METHOD OF HARDNESS MEASUREMENT: There are two types of measurement of hardness of a compounds: • Static indentation • Rebound testing STATIC INDENTATION: • Static indentation involves pressing a ball diamond or other types of indenter under a specified constant load into surface of material and measuring the length width or depth of the indentation. • The measured indentation size is then converted to a hardness number specified to the scale adopted. • In general the harder the material the better the resistance and thus the smaller the indentation. REBOUND TESTING: • Rebound testing involves dropping an indenter o to the surface of specimen and measuring rebound height of the indenter. • The potential energy at the initial height is converted to kinetic energy when the indenter is released. • A fraction of the kinetic energy is consume for plastic deformation on impact living some kinetic energy after impact to convert back to potential energy and achieve a certain rebound height of the indenter. • The rebound height the measure by the instrument is then converted to a hardness number. Hard materials are difficult to cut and shape then softer ones. They are also usually more brittle which means that do not bend much but can shatter. Hard material are used in cutting tool machines and other industrial goods. Hardness test are important in material science. The MOHS scale of mineral hardness test the hardness of minerals. The Brinell scale and various compression tests and rebound test are more used for metals and artificial materials

1. INTRODUCTION:
Hard things resist pressure some examples of hard materials are:
 Diamond
 Boron carbide
 Quartz
 Tempered steel
 Ice
 Granite
 Concrete
“Ability of materials to resist wear, tear scratching, abrasion, and cutting is called
hardness”.
Hard materials are difficult to cut and shape then softer ones. They are also usually more
brittle which means that do not bend much but can shatter. Hard material are used in
cutting tool machines and other industrial goods. Hardness test are important in material
science. The MOHS scale of mineral hardness test the hardness of minerals. The Brinell
scale and various compression tests and rebound test are more used for metals and
artificial materials.
THEORY:
There are two types of compounds.
 Ionic compounds
 Covalent compound
Ionic compounds:
The ionic compounds can be define as;
“The crystalline solids formed by neatly packed ions of opposite charge.q Ionic
compounds are usually formed when metals react with nonmetals”.
In other words:
“Ionic compounds hold together by ionic bonds as classed as ionic compounds.”
EXAMPLES:
 Nacl sodium chloride.
 NaI sodium iodide.

3.  NaF Sodium fluoride.
 NaBr Sodium Bromide.
COVALENT COMPOUNDS:
When a molecule is formed from the covalent bond such compounds are known as a
covalent compound. These compounds share one or more pairs of valence electrons the
covalent compounds is a result of two non-metal reacting with each other such that they
are electrically neutral.
EXAMPLE:
 O2 oxygen
 Cl2 chlorine
 H2O Water
 Hcl hydrogen chloride
HARDNESS OF COMPOUND:
Hardness is resistance of a material to plastic indentation scratching surface penetration
or wear these properties are related to the resistance against plastic flow (permanent
deformation in the material). Hardness test in most cases are rapid and repeat able and
in many instances nondestructive there for hardness test represents an important means
of quality control.
There are different approaches and criteria for hardness measurement some test
methods for certain material provide convenient co relation of hardness to other
mechanical properties.
For example hardness from indentation tests on steel and coper alloys can be used as a
rough guide to estimate tensile strength.
METHOD OF HARDNESS MEASUREMENT:
There are two types of measurement of hardness of a compounds:
 Static indentation
 Rebound testing
STATIC INDENTATION:
 Static indentation involves pressing a ball diamond or other types of indenter under
a specified constant load into surface of material and measuring the length width
or depth of the indentation.

5.  The measured indentation size is then converted to a hardness number specified
to the scale adopted.
 In general the harder the material the better the resistance and thus the smaller
the indentation.
REBOUND TESTING:
 Rebound testing involves dropping an indenter o to the surface of specimen and
measuring rebound height of the indenter.
 The potential energy at the initial height is converted to kinetic energy when the
indenter is released.
 A fraction of the kinetic energy is consume for plastic deformation on impact living
some kinetic energy after impact to convert back to potential energy and achieve
a certain rebound height of the indenter.
 The rebound height the measure by the instrument is then converted to a hardness
number.