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Practical Fatigue Theory

Course Overview

Practical Fatigue Theory is a technical concept class designed to help you understand the role of fatigue in product life.

Important durability concepts are taught by explaining the necessary fatigue theory used in performing fatigue analysis. Emphasis is placed on the practical side of fatigue, with our expert trainers focusing on best practices for engineers.

In this course you will explore common fatigue analysis methods: stress-life (SN), strain-life (EN), and crack growth. For each of these methods, the course defines the basic procedure and assumptions, and provides an understanding of practical applicability. Software is not used during this course, instead focusing on practical concepts that provide an in-depth explanation of what’s going on behind the software. It is equally applicable to test and CAE-based fatigue calculations.

Class time is split between lectures and hands-on sessions where you will put the concepts into action by performing calculations. Case studies are shared to highlight practical applications of theory.

Who Should Attend?

The course is aimed at engineers involved in structural durability, including fatigue life estimation, improvement, or validation testing.

It is assumed that attendees are familiar with material behavior and general structural mechanics, typical of most practicing engineers.

Course Agenda

Duration: 2 days

  • Introduction to Fatigue as a Failure Mode
    • The definition of fatigue
    • Historical and modern practice
  • The Physics of Fatigue
    • Structural failure mechanisms
    • Micro- and macro-structural material response
  • An Overview of Fatigue Analysis Methods
    • Crack initiation vs. crack growth
    • Common methods of assessing durability
  • Stress-Life Approach - SN
    • Concepts of high cycle fatigue and endurance limits
    • Material fatigue properties and their measurement
    • Palmgren-Miner’s Rule for damage accumulation
  • Strain-Life Approach – EN
    • Concepts of high and low cycle fatigue
    • Material fatigue properties and their measurement
    • Localized plasticity and Neuber notch corrections
    • Rainflow cycle counting
  • Multiaxial Fatigue
    • Fatigue under complicated stress states
    • Methods for predicting fatigue under multiaxial stresses
  • Fracture Mechanics and Crack Growth
    • Linear elastic fracture mechanics
    • Quantifying stress on a crack
    • Fast fracture and crack growth analysis
  • Fatigue of Welds
    • How weldments behavior differently under load
    • Methods for predicted weld fatigue life
  • Fatigue and Elevated Temperature
    • Changes to material behavior at high temperature
    • Methods for assessing durability under cyclic and thermal loading
  • Fatigue of Composites and Anisotropic Materials
    • Characterizing strength and stiffness of short- and long-fiber materials
    • Methods for predicted fatigue life of composite materials
  • Applications and Summary
    • Fatigue with measured strain gauge data
    • Fatigue with FEA stresses
    • Method comparison – SN vs. EN vs. crack growth
    • Probability of failure: understanding scatter and its implications
    • Discussion of fatigue modelling and the 5-box trick

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