Double Shear Test on Given Specimen - Computer Programming

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## Sunday, March 13, 2011

Aim: To conduct shear test on given specimen under double shear.

Equipments Required :
1. UTM with double shear chuck
2. Vernier Caliber
3. Test Specimen

Description:
In actual practice when a beam is loaded the shear force at a section always comes to play along with bending moment. It has been observed that the effect of shearing stress as compared to bending stress is quite negligible. But sometimes, the shearing stress at a section assumes much importance in design calculations.
Universal testing machine is used for performing shear , compression and tension.
There are two types of UTM.
1.      Screw  type
2.      Hydraulic type.

Hydraulic machines are easier to operate. They have a testing unit and control unit connected to each other with hydraulic pipes. It has a reservoir of oil, which is pumped into a cylinder, which has a piston. By this arrangement, the piston is made to move up. Same oil is taken in a tube to measure the pressure. This causes movement of the pointer, which gives reading for the load applied.

Details of UTM:
Capacity : 400 KN.
Range      : 0 – 400 KN.

Precaution :

The inner diameter of the hole in the shear stress attachment is slightly greater than that of the specimen.

Procedure:
1.      Measure the diameter of the hole accurately.
2.      Insert the specimen in position and grip one end of the attachment in the upper portion and the other end in the lower portion.
3.      Switch on the main switch on the universal testing machine.
4.      Bring the drag indicator in contact with the main indicator.
5.      Gradually move the head control lever in left hand direction till the specimen shears.
6.      Note down the load at which specimen shears.
7.      Stop the machine and remove the specimen.

Observation:

Diameter of the specimen (d)= ----- mm

Cross sectional area in double shear , (A) = 2 x p d2 / 4      mm2

Shear Load taken by specimen at the time of failure (P) = ------ KN.

Shear strength                          =         Maximum shear force
Area of the specimen.

Result:

Shear strength of the given material = -------- N / mm2