System Design Constraints, RAM-T, a Paradigm Shift Vern Fox United Defense LP.

System Design Constraints, System Design Constraints, RAM-T, a Paradigm ShiftRAM-T, a Paradigm Shift

Vern FoxVern FoxUnited Defense LPUnited Defense LP

2

AgendaAgenda

RAM-T Overview Legacy Methods Legacy Results Paradigm Shift: RAM-T Case Implementation

3

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

4

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


Update design

5

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

6

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

7

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


Update design

Eliminate component reliability driversUpdate design

Eliminate component reliability driversUpdate design Fix integration issues

Update designFix integration issues

Update design


Update design

8

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

9

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

10

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)

11

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

12

Software ToolsSoftware ToolsSoftware ToolsSoftware Tools

Solid Modeling Dynamic Simulation

Finite Element Modeling

Fatigue AnalysisThermal Fluid Analysis

Electronic Circuit Card and IC Toolkits

13

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

14

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

15

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

16

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

17

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

18

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

19

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

20

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

21

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

-3000

-2000

-1000

0

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

-3000

-2000

-1000

0

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

22

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

23

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

24


25


26


27


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)

28


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

29


Environmental Stress Chamber with Unit Under Test (UUT) Powered-up and Functioning under load

Test Equipment Providing real-time status of UUT performance

30

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

31


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.

32


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

33


Emerging Findings, Physics of Failure, FEA Recoil Seal

The gaps show that the whole surface area is not being used to seal.

34

RIWG Projected CostsRIWG Projected Costs

Emerging Findings, RET Rammer Chain Housing Material

Material Sample

Result: Influenced material selectionSignificant parameters: Wear and heat buildup

System Design Constraints, RAM-T, a Paradigm Shift Vern Fox United Defense LP.

Documents

Transcript of System Design Constraints, RAM-T, a Paradigm Shift Vern Fox United Defense LP.