Page 415 - Mechanical Behavior of Materials

9

Fatigue of Materials:

Introduction and

Stress-Based Approach

9.1 INTRODUCTION
9.2 DEFINITIONS AND CONCEPTS
9.3 SOURCES OF CYCLIC LOADING
9.4 FATIGUE TESTING
9.5 THE PHYSICAL NATURE OF FATIGUE DAMAGE
9.6 TRENDS IN S-N CURVES
9.7 MEAN STRESSES
9.8 MULTIAXIAL STRESSES
9.9 VARIABLE AMPLITUDE LOADING
9.10 SUMMARY

OBJECTIVES

• Explore the cyclic fatigue behavior of materials as a process of progressive damage leading
to cracking and failure, including trends for variables such as stress level, geometry, surface
condition, environment, and microstructure.
• Review laboratory testing in fatigue, and analyze typical test data to obtain stress–life curves
and evaluate mean stress effects.
• Apply engineering methods to estimate fatigue life, including the effects of mean stress,
multiaxial stress, and variable-level cyclic loading; also evaluate safety factors in stress and
in life.

9.1 INTRODUCTION

Components of machines, vehicles, and structures are frequently subjected to repeated loads, and
the resulting cyclic stresses can lead to microscopic physical damage to the materials involved.

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