in comparable tempers.

7475 SHEET FRACTURE TOUGHNESS

To characterize the critical plane-stress (Kc ) fracture toughness of thinmaterial, Alcoa uses a specimen 16inches (406.4 mm) wide by 44 inches(1117.6 mm) long with a machined 4 inch(101.6 mm) long center crack. Thisspecimen is shown in Figure 16. Thetest is performed in compliance withASTM Method B646-78 "Standard Practicefor Fracture Toughness Testing ofAluminum Alloys." The analysis of thesetest data utilizes the crack growthresistance curve (R-curve) concept todescribe the material's resistance tofracture during slow stable crackextension. This concept described inASTM Method E561-81 "Standard Practicefor R-Curve Determination" takes intoaccount the growth of the plastic zoneas the crack extends from the sharpnotch. The K data for 7475 sheet arepresented in figure 17.

It is important to note that thetoughness of 7475 sheet, like that of2024-T3 sheet, is too high to be fullydescribed by testing 16 inch (406.4 mm)wide panels. Testing of much widerpanels to minimize net section yieldingwould be required to illustrate the fullpotential of this material. comoar-

ison of 7475's toughness to 7075 issbown in Figure 18.

Alclad 7475-T761 sheet has been theoreferred sheet product for aerospaceapplications because of its resistanceto general and exfoliation corrosioncombined with higher toughness incomparison with bare and alclad 7475-T61. Figure 17 illustrates K data forbare and alclad 7475-T761. On

c

the basisof tensile yield strength, Figure 19shows that 7475 offers a significantlybetter combination of strength andtoughness than 7075-T6.

Fracture toughness tests using16-inch (406.4 mm) wide center-notchedpanels have been conducted by Alcoa at-65 ` F (-54 C) on six lots of alclad7475-T761 sheet. The test data areshown along with data from similar testson bare 2024-T3 and 7075-T6 sheet inTable XI. Results of the tests show anaverage 25 percent (16 to 36 percentrange) reduction in toughness at thesubzero temperature compared to roomtemperature. Similarly, the bare 7075-T6 sheet had a 33 percent reduction inKc toughness.

It has been observed that thecritical stress intensity factor, K ,from tests of 16 inch (406.4 mm)center-notched panels correlatesreasonably well with the notch-yieldratio (notch-tensile strength/tensileyield strength) from tests of 3 inch(76.2 mm) wide edge-notch specimens.(ASTM Method E338, "Standard Method ofSharp Notch Tension Testing of HighStrength Sheet Materials.") The corre-lation between these two parameters,shown in Figure 21, is the basis ofAlcoa's less costly notch-tensile sheetproduct tests for fracture toughnessquality control. Alcoa has proposed theminimum values of K and the criticalvalues of notch-yiefd ratio as accep-tance criteria for 7475 sheet productswhich are shown in Table XII.

7475 PLATE FRACTURE TOUGHNESS

Plane-strain fracture toughness(K

I) data for 7475 plate were developed

perc

ASTM Method E399 "Standard Method

for Plane-Strain Fracture Toughness of

Metallic Materials" and .-.ST_? Method 5545"Standard Practice for ?lane-Strain

Fracture Toughness Testing of Aluminum__lloys." ASTM Method 3645 is usedbecause in many cases for high strength-

high toughness aluminum alloys, it is

impossible to obtain a valid measure of

toughness per ASTM Method F399. ASTM

Method B645 provides a method in whichsome invalid data per ASTM Method 7-399can be considered meaningful. Typical

fracture toughness data for 7475 plateare shown in Figure 20 and Table X. It

can be noted from Table X that 7475

provides a significantly higher level oftoughness and hence an appreciablygreater crack tolerance than 7075 incorresponding tempers. The combination

of strength and toughness provided by

,475 plate is shown in Figure 20. Thistoughness-strength relationship issuperior to that of other high strengthaluminum alloys. Since critical crack

sizes are proportional to the square of

the K 1 value, the effect of the higher

KIc values on design against fractureinstability is quite significant.

Because of the expense involved in

making and testing compact specimens

(ASTM Method E399), Alcoa recommends theuse of indicator tests such as the short

rod test or the notch-yield ratio test(notch-tensile strength/tensile yieldstrength, Figure 22) for fracture tough-

ness production quality control and

acceptance testing of plate. The short

rod specimen used by Alcoa is the

chevron-notched specimen shown in Figure23. The side grooves introduced to the

specimen help promote plane-strain con-

ditions during the test. All of thetests performed by Alcoa, to date, have

been made using the 1 inch (25.4 mm)diameter specimen. The specimen isloaded in a special mechanism designated

as a "Fracjack"® by its manufacturer

TerraTek. The lines of contact on the

Pracjack grip groove are designed sothat the effective load does not changeas the specimen mouth is forced open

under load. Other loading devices are

equally suitable for performing the

test. Results of the short rod test

have been found to be extremely linear

and correlate well to the Fracture

toughness -value _etermined from the

compact specimen. Figure 23 illustratesthe relationship of short rod value toK_ for the 1 inch ( 5.4 mm) %475-T7351snort rod specimen.

The notch-yield ratio data develop-

ed by Alcoa was obtained from tests

using the 0.500 inch (12.7 mm) and 1.060inch (26.9 mm) diameter specimens. The0.500 inch (12.7mm) specimen is used totest material less than 1.250 inches

(31.8 mm) in thickness, while the 1.060inch (26.9 mm) specimen is used to test

material equal to or greater than 1.250

inches (31.8 mm) in thickness. Adescription of the tensile specimen andsignificance of the notch yield ratio isdescribed in ASTM Method X602-81, "Stan-

dard Method for Sharp-Notch Tension

Testing with Cylindrical Specimen." It

has been found that the notch-yieldratios obtained from the 1.060 inch

(26.9 mm) specimens provide a morelinear and discriminating correlationwith the K I values obtained from hightoughness a cluminum alloys. Figure 22

illustrates the relationship of notch-yield ratio with K1 for both the 0.500

inch (12.7 mm) and i.060 inch (26.9 mm)diameter notch-tensile specimens.

The current minimum acceptancevalues for K and the critical short

rod and notch-yield ratio criteria areshown in Table XIII. Care must be exer-cised in interpreting the relationships

between both the short rod value and

notch-yield ratio and K value. Such

relationships differ between alloys,

tempers, and orientations, between

different specimen types and designs and

thus are not interchangeable.

For thin plate 0.250-0.750 inch(6.4-19.1 mm) thick, a quantitativemeasurement of fracture toughness for

lot acceptance and design purposes is

more accurately described by crack-growth resistance curves (R-curves).Alcoa has chosen to quantify the

toughness of intermediate thickness

products by utilizing a compact tensionspecimen and the 25 percent secantoffset value concept, designated as

5 in conjunction with ASTM Method

I, "Standard Practice for R-Curve

4

Tetermination." Me , a single-7;discrete point eycluatibi=1- tn :rack-:: rowth :esistance =rye (R-curve)

feveloped from a test of a compact ten-

tion specimen f, f full material thickness

Ihd a 5 inch (127 am) width. An example

of the relationship between the K70;• aiue and nominal material thickness-isshown in Figure 24.

An alternative way of determiningthe toughness of thin plate is to

determine Kc values from 16 inch (406.4

am) wide, center cracked panels. Be-cause of the high loads associated withtesting this type of specimen, theplates are generally machined to a

common thickness of 0.250 inches (6.4am). No toughness indicator relation-ships (short rod or notch-tensile) havebeen developed for plate in this

thickness range.

The plane-strain fracture toughness,

KID, of 7475-T7351 plate at -65°F

, oC) according to tests of three lots

is only 2 to 10 percent less than thatat room temperature, Table XI. Addi-tional testing may be required to quan-tify the average effect of low tempera-ture on the toughness of high strengthaluminum alloys.

THERMAL TREATMENTS

Alcoa has developed special thermalpractices to optimize the strength andfracture toughness of 7475 sheet andplate products. In situations whereforming may be required in the "0" and"W" condition, Alcoa will provide

recommended procedures for the solutionheat treatment and artificial aging ofAlcoa produced 7475 sheet and plate.Requests for 7475 heat treatingprocedures should be directed to thenearest Alcoa sales office.

FORMING RECOMMENDATIONS

Suggested minimum bend radii for

7 475 sheet and plate products in the

annealed and heat-treated tempers are

shown in Table XIV. Generally 7475

sheet and plate products have :31ightiv

improved :orming characteristics over

075.

CORROSION CHARACT7RIqTTGS

Atmospheric Weathering, afoliation

and Stress-Corrosion Cracking

On a temper-for-temper basis, the

overall corrosion resistance of 7475 isessentially the same as that of 7075where atmospheric weathering, exfolia-

tion and stress-corrosion cracking is

involved. Alcoa has conducted bothexfoliation and stress-corrosion tests

in all tempers of 7475 in acceleratedand atmospheric environments.

The T7351 temper of 7475 isrecommended for optimum resistance tostress-corrosion cracking. Tensile barand C-ring specimens from twenty produc-tion lots were stressed in the short-transverse direction at stresses between36-51 ksi(248-352 MPa), depending onplate thickness and exposed to the AlcoaCenter, Pennsylvania industrial atmos-phere and the Point Judith, Rhode Islandseacoast atmosphere. No failures haveoccurred during eight years exposure tothese environments. Similar testsconducted on fifty-four production lotsof 7075-T7351 resulted in no failuresduring eight years exposure at these twostations.

The T7651 temper of 7475 wasdeveloped to provide a high degree ofresistance to exfoliation corrosionattack and improved resistance tostress-corrosion cracking. Strengthlevels were only slightly lower than theT651 temper. Panels machined to theT/10 plane from seven production lots of7475-T7651 plate and sheet were exposedto seacoast and industrial environmentsfor eight years with no evidence ofexfoliation. Stress-corrosion tests ofshort-transverse specimens from fourproduction lots of 7475-T7651 platestressed at 25 ksi (172 MPa) wereexposed to the same environments foreight years with no failure.

For applications involving corro-sive environments or where ood surfaceappearance is required, it is recom-

mended that the aaterial be alclad,

anodized and/or tainted. treatment and if c on completion ofsuch treatment, :Teets the

Control Tests Required for requirements of above, the platetccentable Corrosion Performance is acceptable.

The exfoliation corrosion Lest

described in specification AST'_: G34-79"Exfoliation Corrosion Susceptibilit y in?XXX and 7XXX Series Aluminum Alloys

(EXCO Test)" is recommended b y AlcoaLaboratories for evaluating the exfoli-

ation corrosion resistance of 7475.

Test results have shown that T761 temper

sheet less than 0.100 (2.5 mm) innominal thickness, examined on thesurface, and T761 temper sheet 0.100

inch (2.5 mm) and over in nominal thick-ness (T) and T7651 plate, examined at a

T/10 plane, will not show exfoliation

equal to or greater than that illus-trated b y Photograph B, Figure 2 of ASTM

G34-72.

The stress-corrosion cracking testdescribed in specification ASTM G47 isrecommended for evaluating the stress-

corrosion cracking resistance of 7475.

Tests have shown that 7475-T7351 plate0.750 inch (19.1 mm) and over in nominal

thickness, which is stressed at 40-45

ksi (276-311 MPa) in the short-transversedirection in accordance with ASTM G4.7,

will not fail by stress-corrosion

cracking. Likewise T7651 plate 0.750

inch (19.1 mm) and over in nominalthickness will not fail by stress-

corrosion cracking when stressed in the

short-transverse direction to 25 ksi(172 MPa) in accordance with ASTM 047.

Electrical conductivity along with

tensile y ield strength has been shown to

correlate with exfoliation and stress-

corrosion resistance, and the following

rules for acceptability have been estab-

lished:

475-T7651 Plate ana 7475-1761 Sheet

_. If the conductivity is 39 percentIACS (International Annealed CopperStandard) or higher, the mechanical

properties meet specified minimum

limits, and the long-transverse

yield strength does not exceed thespecified minimum value by more

than 8 ksi (55 MPa), the sheet orplate is acceptable.

2. The material is considered marginal

and must be corrosion tested if,

(a) the conductivity is 39 percentor higher and the long-transverse

yield strength exceeds the speci-

fied minimum b y more than 8 ksi (56

MPa) or; (b) the conductivity isless than 39 percent but at least

38 percent.

3. Material failing to meet require-ments of paragraph 1. or 2. above

or having a conductivity less than

38 percent is not acceptable.

4. Material found unacceptable may be

given additional precipitation heat

treatment and if, upon competion of

such treatment it meets require-

ments of paragraph 1. or 2. above,

it is acceptable.

FINISHING

The same techniques used foranodizing, hard coating and applying

chemical conversion coatings to 7075 can

be used satisfactorily with 7475.

7475 FORGINGS AND EXTRUSIONS

7475-T7351 Plate

1. If the conductivity is 41 percent

IACS (International Annealed Copper

Standard) or higher and mechanicalproperties meet specified minimum

limits, the plate is acceptable.

2. Plate found to be unacceptable maybe fiven additional precipitation

Alcoa is currently supplying

extruded rod for the manufacture of

7475-T61 aluminum cartridge cases that

require an optimum combination of

strength and toughness. Alloy 7475 handand die forgings have been made experi-mentally. However, 7475 forgings and

extrusions have not been promoted

commercially because other available

6

_1107S EUCh and :ampersh:rrentiY ,ovailable __em :s=sriompinations cf properties aria :DSt morecitable frr these products.

4 75 "UPERPLAST 7 CA= TORMABLE

Alcoa has commercialized an'„l itrafine grain 7475 com position sheetproduct that exhibits superplasticforming characteristics when deformed at'_? 60°,F (515°C) and at strain rates below10-3 sec . Superpiasticity refers tothe ability of a material to reach veryhigh, neck free elongations undercertain combinations of temperature andstrain. A fine equiaxed grain structureis one of the major characteristicsrequired for superplasticity. Super-plastic 7475 sheet can be formed intocomplex shapes in a minimum number offorming operations. This results incost reductions by eliminating the totalnumber of parts required in typicalaircraft subassemblies or by reducingthe number of forming operations.Weight reductions are also possiblebecause of the elimination of rivets andoverlapping joints.

Alcoa is currently supplying 7475-02 temper sheet material to customersfor their superplastic forming opera-tions. After forming, parts are heattreated to 7475-T62 or T762 type tempersdepending upon the strength, toughnessor corrosion resistance required. Ingeneral, 7475 superplastically formed

: arts co not :22=2 :7.2 optimized:oughness associated 7475 sheet and:. late products. 7or :his reason, thesolution heat :rootin g hric aging prac-:ices "__commended :37 7C75 sheet inspecification nIL-14-6o8sF are recommend-.-7: d for 7475 suterplastic formed partshnless there is a toughness requirement.The nearest Alcoa sales office should becontacted for additional 'information or7475 superplastically formable sheet.

CONCLUSIONS AND RECOMMENDATIONS

Alloy 7475 sheet and plate productsprovide a combination of high-strength,high fracture toughness and good resis-tance to fatigue-crack propagation athigh-stress intensities. This combina-tion of properties is particularlyattractive for new high performanceaircraft being designed to durabilityand damage tolerance criteria. Alloy7475 sheet and plate are currently beingused in a number of commercial andmilitary aircraft programs. Alloy 7475sheet and plate should be considered foraircraft structures such as fuselageskins, wing skins, spars and bulkheadswhere high fracture toughness is adesign consideration.

ADDITIONAL INFORMATION

Requests for additional informationshould be discussed with an Alcoa salesengineer.

1. Mechanical Properties, FractureToughness, Fatigue EnvironmentalFatigue Crack Growth Rates andCorrosion Characteristics of High 9.Toughness-Aluminum Alloy Forings,Sheet and Plate," AFML-TR-73-83,1973 April 1.

2. "Exploratory Development for Effortto Obtain Design Data on StructuralAluminum Alloys in RepresentativeAircraft Environments," AFML 10.

TR-77-102, 1977 June.

REFERENCES

3. "New Alloys for Advanced MetallicFighter-Wing Structure," R. R.Wells, Northrop Corp., Hawthorne,California, AIAA, ASME, SAEStructures Structural Dynamics andMaterials Conference, 15th, LasVegas, Nevada 1974 April 17-19.

4. "Material Selection and Evaluationfor Advanced Metallic AircraftStructures," J. M. Shults, GeneralDynamics,AIAA, ASME, SAE StructuresStructural Dynamics and MaterialsConference, 15th, Las Vegas, Nevada1974 April 17-19.

5. "Aluminum Association Position onFracture Toughness Requirements andQuality Control Testing InterimReport," The Aluminum Association,750 Third Ave., New York, New York10017.

for Fatigue and Fracture Resis-tance), 1976 January.

"Selecting Aluminum Alloys toResist Failure b y Fracture Mechan-isms," R. J. Bucci, Presented atAmerican Society of MechanicalEngineers Design EngineeringConference, Chicago, Illinois, 1977May 11.

"Plane-Stress Fracture Toughnessand Fatigue-Crack Propagation ofAluminum Alloy Wide Panels," D. Y.Wang, McDonnell Douglas Corp."Progress in Flaw Growth andFracture Toughness Testing," ASTMSTP 536, American Society forTesting and Materials 1973, pp334-349.

11. "Crack Growth Resistance in Plane-Stress Fracture Testing, " R. H.Meyer and D. E. McCabe, EngineeringFracture Mechanics, 1972, Volume 4,pp 413-430.

12. "The Sharply Notched CylindricalTension Specimens for ScreeningPlane-Strain Fracture Toughness,Part II: Applications in AluminumAlloy Quality Assurance of FractureToughness," R. J. Bucci, S. F.Collis, R. F. Kohm, J. G. Kaufman,ASTM Special Technical Publication632.

6. "Fracture Toughness and Microstruc- 13.

ture of High Strength AluminumAlloys," J. T. Staley, presented atSpring Meeting, MetallurgicalSociety of American Institute ofMining, Metallurgical and PetroleumEngineers, 1974 May 23.

7. "Fracture Mechanics Impact onSpecifications and Supply," R. R.Senz and E. H.' Spuhler, "MetalProgress," 1975 March. 14.

8. "Design o .f Aluminum Alloys for HighToughness and High FatigueStrength," J. G. Kaufman, AGARDConference Proceedings, No. 185(Specialist Meeting on Alloy Design

"Methodology for Evlaution ofFatigue Crack-Growth Resistance ofAluminum Alloys under SpectrumLoading," G. R. Chanani, I.Telesman, G. V. Scarich, NorthropCorporation, and P. E. Bretz,Alcoa, Final Report for period 4August 1980 - 4 August 1981. Con-tract No. N00019-80-C-427, April1982.

"Investigation of Fatigue Crack-Growth Resistance of AluminumAlloys under Spectrum Loading," G.V. Scarich, Northrop Corporationand P. E. Bretz, Alcoa. FinalReport for period 1 October 1981 -30 November 1982, Contract No.

I

N00019-81--C-0550, April 1983.

15. "Alcoa Short Rod Fracture ToughnessIndicator Test," Stanley J. Cieslak,Alcoa, May 26, 1985.

10

!ABLE I

C P0SITTON L- - '1I `' OR ALLOYS . L.i7 AND -27

Y ';EIGHT

7475 7075

Silicon 0.10 max. 0.40 max.iron 0.12 max. 0.50 max.Copper 1.2-1.9 1.2-2.0Manganese 0.06 max. 0.30 max.Magnesium 1.9-2.6 2.1-2.9Chromium 0.18-0.25 0.18-0.35Zinc 5.2-6.2 5.1-6.1Titanium 0.06 max. 0.20 max.Others, Each 0.05 max. 0.05 max.Others, Total 0.15 max. 0.15 max.Aluminum Remainder Remainder

TABLE II

TYPICAL PHYSICAL PROPERTIES OF ALLOY 7475

Density

Electrical Conductivity @ 68°F (20°C)-T651 Temper-T7651 Temper-T7351 Temper

Melting Range

Specific Heat @212°F (100°C)

0.101 lb/in3

2.795 g/cm3

IACS ml (ohms mm 2) ,35 20.340 23.242 24.3

980-1175°F527- 635°C

(0.21-0.23 Btu/(lb °F)963 J/(kg C)

Thermal Conductivity @ 77°F (25°C) Btu/[(hr ft 2 °F)/ft] cal/[(sec cm 2 °C)/cm]-T651 Temper 80 0.331-T7651 Temper 90 0.372-T7351 Temper 94 0.388

Average Coefficient of Thermal Expansion in/in/°F m/m°C

68°-212°F (20-100°C) (12.9-13.0) x 10-6 23.4 x 10-6

Poisson's Ratio 0.33

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17

TABLE IX

ALCOA 7475 SHEET AND PLATE

SPECIFICATION COVERAGE

Product Form Temper Specification MIL-HDBK-5D COVERAGE

Bare Sheet 7475-T61(1)

AMS 4084A Approved

Alclad Sheet 7475-T61(1)

AMS 4207 Approved

Bare Sheet 7475-T761 AMS 4085A Approved

Alclad Sheet 7475-T761 AMS 4100 Approval pending

Plate 7475-T651 AMS 4090A * Approved

Plate 7475-T7651 AMS 4089A * Approved

Plate 7475-T7351 AMS 4202A * Approved

* Mechanical property revisions have been requested

NOTE:

1. Alcoa is currently supplying alclad one-side sheet in 7475-T61 temper.This product has mechanical properties intermediate between bare andtwo-side alclad 7475-T61 sheet. Minimum mechanical properties will beprovided on request.

18

TABLE X

TYPICAL FRACTURE TOUGHNESS VALUES

HIGH STRENGTH ALUMINUM SHEET AND PLATE PRODUCTS

K , ksi in. (MPa ^)

16 Inch (409•4 mm) x 44 Inch (1117.6 mm)Center Cracked Panel

ORIENTATION

ALLOY TEMPER L-T T-L

SHEET

7475 T61 95 (104.4) 88 (96.7)

T761 120 (131.9) 110 (120.9)

2024 T3 -- 124 (136.4)*

7075 T6 -- 81 (89.0)*

K , ksi in. (MPa J)Compact Tension Specimen

(ASTM E399-74)

ORIENTATION

ALLOY TEMPER L-T T-L S-L

PLATE

7475 T651 42 (46.0) 37 (40.7)

T7651 43 (47.3) 37 (40.7)T7351 50 (55.0) 41 (45.0)

7075** T651 26 (28.6) 23 (25.3) 18 (19.8)T7651 27 (29.7) 22 (24.2) 18 (19.8)T7351 30 (33.0) 26 (28.6) 18 (19.8)

7050 T7651 31 (34.0) 28 (31.0) 24 (26.4)

T7451 33 (36.3) 29 (32.0) 25 (28.0)

2024** T351 34 (37.4) 29 (31.9) 24 (26.4)

T851 22 (24.2) 20 (22.0) 17 (18.7)

2124 T851 29 (31.9) 24 (26.4) 24 (26.4)

* Based on limited Alcoa tests of 0.063 inch (1.60 mm) thick sheet.

** These alloys/products do not have guaranteed minimum fracture toughnessvalues.

19

KIc' ksi(MPa

Compact Tension Specimen

(ASTM E399-74)

% Reduction

in Toughnessfrom RT to

-65o

F (-54C)

TABLE XI

TYPICAL FRACTURE TOUGHNESS VALUES

ROOM TEMPERATURE AND -65°F (-54°C)

HIGH STRENGTH ALUMINUM SHEET AND PLATE PRODUCTS

% Reduction

K , ksi Vin. (MPa v71)16 in. (486.4 mm) x 44 in. (1117.6 mm)

Testing Center Cracked Panel in ToughnessThickness Temperature from RT too oAlloy in. (mm) °F ( °C) T-L Orientation -65F (-54 C)

SHEET

2024-T3 0.063 (1.6) R.T. 126.2 (138.7) 12% (increase)-65 (-54) 141.9 (155.9)

0.063 (1.6) R.T. 122.1 (134.2) 7% (increase)-65 (-54) 130.8 (143.7)

7075-T6 0.063 (1.6) R.T. 81.2 ( 89.2) 33-65 (-54) 54.2 ( 59.6)

7475-T761 0.047 (1.2) R.T. 130.3 (143.2) 36

-65 (-54) 81.9 ( 90.0)

0.055 (1.4) R.T. 123.4 (135.6) 36

-65 (-54) 78.9 ( 86.7)

0.063 (1.6) R.T. 111.5 (122.5) 16

-65 (-54) 93.2 (102.4)

0.063 (1.6) R.T. 136.7 (150.2) 26

-65 (-54) 100.9 (110.9)

0.063 (1.6) R.T. 133.8 (147.0) 26

-65 (-54) 98.9 (108.7)

0.071 (1.9) R.T. 135.6 (149.0) 16

-65 (-54) 113.6 (124.8)

Alloy

PLATE

Testing

Thickness Temperatureof

( °C)in. (mm)

Orientation Orientation

L-T T-L L-T T-L

7475-T7351 2.25

2.50

3.00

(57.2)

(63.5)

(76.2)

R.T.

-65 (-54)R.T.

-65 (-54)R.T.

-65 (-54)

52.8

48.944.9

40.254.4

51.5

(58.0)

(53.7)(49.3)(44.2)(59.8)(56.6)

42.740.346.945.8

(46.9)(44.3)(51.5)(50.3)

7

10

5

20

TABLE XII

BARE AND ALCLAD 7475 SHEET

FRACTURE TOUGHNESS ( K r ) MINIMA AND NOTCH YIELD RATIO ACCEPTANCE CRITERIA

criteria(3)Minimum Fracture Toughness Notch Yield Acceptance

K ksi 3 in. (MPa /) (1) (Notch Tensile Strengt /Tensile Yield Strength)(2)c

Sheet Orientation Sheet Test Direction

Thickness Thickness Long

in.(mm) L-T T-L in.(mm) Longitudinal Transverse

7475-T61

Bare 0.040-0.125 - 75.0 Bare 0.040-0.125 - -

(1.02-3.18) - (82.4) (1.02-3.18)

0.126-0.249 60.0 60.0 0.126-0.249 0.68 0.72

(3.20-6.32) (65.9) (65.9) (3.20-6.32)

Alclad 0.040-0.125 - 75.0 Alclad 0.040-0.125 - -

(1.02-3.18) - (82.4) (1.02-3.18)

0.126-0.249 - 60.0 0.126-0.249 - -

(3.20-6.32) - (65.9) (3.20-6.32)

7475-T761

- 1.05(5)Bare 0.040-0.125 - 87.0 Bare 0.040-0.125

(1.02-3.18) (95.6) (1.02-3.18)

- 0.95(5)0.126-0.249 - 80.0 0.126-0.249

(3.20-6.32) (87.9) (3.20-6.32)

0.91(4) 0.98Alclad 0.040-0.125 100.0 87.0 Alclad 0.040-0.125

(1.02-3.18) (109.8) (95.6) (1.02-3.18)

0.126-0.249 80.0 Alclad 0.126-0.249 - 0.94

(3.20-6.32) (87.9) (3.20-6.32)

Notes:

1. Critical stress intensity factor K determined by tests of 16 in. (406.4 mm) wide by 44 in.

(117.6 mm) center crack panels perc

ASTM Method B646-78 "Standard Practice for Fracture Toughness

Testing of Aluminum Alloys."

2. Notch tensile strength to be determined by tests of 3 in. (76.2 mm) wide edge notched tensile

specimens. Reference ASTM E338 "Standard Method of Sharp-Notch Tension Testing of High-Strength

Sheet Materials."

3. Notch yield ratio acceptance criteria are still tentative and may be modified. These values are

also subject to customer acceptance.

4. Long transverse.

5. 100% K testc

21

FRACTURE TOUGHNESS (K

Ic

MINIMA) NOTCH YIELD RATIO ACCEPTANCE CRITERIA

Minimum Plate Thickness(2)

Minimum Fracture(3)

for Applicable Fracture(9)

Toughness, KIc , Plate Thicknesg ) Tentative Minimum NY

Plate Thicii I ss Toughness minima, in. (mm) ksi in. (MPa m) Range for NYR' ShortTemper in. (mm) L-T T-L S-L L-T T-L S-L Test, in. ( mm) Longitudinal Transverse Transvers

-7651 0.250-1.500 1.250 1.250 30.0 28.0 0.250-0.749 (6) (6)(6.4-38.1) (31.8) (31.8) (33.0) (30.8) (6.4-19.0)

0.750-1.500 (6) (6)

(19.1-38.1)

-17651 0.250-1.500 1.250 1.250 33.0 30.0 0.250--0.749 (6) (6)(6.4-38.1) (31.8) (31.8) (36.3) (33.0) (6.4-19.0)

0.750-1.500 (6) (6)

(19.1-38.1)

-17351 0.250-4.000 1.250 1.250 2.500 40.0 33.0 25.0 0.250-1.249 (6)(7) (6)(6.4-101.6) (31.8) (31.8) (63.5) (44.0) (36.3) (27.5) (7.4-31.7)

Short Rod Value(4)

1.250-1.999 (6) 1.37

(31.8-50.7)

54.0 42.0 30.0

2.000-4.000 1.48 1.37 1.20(8)

(50.8-101.6)

Notes:

TABLE XIII

7475 PLATE

FRACTURE TOUGHNESS ( K / c) MINIMA AND NOTCH YIELD RATIO ACCEPTANCE CRITERIA

1. Plate in thicknesses greater than these are subject to inquiry.

2. For plate thickness below those indicated, fracture toughness minima and test method are subject to negotiation.

3. Plane strain critical stress intensity, K for plate, to be determined in accordance with ASTM E399, "Plane Strain Fracture Toughness of

Metallic Materials." The L-T and T-L spe

1

cimens of the standard proportions shown in ASTM E399 shall have crack length of not less than 2.50

In. (63.5 mm), i.e. W=5.00 in. (127.00 mm) and be full thickness for plate up to 2.50 in. (63.5 mm) thick. For plate thickness above 2.50 in.

(63.5 mm) thick, L-T and T-L compact specimens will have "B" thickness of 2.50 in. (63.5 mm) with other dimensions per ASTM E399. All K

values obtained shall meet all validity requirements of ASTM E399 for K

Ic

except that K values which are invalid for the following reasgns shall

be considered meaningful and if equal to or greater than the applicablevalues in TableQ

XI, shall be evidence of acceptable fracture toughness:

a. Insufficient specimen thickness.

b. Excess plasticity as indicated by the ratio of P IF exceeding 1.1.max Q

4. Proposed short rod acceptance values.

5. Notch yield ratio determinations (NTS/TYS) will be made for plate thicknesses 0.75 in. (19.1 mm) and greater using notched round tensile speci-

mens per ASTM E602 "Standard Method for Sharp Notch Tension Testing with Cylindrical Specimens."

6. Type of indicator test and minimum value for lot release to be negotiated.

7. L-T direction may be lot released by long transverse NYR values of 1.30.

8. For plate thickness 2.500-4.00 in. (6.4-101.6 mm).

9. Notch yield ratios are still tentative and may be modified. These values are also subject to customer acceptance.

22

T;BLE IV

SUGGESTED MINIMUM BEND RADII FOR A 90 0 COLD SEND

7475 SHEET AND PLATE

(Bend radii for various thicknesses expressed in terms of `'.-sickness, t)

Sheet Thickness, in. (mm)0.040 0.063 0.090 0.110 0.125 0.249

Alloy Temper (1.016) (1.600) (2.286) (2.794) (3.175) (6.325)

SHEET

1Bare 7475 -0 1.0 t 1.0 t - 1.5 t - 2.0 t

-T61 - - - 4.0 t - 4.5 t

-T761 3.5 t 3.5 t 4.0 t - - -i

Alclad 7475 -0 1.0 t 1.0 t 1.5 t 1.5 t 2.5 t 2.0 t

-T761 3.0 t 3.0 t 3.5 t 3.5 t 3.5 t 4.0 t

PLATE

Plate Thickness, 0.375 1.500iin. (mm) (9.525) (38.100)

Bare 7475 -0 2.0 t 3.0 t-T7351 4.0 t --T7651 4.0 t --T651 5.0 t -

i I

LT—

COMPRESSION-7 '...—

;

1_ —TENSION

TENSION

44 0.

4Pr

%-L-COMPRESSION

LT

LT—LONGL — LONGITUDINAL

TRANSVERSE

500

400

300

200

100

0

8 0

7 0

60

50

30

20

I0

0

40

0 2 4 6 8 1 0 12 14STRAIN, 0.001 in./in. (mm/mm)

COMPRESSIVE TANGENT MODULUS, 10 3 ksi (6.9X10 3 MPa)

TYPICAL STRESS—STRAIN AND COMPRESSIVETANGENT—MODULUS CURVES FOR 7475-T61 SHEET

Figure 1

90

80

500

70

60 400

50

TLT

LT

L' ;

i f

LT- LONGL - LONGITUDINAL

TRANSVERSE

99

20

Li]

0

1 40

0 2 4 6 8 1 0 12STRAIN, 0.01 in. / in. (mm/mm)

TYPICAL TENSILE STRESS-STRAIN CURVES( FULL RANGE) FOR 7475-T61 SHEET

a

300wcc

200

100

U)C

w40

U)

Figure 2

iILT-COMPRESSION-7

1

-4/41"-

,L

Aggit LT-L-COMPRESSIONTENSION

LT

L-TENSION

_

LT-LONGL-LONGITUD

TRANSVERSENAL _

500

400

100

0

80

70

60

50

40

30

20

I 0

0

300

200

0 2 4 6 8 1 0 1 2 1 4STRAIN, 0.001 IN/IN (mm/mm)

COMPRESSIVE TANGENT MODULUS, 103 KSI (6.9X10 3 MPa)

TYPICAL STRESS-STRAIN AND COMPRESSIVETANGENT-MODULUS CURVES FOR 7475-T76I SHEET

6

Figure 3

20

80

70

60

Yvj 50WcrI-

40

30

20

LT

L ;^

LT

L — LONGITUDINALLT — LONG TRANSVERSE

D1s

500

400

300 -

w

100

I 0

0 0

0 2 4 6 8 10 12 14STRAIN, 0.01 in./in. (mm/mm)

TYPICAL TENSILE STRESS — STRAIN CURVES(FULL RANGE) FOR 7475 —T761 SHEET

27

Figure 4

60

50

40

30

20

1 0

0-50 - 40 - 30 -20 - 10 0 10 20 30 40 50 60

MINIMUM STRESS, KSIUNNOTCHED, Kt=

80

70

60

50

40

30

20

1 0

0

1.0500

400

300

— 200

100

c—t7

cncr)

2

7<-

1 0

— 50-40-30-20-10 0 10 20 30 40 50

MINIMUM STRESS, KSINOTCHED, Kt =3

60 70 80

MINIMUM STRESS, (MPa)—400 —300 —200-100 0 100 200 000 Li 00 500 600

MINIMUM STRESS, (MPa)

—400 —300 —200 —100 0 100 200 300 400 500 600

MODIFIED GOODMAN DIAGRAMS

AXIAL-STRESS FATIGUE TESTS, LONGITUDINAL AND LONG-TRANSVERSE SPECIMENSALCLAD 7475-T61 & T761 SHEET 0.090 (2.286 mm) AND 0.125 (3.175 mm) inch THICK

28

Figure

600

mC-

500

cri

400

H-

300 2i

200 <cC

100

I),r

nw

f^

5Jc

2

80

70

60

50

40

30

20

10

0

I

R=-1.0 CYCLES%/ j

I ^ ^ I 0 4 j ', ^ !,

500

400 ((IDw

300

200

100

80

70

60

Ci) 5 0wF- 40U,

30

20

I O

;MINIMUM STRESS. ( MPa)

- 00 — 3 00 —200 —;+30 3 100 no 300 4 +00 500 6 0 0

—50 —40 —30-20 —i 0 0 10 20 30 40 50 60 70 80

MINIMUM STRESS, KS!UNNOTCHED, K^,. =

MINIMUM STRESS. (MPa)

—400 —300 —200 —100 0 100 200 300 400 500 600

— 50 - 40 -30--20--I0 0 10 20 30 40 50 60 70 80MINIMUM STRESS, SCSI

NOTCHED, K 3

MODIFIED GOODMAN DIAGRAMSAXIAL-STRESS FATIGUE TESTS. LONGITUDINAL AND LONG-TRANSVERSE SPECIMENS

BARE 7475-T61 c, T761 SHEET 0.090 (2.286 mm) AND 0.125 (3.175 mm) inch THICK

-inure

29

<> I

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co EE

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WINIVIIMMI wcc MI ARINNENIMIPIZIIMI/

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=Nems imwmilliim...m.....r•mmummimmimUMMNNIM A=MOC)

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n • 44 40411.c 7 W

a_ n11111MMIIIIIMEMIME

11111=

••

co

O

O

ril l.M11•1111M.MIONIMCC

O

11111•11MOIBIMEMINIMITJ

O

<—t

o4•6 =

w=

F-

11

2d1A1 5 SS3E1S

1.r)

Wnvulxvw

O

C) Cr)

CZ)„,•n••SIM1/1/1 /MEMilkoMMION atON

cf)

L1.1

<

0- ci)Lu a

C Q N c=, C)r ••-r Lc, N-

.4(Li_ CO

7, 0.

CD aLC) c:/

h- Lc) C:)

N cNi C-D <=,1.1.1

momIIINNalm37( "-<

cr)CICLl1

C.r)O-J

cc cc

O

u

1.7cq Q a oc:Dl`

2,

2 O cr) ANNE

unImismim

======mnimm.immommommo im ..nmimmill•i1 .1.

422•111111ME I•

O O

)1.1.1 <

O

<1.1.1O

Za:1z0

'SS3ILLS wnwinfw

coW WJ

V U-

'2dw `SS HIS AJnumm

ryT 'Q Y Lo to ^- % O - C

_ ' c I r^ N ^.n _' !.

4 v ,- N M ^7

-

J

_

^p SI ^^ '-L 1

;I ' _: u15 "nWIM

X4 tests

1 0-4

i 1 I 1

L-T orientation

(1) 10-5

c)

— 1 0-6

co

'1 10-7

="-

=

1 40

! 1 ! ! I l i

5 10

ksi , in.

1 0-9

2 K, IVI Pa1 5 1 0

1 0-3

x1)146 7475-T651 plate0.75 in. (19.05 mm) thick

'4 0

10-6

—17

i o-7

- 1 0-8

X x Room temperature

▪

10-9

1 0- 8 —

Moist (RH > 90%) airR= +0.33, f = 25 Hz -1

WOL specimen thickness = 0.25 in. (6.3 mm) 7i o-- 10

x =

Full Range Fatigue Crack Growth Rate Data 7475-T651 PlateFigure 9

i7

`i 0 -3

1 0 -4

2 10-5

z

co

10 -7

1 0-8

10-9 L

1

40

10 -5

10-6

10 -7

E

z10 -8

co

10 -9

10-10

40

AK, MPa vm5 1 0

j 7

Specimen orientationq L-T (1 tes''o T-L (1 tes

0I . i ill. 1111111 till

Room temperatureMoist (RH > 90%) air

n R=+0.33,f=25 HzCT specimen thickness = 0.25 in. (6.3 mm)

I I I

5 10

AK, ksi

Full Range Fatigue Crack Growth Rate Data7475-T7651 Plate

Various Specimen OrientationsFigure 10

J3

10- 7I 1 i

5 10 40

1 0-5

10-6

10-7

10-8

10-9

10-1°

10-5

10-6

10-7

1 0-8

10-9 1

1AK, MBA Pa

5 1 0 40

Specimen orientationL-T (2 tests, WOL specimen)

1 0-4o T-L (1 test, CT specimen)

7475-T7351 plate1.5 in. (38.1 mm) thick

Room temperatureMoist (RH > 90%) air

R= +0.33, f = 10.25 HzSpecimen thickness = 0.25 in. (6.3 mm)

AK, ksi On.

Full Range Fatigue Crack Growth Rate Data7475-T7351 Plate

Various Specimen OrientationsFigure 11

24

1 0-5

1'[.m:a)UA10-7 UI-E

10-8 Zca

1 O-9

10-10

110-3

10-4

a) 10-5AU

C 10-6zM 10-7

10-8

10-9 I1

110-3

10-4

10-6z

10-7

10-8

10-5

10-6a)U

10-7 0E

z1 0-8 —1

co1

1 0-9

3K, MPa v m

5 1 0 40I i I I 1 I F-

EnvironmentRoom temperatureDry (RH < 10%) air (1 test) ,A —Sump water (1 test) °

1 ^ _°

0

T-L orientation

7475-T7351 plate0.75 in. (19.05 mm) thick

R = +0.33, f = 2, 10. 20 .30 HzFull thickness CT specimen

5 10 40AK, ksi 1An.

AK, MPa vm5 10 40

I I I I i i i i I

EnvironmentRoom temperature o °

q Dry (RH < 10%) air (2 tests)o Sump water (2 tests)

°° T-L orientation

7475-T7351 plate3.5 in. (88.9 mm) thick

R = +0.33, f = 2, 10, 20, 30 Hz tWOL specimen thickness - —

0.25 in. (6.3 mm), 1.0 in. (25.4 mm) __ 10-10

10-9 11 5 10 40

3K, ksi

Fatigue Crack Growth Rate Data7475-T7351 Plate

Various Test Environments and Plate ThicknessesFigure 12

35

.. K. MPa rii

5 1 0ii

Environment Room temperature

'Dry(RH < 10%) air (2 tests) 014'9,= xMoist (RH - 90 :',) air (3 tests) (5-_....

:Salt fog (3 tests) - eV-- ma

-

- °1 . .74';'s'

I 0 - 4

40

:4 n'. i:.

Q 9 11 1 0-5

5.l.

1

-g 1 06

40

MPa M

5 1 0

I I I I 1 1 "• Environment - Room temperature

10-4

•

+Ambient air (5 tests)

37-

0 1 0- 8 k

L - T orientation

1 0-3

1 0-5

U

1 0-6

- 10-7

-= 10-8

3

40

1 0-5

R = +0.33, = 13.3 HzFull thickness CCT specimen 1 0- 10

o-6.0•••• 0

L-T orientation

Alclad 7475-161 sheet 1 0 - 90.100 in. (2.54 mm) thick

1

R +0.33, f= 13.3 HzFull thickness CCT specimen 10-10

1 i 1 11

5 1 0 40

AK. ksi in.

ar5 1 0-5

S.. 1 0-6

-1 -

1 0- 7 =-7-7

1 0-8

o-9

1 0-5

--.- 10-8

-A 1 0-7

L-T orientation 1 0-8

7475-T61 plate0.125 in. (3.2 mm) thick 7.v. 10-9

R= +0.33. f= 13.3 HzFull thickness CCT specimen 10-10

( I ti

40

1 0-wH. Alclad 7475-T61 sheet+ 0.088 in. (2.24 mm) thick -1 1 90-

1 0 -5 !=.== R= +0.33. f= 13.3 Hz- Full thickness CCT specimen -A 10-10

I L.iiiii I

5 1 0 40

AK, ksi in.

Fatigue Crack Growth Rate DataBare and Alclad 7475-T61 Sheet

Various Test Environments, Specimen Orientationsand Sheet Thicknesses

Figure 13

E._ Environment H Room temperature

1 0"-4 (RH 1 05'4 air (1 test)• v Moist (RH • 90%) air 11 test),

: Salt fog (1 test)io- 5 L

1 6 - 6 L.-

1 0-7

1 0-5

1 0 - 91 5 1 0

AK, ksi s in.

AK, MPa rT1

1 5 1 0

1 0 - 5

1 0-b

• 1 0

L

1 0- 5 L-

-0

1 0-9

T-L orientation

7475-161 sheet0.125 in. (3.2 mm) thick

40

<,.. ,r

o ,F . 10-7. ---3I6,

0

1 10-8

._. 10-97.'..

-..

40 11 J.- 1 0-3 = , 1 I I I I I . 1

. Environment_ Envir-'51 1 0-5_= _ Room temperature

1 0- 4 6- --Ambient air (2 tests)

I ! I I (

5 1 0

AK. ksi in.

AK, MPa rT15 1 0

36

. K. MPa,,m

5 1 0 40

Environment

Room temperature 'Dry (RH < 10`) air (1 test)

-Moist (RH - 90 : -) air (1 test) ° °^:Salt fog (1 test) t °

`a•^a

L-T orientation

7475-7761 sheet0.125 in. (3.2 mm) thick

R=+-0.33.)= 13.3 HzFull thickness CCT specimen

5 1 0

., K, ksi , in.

_K, MPa m

5 1 0 40

Environment

Room temperatureq Dry (RH < 10':) air (1 test)x Moist (RH > 90':) air (1 test)o Salt fog (1 test)

'SS-m

T-L orientation

4 ;7072) Alclad 7475-T761 sheet° 0.038 in. (0.965 mm) thick

R = +0.33• f 18.3. 20 HzFull thickness CCT specimen

1 Q5

1 0-6

U1 0- 7 U

E

1 0- 8 ?in1

1 0-9

1 0-5

10-6

0U

1 0-7

E

10-8 Z

in1

10-9

1 0-10

1 0-10

40

1 5 10 40

AK, ksi

1 0-3

1 0-4

I

05 !

C 1 0-6

z1 ^

1 0 7

108

1 0 - 9

1 0-3 e

1 0-4

10-5

1 0-6-11

10-7

1 0-8

10-9

K. MPa , m

5 1 0 40

1 0-3° ° 10-5rEnwonmen

omtemperature ep°^10-4 y (RH < 10%) air (3 tests) a

-<Moist (RH '- 90%) air (3 tests 'ii ,' 1 0-6Salt fog t3 tests)

y 10-5 r^.

v F

^

-^ 10-7

10-6 .

-

10 - 8

1 0-7

< -L orientation

-1 E 7475-7761 sheet 1 0-90.125 in. (3.2 mm) thick

1 0 6R=-0.33.f=13.3 Hz 10-10Full thickness CCT specimen =

1 0 -91 I I I I1 5 1 0 40

AK, ksi , in.

5K, MPa (

1 5 1 0 401 0-3

En vironment 1 0-5Room temperature °

1 0-4 .=Dry (RH < 10 %) air (1 test) o o

o-Moist (RH % 90°0) air (2 testsl,m pO

10-6^Salt fog (1 :est)^ y

'^'nh yb °1 0-5 U

TRv

c 1 0-6 z

Z E 1 0-8^I

m 10_ 7 isT-L orientation

_

(7072) Alclad 7475-7761 sheet 1 0-90.128 in. (3.25 mm) thick

1 0-6R=+0.33,f=2. 20 Hz

10-10Full thickness CCT specimen

10-9 1 1 1 1 1 1 1 ) 1 1 I

1 5 1 0 40

AK, ksi ,, in.

Fatigue Crack Growth Rate DataBare and (7072) Alclad 7475-T761 Sheet

Various Test Environments, Specimen Orientationsand Sheet Thicknesses

Figure 14

37

GA 13002 3

Tension dominated spectrum-"" (Fighter wing root)1-7 Tension-compression spectrum

(Fi ghter horizontal tail)

(Average of two duplicate tests)

2024- 7475- 7475- 7050- 7075- 707T351 1651 T7351 17451 17351 T651

-

Tension-dominated spectrum (fighter wing root)

Tension-compression spectrum (Fighter horizontal tail hinge)

25,000

p-or.

20,000 k-

O1 5,000 I-

0.) 10,000

Etq 5,000

0

A. Spectrum life for crack growth from 0.24 in. (6 mm) to failureat a maximum peak stress of 21 ksi (145 MPa)

g 100E

.15a)a)

4.6‘a)c.)U)0- —100

1 00

E

00

a)

a)c.)

a. —100

B. Representative portions of stress history of each spectrum

Fatigue Crack Growth Rate Spectrum Ranking(References 13 and 1 4)

Figure 15

3 8

T T J ___i=

T W

t T

J'77 z W

C

.y

'---' -••.rd

LU _ p

r - l _ ^-' CO =

Hi ^` Q

0r'r W

Wy r F .

z

a}â1^,^ ^'4k3

_

i ail..

-I T+rr

160

Thickness. (mm)1.27 2.54 3.81 5.08 6.35

176 160

- 1 20 1 -O

o 8C18a

O 8

0 132

a_80 2

88Ne'

O

80 -

40L -T Direction

44 40

0.2500.000.25 0.05 0.10 0.15 0.20

Thickness, (in.)Bare 7475-T61

0.00 0.05 0.10 0.15 0.20

Thickness, (in.)Bare 7475-T61

Thickness. (mm)1.27 2.54 3.81 5.08 6.35

I I I

176

132 k0.

88

44

q

0

T-L Direction

• 160160 176

• 8

• 0

•• 0

cP•$

Invalid perASTM E561

132 122.1- 120

80n •

- 1 20

80

a.

88NZ

44 40

T-L Direction

CI Bare- n Alclad40

L-T Direction

- 0 Bare• Alclad

44

0.10 0.15 0.20 0.25

Thickness, (in.)7475-T761

0.0500.00

Thickness, (mm)1.27 2.54 3.81 5.08 6.35

Thickness, ( mm)1.27 2.54 3.81 5.08 6.35

176

qq 132 l'!"

q q 1 2q OE 88

•

0.00 0.05 0.10 0.15 0.20 0.25Thickness. (in.)

7475-7761

Critical Stress Intensity Factor (1(c)Bare and Alclad 7475 Sheet

16 in. x 33 in. (406 x 1117 mm) Center Crack PanelsFigure 17

40

240

220

200

I C

> 160cn

140

z 120

100LU

80U

C-; 6 0

20

260

240

220

200

180

160

Ls

1 40cz

120cc

100

80

60

40

20

( WANG)7475-T761 TEMPER

McCABE)AND0.063 in. (1.6 mmi THICK

(HEYER T-L ORIENTATION7475-T61. T761 TEMPERS 36 AND 120 in.0.063 in. (1.6 mm) THICK (914.4 AND 3048 mmi WIDE

T-L ORIENTATION10.2 in. (259.1 mm) WIDE

CLWL SPECIMEN

CLWL SPECIMEN

00•

— - - - - - - - - j 7 - - -

/

,, ^; /

7, / \

- - - I — - - - - - - - - - -

(HEYER AND McCABE)(.4LCOA) 7475-T761. T761 TEMPERS

O

7475-T761 TEMPER 0.091 in. (2.3 mm) THICK0.063 in. (1.6 mm) THICK T-L ORIENTATIONL-T AND T-L ORIENTATION 10.2 in. (259.1 mm) WIDE16 in. (406.4 mm) WIDE CLWL SPECIMEN

CCT SPECIMEN

(HEYER AND McCABE)

7075-T6 TEMPER0.063 in. (1.6 mm) THICK

T-L ORIENTATION SPECIMEN TYPE

5.1 in. (129.5 mm) WIDE CLWL - CRACK LINE WEDGE LOADEDCLWL SPECIMEN CCT - CENTER CRACK TENSION

0

' + 0

1.8 (in.)

( 45.7) (mm)

0.2 0.6 1.0 1.4(5.1) (15.2) (25.4) (35.6)

CRACK EXTENSION, O a

CRACK RESISTANCE CURVES FOR 7475 SHEET

Figure 18

41

• • • •• • • •

4"

• • • •• • • •

1

16"

I

(406.4 mm)

44"(1117.6 mm)

Kc specimen

2024-T3•

•6061-T6 0

0•Note: Limited Kc data on •2024-T3, 6061-T6, •

7075-T6. Fracture 2024-T86

toughness notguaranteed forthese alloys.

0 7475-T61A 7475-T761

2014-T6 7178-T6

140 154

120 132

110 ;:l

88ct.

66

40 44

20 22

020 30 40 50 60 70 80 90

Tensile yield strength, ksi (Long transverse direction)

GA 18002.17

Tensile yield strength, MPa207 276 345 414 483 552

Critical Stress-Intensity Factor K c vs.Tensile Yield Strength

0.040-0.249 In. (1.0-6.3 mm) Thick SheetFigure 19

42

70

50

L1 40

Y 30

20

70

60

50

40 cz

30

20

10

GA 18002.2

10

TENSILE YIELD STRENGTH, MPa

an snn

COMPACT - TENSIONSPECIMEN

000

1415 NLAIt

O 1651q 17651A 17351

T-L ORIENTATION

0 50 60 70 80 0

TENSILE YIELD STRENGTH, ksi

PLANE - STRAIN STRESS-INTENSITY FACTOR KI D , vs YIELD STRENGTH7475 PLATE 1 TO 3.5 inch (25.4-88.9 mm) THICK

Figure 20

43

GA 18002.18

0160 —

180

140 —

120 —c

• 100 —

Y.)

80 —

I I I I 1

0.6 0.7 0.8 0.9 1.0

60 —

400.5

1 98

176

1 54

132

2

110 3

88

66

44

NYR (L) - 3 inch wide edge-notch specimen

Fracture Toughness, K c (L-T) vs. Notch-Yield Ratio (L)Bare 7475-T61 Sheet - 0.150 thru 0.233 In.

(3.81 thru 5.92 mm)Figure 21

44

48

J44

40

N

36

32

52.8

48.4

44.0

7E

39.6

35.2

56GA 18002.19

61.6

52 n 57.2

Notch diameter28

q 0.500 in. (12.7 mm) 30.8A 1.060 in. (26.9 mm)

24

I 1-_I

26.41.20 1.25 1.30 1.35 1.40 1.45 1.50 1.55 1.60 1.65

NYR (LT) - (dia. as noted)

Fracture Toughness, K 1C (T- L) vs.Notch-Yield Ratio (Long Transverse)

7475-T7351 Plate - 0.984 thru 4.000, in.(25 thru 101.6 mm)

Figure 22

45

50

U

45(r)a)C

En 400

a)hi. 35

co

30

66.0

60.5

55.0 12..

U

49.5CY)

a)44.0 =al

38.5 2..!

33.0 ill

55

60

27.570 75

2530 35 40 45 50 55 60 65

Short rod value (SR4)

Fracture Toughness vs. Short Rod Value for 7475-T7351Plate (L-T, T-L & S-L Orientation)

Figure 23

EEu?vt MCl)OC

V ttjL N

'^ M

ON

EN

.E r

OZ

CT

r

Cl)w

Cl)Cl)0)

Y'+V

I-

0)

HNJ ^

' tLow

T ' a^

N

0Q

Cl)C0CS

Cc

r

04

00C

V_

OO

C)rr

to EO

CE

cr O0z

N

O

J9O ON

00c_

NM ^ r

II C

Y ^C7

Cm

edW sza)i

N 0M r co CO q*r r co co It

0 0 0 0 0 0N 0 co (0 ql

r r r• ui is} i sualui ssa.qs

47