Exp.4: Rubber in Shear Apparatus
Eng. Ahmed Y Manama
Eng. Saeed A Shurab
Eng. Ahmed Al Afeefy
Objectives
 Measure the shear deformation of the block.
 Determine of modulus of rigidity.
Introduction
 Rubber blocks in shear force are often used on
engine and in equipment mounting to isolate
vibrations. They do this by absorbing shock energy by
deforming. This deformation leads to a decrease in
cross-section as the block lengthens, an effect
described by Poisson's Ratio.
Introduction
Shear Stress and Strain
Introduction
 The force F acting at angle theta with respect
to the horizontal , the force resolved to it’s
component ( perpendicular and parallel to the
surface area).
 The perpendicular component will produce an
Axial
Stress
The parallel component will effect the rod by
producing a Shear Stress.
 The units of both Axial and Shear Stress will
normally be lb/in2 or N/m2
Introduction
 Shear Strain
The shear stress produces a displacement of the rod
which produces a shear strain.
The edge of the rod is
displaced a horizontal distance, from its initial position
,this displacement (or horizontal deformation) divided by
the length of the rod L is equal to the Shear Strain.
Introduction
Introduction
Tan γ = γ = δ / L
Where :
δ is the deformation
γ shear strain
L original length
The shear strain is dimensionless.
Shear Modulus (Modulus of Rigidity)
 The modulus of rigidity ( shear modulus) (denoted by G or
sometimes S or μ,) is concerned with the deformation of a
solid when it experiences a force parallel to one of its
surfaces while its opposite face experiences an opposing
force (such as friction).
 Shear modulus is usually measured in GPa or ksi
(thousands of pounds per square.
Shear Modulus (Modulus of Rigidity)
 It’s defined as the ratio of shear stress to the shear
strain:
 where
 F is the force which acts
 A is the area on which the force acts
 Δx is the transverse displacement
 I is the initial length
Equipment
 A rubber block 150 x 75 x 25mm is bonded to two
aluminum alloy plates.
Results
Load
(N)
0
10
20
30
40
50
60
70
80
90
100
110
120
Dial Gauge
(mm)
Deflection
(mm)