Tensile test on mild steel

AIM

To conduct a tensile test on a mild steel specimen and determine the following:

APPARATUS
Universal Testing Machine (UTM), Mild steel specimens , Graph paper , Scale, Vernier Caliper

THEORY

The tensile test is most applied one, of all mechanical tests. In this test ends of test piece are fixed into grips connected to a straining device and to a load measuring device. 

If the applied load is small enough, the deformation of any solid body is entirely elastic. An elastically deformed solid will return to its original from as soon as load is removed. 

However, if the load is too large, the material can be deformed permanently. The initial part of the tension curve which is recoverable immediately after unloading is termed. 

As elastic and the rest of the curve which represents the manner in which solid undergoes plastic

deformation is termed plastic. The stress below which the deformations essentially entirely elastic is known as the yield strength of material. 

In some material the onset of plastic deformation is denoted by a sudden drop in load indicating both an upper and a lower yield point. However, some materials do not exhibit a sharp yield point. During plastic deformation, at larger extensions strain hardening cannot compensate for the decrease in section and thus the load passes through a maximum and then begins to decrease. 

This stage the “ultimate strength”’ which is defined as the ratio of the load on the specimen to original cross-sectional area, reaches a maximum value. Further loading will eventually cause ‘neck’ formation and rupture.

PROCEDURE:-
1) Measure the original length and diameter of the specimen. The length may either be length of gauge section which is marked on the specimen with a preset punch or the total length of the specimen.
2. Insert the specimen into grips of the test machine and attach strain-measuring device to it.
3. Begin the load application and record load versus elongation data.
4. Take readings more frequently as yield point is approached.
5. Measure elongation values with the help of dividers and a ruler.
6. Continue the test till Fracture occurs.
7. By joining the two broken halves of the specimen together, measure the final length and diameter of specimen.

OBESERVATION

A) Material:
A) Original dimensions
Length = ------------
Diameter = ---------
Area = --------------
B) Final Dimensions:
Length = -------------------
Diameter = -----------------
Area = ------------------------

OBESERVATION 

(i) Limit pf proportion
(ii) Elastic limit = load at elastic limit N/mm2
Original area of c/s
(iii) Yield strength
(iv) Ultimate strength
(v) Young’s modulus, E -= stress below propornality limit N/mm2 Corresponding strain

S.No	Load(N)	Original Gauge length	Extension (mm)	Stress (N/mm2)	Strain
1
2
3
4
5

RESULT

i) Average Breaking Stress =
ii) Ultimate Stress =
iii) Average % Elongation =

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