Shear stress test on mild steel and aluminium standard specimen

Becky September 24, 2013

Theory

A structural member is subjected to shear bending rod and torsion. Concrete members subjected to above forces are reinforced with mild steel or deformed steel. Therefore for the safe design of R.C.C. member it is necessary to determine the shear strength of the material is determined both under single and double shear.


Application

Mild steel is widely using as a reinforcement material where as aluminium is used as fabrication of structural components and in rivets. Both the materials are subjected to the action of single and double shear therefore the shear test in single and double shear finds wide application.


Items required

1.      Specimen of mild steel and aluminium

2.    Universal testing machine

3.    Shear test attachment

4.    Vernier caliper


Diagram




Procedure

  1. The diameter of the test specimen is measured and it is inserted in the shear test block.
  2. The assembly is placed between the robust base and the lower cross head.
  3. The specimen is placed between two covers plates in order to ensure uniform distribution of load.
  4. The right hand side valve of the universal testing machine is opened for the application of load.
  5. For double shear test the simultaneous failure at both ends is ensured.
  6. The corresponding load at failure is recorded.






Precaution

1. The fixture for shear attachment are selected according to the diameter of specimen.

2.  The friction between the test specimen and the shear attachment is reduced by the application of a lubricant.

3.  The inner wedge is put in right direction in order to maintained a gap between the lower edge of the base at the time of a failure.


Observation

1.      Diameter of specimen of mild steel = 11.16 mm

2.    Diameter of a aluminium bar = 12.6 mm


Observation table

METAL BAR
% OF BAR mm
AREA IN mm2
LOAD AT FAILURE (P)
STRESS SINGLE & DOUBLE
M.S. BAR
11.16 mm
97.82 mm2
3800 kg
SINGLE SHEAR = 388.47
DOUBLE SHEAR = 194.23
ALUMINIUM
12.6 mm
124.69 mm2
2120 kg
SINGLE SHEAR = 170.00
DOUBLE SHEAR
= 85.07


Calculation

A.   Single shear stress

1.      On mild steel = P/A 
                            =3800 x 10 / 2 x 97.82
                            = 388.47 N/mm2

2.    On aluminium = P/A 
                               = 2120 x 10 / 124.69 
                               = 170.02 N/mm2

B.    Double shear stress

1.      On mild steel = P2/A 
                            = 3800 x 10 / 2 x 97.82 
                            = 194.23 N/mm2


2.    On aluminium =P2/A
                              = 2120 x 10 / 2 x 124.69
                              = 85.01 N/mm2



Becky

Posted by Becky