System Design Constraints, System Design Constraints, RAM-T, a Paradigm ShiftRAM-T, a Paradigm Shift
Vern FoxVern FoxUnited Defense LPUnited Defense LP
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AgendaAgenda
RAM-T Overview Legacy Methods Legacy Results Paradigm Shift: RAM-T Case Implementation
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RAM-T OverviewRAM-T Overview What is RAM-T
Reliability - The ability of a system or component to perform its required functions under stated conditions for a specified period of time.
Availability – the ability of a product to be ready for use when the customer wants to use it (uptime/uptime+downtime)
Maintainability - the relative ease and economy of time and resources with which an item can be retained in, or restored to, a specified condition when maintenance is performed by personnel having specified skill levels, using prescribed procedures and resources at prescribed level of maintenance and repair.
Testability – A design characteristic which allows the status (operable, inoperable or degraded) of an item to be determined and the isolation of failures within the item to be performed in a timely manner.
System Design Constraints
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Legacy MethodsLegacy Methods
Perform predictions Based on handbook data Based on similar equipment
Address SOME RAM-T drivers RAM-T optimized during test
Low initial RAM-T High test hours, high $’s
Legacy Approach
Assessments Subsystem IntSystem Intand Test
Preliminary Design Detailed Design Test Fielding
Late identification of component RAM-T shortcomings
limits corrective action
Eliminate some component RAM-T driversFix integration issues
Update design
Eliminate some component RAM-T driversFix integration issues
Update design
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Legacy ResultsLegacy Results
Of Failed Tests, 75 % Of Systems Failed to Achieve Even Half Of TheirRequirement!
Of Failed Tests, 75 % Of Systems Failed to Achieve Even Half Of TheirRequirement!
Demonstrated Reliability Versus Requirements for Operational TypeTests
0
100
200
300
400
500
600
700
800
900
1000
0 200 400 600 800 1000 1200 1400Requirement MTB_
De
mo
ns
tra
ted
MT
B_
FIELD
LUT
FOT
IOT
DT/OT
4500
Not Met
Met
(Data 1996 - Oct 01)
Only 30%
Success
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Paradigm Shift: RAM-T CaseParadigm Shift: RAM-T Case Legacy methodologies failing Methodology required for infusing RAM-T into design
Criteria• Early, influence design during design phase
• Return on Investment (ROI) Result: Paradigm Shift – RAM-T Case
• Make case for how RAM-T requirements will be met Combination of analyses and tests
o Physics of Failure (PoF) analyseso RAM-T Enhancement Tests (RET)
RAM-T Case Management Plan RAM-T Case Report
• Elevate RAM-T constraint importance
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Paradigm ShiftParadigm Shift
Legacy Approach
RAM-T Case Approach
Emphasize: Early identification and elimination of RAM-T shortcomingsExample: Achieve Higher Mi on prototype delivery
Assessments Subsystem IntSystem Intand Test
Preliminary Design Detailed Design Test Fielding
PoF RET Subsystem IntSystem Int and Test
Early identification and elimination of component level failures
Late identification of component RAM-T shortcomings
limits corrective action
Eliminate some component RAM-T driversFix integration issues
Update design
Eliminate component reliability driversUpdate design
Eliminate component reliability driversUpdate design Fix integration issues
Update designFix integration issues
Update design
Eliminate some component RAM-T driversFix integration issues
Update design
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Paradigm Shift: RAM-T CaseParadigm Shift: RAM-T Case Make case for meeting RAM-T requirements
Documented in RAM-T Case Management Plan• A living document, updated throughout the program• Plan and supporting data subject to approval• RAM-T requirements are clearly understood• Methods/activities to be performed to make case• Ensure RAM-T is key factor in the design process• Ensure RAM-T is of equal weight with other engineering
disciplines RAM-T Case Report
• A living document, updated throughout the program• Reasoned, auditable documentation of progressive
assurance that RAM-T requirements will be met• Audit trail of engineering considerations, trade studies,
analyses and assessments
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Paradigm Shift: RAM-T CaseParadigm Shift: RAM-T Case A RAM-T Case Program/Plan sample contents
• Benchmarking RAM-T Requirements • Dynamic/static design modeling, simulation, or probabilistic
analysis• Critical component identification • RAM-T Modeling, Optimization and Component/System Testing• Environmental stress (operate and storage)• Physics-of-Failure (PoF)• Structural finite-element stress analysis• Fatigue analysis• Wear-out/service life analysis• Long-term storage (shelf life) assessment• Prognostics analysis• Fault detection/isolation analysis• Built-in Test False alarm rate analysis • Availability Analysis• On-board Sparing: Supportability analysis• RAM-T Block Diagram• RAM-T Assessments Analysis• Risk assessment & mitigation• Diminishing resources/obsolescence plan• Pit Stop Engineering
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Paradigm Shift: RAM-T CaseParadigm Shift: RAM-T Case RAM-T Case Management Plan
Methods/activities to be performed to make case• Goal - Robust designs• Physics of Failure (PoF)
Finite Element Analysis (FEA) Fatigue Analysis Probabilistic Analysis calcePWA Analysis Pit-Stop Engineering
• RAM-T Enhancement Testing (RET) Highly Accelerated Life Testing (HALT) Accelerated Life Testing (ALT)
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Physics of Failure, -Model the root causes of failure (e.g., fatigue, fracture, corrosion & wear)
CAD tools developed - By industry/academia/government - To address specific materials, sites, & architectures
Benefits•Design-in reliability•Eliminate failures prior to test•Increased fielded reliability•Decreased O&S costs
Benefits•Design-in reliability•Eliminate failures prior to test•Increased fielded reliability•Decreased O&S costs
Stress (e.g., vibration) is propagated from system level to failure site
Root-cause failure is cracking of solder joint
Engineering-Based ReliabilityEngineering-Based ReliabilityEngineering-Based ReliabilityEngineering-Based Reliability
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Software ToolsSoftware ToolsSoftware ToolsSoftware Tools
Solid Modeling Dynamic Simulation
Finite Element Modeling
Fatigue AnalysisThermal Fluid Analysis
Electronic Circuit Card and IC Toolkits
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CalcePWACircuit Card
Tool
CalcePWACircuit Card
Tool
PoF-Based ESSPoF-Based ESS
Accelerated Life Testingon critical board or IC failure
mechanisms
Accelerated Life Testingon critical board or IC failure
mechanisms
Thermal Conditions
Thermal Conditions
Enclosure DesignVibration/Shock Environment
Vibration/Shock Environment
Physics of Failure to Evaluate ElectronicsPhysics of Failure to Evaluate ElectronicsPhysics of Failure to Evaluate ElectronicsPhysics of Failure to Evaluate Electronics
Computational Fluid
Dynamics Model
Computational Fluid
Dynamics Model
Circuit Card Design
Determine if electronics are acceptable based on analysisDetermine if circuit card or enclosure can be redesigned to eliminate failure mechanism
Determine if electronics are acceptable based on analysisDetermine if circuit card or enclosure can be redesigned to eliminate failure mechanism
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Examples: ICEPAK, FLOWMAX, University of Maryland CalceCFD
Inputs• Exterior ambient air temperature• Initial temperature• Fan properties• Power dissipated for each CCA Outputs• Interior air velocity• Interior air temperature• CCA edge temperature
Outputs from CFD analysis used as boundary conditions for CCA thermal modeling
Computational Fluid Dynamics (CFD) ModelingComputational Fluid Dynamics (CFD) ModelingComputational Fluid Dynamics (CFD) ModelingComputational Fluid Dynamics (CFD) Modeling
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Reports and documentationToolbox
Architecture & environmentmodeling
Thermal analysisVibration analysis
Failure assessment& sensitivity analysis
UMD CalcePWA Software ToolUMD CalcePWA Software ToolUMD CalcePWA Software ToolUMD CalcePWA Software Tool
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Radar Ground StationRadar Ground Station
• Analysis showed commercial circuit card OK
• Identified weak link in design & verified
• Validated with testing
Tri-Service RadioTri-Service Radio $27M CostAvoidance
• Air Force analysis showed commercial ICs OK
Army HelicopterArmy Helicopter
Tracked VehicleTracked Vehicle
• Identified potential thermal & vibration problems
Air & Ground System ElectronicsAir & Ground System Electronics
• Circuit card & thermal box-level analyses
• Identified problems & ensured reliable expansion of capability
Missile SystemMissile System$50MSavings
• Analysis on Plastic Ball Grid Array IC package
$1.2M Saved IncreasedReliability
Evaluate New Technology
Design ChangesRecommended
Electronics Circuit Card Success StoriesElectronics Circuit Card Success StoriesElectronics Circuit Card Success StoriesElectronics Circuit Card Success Stories
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List of Critical Nodes
Dynamics Analysis
FE Model
System Model
FEA
Fatigue Life Assessment Reliability Based Design Optimization
DR
AW
DR
AW
Pro
/EP
ro/E
DA
DS
DA
DS
NASTRANNASTRAN
Dynamic Load AnalysisSolid Modeling
Component Stress Analysis
Reliability Analysis
Fatigue Analysis Using Dynamic Simulation & FEA Fatigue Analysis Using Dynamic Simulation & FEA Fatigue Analysis Using Dynamic Simulation & FEA Fatigue Analysis Using Dynamic Simulation & FEA
Terrain Model
Test Course MicroprofileATC Cross Country 3 Course - Left and Right Tracks
November, 1998De-trended Data
-15
-10
-5
0
5
10
15
100 200 300 400 500 600 700
Distance - Feet
Disp
lace
men
t - In
ches
Right Track
Left Track
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CAD: Pro/Engineer, AUTOCAD, I-deas, Solidworks, Used for design and manufacture Used to develop Finite Element Analysis & Dynamic Analysis
models
Three-Dimensional CAD Solid ModelsThree-Dimensional CAD Solid ModelsThree-Dimensional CAD Solid ModelsThree-Dimensional CAD Solid Models
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Examples: NASTRAN, ANSYS, ABACUS, Pro/Mechanica, I-deas
Calculates vibration modes Calculates stress and strain Input into fatigue analysis Used for structural stress evaluation
Finite Element Analysis (FEA) Models Finite Element Analysis (FEA) Models Finite Element Analysis (FEA) Models Finite Element Analysis (FEA) Models
Mode 1
Mode 2
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Examples: DADS & ADAMS
• Multi-body approach
• Use input from solid model & FEA model
• Experimental data used for model inputs of tire, shock absorbers & suspension
• Determines force/ acceleration time history at all locations on trailer
Vehicle traversing simulated terrain profile
Flexible-Body Dynamic Analysis Model Flexible-Body Dynamic Analysis Model Flexible-Body Dynamic Analysis Model Flexible-Body Dynamic Analysis Model
Input into FEA & fatigue analyses
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Fatigue Analysis Software Fatigue Analysis Software Fatigue Analysis Software Fatigue Analysis Software
Examples: nCode, LMS, University of Iowa DRAW
• Edits & characterizes strain time histories
• Rainflow counting & mean stress correction of strain cycles
• Estimates plastic strain based on elastic stress or strain calculations
• Calculates fatigue life based on measured (strain gauge) or FEA strain time histories
15.2 15.4 15.6 15.8-4000
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1000
A M P 1 .D A CS tr a i nu E
A M P 1 .R S DS tr a i nu E
A M P 1 N .R S DS tr a i nu E
Time Secs Screen 1
15.2 15.4 15.6 15.8-4000
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A M P 1 .D A CS tr a i nu E
A M P 1 .R S DS tr a i nu E
A M P 1 N .R S DS tr a i nu E
Time Secs Screen 1
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Trailer Physics-of-Failure ProjectTrailer Physics-of-Failure Project Trailer Physics-of-Failure ProjectTrailer Physics-of-Failure Project
White represents low fatigue life
Fatigue life estimates of drawbar consistent with
failure data
Enlargement of Critical Region
Lif
e (B
lock
s)
Critical Point
Benefits:
Early identification of failure modes
Better test planning and design
Improved maintenance procedures
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Paradigm Shift: RAM-T CaseParadigm Shift: RAM-T Case
Pit-Stop Engineering User/Maintainer hardware interface as a key design parameter Develop Standards of Excellence
• Defines the critical parameters
• Examples 37 pounds maximum for an electrical assembly. Spares on board to provide on board failure recovery. Placement of electronics should be on exterior man accessible
surfaces, no buried electronics. No cables in places where they cannot be accessed. Use common connectors throughout. Etc.
Visualization for decision making
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Paradigm Shift: RAM-T CaseParadigm Shift: RAM-T Case
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Paradigm Shift: RAM-T CaseParadigm Shift: RAM-T Case
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Paradigm Shift: RAM-T CaseParadigm Shift: RAM-T Case
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Paradigm Shift: RAM-T CaseParadigm Shift: RAM-T Case
Reliability Enhancement Testing (RET) Testing focused on Reliability improvement Objective
• Find failure modes
• Eliminate failure modes
• Mitigate those not able to eliminate Period of performance
• Once hardware is available Methodologies
• Use up the life of the product Normal use (years) Accelerated life test (weeks or months) Highly accelerated life test (days)
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Paradigm Shift: RAM-T CaseParadigm Shift: RAM-T Case
Load LevelsUpper Destruct LimitUpper Operating LimitUpper Design LimitUpper Specification Limit
Lower Specification LimitLower Design LimitLower Operating LimitLower Destruct Limit
Nominal
Upper DesignMargin
Lower DesignMargin
Upper DestructMargin
Lower DestructMargin
Upper OperatingMargin
Lower OperatingMargin
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Paradigm Shift: RAM-T CaseParadigm Shift: RAM-T Case
Environmental Stress Chamber with Unit Under Test (UUT) Powered-up and Functioning under load
Test Equipment Providing real-time status of UUT performance
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ImplementationImplementation
Embrace the philosophy Determine critical items Put together multi-disciplined team
Reliability Improvement Working Group (RIWG) Determine RAM-T Case methodologies Document in Action Plan
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ImplementationImplementation
Reliability Improvement Working Groups Integrated, collaborative team composed of design,
specialty, and test personnel to develop Action Plans for critical components to improve the reliability early in the design process.
Action Plans cover proactive reliability tasks such as design reviews, load/stress surveys, failure mode analysis, physics of failure, probabilistic analysis, and reliability enhancement testing.
Forum for discussing Action Plans with and receiving input from reliability improvement experts from customer, OPM, AMSAA, AEC, and other government and industry organizations.
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ImplementationImplementation
Risk Mitigation & Proactive Reliability Tasks
Failure Mode Analysis
Conceptual Prognostic Approach PoF RET
Probabilistic Analysis
Recoil Seal Completed Ongoing PlannedRammer Chain Completed Ongoing PlannedLaser Flash Tube Ongoing Planned Planned (1)Servo Control Unit Connector Completed PlannedDigital Servo Controller Circuit Card Completed Planned Planned (1)Dynamic Cable CompletedSplit Idler Planned Planned PlannedRoad Wheels Planned Planned PlannedSuspension Subsystem Planned Planned
Note: Planned through March 2004 unless otherwise indicatedNote (1): Planned by PDR
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ImplementationImplementation
Emerging Findings, Physics of Failure, FEA Recoil Seal
The gaps show that the whole surface area is not being used to seal.
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RIWG Projected CostsRIWG Projected Costs
Emerging Findings, RET Rammer Chain Housing Material
Material Sample
Result: Influenced material selectionSignificant parameters: Wear and heat buildup
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