Page 117 - Mechanical Behavior of Materials

4

Mechanical Testing: Tension

Test and Other Basic Tests

4.1 INTRODUCTION
4.2 INTRODUCTION TO TENSION TEST
4.3 ENGINEERING STRESS–STRAIN PROPERTIES
4.4 TRENDS IN TENSILE BEHAVIOR
4.5 TRUE STRESS–STRAIN INTERPRETATION OF TENSION TEST
4.6 COMPRESSION TEST
4.7 HARDNESS TESTS
4.8 NOTCH-IMPACT TESTS
4.9 BENDING AND TORSION TESTS
4.10 SUMMARY

OBJECTIVES
• Become familiar with the basic types of mechanical tests, including tests in tension,
compression, indentation hardness, notch impact, bending, and torsion.
• Analyze data from tension tests to determine materials properties, including both engineering
properties and true stress–strain properties.
• Understand the significance of the properties obtained from basic mechanical tests, and
explore some of the major trends in behavior that are seen in these tests.

4.1 INTRODUCTION

Samples of engineering materials are subjected to a wide variety of mechanical tests to measure
their strength or other properties of interest. Such samples, called specimens, are often broken or
grossly deformed in testing. Some of the common forms of test specimen and loading situation are
shown in Fig. 4.1. The most basic test is simply to break the sample by applying a tensile force, as in
(a). Compression tests (b) are also common. In engineering, hardness is usually defined in terms of
resistance of the material to penetration by a hard ball or point, as in (c). Various forms of bending
test are also often used, as is torsion of cylindrical rods or tubes.
The simplest test specimens are smooth (unnotched) ones, as illustrated in Fig. 4.2(a). More
complex geometries can be used to produce conditions resembling those in actual engineering

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