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

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

3. RAM-T Overview What is RAM-T System Design Constraints
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 Methods Perform predictions Address SOME RAM-T drivers
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
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

5. Of Failed Tests, 75 % Of Systems Failed to Achieve Even Half Of Their
Legacy Results
Only 30% Success
(Data Oct 01)
Of Failed Tests, 75 % Of Systems Failed to Achieve Even Half Of Their
Requirement!

6. 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

7. 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
System Int and Test
PoF
RET
Subsystem Int
Emphasize: Early identification and elimination of RAM-T shortcomings
Example: Achieve Higher Mi on prototype delivery

8. 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
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 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 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. 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
Physics of failure is a science-based approach to addressing reliability in the design process. Physics-of-failure is an approach to developing reliable products that uses knowledge of basic failure processes to prevent product failures through robust design and manufacturing practices. This approach incorporates reliability into the design process by establishing a scientific basis for evaluating new materials, structures, and electronics technologies.
By understanding the basic causes of failure, or failure mechanisms, the design engineers can use this information to reduce and focus reliability testing.
The greatest benefit of physics of failure is the insight it provides into reliability throughout the expected life cycle of a system. This insight provides the ability to predict the reliability of the design before the system is built and to assess the reliability of commercial components. The bottom line is that the use of physics of failure leads to an increase in system reliability. This increase in system reliability enhances system availability and decreases cost. Not only can physics of failure decrease acquisition cost, but it can also decrease operations and support costs.
Benefits
Design-in reliability
Eliminate failures prior to test
Increased fielded reliability
Decreased O&S costs
Root-cause failure is cracking of solder joint

12. Software Tools Finite Element Modeling Solid Modeling
Dynamic Simulation
AMSAA has or will be utilizing several software tools to complete PoF-based analyses of Army electronics and mechanical systems. The most employed tool has been the U. of Maryland’s Electronic Packaging Research Center’s (EPRC) CCA-level CalcePWA toolkit. This toolkit allows for integrated vibration and thermal analyses of CCAs and utilizes PoF-based models of solder-joint fatigue and PTH fatigue to predict the fatigue lives and reliability of CCAs.
Another EPRC toolkit that has been used by AMSAA is the device (or IC) level CADMP (Computer-Aided Design of Microelectronic Packages) toolkit. CADMP is a set of integrated software programs that can be used to design and assess the reliability of both single chip packages and multichip modules (MCMs). CADMP utilizes PoF methodology to assess reliability and do trade-off analyses by investigating over 40 different failure mechanisms, failure sites, and root causes of failures.
The DROW (Durability and Reliability Optimization Workspace) is a mechanical PoF-based toolkit developed at the U. of Iowa’s Center for Computer Aided Design, which AMSAA plans to utilize in a future mechanical PoF demonstration program. DROW utilizes rigid or flexible body dynamics simulation and commercial FEA codes to develop stress states on mechanical designs, and predict reliability based on specified operational conditions.
Electronic Circuit Card and IC Toolkits
Fatigue Analysis
Thermal Fluid Analysis

13. 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
Physics-of-failure uses knowledge of root cause failure processes to prevent product failures through robust design and manufacturing practices. This approach involves the following steps:
examine the operational/environmental loads and the preliminary design, identify potential failure mechanisms (chemical, electrical, physical, mechanical, structural, or thermal processes leading to failure); failure sites; and failure modes (which result from the activation of failure mechanisms, and are usually precipitated as shorts, opens, or electrical deviations beyond specifications);
perform a stress analysis on the stresses (e.g., thermal, vibrational, shock, humidity, & current) that accelerated the potential failure mechanisms;
identify the appropriate failure models and their input parameters, including those associated with material characteristics, damage properties, relevant geometry at failure sites, manufacturing flaws and defects, and environmental and operating loads;
determine the variability for each design parameter when possible;
predict the time-to-failure, or life of the potential failure mechanisms;
perform accelerated life testing to verify that the potential failure mechanisms will occur, to verify the stress/life relationship (failure mechanism model), and to determine if unexpected failure mechanisms would occur.
accepting the design, if the life is acceptable, re-design failure mechanisms out of the life cycle, or use preventative maintenance (prognostics) to replace the equipment before it causes a system failure.
PoF-Based ESS
Accelerated Life Testing
on critical board or IC failure mechanisms

14. 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
In order to determine internal enclosure temperatures of the BFCC at different power loads, a commercial CFD solver known as ICEPAK was utilized to calculate and graphically display temperature distributions within the enclosure walls. The first step in developing the appropriate CFD model for this study was to determine what results were expected from the solver. Based on the fact that the PM was concerned with the internal temperatures of the enclosure, it was determined that not all of the features of the BFCC would necessarily have to be modeled. Therefore, in order to simplify the model the air flow through the finned side wall channels was not modeled. Instead, a forced convection boundary layer along either side of the enclosure with a constant convection coefficient of 170 W/m2-oC per side was used in the analysis. This constant was determined to be a conservative representation of a 50 Cubic Feet per Minute (CFM) flow over aluminum plain fins with dimensions of 17.5x5.25x0.5 inches with 14 fins per inch and 0.01 inch thickness. Also, the effects of radiation were assumed to be negligible for determining the internal feature temperatures. These assumptions allowed the CFD modeling to focus more on the conduction and convection resistive networks within the BFCC and less on the external features of the BFCC such as air flow through the fins.
Therefore, the features of the BFCC modeled in ICEPAK included only the cold plate structure, the powered CCA board structures (to include an aluminum heatsink layer and a FR-4 epoxy layer), and the six sheet metal panels that enclose the internal features of the BFCC. The power load applied to each CCA was distributed evenly among corresponding finite elements of each card.
Outputs from CFD analysis used as boundary conditions for CCA thermal modeling

15. UMD CalcePWA Software Tool
Architecture & environment
modeling
Reports and documentation
Toolbox
Failure assessment
& sensitivity analysis
Vibration analysis
Thermal analysis
CalcePWA is a CCA-level toolkit developed at the U. of Maryland’s Electronic Products and Systems Center (ESCC) that contains several stress assessment tools and PoF-based fatigue models to predict the reliability of CCAs. The toolkit contains an integral finite difference-based thermal analysis tool that analyzes component temperatures and the board-level temperature distributions based on several different operator selected cooling mechanisms. It also contains an integral finite element analysis (FEA)-based vibration modal analysis tool that determines the fundamental resonant frequencies of the board, the corresponding mode shapes, and maximum displacement of the board. These integral stress analysis tools identify the stresses present on the board for any given boundary condition, and develop the input to the solder-joint and plated through-hole (PTH) fatigue analysis models. These fatigue analysis models utilize this stress data to predict the fatigue life of the component solder-joints and PTHs. The toolkit can be used to do any number of trade-off studies, and has been used in that fashion to validate the use of commercial components for certain military environments.
Future extensions of CalcePWA include a humidity stress analysis tool, a conductive filament formation model (in latest version - metal growth from one conducting metal line to another through the board, which causes a short circuit), and a metal line corrosion model (causes signal distortion).

16. 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
$27M Cost
Avoidance
Air & Ground System Electronics
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

17. Fatigue Analysis Using Dynamic Simulation & FEA
Solid Modeling
Dynamic Load Analysis
Terrain Model
System Model
Dynamics Analysis
DADS
Pro/E
Component Stress Analysis
FE Model
FEA
NASTRAN
Reliability Analysis
Reliability Based
Design Optimization
Fatigue Life Assessment
List of Critical Nodes
DRAW

18. 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

19. 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 2

20. 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

21. 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

22. Trailer Physics-of-Failure Project
Fatigue life estimates of drawbar consistent with failure data
Critical Point
Life (Blocks)
White represents low fatigue life
Benefits:
Early identification of failure modes
Better test planning and design
Improved maintenance procedures
Enlargement of
Critical Region

23. 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

24. Paradigm Shift: RAM-T Case

25. Paradigm Shift: RAM-T Case

26. Paradigm Shift: RAM-T Case

27. 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)

28. Paradigm Shift: RAM-T Case
Load Levels
Upper Destruct Limit
Upper Operating Limit
Upper Design Limit
Upper Specification Limit
Lower Specification Limit
Lower Design Limit
Lower Operating Limit
Lower Destruct Limit
Nominal
Upper Design
Margin
Lower Design
Upper Destruct
Lower Destruct
Upper Operating
Lower Operating

29. Paradigm 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

30. Embrace the philosophy Determine critical items
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

31. Reliability Improvement Working Groups
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.

32. Implementation
Risk Mitigation & Proactive Reliability Tasks
Note: Planned through March 2004 unless otherwise indicated
Note (1): Planned by PDR

33. The gaps show that the whole surface area is not being used to seal.
Implementation
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 Costs Result: Influenced material selection
Emerging Findings, RET
Rammer Chain Housing Material
Material Sample
Result: Influenced material selection
Significant parameters: Wear and heat buildup