The tensile test, as known as the
is one of a most fundamental type of mechanical test that used on a material.
Tensile test is really inexpensive which makes this test more preferable.
From tensile test, how the
material will react to forces being applied in tension can be determined. As
the material is pulled by machine, material’s strength can be found along its
From the stress-strain curve
of the tensile test, the values which can be found are Modulus of Elasticity,
Yield Strength, the Tensile Strength, Percentage of Elongation and the
Reduction in Area. Also the Toughness, Resilience, Poisson’s ratio can be found
by using the tensile test.
In the report, these values
will be found by doing the calculations and in the Results and Discussion part
of the report, these calculations will be explained and discussed. This
experiment is made with two different specimens.(one is made from aluminum and
the other is made from steel)
raw material = Aluminum
Specimen’s raw material = Steel
specimen = 12 mm
Diameter of specimen = 15 mm
= 59 mm Gage length = 84 mm
length = 69 mm Final Gage length
= 95 mm
After fracture :
Max.load = 86.94378 (kN)
Max.stress = 349.8033 (MPa) Max stress = 492
?Theory of Experiment
Formulas That Will Be Used in Lab Report
Engineering stress can be found by dividing the Applied
Force to Cross Sectional area of the specimen before the deformation has taken
True stress can be found by dividing the Applied
Force to Cross Sectional area of the specimen at the point which the load is applied.
? = ? / L0
Engineering strain can be found by dividing the
Total Elongation to Original value of the gage length.
?T = ?(1/L)dL = ln(L/L0)
True strain can be found by taking the integral of
(1/(Changed value of gage length)) which is equal to ln((Changed value of gage
length)/(Original value of the gage length)).
? = Normal Stress
? = ? * E ? = Normal
E = Modulus of Elasticity(Young’s
In order to find the yield point, take the load at the point where
strain is (0.2%) divided by the cross-sectional area.
Ductility is ability of
material that undergoes permanent deformation (through the reduction in cross
section area) by flexing or twisting at room temperature without fracturing.
Distance along the specimen
that the calculations of extension are made is called ”gage length”. Sometimes,
distance between the grips are taken as gage length.
Difference Between Engineering
and True Stress/Strain
True stress and strain are often not required. When the yield
strength is surpassed, the material deforms. The component has
failed because it doesn’t have the original intended shape anymore.
Furthermore, a significant difference develops between the two curves only when necking begins.
But when the necking begins, the component is extremely deformed and no longer
supplies its expected use. In the graph, true stress continues increasing after necking,
although the load required
decreases, the area decreases even and even more.
Used in Experiment
Caliper Instron Load
?Procedure of Experiment
To determine the gage length
and the diameter of the cross section of aluminum specimen, the aluminum
specimen was measured with the caliper. The diameter of the aluminum specimen
was determined (12.00 mm), the gage length of it was determined (59.00 mm) and
scribed into the specimen in order to measure the distance between the two marks
after the tensile test was completed. After that, same measurements are made
for the steel specimen and the gage length was determined (84.00 mm), the
diameter was determined (15.00 mm).
To space the specimen equally between the two
clamps, the specimen got loaded to Instron load frame’s jaws. The extensometers
were fitted to the reduced gage section of the specimen, providing that the
axial extensometer was set correctly when attaching it to the gage and that the
transverse extensometer was attached to complete the diameter of specimen.
The Instron load frame was loaded
by using the scroll wheel to provide that the specimen was accurately loaded into
the frame and ensured that it wasn’t slipping in the jaws. After that, by using
the software, load was released so that the extensometers were zeroed. The test
got started and the specimen was loaded, resulting in a mensureable strain.
This increase in the rate of strain may caused some error but this increase
sped up the test.