Machine Design Viva Question and Answers / Machine Design Interview Q & A For Fresher

Machine Design

While designing a parallel sunk key it is assumed that the distribution of force along the length of the key

a) Varies linearly

b) is uniform throughout

c) varies exponentially, being more at the torque input end

d) varies exponentially, being less at torque output end

Answer: (c) Parallel sunk key. The parallel sunk keys may be of rectangular or square section uniform in width and thickness throughout. It may be noted that a parallel key is a taper less and is used where the pulley, gear or other mating piece is required to slide along the shaft. In designing a key, forces due to fit of the key are neglected and it is assumed that the distribution of forces along the length of key is uniform.


Which sunk key made in the form of a segment of a circular disc of uniform thickness, known as?

 

a) Feather key

b) Kennedy key

c) Woodruff key

d) Saddle key

Answer: c) Woodruff Key


The piston rod and the cross head in a steam engine are usually connected by means of

a) Cotter joint

b) Knuckle Joint

c) Ball Joint

d) Universal Joint

Answer: a) Cotter Joint

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Explanation: Piston Connecting Rod in the cross head of a steam engine, valve rod and its stem etc. are examples of cotter joint


In the assembly of pulley, key and shaft

a) Pulley is made the weakest

b) Key is made the weakest

c) Key is made the strongest

d) All the three are designed for equal strength

Answer: b) Key is made the weakest so that it is cheap and easy to replace in case of failure


A spur gear transmitting power is connected to the shaft with a key of rectangular section. The type of stresses developed in the key is fare

a) Shear stress alone

b) Bearing stress alone

c) Both shear and bearing stresses

d) Shearing, Bearing and Bending stresses

Answer: c) Key develops both shear and bearing stresses


A cotter joint is used when no relative motion is permitted between the rods joined by the cotter. It is capable of transmitting

a) Twisting Moment

b) An axial tensile as well as compressive load

c) The bending moment

d) Only compressive axial load

 

Answer: b) An axial tensile as well as compressive load

Explanation: A cotter is a flat wedge shaped piece of steel. This is used to connect rigidly two rods which transmit motion in the axial direction, without rotation. These joints may be subjected to tensile or compressive forces along the axes of the rods

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A square key of side d/4 is to be fitted on a shaft of diameter d and in the hub of a pulley. If the material of the key and shaft is same and the two are to be equally strong in shear, what is the length of the key?

a) π d / 2

b) 2π d / 3

c) 3π d / 4

d) 4π d / 5

Answer: a) π d / 2


In a gib and cotter joint, the gib and cotter are subjected to

a) Single Shear only

b) Double Shear only

c) Single shear and crushing

d) Double shear and crushing

Answer: d) Double Shear and Crushing because a cotter joint is a temporary fastening and is used to connect rigidly two co-axial rods or bars which are subjected to axial tensile or compressive forces.


A key connecting a Flange coupling to a shaft is likely to fail in

a) Shear

b) Tension

c) Torsion

d) Bending

Answer: a) Shear is the dominant stress on the key

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