Mar 22, 2023  
2015-2016 Undergraduate Academic Catalog 
2015-2016 Undergraduate Academic Catalog [ARCHIVED CATALOG]

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ME 4220 - Fatigue and Fracture in Mechanical Design

3 lecture hours 0 lab hours 3 credits
Course Description
This course provides a detailed treatment of fatigue failure due to cyclic loading of mechanical components.  Design approaches for high cycle (stress-life) are briefly reviewed. Methods for low cycle (plastic strain-life) problems are presented. Numerous design examples are provided including: stress concentration, notch sensitivity, mean stress, multi-axial stress and variable amplitude loading. Linear Elastic Fracture Mechanics concepts are introduced, with applications to predicting catastrophic failure of components or problems in fatigue crack growth rate. Microscopic and macroscopic features of fatigue and fracture are discussed in the context of performing failure analysis of failed parts. (prereq: ME 363 )
Course Learning Outcomes
Upon successful completion of this course, the student will be able to:
  • Understand the distinction between “high” cycle versus “low” cycle fatigue problems and correctly choose an appropriate analysis method for a design problem
  • Understand cyclic plastic strain behavior and be able to apply mathematical models for cyclic plastic strain to design problems
  • Apply strain-life methods for low cycles fatigue
  • Combine notch-strain analysis with low cycle fatigue analysis for component life predictions
  • Understand basic concepts in Linear Elastic Fracture Mechanics (LEFM)
  • Apply basic LEFM models to problems in 1) fracture of metals, 2) fatigue crack growth rate and 3) fail safe design

Prerequisites by Topic
  • Stress-Life approach to fatigue problems
  • Mechanics of Materials

Course Topics
  • Review - Fatigue basics, Stress-Life Diagrams, Stress Concentrations, Notch Sensitivity, Mean Stress Effects
  • Multi-axial States of Stress
  • Variable Amplitude Load Histories
  • Low cycle fatigue (Plastic strain cycling, 2 to 1000 cycle life)
  • Cyclic Stress-strain Curves & Plastic Strain-life Diagrams (ε-N diagrams)
  • Notch Strain Analysis, Neuber’s Rule
  • Microscopic/Material Aspects of Fatigue, Fracture Mechanics (LEFM, Linear Elastic Fracture Mechanics) Stress Intensity Factor & Plane Strain Fracture Toughness
  • LEFM and  Fatigue Crack Growth Rate
  • Failure Analysis - Observations on Failed Parts
  • “Fail Safe” Design Practices

Mathew Schaefer

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