Strength Of Materials
EXPERIMENT NO.: 01
AIM:To conduct a tension test on ductile material using extensometer.
1. To learn how to conduct tension test on a material.
2. To learn how to determine various properties of metal, observe deformation of
material under axial loading and plotting of stress strain diagram.
1. Universal Testing Machine (U.T.M.)
2. Standard specimen.
Stress – strain diagram provides us the information about mechanical properties
and behavior of material under the action of external load and to plot this stress strain
diagram a material is to be tested in materials testing laboratories.
The most common materials test is the tension test, in which a test specimen of
circular, square or rectangular cross- section of a suitable size is prepared from the
material to be tested. The specimen is held by suitable means between the two heads of a
testing machine subjected to a progressively increasing tensile load until it fractures. A
record of load on the specimen with progressive extension of the specimen is obtained.
Tensile tests are done on fixed lengths called as gauge lengths. Before
commencement of the test, two permanent marks are made on the specimen at appropriate
distance called as the original gauge length.
ENGINEERING (i.e. Nominal or Conventional) STRESS-STRAIN CURVES
These curves are obtained from load extension curves on the assumption that
dimensions of sample does not change during testing. In fact during testing of a sample
length increases and cross-sectional area decreases; but still as a matter of convenience it
is assumed that they remain unchanged.
TRUE STRESS-STRAIN CURVES
These curves are plotted by using the values of true stress and true strain from instant
to instant during tensile testing. As the test proceeds, the length of the sample increases
and correspondingly the area of the sample decreases. The value of the true stress gradually
increases because of continuous decrease in cross-sectional area and true strain decreases due
to continuous increase in length.
Pepared by Parkhe R. A.