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EXPERIMENT

EXPERIMENT: TENSILE TESTING
OBJECTIVES:
To determine how the material will react to forces being applied in tension.
To find the strength of material along with how much it will elongate.
THEORY:
Tensile test is used to provide information that will be used in design calculations or to demonstrate that a material complies with the requirements of the appropriate specification.

The test is made by gripping the ends of a suitably prepared standardised test piece in a tensile test machine and then applying a continually increasing axial load until such time as failure occurs.

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Both the load/stress (?) and the test piece extension/strain (?) denoted as F and ?l A l respectively are measured and from this data an engineering stress/strain curve is constructed. 018097500
Fig.4. Stress/strain curve
The tensile strength also known as the ultimate tensile strength is the load at failure
divided by the original cross sectional area. ?max ? Fmax3147060-2921000AO
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where? max = maximum tensile strength, Fmax = maximum load,
A o = original cross sectional area.

The yield point (YP), is the stress at which deformation changes from elastic to plastic behavior i.e. below the yield point unloading the specimen means that it returns to its original length, above the yield point permanent plastic deformation has occurred. Yield
point is denoted as YP or y = FYP AO where 1574165-49339500
y = yield stress,
FYP = load at the yield point,
A o = original cross sectional area.

The modulus of elasticity (?) is a measure of the stiffness of the material, but it only applies in the linear region of the curve. If a specimen is loaded within this linear region, the material will return to its exact same condition if the load is removed. Modulus of
elasticity is denoted as ? = ??
APPARATUS:
Tensile testing machine
PROCEDURE:
Prepare a standard specimen as shown below,
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Clamp the ends of the sample and separate them at a constant speed in opposite directions.

Then record the tension or force required doing this.

Use a power-driven machine in order to maintain a uniform rate of grip separation. Connect the system to a computer to generate data electronically, thereby minimizing human error.

Show the test results as a stress-strain curve, the shape of which provides information about the elastic behavior of the sample.

RESULTS:
TABLE 1: Tensile strength of Mild Steel
Force (N) Elongation (mm) 200 400 600 800 1000 1200 1400 8 The following calculations can be made from tensile test results:
tensile strength (at yield and at break)
tensile modulus
strain
elongation and percent elongation at yield
elongation and percent elongation at break
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REFERENCES:
Internet, Google
1 http://nhml.com/resources_NHML_Hardness-Testing.php
2 http://www.instron.co.uk/
3http://www.ccac.edu/files/
4 http://www.calce.umd.edu/
5 http://en.wikipedia.org/wiki/Vickers_hardness_test
6 http://en.wikipedia.org/wiki/Charpy_impact_test
7 http://www.instron.us/wa/

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