NDLI: Extended Aging Theories for Predictions of Safe Operational Life of Critical Airborne Structural Components

Please wait, while we are loading the content...

Extended Aging Theories for Predictions of Safe Operational Life of Critical Airborne Structural Components

Content Provider	Semantic Scholar
Author	Chen, Tony
Copyright Year	2006
Abstract	The.previously.developed.Ko.closed-form.aging.theory.has.been.reformulated.into.a.more. compact.mathematical.form.for.easier.application ..A.new.equivalent.loading.theory.and.empirical. loading.theories.have.also.been.developed.and.incorporated.into.the.revised.Ko.aging.theory.for. the. prediction. of. a. safe. operational. life. of. airborne. failure-critical. structural. components ..The. new set of aging and loading theories were applied to predict the safe number of flights for the B-52B.aircraft.to.carry.a.launch.vehicle,.the.structural.life.of.critical.components.consumed.by. load. excursion. to. proof. load. value,. and. the. ground-sitting. life. of. B-52B. pylon. failure-critical. structural components. A special life prediction method was developed for the preflight predictions of.operational.life.of.failure-critical.structural.components.of.the.B-52H.pylon.system,.for.which. no flight data are available. noMenCLAtURe A. . crack.location.parameter.(A.=.1 .12.for.a.surface.crack) a . . depth..of.semi-elliptic.surface.crack,.in . ac o. . operational.limit.crack.size,.in .,. a Q K AM f a f c o IC K c p =       = π σ* 2 2 ac p. . initial.crack.size.associated.with.proof.(or.limit).load,.in .,. a Q K AM c p IC K =       π σ* 2 ( ) ac p old... initial.crack.based.on.original.proof.load.test,.in . ( ) ac p new... initial.crack.based.on.revised.proof.load.test,.in . a1. . crack.size.at.the.end.of.the.first.flight,.in .. a a c p + ∆ 1 C.. . coefficient.of.Walker.crack.growth.equation,. in . cycle ksi in . m ( ) c. . half-length.of.surface.crack,.in . D. . diameter E. . complete.elliptic.function.of.the.second.kind, E k d = − ∫ 1 sin 2 2φ φ π 0 2 F1 . . number.of.flights.predicted.from.Ko.closed-form.aging.theory Fp . . number.of.flights.consumed.by.the.proof.load f operational.load.factor.associated.with.the.worst.cycle.of.a.random.loading. . . . spectrum,. f V V f o = < max ,( ) 1 f equivalent.loading.factor.associated.with.an.equivalent-constant-amplitude. . . . loading.spectrum,. f V V f f = < max * ,( ) HF. . B-52H.front.hook HR.. . B-52H.rear.hook HFF. . B-52H.front.fitting 2 HRF. . B-52H.rear.fitting HLSB.... B-52H.pylon.lower.sway.brace. HXLV... Hyper-X.launch.vehicle i 1,.2,.3,.... ..,.integer.associated.with.the.i-th.half-cycle KIC . . mode.I.critical.stress.intensity.factor,.ksi in . Kmax. . mode.I.stress.intensity.factor.associated.with. σmax,.ksi in . ∆K .. . mode.I.stress.intensity.amplitude.associated.with.stress.amplitude,.(σ σ max min − ),. . . ksi in . ksi. . 1000.times.lb/in2 k modulus.of.elliptic.function,. k a c = − ( ) 1 2 Mk . . flaw.magnification.factor.(Mk =.1.for.a.shallow.crack) m. . Walker.exponent.associated.with. Kmax N. . number.of.stress.cycles. N1. . number.of.stress.cycles.consumed.during.the.first.flight n Walker.exponent.associated.with.R. Q. . surface.flaw.and.plasticity.factor,.Q E k Y = ( )   − ( ) 2 2 0 .212 σ σ * R. . radius Ro . . stress.or.load.ratio.associated.with.the.worst.cycle.of.random. . . . loading.spectrum,. R V V o o o o o = = σ σ min max min max / R. . stress.or.load.ratio.associated.with.constant-amplitude. . . . loading.spectrum,. R V V = = σ σ min max min max / SRB/DTV. solid.rocket.booster/drop.test.vehicle SUL. . Pegasus.pylon,.left.shackle.upper.part SUR.. . Pegasus.pylon,.right.shackle.upper.part SLL.. . Pegasus.pylon,.left.shackle.lower.part SLR.. . Pegasus.pylon,.right.shackle.lower.part t . . thickness,.in . V. . hook.load,.lb 3 VA B-52B.pylon.front.hook.load,.lb VBL . . B-52B.pylon.left.rear.hook.load ..lb. VBR . . B-52B.pylon.right.rear.hook.load,.lb VPFL . . Pegasus.pylon.front.left.hook.load,.lb VPFR . . Pegasus.pylon.front.right.hook.load,.lb VPRL . . Pegasus.pylon.rear.left.hook.load,.lb. VPRR . . Pegasus.pylon.rear.right.hook.load,.lb VA B-52B.pylon.front.hook VBL. . B-52B.pylon.left.rear.hook. VBR. . B-52B.pylon.right.rear.hook VPFL. .. Pegasus.pylon.front.left.hook. VPFR. .. Pegasus.pylon.front.right.hook. VPRL. .. Pegasus.pylon.rear.left.hook. VPRR. .. Pegasus.pylon.rear.right.hook. V* . . proof.load.for.any.critical.structural.component,.lb V . . applied.load.for.any.critical.structural.component,.lb V o max . . maximum.load.of.the.worst.cycle.of.random.loading.spectrum,.lb V o min . . minimum.load.of.the.worst.cycle.of.random.loading.spectrum,.lb Vmax . . maximum.load.of.equivalent.constant.amplitude.loading.spectrum,.lb Vmin . . minimum.load.of.equivalent.constant.amplitude.loading.spectrum,.lb VS . . mean.load.of.equivalent.constant.amplitude.loading.spectrum,.lb,.. . . . . V V V S = + ( )( ) max min 1 2 W. . weight.of.launch.vehicle,.lb α . . coefficient.of.thermal.expansion ∆a1. . amount.of.crack.growth.induced.by.the.first.flight,.in . ∆aG . . ground-sitting.crack.growth,.in . ∆ap. . amount.of.crack.growth.induced.by.the.proof.load,.in . δai . . crack.growth.induced.by.the.i-th.half.cycle,.in . 4 η stress-load.coefficient,.ksi/lb,.η σ = * * / V θc . . angular.location.of.critical.stress.point,.rad ν . . Poisson.ratio ρ . . density,.lb/in3 σ. . tangential.stress.at.critical.stress.point.induced.by.the.proof.(limit).load.V,.ksi, . . . σ η * * = V σ A. . tangential.stress.at.critical.stress.point.of.B-52B.pylon.front.hook.induced.by. . . . VA ,.ksi σ BL. . tangential.stress.at.critical.stress.point.of.B-52B.pylon.rear.left.hook.induced.by. . . . VBL ,.ksi. σ BR. . tangential.stress.at.critical.stress.point.of.B-52B.pylon.rear.right.hook.induced.by. . . . VBR ,.ksi. σ PFL. . tangential.stress.at.critical.stress.point.of.Pegasus.pylon.front.left.hook.induced.by . . . VPFL,.ksi. σ PFR. . tangential.stress.at.critical.stress.point.of.Pegasus.pylon.front.right.hook.induced. . . . by.VPFR,.ksi. σ PRL . . tangential.stress.at.critical.stress.point.of.Pegasus.pylon.rear.left.hook.induced.by. . . . VPRL ,.ksi. σ PRR . . tangential.stress.at.critical.stress.point.of.Pegasus.pylon.rear.right.hook.induced. . . . by.VPRR ,.ksi. σmax o .. . tangential.stress.at.critical.stress.point.associated.with.operational.peak.load,. . . . V o max ,.ksi σU . . ultimate.tensile.stress,.ksi σY . . yield.stress,.ksi σmax . . maximum.stress.of.constant.amplitude.loading.cycles,..ksi σmin . . minimum.stress.of.constant.amplitude.loading.cycles,.ksi σ t . . tangential.stress.along.hook.inner.boundary,.ksi ( )max σ t . maximum.value.of.σ t ,.ksi σθ . . tangential.stress.in.θ -direction,.ksi ( )max σθ . maximum.value.of.σθ ,.ksi 5 τU . . ultimate.shear.stress,.ksi φ . . angular.coordinate.for.semielliptic.surface.crack,.rad (.)i . . quantity.associated.with.the.i-th.half-cycle.of.random.loading.spectrum (.)*. . quantity.associated.with.proof.load. IntRoDUCtIon Load-carrying. structural. components. with. L-shaped. geometry. or. containing. holes. will. certainly.have.stress.concentration.problems ..When.subjected.to.cyclic.loading,.the.peak.stress. concentration.point.could.be.with.fatigue.crack.initiation.sites ..The.structural.components,.which. contain.stress.concentration.sites,.may.be.called.failure-critical.structural.components .... The NASA Dryden B-52B launch aircraft has been used to carry various types of flight research. vehicles. for. high-altitude. air-launching. tests ..The. test. vehicle. is. mated. to. the. B-52B. aircraft. pylon. through. one. L-shaped. front. hook. and. two. identical. L-shaped. rear. hooks .. The. L-shaped.geometry.always.induces.a.stress.concentration.problem.in.the.hooks ..The.critical.stress. point.at.the.hook.inner.boundary,.where.the.tangential.tensile.stress.reaches.a.maximum.at.the. inner.curved.boundary,.is.the.potential.fatigue.crack.initiation.site .. During. the. early. stages. (1983). of. the. air-launching. tests. of. the. solid. rocket. booster. drop. test.vehicle.(SRB/DTV,.49,000.lb),.the.two.B-52B.pylon.rear.hooks.(made.of.4340.steel).failed. almost. simultaneously.during. the. towing.of. the.B-52B.carrying. the.SRB/DTV.on. a. relatively. smooth.taxiway.(low-amplitude.dynamic.loading) ..Microscopic.examinations.of.the.hook.fracture. surfaces.revealed.that.the.left.rear.hook.had.a.micro-surface.crack.of.0 .031.in ..deep,.and.the.right. rear.hook.had.a.0 .038-in ..deep.micro-surface.crack.at.the.respective.critical.stress.points.at.each. hook inner boundary (ref. 8). Those micro-surface cracks escaped preflight detection because of masking by the plating film. Those fatigue cracks must have been initiated from the past repeated cyclic loadings under different flight test programs, and possibly from surface corrosion. Fortunately,.the.hook.failures.occurred.during.taxiing ..If.the.hook.failures.would.have.occurred. during the takeoff run or during the captive flight, a catastrophic accident could have occurred. This.type.of.accident.underscores.the.need.for.development.of.reliable.aging.theories.for.accurate. operational.life.predictions.of.failure-critical.structural.components.of.any.air.launching.system. (e .g .,.B-52B.pylon,.Pegasus®.(Orbital.Sciences.Corporation,.Dulles,.Virginia).adapter.pylon,.and. B-52H.pylon) .. Currently,. the. B-52B. aircraft. is. to. carry,. through. a. special. Pegasus. adapter. pylon,. the. Hyper-X launch vehicle (HXLV) air-launching of (40,000 lb) for the X-43 flight research vehicle . (3,000 lb) for a Mach 7~10 hypersonic flight test. The Pegasus adapter pylon has several . failure-critical.components.(two.identical.Pegasus.adapter.shackles.with.rectangular.and.circular. holes,.and.four.identical.L-shaped.Pegasus.hooks) ..The.operational.life.spans.of.those.components. are.still.not.known .
File Format	PDF HTM / HTML
Alternate Webpage(s)	https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070035048.pdf
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article

Central Library (ISO-9001:2015 Certified)
Indian Institute of Technology Kharagpur
Kharagpur, West Bengal, India | PIN - 721302

See location in the Map
03222 282435
Mail: support@ndl.gov.in

Sl.	Authority	Responsibilities	Communication Details
1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
5	Website/Portal (Helpdesk)	Queries regarding NDLI and its services	support@ndl.gov.in
6	Contents and Copyright Issues	Queries related to content curation and copyright issues	content@ndl.gov.in
7	National Digital Library of India Club (NDLI Club)	Queries related to NDLI Club formation, support, user awareness program, seminar/symposium, collaboration, social media, promotion, and outreach	clubsupport@ndl.gov.in
8	Digital Preservation Centre (DPC)	Assistance with digitizing and archiving copyright-free printed books	dpc@ndl.gov.in
9	IDR Setup or Support	Queries related to establishment and support of Institutional Digital Repository (IDR) and IDR workshops	idr@ndl.gov.in