UCLA Extension

Fracture Mechanics of Engineering Materials

Understanding and harnessing various failure modes, including fracture failure mechanism, is vital to a successful failure analysis and design development. In fact, fracture often has been overlooked as a potential mode of failure at the expense of an overemphasis on strength. This course benefits both engineers and designers who are interested in gaining a broader knowledge, insight, and ability toward a successful design process and development for structures and components, as well as managers interested in understanding the significance of fracture failure as part of the design process.

Complete Details

The course covers deformation and fracture behavior of engineering materials for both monotonic and cyclic loading conditions. Both microscopic and macroscopic aspects of deformation and fracture mechanism of engineering materials are covered. Instruction begins with an historical perspective and origin of fracture mechanics. Examples of well-known failures and accidents attributed to fracture are discussed. A brief overview of solid mechanics provides the necessary background for those who might not have the necessary solid mechanics background. The basics and foundations of fracture mechanics are then presented from both stress intensity and energy method perspectives for Linear Elastic Fracture Mechanics (LEFM). The microstructural basis of fracture toughness also is covered, including cleavage and ductile fracture mechanisms and fracture toughness testing of metals.

Elastic-Plastic Fracture Mechanics (EPFM), including J-Integral and Crack Tip Opening Displacement (CTOD) and fully plastic analysis, provide information and perspective on the significance of plastic zone and crack tip plasticity.

Topics on high- and low-cycle fatigue, including fatigue crack nucleation and formation, are followed by crack propagation aspects in fatigue, crack closure, crack tip shielding, and fatigue testing. Additional topics briefly covered are time-dependent crack growth; environmentally assisted cracking, including stress corrosion cracking and hydrogen embrittlement; and probabilistic failure analysis. The course ends with discussions on the latest work and technologies with regard to fracture and fatigue, including virtual testing, multi-scale modeling, and nanotechnology.

Course Materials

The text, Fracture Mechanics: Fundamentals and Applications, Third Edition, T.L. Anderson (CRC Press, 2005), and lecture notes are distributed on the first day of the course. The notes are for participants only and are not for sale.

Coordinator and Lecturer

Hamid Saghizadeh, PhD, MBA, Boeing Technical Fellow, Boeing IDS, Space and Intelligence Systems (S&IS), El Segundo, California. Dr. Saghizadeh is the focal leader in fracture mechanics/durability and damage tolerance for Boeing S&IS and leads the Fatigue and Fracture Technologies Technical Interest Group for the Boeing Enterprise. He also developed Mechanical and Structural Engineering Knowledge and Technology Management (MSEKM) at Boeing S&IS, is a pioneer in the areas of elastic-plastic fracture mechanics (EPFM) and fracture of composites, and is recognized as an industry expert in EPFM. In addition to structural analysis and testing and qualification test requirements, his areas of expertise include fatigue, fracture mechanics, and failure analysis, including mechanism of hydrogen-environment embrittlement, stress corrosion cracking, and rupture and time-dependent failure mechanism. His areas of interest also include nanotechnology, virtual testing, and multi-scale modeling.

Dr. Saghizadeh conceived of and developed an innovative and original fatigue virtual testing technology with significant industry impact. It is based on a closed form solution to generate fatigue S-N data, thus avoiding costly and time-consuming tests. He provides technical expertise and consultation to organizations across the industry, including NASA, Southwest Research Institute, The Aerospace Corporation, and various Boeing vendors. Dr. Saghizadeh has three disclosed patents for his technology and design developments. He developed and published (through ASME) two original models on fracture of composites that have been cited over 18 times in international journals, and has made over 200 presentations and over 100 Boeing significant writings.

Dr. Saghizadeh’s vision to further strengthen Boeing’s relationship and networking capability with academia and industry has led to the development of the Boeing academia and industrial educational program (BAIP), which includes UCLA. BAIP encourages its employees to participate in the identification, development, and teaching of training courses tailored to Boeing needs. He is the primary point of contact at IDS for space products representing Boeing at Southwest Research Institute and NASA for NASGRO Worldwide Consortium.

Dr. Saghizadeh holds BSME, MS, and PhD degrees in mechanical engineering from the University of California at Berkeley, and an MBA from UCLA Anderson School of Management. He also is an honorary (Summa Cum Laude) member of SAMPE.

Course Program

Basics and Overview

  • Structural Design: Overview
  • Structural Design Process
  • Failure Mechanisms
    —High-Cycle Fatigue
    —Low-Cycle Fatigue
    —Fatigue Crack Propagation
  • The Nature of Fracture
    —Classification of Fracture Mechanics Regimes
    —Linear-Elastic Fracture Mechanics (LEFM)
    —Elastic-Plastic Fracture Mechanics (EPFM): J Integral, CTOD
    —Time-Dependent Fracture Mechanics (TDFM)
    —The Fracture Mechanics Approach to Design
  • Slow vs. Fast Crack Growth
  • Elastic vs. Plastic
  • Brittle vs. Ductile
  • Macroscopic vs. Microscopic
  • Historical Aspects
  • The Evolution of Structural Design
  • Solid Mechanics: A Brief Overview

LEFM (Linear Elastic Fracture Mechanics) Energy Approach

  • The Ideal Strength and Mechanisms of Failure
  • An Atomic View of Fracture
  • Stress Concentration of an Elliptic Hole
  • The Energy Approach
    —Griffith’s Work
    —Griffith’s Modification
    —Irwin’s Work: Role of Plasticity
    —Strain Energy Release Rate: G
    —G Measurement: Calculation
    —Practice Problem/Case Study
    —Load Control vs. Displacement Control
    —Estimation of G: Experiment
    —Estimation of G: Analytical Approach
  • Instability and R Curve
    —R-Curve Shape
  • Crack Branching
  • Crack Arrest

LEFM: Stress Intensity Approach

  • Stress Intensity Approach to Fracture Mechanics
  • Linear Elastic Fracture Mechanics (LEFM)
    —Basic Modes of Fracture
    —State of Stress and Displacements near Crack Tip
  • Linear Elastic Fracture Mechanics (LEFM)
    —Stress Intensity Solutions
    —Finite Size Effect
    —Principle of Superposition
  • Design Philosophy Based on LEFM
  • Practice Problem/Case Study
  • Techniques for Calculation of the Stress Intensity Factors
  • Numerical Determination of SIF
  • Relationship between K and G

Crack Tip Plasticity

  • Plastic Zone
  • Plastic Zone Size Estimation
    —Irwin’s Method
    —Strip Yield Model
  • Stress Intensity Estimation
  • Plastic Zone Shape
  • Plane Stress/Plane Strain Transition: Triaxial State of Stress
  • Fracture Criterion, KI = KIC
    —Validity and Size Limitations for Use of KI = KIC
  • Small Scale Yielding: SSY
  • Critical Crack Size, ac—Design Philosophy
    —LBB (Leak Before Burst)
  • Practice Problem
  • Experimental Determination of SIF (Stress Intensity Factor)
    —Strain Gage Method
    —Photoelasticity Method
  • Fracture Toughness Testing
  • Plane Strain Fracture Toughness
  • Test Technique: KIC Measurement
  • ASTM Specimen Test Standards
  • Case Study/Practice Problem
  • Present Challenge in the Satellite Industry

EPFM (Elastic-Plastic Fracture Mechanics)

  • Elastic-Plastic Parameters
  • CTOD (Crack Tip Opening Displacement)
    —Irwin’s Model
    —Strip-Yield Model
  • CTOD: G (J) relationship
  • J-Integral
  • Characteristics of J-Integral
  • J as Stress Intensity Parameter
  • Fully Plastic Analysis
  • Size Limitations: Validity of J
    —Irwin’s Method
    —Strip Yield Model
  • Determination of the J-Integral
  • Laboratory Measurement of J
  • JIC Test Methods
  • Determination of KIC from JIC
  • JIC measurement
  • Experimental Determination of Critical CTOD
  • HRR Singularity and Small-Scale Yielding (SSY)
  • Energy Release Rate: Dynamic Definition
  • Crack Speed
  • Codes and Standards
    —FAD Diagram
    —R6 Approach

Fatigue Crack Propagation

  • Fatigue
    —Fatigue Crack Nucleation and Formation
  • Early Design: Significance of NDE and Material Selection
  • Fracture Surface
  • High-Cycle Fatigue: Classical Fatigue Approach
  • Time-Varying Stress or Cumulative Damage
  • Low-Cycle Fatigue: Stress-Strain Life Approach
  • Practice Problem
  • Crack Propagation Aspects in Fatigue
  • Short Cracks
  • Crack Closure
  • Crack Tip Shielding
  • Fatigue Testing
    —Tools
  • Case Study
  • Future Work and Technologies

Creep: Time-Dependent Crack Growth, Environmentally Assisted Cracking, Probabilistic Failure Analysis (EAC)

  • Creep
  • Creep Mechanism
  • Creep Crack Growth
  • Environmentally Assisted Cracking (EAC)
  • Environmentally Assisted Sub-Critical Crack Growth
  • Environmentally Assisted Sustained Load Cracking
  • Mechanisms of EAC
  • Fracture Mechanics Approach to EAC Growth
  • V-KI curve
  • Methods of Determining da/dt and KISCC
  • Case Study
  • Probabilistic Failure Analysis

For more information contact the Short Course Program Office:
shortcourses@uclaextension.edu | (310) 825-3344 | fax (310) 206-2815

image_print