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