Page 18 - Mechanical Behavior of Materials

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Introduction

1.1 INTRODUCTION
1.2 TYPES OF MATERIAL FAILURE
1.3 DESIGN AND MATERIALS SELECTION
1.4 TECHNOLOGICAL CHALLENGE
1.5 ECONOMIC IMPORTANCE OF FRACTURE
1.6 SUMMARY

OBJECTIVES

• Gain an overview of the types of material failure that affect mechanical and structural design.
• Understand in general how the limitations on strength and ductility of materials are dealt
with in engineering design.
• Develop an appreciation of how the development of new technology requires new materials
and new methods of evaluating the mechanical behavior of materials.
• Learn of the surprisingly large costs of fracture to the economy.

1.1 INTRODUCTION

Designers of machines, vehicles, and structures must achieve acceptable levels of performance and
economy, while at the same time striving to guarantee that the item is both safe and durable. To
assure performance, safety, and durability, it is necessary to avoid excess deformation—that is,
bending, twisting, or stretching—of the components (parts) of the machine, vehicle, or structure.
In addition, cracking in components must be avoided entirely, or strictly limited, so that it does not
progress to the point of complete fracture.
The study of deformation and fracture in materials is called mechanical behavior of materials.
Knowledge of this area provides the basis for avoiding these types of failure in engineering
applications. One aspect of the subject is the physical testing of samples of materials by applying
forces and deformations. Once the behavior of a given material is quantitatively known from
testing, or from published test data, its chances of success in a particular engineering design can
be evaluated.

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