Failure Analysis Skill
Purpose
The Failure Analysis skill provides systematic methodology for investigating mechanical component failures, enabling root cause identification through fractography, metallography, stress analysis, and structured problem-solving approaches.
Capabilities
- •Fractography interpretation (SEM, optical)
- •Metallographic examination guidance
- •Root cause analysis frameworks (5-Why, Fishbone)
- •Failure mode identification (fatigue, corrosion, overload)
- •Stress analysis correlation to failure location
- •Chemical analysis interpretation
- •Corrective action development
- •Failure analysis report generation
Usage Guidelines
Investigation Process
Phase 1: Evidence Preservation
- •
Documentation
- •Photograph failed components as-received
- •Document orientation and assembly position
- •Record operating conditions at failure
- •Preserve all fragments
- •
Chain of Custody
- •Log all handling
- •Secure storage
- •Controlled access
- •Document any cleaning or cutting
Phase 2: Visual Examination
- •
Macroscopic Features
Feature Indication Beach marks Fatigue Chevron marks Brittle fracture Shear lips Ductile overload Corrosion products Environmental attack Wear patterns Tribological failure - •
Fracture Origin
- •Identify initiation site
- •Look for stress concentrations
- •Check for material defects
- •Document surface conditions
Phase 3: Fractography
- •
Optical Microscopy
- •Low magnification overview
- •Document fracture features
- •Identify regions of interest
- •
Scanning Electron Microscopy (SEM)
Fracture Feature Failure Mode Striations Fatigue crack growth Dimples Ductile overload Cleavage facets Brittle fracture Intergranular Creep, SCC, hydrogen Quasi-cleavage Mixed mode - •
EDS Analysis
- •Identify corrosion products
- •Detect contamination
- •Verify material composition
Phase 4: Metallography
- •
Sample Preparation
- •Section perpendicular to fracture
- •Mount in appropriate media
- •Grind and polish
- •Select appropriate etchant
- •
Examination
- •Grain structure
- •Heat treatment condition
- •Inclusions and defects
- •Microcracking
- •Decarburization
Failure Mode Identification
Fatigue Failure
code
Characteristics: - Beach marks (macroscopic) - Striations (microscopic) - Origin at stress concentration - Minimal plastic deformation - Flat fracture surface Contributing Factors: - Cyclic loading - Stress concentration - Residual stress - Material defects - Environmental effects
Overload Failure
code
Ductile: - Significant plastic deformation - Cup-and-cone fracture (tensile) - Shear lips - Dimpled fracture surface Brittle: - Little plastic deformation - Flat fracture surface - Chevron marks pointing to origin - Cleavage or intergranular fracture
Corrosion Failures
| Type | Characteristics | Environment |
|---|---|---|
| Uniform | General metal loss | Acids, bases |
| Pitting | Localized attack | Chlorides |
| SCC | Branching cracks | Specific ion + stress |
| Corrosion fatigue | Accelerated fatigue | Cyclic + corrosive |
| Hydrogen embrittlement | Intergranular fracture | Hydrogen source |
Wear Failures
| Type | Mechanism | Evidence |
|---|---|---|
| Adhesive | Material transfer | Galling, scoring |
| Abrasive | Hard particle cutting | Grooves, scratches |
| Erosive | Fluid/particle impact | Surface damage pattern |
| Fretting | Small amplitude motion | Oxide debris, pitting |
Root Cause Analysis
5-Why Method
code
Problem: Shaft failure Why 1: Fatigue fracture Why 2: High stress concentration at keyway Why 3: Sharp corner radius Why 4: Drawing did not specify radius Why 5: Design review did not catch omission Root Cause: Inadequate design review process
Fishbone Diagram Categories
- •Material: Composition, defects, properties
- •Machine: Equipment condition, maintenance
- •Method: Process, procedure, design
- •Man: Training, error, supervision
- •Environment: Temperature, humidity, contamination
- •Measurement: Calibration, accuracy
Process Integration
- •ME-016: Failure Analysis Investigation
Input Schema
json
{
"failed_component": {
"part_number": "string",
"material": "string",
"service_history": "string",
"failure_date": "date"
},
"operating_conditions": {
"loads": "string",
"environment": "string",
"temperature": "number (C)",
"cycles_or_hours": "number"
},
"available_evidence": {
"fracture_surfaces": "boolean",
"mating_parts": "boolean",
"lubricant_samples": "boolean",
"maintenance_records": "boolean"
},
"analysis_scope": "preliminary|comprehensive"
}
Output Schema
json
{
"failure_mode": "fatigue|overload|corrosion|wear|other",
"root_cause": "string",
"contributing_factors": "array",
"evidence_summary": {
"visual": "string",
"fractography": "string",
"metallography": "string",
"chemical": "string"
},
"corrective_actions": [
{
"action": "string",
"category": "design|material|process|maintenance",
"priority": "high|medium|low"
}
],
"preventive_recommendations": "array",
"report_reference": "string"
}
Best Practices
- •Preserve evidence before any destructive examination
- •Document all observations photographically
- •Follow systematic investigation process
- •Consider multiple failure mechanisms
- •Correlate fracture features with stress analysis
- •Validate root cause with evidence
Integration Points
- •Connects with FEA Structural for stress analysis
- •Feeds into Material Selection for improved materials
- •Supports Design Review for lessons learned
- •Integrates with Quality for corrective actions