Career Point university Kota, Rajasthan

Presentationon

“Torsion Test.”

Prepare By-Abhishek {K11535} & Ajay {K11876}B.Tech M.E. 2nd year

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.

Torsion uses in daily life applications.

Torsion Test

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 observe the mode of the failure of the metal.

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, Where, J J is the polar moment of inertia, mm2is the polar moment of inertia, mm2 G G is the shear modulus, N/mm2 is the shear modulus, N/mm2 is degree of rotation, radianis degree of rotation, radian r r is the radius of the cylindrical bar, is the radius of the cylindrical bar, mm or inmm or in L L is the length of the cylindrical bar, is the length of the cylindrical bar, mm or inmm or inis the shear stress, N/mm2 is the shear stress, N/mm2

How specimen broke up under stress-strain curve.

Mild steel and cast iron properties

Mild steel•Carbon % - less than 0.25% carbon• Iron-Carbon alloy•More ductile and less hard•Unsuitable for structural work

Cast ironProduced by remelting of pig iron.C- carbon graphite and combined carbon cementite.Carbon %- 2 to 4.3%Strong in compressor.Melted at 1130 CDifficult to weld.

Microstructure

Failure of cast iron and mild steel

Stress strain curve

Mild steel Cast iron

Conclusion

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.