The tensile test, as known as the

“tension test”,

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

elongation.

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)

Specimen’s

raw material = Aluminum

Specimen’s raw material = Steel

Diameter of

specimen = 12 mm

Diameter of specimen = 15 mm

Gage length

= 59 mm Gage length = 84 mm

Final Gage

length = 69 mm Final Gage length

= 95 mm

After fracture :

Max.load =

39.56276(kN)

Max.load = 86.94378 (kN)

Max.stress = 349.8033 (MPa) Max stress = 492

(MPa)

?Theory of Experiment

Formulas That Will Be Used in Lab Report

Engineering Stress

?

= P/A0

Engineering stress can be found by dividing the Applied

Force to Cross Sectional area of the specimen before the deformation has taken

place.

True Stress

?T =

P/A

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.

Engineering Strain

? = ? / L0

Engineering strain can be found by dividing the

Total Elongation to Original value of the gage length.

True

Strain

L

?T = ?(1/L)dL = ln(L/L0)

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)).

Hooke’s Law

? = Normal Stress

? = ? * E ? = Normal

Strain

E = Modulus of Elasticity(Young’s

Modulus)

Yield Point

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

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.

Gage Length

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.

Tools

Used in Experiment

Aluminum Steel

Specimen

Specimen

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.