In materials
science, hardness is the characteristic of a solid material
expressing its resistance to permanent deformation. In
mineralogy the property of matter commonly described as the
resistance of a substance to being scratched by another
substance. In metallurgy hardness is defined as the ability of a
material to resist plastic deformation. The Metals
Handbook defines hardness as "Resistance of metal to plastic
deformation, usually by indentation. However, the term may also
refer to stiffness or temper or to resistance to scratching,
abrasion, or cutting. It is the property of a metal, which gives
it the ability to resist being permanently, deformed (bent,
broken, or have its shape changed), when a load is applied. The
greater the hardness of the metal, the greater resistance it has
to deformation.
For more information on the principle
operational definitions of hardness click
here. For application examples (& see
video below)
click here. For a understanding of the "Evolution of Hardness
Testing" click here.
The following
definition is the one we will be most
concerned with in the application of this lab.
The dictionary of
Metallurgy defines the indentation hardness as the resistance of
a material to indentation. This is the usual type of hardness
test, in which a pointed or rounded indenter is pressed into a
surface under a substantially static load.
The lab is intended
to accomplish five goals:
To introduce the
Rockwell hardness Tester, (a basic tools used in
manufacturing shops) and its related terminologies to the
students.
To learn the
importance of the concept of hardness in manufacturing.
To practice the
team work concept through a hands-on practice.
To practice
safety related to working in a manufacturing environment.
To provide an
experiment through which students recognize and see the
concepts of hardness explained in the textbook.
The Lab
Each group will
test each of the seven (7) specimens. You are to place it in the hardness tester
and perform at least three (3) separate tests on each specimen. You will average the
test hardness ratings for each specimen. Using the textbook (Table 3.6, on
page 54 of your text [or page 55 of the new text]) or whatever
other source available to you to determine the material type of
each given sample. From your collected data, try to
distinguish between materials, if
possible. Do list which sample is the hardest in the report. Submit your data in
table format in your report.
To identify the samplesclick here.
