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Paper / Subject Code: 89421 / Machine Design

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1T01436 - T.E.(Mechanical) Engineering)(SEM-VI)(Choice Base Credit Grading System ) ((R-20-21) (C Scheme) / 89421 -

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Machine Design

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QP CODE: 10012982 DATE:07/12/2022

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(3 Hours) [ Total Marks : 80]

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N.B. (1) Question no. 1 is compulsory.

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(2) Attempt any three questions out of remaining five questions.

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(3) Use of standard data book like PSG, Mahadevan is permitted.

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(4) Figures to the right indicate full marks.

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1. Attempt any FOUR of the following :

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(a) Explain the safe region and boundary conditions with suitable sketch for the

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maximum principal stress theory.

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(b)
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Describe various stresses in a belt with formula and its meaning.

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(c) Compare between rolling contact and sliding contact bearing.
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(d) Give detail classification of coupling.

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2m (e)

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Which threads are used in power screw? Give reason for your answer.

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2. (a) Design a knuckle joint to connect two rods subjected to a load of 40 KN. The (12)

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material for rod and knuckle pin can be assumed as 40C8. A suitable factor of safety
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can be considered if required for designing the joint.

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(b) A helical compression spring is subjected to a load that ranges from 600 N to 1200 (08)

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N. If the compression in the spring for the maximum load is 30 mm and spring index
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in 6, design the spring. The yield stress in shear for the spring material is 960MPa,
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endurance strength on shear as 480MPa and modulus of rigidity as 80 x 103 MPa.

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3. Determine the life of a mechanical element subjected to complete reversed bending (12)
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stress cycle as follows:

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i) ± 300 MPa for 30% of time ii) ± 275 MPa for 25% of time
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iii) ± 400 MPa for 10% of time iv) ± 325 MPa for 25% of time
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v) 0 MPa for 10% of time

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The material has ultimate tensile strength of 1200MPa. The operating temperature
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is 400°C and fatigue stress factor = 0.7.

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5.3 flywheel
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(b) Explain the terms: coefficient of speed fluctuation and coefficient of steadiness. (08)
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4. (a) A welded joint as shown in Fig. 1, is subjected to an eccentric load of 60 KN in the (10)
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plane of the welds. Determine the size of the welds, if the permissible shear stress
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for the weld is 100 N/mm2. Assume static conditions.

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Figure 1 – Q 4 (a)
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Paper / Subject Code: 89421 / Machine Design

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(b) Explain with a suitable sketch the working of a single plate clutch. (10)

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5. (a) Determine the suitable diameter for the solid shaft, if it is supported by two bearings (10)

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placed 1m apart. A 300 mm diameter pulley is mounted at a distance of 250 mm to

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the right of left hand bearing and this drives a pulley directly below it with the belt.

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Another pulley 400 mm diameter is placed 350 mm to the left of right hand bearing

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and is driven with the help of electric motor and belt, which is placed horizontally

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to the right. The angle of contact for both the pulley is 180˚ & μ = 0.3. The shaft

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transmits 10KW at 1440 rpm and weight of pulley A is 250N and that of B is 500

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N. Assume that the torque of one pulley is equal to that of the other pulley.
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(b) A hydrodynamically lubricated full journal bearing is used to support a radial load (10)
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of 15 KN. The speed of journal is 1500 r.p.m. and l/d ratio is 1. If the permissible
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bearing pressure is 1.5 N/mm2, determine the following:

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i) length and diameter of bearing

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ii) minimum oil film thickness
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iii) coefficient of friction
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iv) oil flow rate

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v) temperature rise.

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Select a suitable deep groove ball bearing for the shaft diameter of 60 mm and (10)
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reliability of 98 %. The shaft rotates at 1440 r.p.m. and the bearing carries a radial
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load of 2500 N and an axial load of 1200N. Expected life of braring is 25000 hoursEC
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and consider a load factor of 1.2.
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1m (b) Explain the various design considerations for casting with suitable sketches (10)
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wherever applicable.
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