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190 Part III: Inspection and Test
Part III.D.3
Hardness Testing. Hardness is the property of a material that enables it to resist
plastic deformation, usually by penetration. However, the term hardness may also
refer to resistance to bending, scratching, abrasion, or cutting. Hardness is not an
intrinsic material property dictated by precise definitions in terms of fundamental
units of mass, length, and time. A hardness property value is the result of a
defined measurement procedure. Relative hardness of minerals can be assessed by
reference to the Mohs scale, which ranks the ability of materials to resist scratching
by another material. Similar methods of relative hardness assessment are also
commonly used.
Relative hardness tests are limited in practical use and do not provide accurate
numeric data or scales, particularly for modern-day metals and materials. The
usual method to calculate a hardness value is to measure the depth or area of an
indentation left by an indenter of a specific shape, with a specific force applied,
for a specific time. There are three principal standard test methods for expressing
the relationship between hardness and the size of the impression, these being
Brinell, Vickers, and Rockwell (see Section 4 for more details about these types
of hardness testing). For practical and calibration reasons, each of these methods
is divided into a range of scales, defined by a combination of applied load and
indenter geometry (Surface Engineering Forum 2008).
Metallography. Metallography is the microscopic study of structural characteristics
of a metal or an alloy. The microscope is by far the most important tool of the
metallurgist from both the scientific and technical standpoints. It is possible to
determine grain size, and the size, shape, and distribution of various phases and
inclusions, which have a great effect on the mechanical properties of the metal
(ASM International 2005).
3. FUNCTIONALITY TESTING
Define methods such as tension, torque, and
compression. (Knowledge)
Body of Knowledge III.D.3
Functionality testing is used to verify whether a product meets the intended
design specifications and functional requirements stated in the development documentation
(nResults 2008).
Functionality testing can identify potential product bugs, verify the success of
fixes, and verify that product is within standards.
Functionality Testing Objectives
Functionality testing helps ensure products with a minimum number of bugs
or problems. This type of testing will ensure that a product will function as