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

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System Design Constraints, RAM-T, a Paradigm Shift

Vern FoxUnited Defense LP

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

RAM-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

Legacy Methods

Legacy Approach

Eliminate some component RAM-T drivers

Fix integration issues

Update design

Eliminate some component RAM-T drivers

Fix integration issues

Update design

  • 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

Late identification of component RAM-T shortcomings

limits corrective action

System Int

and Test

Assessments

Subsystem Int

Preliminary Design

Detailed Design

Test

Fielding

Legacy Results

Only 30% Success

(Data 1996 - Oct 01)

Of Failed Tests, 75 % Of Systems Failed to Achieve Even Half Of Their

Requirement!

Paradigm 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
          • Physics of Failure (PoF) analyses
          • RAM-T Enhancement Tests (RET)
        • RAM-T Case Management Plan
        • RAM-T Case Report
      • Elevate RAM-T constraint importance

Paradigm Shift

Legacy Approach

Eliminate some component RAM-T drivers

Fix integration issues

Update design

Eliminate some component RAM-T drivers

Fix integration issues

Update design

Late identification of component RAM-T shortcomings

limits corrective action

System Int

and Test

Assessments

Subsystem Int

Preliminary Design

Detailed Design

Test

Fielding

RAM-T Case Approach

Eliminate component reliability drivers

Update design

Fix integration issues

Update design

Eliminate component reliability drivers

Update design

Fix integration issues

Update design

Early identification and elimination of component level failures

SystemInt and Test

PoF

RET

SubsystemInt

Emphasize: Early identification and elimination of RAM-T shortcomings

Example: Achieve Higher Mi on prototype delivery

Paradigm 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

Paradigm 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

Paradigm 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)

Engineering-Based Reliability

  • 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

Stress (e.g., vibration) is propagated from system level to failure site

  • Benefits
  • Design-in reliability
  • Eliminate failures prior to test
  • Increased fielded reliability
  • Decreased O&S costs

Root-cause failure is cracking of solder joint

Software Tools

Finite Element Modeling

Solid Modeling

Dynamic Simulation

Electronic Circuit Card and IC Toolkits

Fatigue Analysis

Thermal Fluid Analysis

Physics of Failure to Evaluate Electronics

Enclosure Design

Circuit Card Design

Vibration/Shock Environment

Computational

Fluid

Dynamics Model

CalcePWA

Circuit Card

Tool

Thermal Conditions

Determine if electronics are acceptable based on analysis

Determine if circuit card or enclosure can be redesigned to eliminate failure mechanism

PoF-Based ESS

Accelerated Life Testing

on critical board or IC failure mechanisms

Computational Fluid Dynamics (CFD) Modeling

  • 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

Architecture & environment

modeling

Reports and documentation

Toolbox

Failure assessment

& sensitivity analysis

Vibration analysis

Thermal analysis

UMD CalcePWA Software Tool

Electronics Circuit Card Success Stories

Tracked Vehicle

Increased

Reliability

$1.2M Saved

Radar Ground Station

  • Identified potential thermal & vibration problems
  • Analysis showed commercial circuit card OK

Air & Ground System Electronics

$27M Cost

Avoidance

Tri-Service Radio

Design Changes

Recommended

  • Identified weak link in design & verified
  • Validated with testing
  • Circuit card & thermal box-level analyses
  • Identified problems & ensured reliable expansion of capability

Army Helicopter

$50M

Savings

Missile System

  • Air Force analysis showed commercial ICs OK
  • Analysis on Plastic Ball Grid Array IC package

Evaluate New Technology

Fatigue Analysis Using Dynamic Simulation & FEA

Dynamic Load Analysis

Solid Modeling

Dynamics Analysis

System Model

Terrain Model

DADS

Pro/E

Component Stress Analysis

FE Model

FEA

NASTRAN

Reliability Analysis

Reliability Based

Design Optimization

Fatigue Life Assessment

List of Critical Nodes

DRAW

Three-Dimensional CAD Solid Models

CAD: Pro/Engineer, AUTOCAD, I-deas, Solidworks,

  • Used for design and manufacture
  • Used to develop Finite Element Analysis & Dynamic Analysis models

Finite Element Analysis (FEA) Models

Examples: NASTRAN, ANSYS, ABACUS, Pro/Mechanica, I-deas

  • Calculates vibration modes
  • Calculates stress and strain
  • Input into fatigue analysis
  • Used for structural stress evaluation

Mode 1

Mode 2

Flexible-Body Dynamic Analysis Model

  • 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

Input into FEA & fatigue analyses

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

Trailer Physics-of-Failure Project

Fatigue life estimates of drawbar consistent with failure data

Life (Blocks)

Critical Point

White represents low fatigue life

Benefits:

  • Early identification of failure modes
  • Better test planning and design
  • Improved maintenance procedures

Enlargement of

Critical Region

Paradigm 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

Paradigm Shift: RAM-T Case

Paradigm Shift: RAM-T Case

Paradigm Shift: RAM-T Case

Paradigm 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)

Load Levels

Upper Destruct Limit

Upper Operating Limit

Upper Destruct

Margin

Upper Design Limit

Upper Operating

Margin

Upper Design

Upper Specification Limit

Margin

Nominal

Lower Specification Limit

Lower Design

Margin

Lower Design Limit

Lower Operating

Margin

Lower Destruct

Margin

Lower Operating Limit

Lower Destruct Limit

Paradigm Shift: RAM-T Case

Paradigm Shift: RAM-T Case

Test Equipment Providing real-time status of UUT performance

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

Implementation

  • 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

Implementation

  • 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.

Implementation

  • Risk Mitigation & Proactive Reliability Tasks

Note: Planned through March 2004 unless otherwise indicated

Note (1): Planned by PDR

Emerging Findings, Physics of Failure, FEA

Recoil Seal

Implementation

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

Emerging Findings, RET

Rammer Chain Housing Material

RIWG Projected Costs

Material Sample

Result: Influenced material selection

Significant parameters: Wear and heat buildup

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