Failure Analysis Course Quiz

Course Information

• Course Title: Failure Analysis
• Course Code: IM417
• Lecture Hours: 2
• Tutorials: 2
• Credit: 3
• Prerequisites: IM315
• Lecturer: Dr. Mohamed Khamis
• Assistant: Eng. Nouran
• Delivery Method: Lectures and Tutorials Offline, Room 107

Grading

• Week 7: 30% (20% exam + 10% assignments, quizzes, and attendance)
• Week 12: 20% (10% exam + 10% assignments, quizzes, and attendance)
• Continuous Assessment: 10% (9th week project and 13th week case study)
• Final Exam: 40%

Course Description

• Techniques for failure analysis
• Modes of mechanical failure
• Residual stresses
• Brittle and ductile fracture
• Fatigue fracture
• Wear
• Corrosion
• Elevated-temperature failures
• Non-destructive testing
• Case histories

Textbooks and References

• Textbook: Wulpi, D.J. - Understanding How Components Fail - American Society for Metals, Metals Park, Ohio, 1985.
• References:
  • Hutching, F.R. and Unterweiser, P.M. - Failure Analysis: The British Engine Technical Reports - American society for Metals, Metals Park, Ohio, 1981.
  • Barer, R.D. and Peters, B.F. - Why Metals Fail - Gordon & Breach, Science Pub., 1970.
  • ASM - Metals Hand Book, Volumes 9, 10, American Society for Metals, Metals Park, Ohio, 1983.

Course Outline

• Week 1: Introduction
• Week 2: Mechanical Behavior of Materials I
• Week 3: Mechanical Behavior of Materials II
• Week 4: Techniques of Failure Analysis
• Week 5: Residual stresses
• Week 6: Material Defects I
• Week 7: Exam
• Week 8: Material Defects II
• Week 9: Elevated Temp Failures (CREEP)
• Week 10: Ductile and Brittle Fracture
• Week 11: Fatigue Failures
• Week 12: 12th week Exam
• Week 13: Wear
• Week 14: Corrosion Failures
• Week 15: NDT
• Week No. 16: Final Exam

Failure Analysis

• Failure is a significant issue.
• Many failure modes and mechanisms.
• Overlapping failures often occur.
• Disagreements in failure analysis exist.
• Exceptions to general failure patterns are common.
• The course will focus on common failures and the failure analysis process.
• Examples of interesting failures, particularly in steel, although applicable to many materials.

What is Failure?

• A part or system no longer meets its design intent.
• Failure is not always structural.
• Examples include leaking hydraulic seals, inappropriate component stiffness, and operating/maintenance costs.
• Failure may involve any design parameter or aspect.

Objective of Failure Analysis

• Investigate material facts related to a part or system failure.
• Determine:
  • Timeline of events and chain of events.
  • Root-cause of incident and contributing factors.
  • Fitness for purpose post-incident.
  • Repair options
  • Mitigating future failures.

Contributing Factor Areas

• Original Design
• Material Properties
• Manufacturing and processing
• Service Factors (Loading, Environment)
• Repair Procedures (Weld Repair)

Failure Analysis Process

• 1. Problem definition
• 2. Background data collection
• 3. Hypothesis formulation
• 4. Developing test methodologies
• 5. Implementing tests and collecting data
• 6. Review results, revise hypothesis
• 7. End with budget, new design, or recommendations.
• ASM process to follow (https://www.asminternational.org/home)

Technological Tools

• Photography and Lighting
• Optical Microscopy (up to 600x)
• Scanning Electron Microscopy (SEM) (over 10,000x)
• Chemical Analysis (SEM/EDS, Spark Emission Spectroscopy)

Optical Microscopy

• Use polished and etched specimens.
• Limited depth of field.
• Shows individual grain structure.

SEM Image

• Shows individual grains.
• Large depth of field.
• Vacuum chamber.

Energy Dispersive X-ray (EDS)

• Elements produce distinct X-ray peaks (often primary and secondary)

Alloys

• Most metals are used in alloy form.
• Adding other elements creates a range of properties modifiable via composition and heat treatment.
• Examples: Steels and aluminum alloys

SEM Image of Alloys

• Constituents (overall composition, number/composition/weight fraction of phases, shape and size of phases).
• Mechanical properties depend on phases and manufacturing techniques (casting, heat treatments)

Processing Methods

• Metals: Casting, powder processing, cold/hot working, surface treatment, heat treatment, joining methods.
• Polymers: Injection molding, extrusion, blow molding, fibers, foaming.

Engineering Material Families

• A classification of various material groups (metals, ceramics, glasses, plastics, composites, hybrids).

Main Engineering Metals

• Steels (Low-carbon, High-carbon, Stainless, Tool).
• Cast irons (Grey, White).

Selection of Materials

• Material selection considers multiple properties.
• Example: Jet engine turbine blade
  • Stiffness, high-temperature strength, thermal expansion, thermal conductivity, oxidation resistance, impact resistance, fatigue resistance, cost.

Material Properties

• Physical properties (density, melting point, resistivity, dielectric constants)
• Mechanical properties (elastic modulus, yield strength, fracture toughness)
• Thermal properties (thermal conductivity, expansion, specific heat)
• Electrical/Magnetic properties
• Environmental interactions (corrosion, wear)
• Economic factors (price, availability, production)
• Aesthetic factors (colour, texture)

Stress

• Stress equals force per unit area.
• Types of stress:
  • Normal stress (simple tension/compression)
  • Shear stress (direct shear, torsion)

Strain

• Normal strain: elongation per unit length.
• Shear strain: change in angle between side faces (before deformation)

Elasticity

• Interatomic bonds act like springs, linking neighboring atoms.
• Stretching/rotation of bonds leads to elastic deformation.

Measurement of Elastic Modulus

• Elastic modulus measured experimentally in engineering practice.
• Methods include tension/compression tests, beam vibration tests (natural frequency), and acoustic tests (acoustic wave velocity).

Nonlinear Elasticity

• "Elastic" implies no permanent deformation on unloading.
• Stress-strain relation can be linear or nonlinear (example: rubber).
• Tangential modulus = do / de

Beyond Elasticity

• All solid materials have an elastic limit.
• Beyond the elastic limit, brittle materials fracture, and ductile materials deform plastically.

Young's Moduli of Some Materials

• Values for various materials (e.g., diamond, tungsten, alumina, steel, copper, aluminum, concrete, nylon, rubber). Values are given in GPa.