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Techniques to Evaluate

Long-Term Aging of Systems

Prepared by:

Quanterion Solutions Incorporated

100 Seymour Rd.

Suite C101

Utica, NY 13502-1311

Prepared for:

Reliability Information Analysis Center (RIAC)

100 Seymour Rd.

Suite C101

Utica, NY 13502-1311

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ISBN-10: 1-933904-34-8 (Download)

ISBN-13: 978-1-933904-34-4 (Download)

Copyright © 2011 by Quanterion Solutions Incorporated. This publication was developed by Quanterion Solutions Incorporated, in support of the prime contractor (Wyle Laboratories) in the operation of the Department of Defense Reliability

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Techniques to Evaluate Long-Term Aging of Systems (LAST)

100 Seymour Rd., Suite C101, Utica, NY 13502-1311 877.808.0097 i

Table of Contents

1

1

1. Introduction

2. General Design Considerations for In-Service Conditions 2

2

4

5

6

2.1.1 2.1.2 2.1.3 2.1.4 2.1.5

Temperatures

Solar Radiation (UV)

Dust (Airborne and Ground)

Thermal Temperature Cycling

Humidity 6

7

7

2.1.62.1.72.1.8 7

2.2 7

7

8

9

9

2.2.12.2.22.2.32.2.4 2.2.5

Temperature

Solar Radiation (UV)

Dust (Airborne and Ground)

Thermal Cycling

Humidity 9

2.2.6 Chemical 11

2.2.7 Compatibility 11

2.2.8 Interactions 12

2.3 12

2.3.1 Temperature 12

2.3.2 Solar Radiation (UV) 12

2.3.3 Dust (Airborne and Ground) 13

2.3.4 Thermal Cycling 13

2.3.5 Humidity 14

2.3.6 Chemical 14

2.3.7 Compatibility 15

2.3.8 Interactions 15

3. Aging Factors Related to Ferrous and Non-Ferrous Metals 15

3.1 Properties of Metals 15

3.1.2 Metal Basics 15

3.2 Failure Modes and Mitigation Techniques 18

3.2.1 Yielding 18

3.2.2 Elastic Deformation 21

3.2.3 Brinelling 21

3.2.4 False Brinelling 22

ChemicalCompatibilityInteractions

2.1

Tropical Environments

Arctic Environments

Desert Environments

Techniques to Evaluate Long-Term Aging of Systems (LAST)

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3.2.5 Brittle Fracture 23

3.2.6 Ductile Fracture 24

3.2.7 Buckling 25

3.2.8 Creep 25

3.2.9 Galling 26

3.2.10 Spalling 27

3.2.11 Wear 28

3.2.12 Fatigue 29

3.2.13 Corrosion 32

3.2.13.1 Uniform Corrosion 33

3.2.13.2 Galvanic Corrosion 36

3.2.13.3 Crevice Corrosion 42

3.2.13.4 Pitting Corrosion 44

3.2.13.5 Stress Corrosion Cracking 47

3.2.13.6 Corrosion Fatigue 55

3.2.13.7 Intergranular Corrosion 57

3.2.13.8 Selective leaching 59

3.2.13.9 Erosion corrosion 60

3.2.13.10 Exfoliation 61

3.2.13.11 Microbiological Influenced Corrosion (MIC) 62

3.2.13.12 Filiform Corrosion 64

3.2.13.13 Hydrogen Damage 65

3.2.13.14 Hot Corrosion 65

4. Polymers 69

4.1 What is a Polymer 69

4.1.1 Monomers and Macromolecules 70

4.1.2 Thermoplastics, Thermosets and Elastomers 71

4.1.2.1 Blends 72

4.1.2.2 Crystalline or Amorphous 72

4.1.2.3 Molecular Weight 73

4.1.2.4 Formation Process 73

4.1.2.5 Process Considerations for Curing Thermosets 74

4.1.2.6 Glass Transition 74

4.1.2.7 Stress-Strain 75

4.1.3 Fluids 80

4.1.4 Thermal Conductivity 81

4.1.5 Aging 81

4.2 Failure Modes and Special Environmental Considerations 82

4.2.1 Specific Design Considerations for Polymers in Out-of-Service Conditions 82

4.2.2 Specific Design Considerations for Polymers in In-Service Conditions 82

Techniques to Evaluate Long-Term Aging of Systems (LAST)

100 Seymour Rd., Suite C101, Utica, NY 13502-1311 877.808.0097 iii

4.2.2.1 High Temperature 82

4.2.2.2 Low Temperature 83

4.2.2.3 Solar Radiation (UV) 83

4.2.2.4 Thermal Temperature Cycling 83

4.2.2.5 Cyclic Mechanical Load Cycling 83

4.2.2.6 Humidity 84

5. General Reliability Design and Analysis Considerations 97

5.1 Understanding Life Cycle Cost Concepts 97

5.2 The System Design Process 110

5.3 Design for Reliability 114

5.4 Materials and Parts Selection and Control Strategies 115

5.5 Reliability Physics 122

5.6 Failure Modes, Effects and Criticality Analysis (FMECA) 125

5.7 Fault Tree Analysis (FTA) 135

5.8 Life Modeling and Testing 141

5.8.1 Acceleration Factors Used in Life Models 143

5.8.2 Accelerated Life Testing 150

5.8.3 Highly Accelerated Testing 159

5.8.3.1 Step-Stress Testing 160

5.8.3.2 Progressive Stress Testing 162

5.8.3.3 Highly Accelerated Life Testing (HALT) 163

5.8.3.4 Highly Accelerated Stress Test (HAST) 166

5.8.4 Design of Experiments 167

5.9 Reliability Testing 177

5.9.1 Reliability Growth Testing and Reliability Demonstration Testing 182

5.10 Data Collection and Analysis 200

5.10.1 Types and Sources of Data 215

5.11 Failure Analysis 217

5.11.1 Root Failure Cause Analysis 224

APPENDIX A: References Reviewed A-1

Techniques to Evaluate Long-Term Aging of Systems (LAST)

100 Seymour Rd., Suite C101, Utica, NY 13502-1311 877.808.0097 1

1. INTRODUCTION

The Reliability Information Analysis Center mission has continued to evolve over the years

(including its years as the Reliability Analysis Center (RAC)) with the greater recognition that

reliability, maintainability, and quality are critical military system and commercial product

attributes. Coincident with the evolution has been the recognition that these attributes have much

more encompassing impacts than their specific attained metrics. For example, where at one time

the measure of reliability called mean-time-between-failure (MTBF) was of interest in itself, now

management and system planners have expanded their interest because of how that MTBF impacts

such issues as sustainability and total ownership costs. Part of the refocusing of reliability-related

needs is the concern over long-term aging effects on systems in operation and in storage brought

about by systems having to last longer.

The objective of this report is to highlight the impact of long-term aging effects on parts,

assemblies and equipments by investigating characteristics of aging as they impact specific

material classes.

The report is broken down into the following sections:

Section 2 addresses general environmental design considerations for aging during

in-service conditions

Section 3 discusses aging factors as they relate to ferrous and non-ferrous metals

Section 4 provides an overview of aging as it applies to polymer materials

Section 5 covers general reliability design considerations and appropriate tasks/techniques

2. GENERAL DESIGN CONSIDERATIONS FOR IN-SERVICE CONDITIONS

Various environmental extremes can accelerate material failure mechanisms, thereby affecting the

aging of designs in which they are used. Some environments may introduce peculiar stress

conditions that may not be of major concern in any of the other environments.

Although the following sub-sections address individual components of environmental stress

parameters (temperature, humidity, UV, etc.) it must be recognized that many of these components

may act in concert with one-another. A failure to consider the potential combined effects of these

parameters can lead to a serious underestimation of their overall effect on material aging.

In the sections related to environment, the terms desert, arctic and tropical are used to identify

major, non-temperate terrestrial environments on earth that present extreme environmental

conditions that may impact material selections for a design.

The word ‘desert’ usually brings to mind the hot deserts such as the Sahara. Technically, however,

a desert is any land area that has an annual moisture deficit. Accordingly, the polar and tundra land

areas are also deserts and, in fact, constitute the majority of all desert area. In addition, the term hot

desert and ‘tropical desert’ are often used synonymously.

Due to the potential confusion of terms, and because the environments cannot be definitely

associated with boundaries, this guideline will loosely define the three environments as follows:

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