Fracture Mechanics

4.

Fatigue Crack Growth

4.1.

Fatigue Fundamentals

4.1.1.

Cyclic Loading Effects

4.1.1.1.

4.1.1.2.

4.1.1.3.

Mean Stress Effects

4.1.1.4.

Frequency Considerations

4.1.2.

Crack Initiation Mechanisms

4.1.2.1.

Surface Roughness Effects

4.1.2.2.

Inclusion Sites

4.1.2.3.

Microstructural Features

4.1.2.4.

Stress Concentrations

4.1.3.

Crack Propagation Stages

4.1.3.1.

Stage I Microcrack Growth

4.1.3.2.

Stage II Macrocrack Growth

4.1.3.3.

Crystallographic vs Mechanical Driving

4.1.4.

High-Cycle vs Low-Cycle Fatigue

4.1.4.1.

Stress-Life Approach

4.1.4.2.

Strain-Life Approach

4.1.4.3.

Transition Regions

4.2.

Fatigue Crack Growth Characterization

4.2.1.

Growth Rate Parameters

4.2.1.1.

Crack Growth per Cycle

4.2.1.2.

Stress Intensity Range

4.2.1.3.

Cyclic Loading Characterization

4.2.2.

da/dN vs ΔK Relationship

4.2.2.1.

Three-Region Behavior

4.2.2.2.

Threshold Region

4.2.2.3.

Paris Law Region

4.2.2.4.

Final Fracture Region

4.2.3.

Threshold Stress Intensity

4.2.3.1.

ΔKth Definition

4.2.3.2.

Measurement Methods

4.2.3.3.

Material and Environmental Effects

4.2.4.

4.2.4.1.

Mathematical Formulation

4.2.4.2.

Material Constants

4.2.4.3.

Applicability Range

4.2.4.4.

4.3.

Factors Affecting Growth Rates

4.3.1.

Stress Ratio Effects

4.3.1.1.

R-Ratio Definition

4.3.1.2.

Mean Stress Influence

4.3.1.3.

Crack Closure Implications

4.3.2.

Load Interaction Effects

4.3.2.1.

Overload Retardation

4.3.2.2.

Underload Acceleration

4.3.2.3.

Variable Amplitude Loading

4.3.3.

Crack Closure Phenomena

4.3.3.1.

Plasticity-Induced Closure

4.3.3.2.

Roughness-Induced Closure

4.3.3.3.

Oxide-Induced Closure

4.3.3.4.

Effective Stress Intensity

4.3.4.

Environmental Effects

4.3.4.1.

Corrosion Fatigue

4.3.4.2.

Temperature Effects

4.3.4.3.

Frequency Effects

4.3.4.4.

Atmospheric Conditions

4.3.5.

Material Microstructure

4.3.5.1.

Grain Size Effects

4.3.5.2.

Phase Distribution

4.3.5.3.

Inclusion Content

4.3.5.4.

Heat Treatment Effects

4.4.

Life Prediction Methods

4.4.1.

Integration Approaches

4.4.1.1.

Analytical Integration

4.4.1.2.

Numerical Integration

4.4.1.3.

Closed-Form Solutions

4.4.2.

Variable Amplitude Loading

4.4.2.1.

Cycle Counting Methods

4.4.2.2.

Rainflow Counting

4.4.2.3.

Load Spectrum Analysis

4.4.3.

Retardation Models

4.4.3.1.

4.4.3.2.

Willenborg Model

4.4.3.3.

Generalized Willenborg

4.4.4.

Probabilistic Approaches

4.4.4.1.

Statistical Crack Growth

4.4.4.2.

Reliability Analysis

4.4.4.3.

Safety Factor Determination

4.5.

Design Philosophy Applications

4.5.1.

Safe-Life Design

4.5.1.1.

No-Crack Assumption

4.5.1.2.

Conservative Factors

4.5.1.3.

Inspection Requirements

4.5.2.

Damage Tolerant Design

4.5.2.1.

Initial Flaw Assumptions

4.5.2.2.

Crack Growth Allowance

4.5.2.3.

Inspection Intervals

4.5.3.

Fail-Safe Design

4.5.3.1.

Multiple Load Paths

4.5.3.2.

Crack Stopping Features

4.5.3.3.

Redundancy Requirements

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