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Mechanical - Strength of Materials - Torsion

**TORSION**

**1. ****What
are the assumptions made in torsion equation?**

The material of
the shaft is
homogeneous, per

Twist is uniform along the
length of the shaft and

The stress does not exceed
the limit of proportionality

**2. Write down the expression for power
transmitted by a shaft.**

Power, P = 2пNT/ 60

Where,

T –Torque in kN.m

N –Speed in r.p.m.

P –Power in Kw

**3. Define polar modulus. **

It is the ratio between
polar moment of inertia and radius of the shaft.

**4. State the differences between closed
and open coil helical springs.**

**Closed coiled helical springs**

Adjacent coils are very
close to each other

It can carry only tensile
loads .

Helix angle is negligible

**Open coiled helical springs**

Large gap between adjacent
coils

It can carry Both tensile
and Compression loads.

Helix angle is
considerable

**5.Find
the torque which a shaft of 50mm diameter can transmit safely, if the allowable
shear stress in 75 N/mm²?**

T = п/ 16 x fsx d3

T = п/ 16 x 75 x (50)3

T = 1.840 kN.m

6. What is mean by stiffness?

The stiffness of the spring is defined as the load
required to product unit deflection.

**7.Classify
the types of springs.**

Torsion spring and

Bending spring

**8.What
is meant by spring?**

Spring is a device which is used to absorb energy by
taking very large change in its form without permanent deformation and then
release the same when it is required.

**9.Define
torsion.**

When a pair of forces of equal magnitude but
opposite in direction acting on body, it tends to twist the body. It is known
as twisting moment or simply as torque.

**10.what
is meant by torsion spring?**

A
spring, which is subjected to torsion or twisting moment only is known as
torsion spring.

**11. What is the ratio of
maximum shear stress to the average shear stress in the case of solid circular
section?**

Q_{max} is 4/3 times the Q_{avg}.

**12. What is the shear stress distribution value of Flange
portion of the I-section?**

Where, D- depth

y- Distance from neutral axis

**13. Where the shear stress is max for Triangular section?**

In the case of triangular
section, the shear stress is not max at N A. The shear stress is max at a
height of h/2

**14. Define: Mohr’sTheorem for slope**

The change of slope
between two points of a loaded beam is equal to the area of BMD between two
points divided by EI.

**15. Define: Mohr’sTheorem for deflection**

The deflection of a point with respect
to tangent at second point is equal to the first moment of area of BMD between
two points about the first point divided by EI.

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