MACHINE DESIGN 1 PAPER

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MACHINE DESIGN I ME 301 5th Sem May 2k5
Max marks 60

Note: Section A is compulsory. Attempt any Four questions from Section B and any Two questions from Section C.

Section A Marks 2 each

1.
(a) Define Machine Design
(b) Explain stiffness and rigidity.
(c) Differentiate endurance strength and endurance limit.
(d) What is an 18-8 steel? Mention two applications of it.
(e) Sketch fatigue, brittle and ductile failure.
(f) What is size factor and surface finish?
(g) What kind of fit would you suggest for pin of knuckle joint?
(h) Discuss various types of threads used for power transmission. Give at least two applications of each.
(i) How is welding stress relieved?
(j) Discuss various types of labyrinth seal.

Section B Marks 5 each

2. A machine component is subjected to 2-D stresses. The tensile stress in the x direction varies from 40 to 100 N/mm2 while the tensile stress in the y direction varies from 10 to 80 N/mm2. The frequency of variation of these stresses is equal. The corrected endurance strength of the component is 270 N/mm2. The ultimate tensile strength of the component is 60 N/mm2. Determine the factor of safety used by designer.

3. A circular shaft 50 mm in diameter is welded to a support by means of a fillet weld as shown in fig 1/ Determine the size of the weld if the permissible shear stress in the weld is limited to 100 N/mm2. (please see the attachment)

4. An M 12 steel bolt, 250 mm long is subjected to an impact load. The kinetic energy to be absorbed Is 4 J.
(a) Determine the stress in the shank of the bolt if there is no threaded portion between the nut and the bolt head.
(b) find the stress in the shank if the area of the shank is reduced to that of the root area of the threads.

5. A medium force 0.22mm fit on a 75 mm shaft requires a hole tolerance of 0.225 mm, a shaft tolerance of 0.223 mm and an average interference of 0.0375 mm. Determine the proper hole and shaft dimensions with basic hole standard.

6. A band brake is required to balance a torsional moment of 300 Nm on the drum shaft. The drum is to be made 360 mm in diameter and keyed to the shaft. The band is to be lined with asbestos as fabric having coefficient of friction 0.3 and arc of contact 270 degrees. The brake lever and pins are to be made of mild steel. Find the dimension of the steel lever and pins. Permissible stresses for tension and crushing for steel used are 70 N/mm2 and shear stress in 55 N/mm2.

Section C Marks 10 each

7. A marine type flange coupling is required to transmit 2900 kW power at a speed of 100 rpm. Flanges are connected by 8 bolts having allowable shear stress of 60 MPa. The material for shaft and bolts used is same. Design the flange coupling and determine the shaft diameter.

8.Design a knuckle joint to connect two mild steel rods. The joint has to transmit a load of 100 kN. Draw two views of the joint.

9. A horizontal power transmission shaft is supported by two bearings 1 m apart. The shaft overhangs the right hand bearing and supports a 0.75 m pitch diameter straight tooth spur gear 0.03 m from the bearing. It supports a 1.25 m flat belt pulley 0.25 m to the left of the left hand bearing. The gear weighs 3 kN and the pulley weighs 10 kn. The gear is driven by a pinion such that the tangential turning force acts upward (Ignore radial force).

The pulley that delivers the power vertically downwards has a belt tension ratio of 2.5:1. The shaft must transmit 20 kW at 150 rpm. Assume transmission efficiency as 100%. Determine the shaft diameter based on maximum normal stress theory. Assume suitable other data.