Aircraft Structural Aircraft Structural MetalsMetals

Explanation of TermsExplanation of Terms Ferrous Metals – have ironFerrous Metals – have iron StrengthStrength

– Tensile strengthTensile strength– Yield strengthYield strength– Shear strengthShear strength– Bearing strengthBearing strength– Strength to weight ratioStrength to weight ratio

Explanation of Terms cont.Explanation of Terms cont. HardnessHardness MalleabilityMalleability DuctilityDuctility BrittlenessBrittleness ConductivityConductivity

– Thermal and electricalThermal and electrical

Explanation of Terms cont.Explanation of Terms cont. ElasticityElasticity ToughnessToughness FusibilityFusibility DensityDensity

Five Kinds of StressFive Kinds of Stress TensionTension CompressionCompression ShearShear TorsionTorsion BendingBending

Tensile and Compression TestingTensile and Compression Testing

Stress Strain DiagramStress Strain Diagram The point at wich The point at wich

permanent permanent deformation begins is deformation begins is known as the yield known as the yield point, or yield stresspoint, or yield stress

Increasing stress Increasing stress beyond the yield point beyond the yield point causes a rapid rate of causes a rapid rate of strain or deformation strain or deformation to occur until the to occur until the material ruptures, or material ruptures, or failsfails

Stress-Strain DiagramStress-Strain Diagram The portion of the The portion of the

diagram from the origin diagram from the origin (O) to the elastic limit (O) to the elastic limit (A) is known as the (A) is known as the elastic range of the elastic range of the material. material.

From the yield point (B) From the yield point (B) to the ultimate tensile to the ultimate tensile strength © the material strength © the material is in the plastic range.is in the plastic range.

Ductile MetalDuctile Metal Some materials do Some materials do

not exhibit an not exhibit an abrupt increase in abrupt increase in strain at the yield strain at the yield point.point.

Comparison of Four MetalsComparison of Four Metals See page 178 and See page 178 and

179179

Stress-Strain for Elastic MaterialStress-Strain for Elastic Material Stress-strain Stress-strain

diagram for a diagram for a highly elastic highly elastic material, such as material, such as rubberrubber

Tensile & Shear Failure of JointTensile & Shear Failure of Joint Tensile failure is Tensile failure is

related to the related to the tensile strength of tensile strength of the material.the material.

Shear failure is Shear failure is when a load is when a load is sufficient to cause sufficient to cause the fastener to fail the fastener to fail by shearing.by shearing.

Bearing & Tear-out Failure of JointBearing & Tear-out Failure of Joint

Bearing failure is a Bearing failure is a type of type of compressive failure compressive failure from the fastener from the fastener pushing, or bearing pushing, or bearing against the sheet.against the sheet.

Placing a fastener Placing a fastener too close to the too close to the edge of the sheet edge of the sheet will result in tear-will result in tear-out failure.out failure.

Common Unit-Cell Types for MetalCommon Unit-Cell Types for Metal

Three common Three common atom atom arrangements for arrangements for metal.metal.

Some metals will Some metals will crystallize on one crystallize on one form and upon form and upon further cooling further cooling change into change into another form.another form.

Crystal Growth As Metal SolidifiesCrystal Growth As Metal Solidifies

Nonferrous MetalsNonferrous Metals AluminumAluminum Aluminum AlloysAluminum Alloys

– 1000 series – 99% pure 1000 series – 99% pure – 2000 series – copper2000 series – copper– 3000 series – manganese3000 series – manganese– 4000 series – silicon4000 series – silicon– 5000 series – magnesium5000 series – magnesium– 6000 series – magnesium and silicon6000 series – magnesium and silicon– 7000 series – zinc7000 series – zinc

Thermal TreatmentThermal Treatment AnnealingAnnealing

– Heating the metal to a given Heating the metal to a given temperature, holding or soaking for a temperature, holding or soaking for a length of time and then cooling in still length of time and then cooling in still airair

– Prolonged forming necessitates Prolonged forming necessitates additional annealing additional annealing

Conditions for heat treatmentConditions for heat treatment Temperature – Table 2-2Temperature – Table 2-2 Time at temperature – aka soaking timeTime at temperature – aka soaking time QuenchingQuenching

– Cold water, hot water, sprayCold water, hot water, spray Lag between soaking and QuenchingLag between soaking and Quenching Reheat treatmentReheat treatment

Precipitation heat treatmentPrecipitation heat treatment Used to prevent intergranular Used to prevent intergranular

corrosioncorrosion Aka. Artificial agingAka. Artificial aging Soak at temps between 245 to 375 F Soak at temps between 245 to 375 F

for specified time periodsfor specified time periods Locks the grain structure linkageLocks the grain structure linkage

Strain hardeningStrain hardening Mechanically working Mechanically working

metals at temperatures metals at temperatures below their critical rangesbelow their critical ranges

Rolling, drawing, stamping Rolling, drawing, stamping or pressingor pressing

Strength, hardness, and Strength, hardness, and elasticity are increasedelasticity are increased

Ductility decreases, Ductility decreases, becoming more brittlebecoming more brittle

Hardness IdentificationHardness Identification

Cold worked metalsCold worked metals– F – as fabricatedF – as fabricated– O – annealedO – annealed– H – strain hardenedH – strain hardened– H1 – strain hardened onlyH1 – strain hardened only– H2 – strain hardened and stabilizedH2 – strain hardened and stabilized

Hardness IdentificationHardness Identification

Solution heat-Solution heat-treatingtreating

See page 28 See page 28 for listingfor listing

CladdingCladding Manufactures of sheet stock apply Manufactures of sheet stock apply

pure aluminum as approx 10% of pure aluminum as approx 10% of thickness a corrosion protection thickness a corrosion protection agentagent

Substitution of Aircraft MetalsSubstitution of Aircraft Metals Check the SRMCheck the SRM Must considerMust consider

– Contour and aerodynamic Contour and aerodynamic smoothnesssmoothness

– Original weightOriginal weight– Original corrosion-resistant Original corrosion-resistant

propertiesproperties

Magnesium Magnesium Two-thirds the weight of aluminumTwo-thirds the weight of aluminum Alloys have the highest strength-to-Alloys have the highest strength-to-

weight ratio of any common metalsweight ratio of any common metals Alloyed with aluminum, Alloyed with aluminum,

manganese, and zincmanganese, and zinc Magnesium dust and chips ignite Magnesium dust and chips ignite

easily and should be extinguished easily and should be extinguished with powderswith powders

Titanium and Titanium AlloysTitanium and Titanium Alloys High strength-to-weight ratio and High strength-to-weight ratio and

corrosion resistancecorrosion resistance Alpha, Alpha-Beta, and Beta alloysAlpha, Alpha-Beta, and Beta alloys

Nickel AlloysNickel Alloys

MonelMonel 68% nickel, 29% copper68% nickel, 29% copper Cannot be hardened by heat treatedCannot be hardened by heat treated 80 – 125,000 psi – tough alloy class80 – 125,000 psi – tough alloy class High strength and corrosion resistanceHigh strength and corrosion resistance

InconelInconel Similar to stainless steelSimilar to stainless steel 100-125,000 psi – tough alloy class100-125,000 psi – tough alloy class Salt water and high temp resistant (1,600 F)Salt water and high temp resistant (1,600 F)

Ferrous Aircraft MetalsFerrous Aircraft Metals Iron – iron ore combined with limestone to Iron – iron ore combined with limestone to

form pig ironform pig iron Steel – iron combined with carbon to form Steel – iron combined with carbon to form

carbon steelcarbon steel– Low, medium and high carbon steelLow, medium and high carbon steel

Steel alloy is formed when carbon steel is Steel alloy is formed when carbon steel is combined with other metalscombined with other metals

Alloying Agents in Steel CarbonAlloying Agents in Steel Carbon SulfurSulfur ManganeseManganese SiliconSilicon PhosphorusPhosphorus NickelNickel

MolybdenumMolybdenum ChromiumChromium VanadiumVanadium TitaniumTitanium TungstenTungsten

Alloy SteelsAlloy Steels Chromium-Molybdenum Chromium-Molybdenum

SteelSteel Nickel SteelNickel Steel

– Chromium-nickel steelsChromium-nickel steels– Stainless steelStainless steel

18-8 (18%chromium and 8% 18-8 (18%chromium and 8% nickel)nickel)

Alloy SteelsAlloy Steels

Heat Treatment of SteelHeat Treatment of Steel

Annealing Annealing – relieve internal relieve internal

stresses, soften the stresses, soften the metal, ductile, and metal, ductile, and refine the grain refine the grain structurestructure

NormalizingNormalizing– Removes internal Removes internal

stresses from stresses from welding, machining, welding, machining, and formingand forming

Heat Treatment of SteelHeat Treatment of Steel

INFRARED ON-LINE HEATER applications include drying, preheating, annealing, stress relieving, boosting current processes and much more.

Heat Treatment of SteelHeat Treatment of Steel HardeningHardening

– Steel is heated above Steel is heated above critical point, soaked, critical point, soaked, cooled rapidly with oil, cooled rapidly with oil, water, or brinewater, or brine

TemperingTempering– Follows hardening and Follows hardening and

reduces brittleness and reduces brittleness and softens the steel.softens the steel.

CasehardeningCasehardening CarburizingCarburizing

– Pack carburizingPack carburizing– Gas carburizingGas carburizing– Liquid carburizingLiquid carburizing

Vacuum Carburizing FurnaceVacuum Carburizing Furnace

Carburized partsCarburized parts

NitridingNitriding

NitridingNitriding– Ammonia gas is circulated within a Ammonia gas is circulated within a

specially constructed furnace chamber specially constructed furnace chamber and the nitrogen reacts with the iron to and the nitrogen reacts with the iron to form iron nitrideform iron nitride

                                                1.SOURCE OF PROCESS GAS (TANKS, PROCESS GAS GENERATOR) 2.GAS PROCESS CONTROL SYSTEM 3.NITRIDING FURNACE  4.TURBO-COOLING SYSTEM  5.CLOSED LOOP WATER COOLING SYSTEM 6.RACKING 7.EXHAUST GAS (AMMONIA) NEUTRALIZING EQUIPMENT 

Nitrided PartsNitrided Parts

Brinell Hardness Testing Brinell Hardness Testing

– Microscope measures diameter of Microscope measures diameter of impression left by a pressed ballimpression left by a pressed ball

Rockwell Hardness Testing Rockwell Hardness Testing

– Microscope measures depth of Microscope measures depth of impression left by a pressed ballimpression left by a pressed ball

Vickers Hardness TestingVickers Hardness Testing

– A small pyramidal diamond is pressed A small pyramidal diamond is pressed into the metal and the ratio of the load into the metal and the ratio of the load applied to the surface area of indention applied to the surface area of indention is given a Vickers Hardness number HVis given a Vickers Hardness number HV

Webster Hardness GaugeWebster Hardness Gauge

– Used for parts too large for a standard Used for parts too large for a standard bench testerbench tester

Heat-Treatable AluminumHeat-Treatable Aluminum 2014, 2017, and 2024 will turn black 2014, 2017, and 2024 will turn black

when sodium hydroxide is appliedwhen sodium hydroxide is applied 6053, 6061, and 7075 must be 6053, 6061, and 7075 must be

tested in a laboratorytested in a laboratory