58:158 (53:148) Fatigue/Durability in Design

Spring Semester 2002

2002 Catalog Data: 58:158 (53:148) 3 s.h.

Description:

Macro- and micro mechanisms of fatigue behavior, design of engineering materials/components/structures subjected to cyclic loading, emphasis on metals; stress-life, strain-life, and linear elastic fracture mechanics approach to fatigue crack growth; safe-life, fail-safe and damage tolerant design; constant and variable amplitude life predictions; notches, residual stress, corrosion, temperature, multiaxial, weldments.

Textbook:

R.I. Stephens, A. Fatemi, R.R. Stephens, and H.O. Fuchs, METAL FATIGUE IN ENGINEERING 2nd Edition, Wiley Interscience, 2000.

Coordinator:

Ralph I. Stephens PhD, PE, Professor Mechanical Engineering

Goals:

To provide mechanical, civil, and biomedical engineering students with proper fatigue mechanisms, design criteria and realistic examples to avoid and predict fatigue/durability failures in structures and components. The major emphasis of the course is fatigue of metals as applied to a variety of engineering structures and components, including both fatigue mechanisms and design applications. The material is applicable to ground vehicles, buildings/bridges, aerospace vehicles, ships, nuclear pressure vessels, metal implants/prostheses, and others. Thus, the course is designed for a multidisciplinary student body. Both constant amplitude and variable amplitude fatigue life situations are considered. The solving of homework, both theoretical and applied, is required for all topics covered. A written and oral term paper chosen by the student is required later in the semester.

Learning Objectives:

  • The student will have an understanding of the historical aspects of the development of fatigue knowledge and who contributed to this knowledge.
  • The student will have an understanding of different failure modes in engineering.
  • The student will have an understanding of infinite-life, safe-life, fail-safe, and damage tolerant fatigue design.
  • The student will have an understanding of macro and micro mechanisms of fatigue of metals.
  • The student will have an understanding of different fatigue test loadings, fatigue test specimens/components and fatigue test machines.
  • The student will have an understanding of the stress-life (S-N) approach for both unnotched and notched fatigue design with both constant and variable amplitude loading.
  • The student will have an understanding of the local strain, strain-life (-N), approach for both unnotched and notched fatigue design with both constant and variable amplitude loading.
  • The student will have an understanding of LEFM as applied to fatigue crack growth for both small and long fatigue cracks with both constant and variable amplitude loading.
  • The student will have an understanding of mean stress and residual stress effects on fatigue.
  • The student will have an understanding of environmental effects on fatigue including corrosion, fretting, low and high temperature, and neutron irradiation.
  • The student will have an understanding of fatigue of weldments.
  • The students will have an understanding of the variability and statistical aspects of fatigue.
  • The student will have enhanced written and oral communication skills through a written term paper, daily homework, and an oral presentation.

Prerequisites by topic:

51:085 or 53:034 or 58:085 or 51:151 or 53:140 or 58:150 or equivalent.

Materials Science, Mechanics of Deformable Bodies, and Mechanical Systems Design or equivalent.

Topics (Class Hours):

  1. Introduction, Failure Modes, and Historical Overview(3)
  2. Fatigue Design Methods(1)
  3. Macro/Micro Aspects of Fatigue of Metals(2)
  4. Fatigue Tests and Stress-Life (S-N) Approach(3)
  5. Cyclic Deformation and Strain-Life( -N) Approach(3)
  6. Fundamentals of LEFM and Applications to Fatigue Crack Growth(7)
  7. Notches and their Effects(6)
  8. Residual Stresses and their Effects on Fatigue Resistance(2)
  9. Fatigue from Variable Amplitude Loading(4)
  10. Multiaxial Stresses(0)
  11. Environmental Effects: corrosion, fretting, low and high temperature, neutronirradiation (5)
  12. Fatigue of Weldments(2)
  13. Statistical Aspects in Fatigue(1)
  14. Written and oral term paper(4)
  15. Two hour exams and one final exam(4)

___

(47)

Computer usage:

Many homework problems will, or must, be solved using computational methods usually involving Excel or Matlab programs. Commercial software such as EASE, nCode, or NASGRO will be used in making complex fatigue life predictions.

Laboratory Projects:

The Fatigue and Fracture Mechanics Laboratory will be used to demonstrate different fatigue testing conditions.