Page 122 - Mechanical Behavior of Materials

Section 4.2 Introduction to Tension Test 123

Table 4.1 Volumes in the ASTM Standards
Containing Basic Mechanical Test Methods
Class of Material or Item Volume(s)
Iron and steel 01.01 to 01.08
Aluminum and magnesium alloys 02.02
Metals test methods 03.01
Concrete 04.02
Stone and rock 04.07 to 04.09
Wood and plywood 04.10
Plastics 08.01 to 08.03
Rubber 09.01 to 09.02
Medical devices 13.01
Ceramics, glass, and composites 15.01 to 15.03

and glass. The ASTM standards are organized according to such classes of material, with Table 4.1
identifying the volumes that contain standards for mechanical testing.
Volume 03.01 contains numerous test standards for metals, including a variety of basic
mechanical tests. Other mechanical testing standards are included in the volumes for more specific
classes of material, along with standards of other types. For each class of material, there are one or
more standard methods for tests in tension, compression, and bending, and also often for hardness,
impact, and torsion. Volume 13.01 contains standards for materials and devices used in medicine,
such as mechanical tests for bone cement, bone screws, fixation devices, and components of artificial
joints. The various national organizations, the EU, and ISO have standards that parallel those of
ASTM in many areas, with the details for a given test sometimes differing among these.
Test standards give the procedures to be followed in detail, but the theoretical basis of the test
and background discussion are not generally given. Hence, one purpose of this book is to provide
the basic understanding needed to apply materials test standards and to make intelligent use of the
results.
Measured values of any property of a given material, such as its elastic modulus, yield strength,
or hardness, are subject to statistical variation. This issue is often addressed in test standards, and it
is discussed in Appendix B of this book. Note that multiple measurements of a given property are
needed to obtain an average value and to characterize the statistical scatter about this average.

4.2 INTRODUCTION TO TENSION TEST

A tension test consists of slowly pulling a sample of material with an axial force, as in Fig. 4.1(a),
until it breaks. This section of the chapter provides an introduction to the methodology for tension
tests, as well as some additional comments. Sections that follow discuss tension testing in more
detail, after which other types of test are considered.

4.2.1 Test Methodology
The test specimen used may have either a circular or a rectangular cross section, and its ends are
usually enlarged to provide extra area for gripping and to avoid having the sample break where it is