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Embed code for: MOS ALA Torsion Test
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Gandhinagar institute of technology
Mechanics of solid (2131906)
Name : Raval Umang Y.
Class : 3D1
Guided by :
Torsion uses in daily life applications.
In many areas of engineering applications, materials are sometimes subjected to torsion in services, for example, drive shafts, axles and twisted drills.
Moreover, structural applications such as bridges, springs, car bodies, airplane fuselages and boat hulls are randomly subjected to torsion.
The materials used in this case should require not only adequate strength but also be able to withstand torque in operation.
Torsion test is applicable for testing brittle materials such as tool steels and cast iron.
Generally, torsion occurs when the twisting moment or torque is applied to a member.
The torque is the product of tangential force multiplied by the radial distance from the twisting axis and the tangent, measured in a unit of N.m.
In torsion testing, the relationship between torque and degree of rotation is graphically presented and parameters such as ultimate torsional shearing strength (modulus of rupture), shear strength at proportional limit and shear modulus (modulus of rigidity) are generally investigated
Objective of Torsion test.
To understand the principles of torsion testing, practice their testing skills and interpreting the experimental results of the provided materials when failed under torsion.
To determine the maximum shearing stress, shear stress at proportional limit, shear modulus or modulus of rigidity and relationships between torque and degree of rotation of the tested materials.
To differentiate the ability of materials such as cast iron and brass to withstand torque prior to torsion failure. Analysis and interpretation of the test parameters obtained should be carried out in relation to the failure nature of each material.
To be capable of selecting materials for engineering applications associated with torsion.
Torsion testing machine.
1 Test specimens
2 Micrometer or vernia-caliper
3 Permanent pen
4 Torsion testing machine
Equipment used in testing
Formula used for calculating Torsion
Where, J is the polar moment of inertia, mm2
G is the shear modulus, N/mm2
is degree of rotation, radian
r is the radius of the cylindrical bar, mm or in
L is the length of the cylindrical bar, mm or in
is the shear stress, N/mm2
How specimen broke up under stress-strain curve.
Failure of cast iron and mild steel
Stress strain curve
Torsion failures are different from tension failures and normally provide little deformation or elongation.
The characteristic of the fracture surface is related to the state of stress at the point on the bar surface.
It can be seen that the maximum shear stresses exist along two planes, which are perpendicular to each other.
The characteristics of torsion fractures are influenced by torsional and tensile forces.
These result in two types of torsion failures;
1) ductile failure due to the shear stresses in mild steel.
2) brittle failure due to the tensile stresses in cast iron.