This document discusses various mechanical tests used to evaluate material properties including tensile tests, compression tests, hardness tests, impact tests, creep tests, and fatigue tests. Tensile tests are used to determine properties like yield point and ductility. Compression tests are similar but for brittle materials. Hardness tests evaluate effects of processing and determine machinability. Impact and creep tests evaluate material behavior under sudden loads and prolonged high-temperature loading. Fatigue tests determine how materials fail under repeated cyclic stresses. These standard tests are important for understanding and predicting material performance in applications.

1. MECHANICAL TESTS
BY
Dr. K. SENTHILARASAN
ASSISTANT PROFESSOR
DEPARTMENT OF PHYSICS
E.G.S.PILLAY ARTS & SCIENCE COLLEGE
NAGAPATTINAM-611002

2. Types of mechanical tests
The mechanical properties of metals are
established by conducting various mechanical tests.
These are standardised by Indian Standards Institute
(ISI) in India and by the American Society for
Testing and Materials ASTM in USA.
Important mechanical tests are:
1. Tensile test
2. Compression test
3. Hardness test
4. Impact test
5. Creep test
6. Fatigue test

3. Tensile test
Tensile strength is generally performed on a
piece of material to determine its proportion limit
and elastic limit, yield point.
Ultimate tensile strength and percentage
elongation and reduction of area for knowing
ductility and brittleness.
The tensile test for a ductile material is
generally carried out with the help of a universal
testing machine.
The test piece made from the material to be
tested is pulled out at a constant rate gradually
increasing the axial pull till the rupture takes place.

4. Compression test:
The compression test is opposite of the
tensile test.
It is generally performed for testing brittle
materials.
The compressive load is gradually
increased on the specimen using universal testing
machine and the corresponding reduction in the
length of the specimen are recorded.

5. Hardness test
The hardness tests are mainly performed for
evaluating the effects of various hot and cold
working process and heat treatments upon the basic
properties of metals. Hardness of a metal determines
its resistance against indentation, scratching, wear
and abrasion. Further it also it also determines its
machinability and ability.
Different test: brittle hardness test, Rockwell
hardness test, Vickers Hardness test, Knoop’s
hardness test and Monotron hardness test.

6. Impact test
Impact test are used to determine the ability
of the materials to withstand impact or shock or
suddenly applied load while in service.
Further it is also used to determine the
tendency of material towards brittle fracture.
It signifies toughness of material.

7. Creep test
Creep test is essential to predict the working
life of machine components which are subjected to
creep.
The test piece of metal is held in a steel
stricture such that one of its ends is held in a holder
and the other end is loaded through a lever.
Surrounding the specimen there is a
temperature controlled chamber by which we can do
the creep testing at a constant temperature over a
long period of time.
First the zero reading of length is noted. Load
is then applied and after few minutes extension is
measured periodically throughout the test.

8. Fatigue test
The failure of a material, under repeatedly applied stress is
called fatigue.
The fatigue strength of a material is increased by the surface
compressive residual stress and decreased by stress concentration due
to notch or hole.
The test piece is loaded in pure bending and rotated about its
axis with the help of motor. With each rotation, the stress at any part of
the cross section of the specimen varies sinusoidal between maximum
tensile and maximum compressive stresses.
Each revolution thus constitutes one cycle of stress reversal.
The speed of the motor will indicate the frequency of the stress reversal
and it is indicated by a revolution counter.
The stress is varied using different loads and the number or
cycles till failure occur is noted for each load.