To perform direct shear test on a plane steel bar and punching shear test on steel plate

Job 3

To perform direct shear test on a plane steel bar and punching shear test on steel plate

Objective:

To determine the shear strength of steel samples

Apparatus:

1. 10 ton Buckton UTM
2. Shear jigs
3. Vernier calipers
4. Steel bar
5. Steel plate

Related theory:

• Shear force (V) :

A force which tends to slide one part of a section against the adjacent is known as shear force.

• Shear stress / tangential stress (
  $\tau$

  ):

It is the intensity of the internal forces on a plane area when the forces are acting parallel to the section.

Note: A uniform shearing stress will exist when the resultant shear force passes through the centroid of the cross section being sheared.

• Types of shear stress:

1. Direct shear:

If the force applied is parallel to the area being sheared, then it is direct shear.

Following are the types of direct shear.

• Single shear:

Shear stress induced due to a force causing single area of cross section to be sheared is called single shear.

• Double shear:

Shear stress induced due to a force causing double area of cross section to be sheared.

 

• Punching shear:

Shear stress induced due to a force causing one part to be punched into the other.

Area being sheared is again parallel to applied load.

 

 

2. Induced shear:

Shearing stress induced due to a force which acts at an angle to the area being sheared.

Procedure:

1. Insert the specimen in position and grip one end of the attachment in the upper portion and one end in the lower position
2. Switch on the UTM
3. Bring the drag indicator in contact with the main indicator.
4. Select the suitable range of loads and space the corresponding weight in the pendulum and balance it if necessary with the help of small balancing weights
5. Operate (push) the button for driving the motor to drive the pump.
6. Gradually move the head control ever in left hand direction till the specimen shears.
7. Note down the load at which the specimen shears.
8. Stop the machine and remove the specimen.

Repeat the experiment with other specimens.

Observations and calculations

For direct shear test on plane steel bar:

Shear load		Diameter (d)			Avg. (d)	Area= $\pi d²/4$	Shear strength= $\tau =V/A$
		(mm)
Tons	N	D1	D2	D3	mm	mm2	MPa	Psi
1.132	10074.8	6.50	6.55	6.70	6.58	34	296.3	42975

 

For punching shear test on a steel plate:

Shear load		Diameter of jigs (d)		Avg. (d)	Plate thickness (t)	Shear area $(\pi dt$ )	Shear strength= $\tau =V/A$
		(mm)
Tons	N	Upper jig	Lower jig	mm	mm	mm2	MPa	Psi
2.586	23015.4	14.90	15.20	15.05	2.10	99.29	231.79	33618.9