Final Design ReviewMEMS-based Corrosion Health MonitoringFri aeiynCucfedJanineCrsohrOMihe erncT ioLiaison Engineers:Pec ucesTr lwFaculty Coach:Jh .AboePD E

Introduction

Corrosion occurs on electronic chassis of aircraftcauses loss of integrity of EMI seal

Lockheed Martin techniciansresponsible for avoiding critical corrosion damagemonitor the health of the chassis on a scheduled basisthe chassis is relatively inaccessible within the aircraftin most cases, the chassis is corrosion freetime and money are wasted by this inefficiency

AimTo reduce unnecessary corrosion related service activities with a stand alone system that can alert a technician of a needed inspectionReliable measurement of the environmental corrosivity seen by the chassisLED alert systemviewed from exterior of the chassis1-10 level of need for service activity

Business CaseLife cycle cost for the Apache Helicopter fleet* $14.3 billionPercent Dedicated to Inspection**x 25%------------------Inspection cost for the Apache Helicopter$3.575 billionPercent inspections eliminated by SDX-4912 x 33%------------------TOTAL PROGRAM SAVINGS $1.18 billionLife cycle of Apache helicopter* 20 years------------------TOTAL ANNUAL SAVINGS* $59 millionTOTAL LIFE CYCLE SAVINGS/helicopter*** $1.5 million

*These estimates, in constant fiscal 1994 dollars, are provided in Annex D of the Longbow Apache Test and Evaluation Master Plan, which cites December 1993 estimates from the Longbow Program Office and the Presidents fiscal 1995 budget as the original source.**Provided from the Military Analysis Network created by the FAS, Federation of American Scientists (non-profit, tax exempt, 501c3 organization)***Costs assuming that the SDX-4912 is installed in full apache fleet (assuming fleet size 800)

Elements of Chassis

Galvanic coupling of aluminum and nickel

Aluminum = anodeNickel = cathode

Electrolyte provides driving force for corrosion

Galvanic CorrosionAs a result of nickel contact:Corrosion potential of aluminum (M) increasedCorrosion rate of aluminum (M) is increasedNickelAluminumCouple

Customer Requirements

GENERAL NEEDS:

Operate Under Harsh ConditionsNon-Intrusive FeedbackLong Life SpanMEMS BasedLight WeightSmall Size

Hardware Design

Hardware DesignFunctional Diagram

Power Supply

Location

Aircraft In-situ Operation

Sensor(s)

Processing

Feedback

Aircraft Structure

Maintenance Opportunity

Storage

Hardware Design

Macroscopic System

Hardware Design

Near Linear ApproximationModule Expiration DetectionManufacturabilityR = V / IapplR = L / r2

Electrical Resistance Sensor Concept:

Sensor SamplingData sample taken hourly

All data stored on Flash

Light Emitting Diodes (LEDs)4 red, 3 yellow, 2 green1-10 level of corrosion damageRelate to need for technician to perform service activityLevel 7 (1st Red LED) correlates to critical corrosion damage

Output MethodCorrosion will cause reduction in ER sensors cross-sectional areaAt critical % area reduction critical voltage

Sensor SamplingControl Wire

Testing

Verification TestingHardware Unit TestSensor Proof of Concept5 days in Salt Spray MachineSoftware Unit TestData Interface to software and LED displayAcceptance Testing Functional Acceptance Test (Integration)Environmental Acceptance Test (Survivability)

Proof of Sensor Concept48 hour test -24 hours immersed in salt bath -24 hours in atmosphere

Proof of Sensor Concept Ground to 50% diameter along longitudinal plane and polished Large cathode (Ni) to anode (Al) ratio

Damage to nickel plating on aluminum wire

TestingASTM B117 Salt Fog ChamberConstant corrosive vapor applied for 5 days5 Test coupons removed at daily intervalsData samplings recorded as voltagesRecorded using a dataloggerData sampling = once per minute

Example of Salt Spray Chamber

Wireless - ZigBeeProven feasible up to 6 thickness of casingDue mainly to chamber reflectionsMinimal aperture required

Wireless communication pursuit ended 2/7/05 given risk and manpower

Testing Results

Results

ResultsASTM D3359 Coating Adherence TestMeasures Amount of Undercut Nickel Plating Designations: 5A (Least Corrosion)0A (Most Corrosion)5 coupons tested24 hr: 5A48 hr: 4A 71 hr: 2A139 hr (1): 1A139 hr (2): 2A

Coupon 139 hr (1)

Measurement CorrelationCouponsMinimal corrosion product for 24 & 48 hr couponsVisible Al203 for 71 &139 hr couponsMeasurementsRapid Increase in ER sensor at onsetMinimal Corrosion Product formingAl+3 ions lost in aqueous solutionResistance change levels off Corrosion product protection

Sensor LifespanElectrical resistance sensor Survived 5-day salt fog Provided data throughout lifespan of operating board TemperatureSurvived 2-day salt fog Humidity Survived 1-day salt fog Potentially a conformal coating problem on board

Environmental SurvivabilityHarshest of Possible EnvironmentsEnvironmental Sensorsnot conformally coatedsurvivable in constant spray for 1-2 daysMacroscopic Systemconformal coating spot failures spot corrosionemitted heat from conducting wiressurvivable in constant spray for 4 days

Prototype Demonstration

LEVEL 7

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Conclusion

Recommendations

Wireless LinkStand-Alone Custom GUI Additional Low Power ResearchLaser Etched Sensor Manufacturing

AcknowledgementsThank YouLockheed MartineyunsslewlingKaaraUniversity of FloridaohnAoPEithanfillD,an MMarilyn Marlow

Questions

Were assigned the Longbow chassis because LM identified as problem. Observed corrosion. on EMI seals . due to galvanic coupling of Al/Ni. AL will corrode and compromise the integrity of the seal making the electronics susceptible to EMIDELETE OR ADDcorrodes linearly with time

we can easily detect when sensor needs to be replaced, it will corrode to the point that it will not longer conduct

easily manifested due to simple selective electro-less plating of an AL wire with nickel