Rajasthan Technical University 2010 B.Tech Mechanical Engineering Design of Machine Elements-I (mechanical Engg.) - Question Paper
RTU Design of Machine Elements-I (mechanical Engg.)
Rajasthan tech. University
B.tech four sem (Main/back)
Year July 2010
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[Min. Passing Marks: 24 | |||||||||||||||||||
Attempt any five questions selecting one question from each unit. All questions carry equal marks. Schematic diagrams must be shown wherever necessary. Neat free hand sketches will be given full credit. Any data you feel missing may suitably be assumed and
stated clearly.
Use of following supporting material is permitted during examination. (Mentioned in form No. 205)
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1._Design Data Book__2._Nil_
UNIT -1
1 (a) Classify engineering materials. Enlist main effects of
C, Cr, Co, V and Mo alloying elements in sheets.
3+5
(b) Discuss in brief the main properties of engineering materials that are important in deciding their suitability for manufacture of machine elements.
4
(c) Suggest suitable materials for the following machine parts :
(i) Keys
(ii) Laminated leaf spring
(iii) Shafts and
(iv) Couplings.
4
2 (a) Define and write short notes on :
(i) Tolerance
(ii) Allowance
(iii) Fits and
(iv) Interchangeability. How tolerances are designated ?
4+2
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What are practical considerations in design of castings ? Support your answer with proper sketches.
10
(b)
3 (a) (b)
4 (a) (b)
5 (a) (b)
6 (a) (b)
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UNIT - II
(i) What is meant by stress concentration ? Illustrate how the stress concentration in machine components can be reduced.
(ii) How would you differentiate between ductile, brittle and fatigue failures ? State the factors to be considered while designing to avoid fatigue failure.
4+4
A circular cross-section steel part is subjected to a torsional load that varies from +36 kN-cm to -12 kN-cm and a bending load that varies from + 48kN-cm to -24 kN-cm. The ultimate strength of material is 560 N/mm2 and yield strength is 400 N/mm2. Determine the diameter of the part assuming suitable values of type of loading factor, size factor and surface finish factor. A minimum factor of safety of 1.5 may be used in soderberg equation.
8
Differentiate between strength, stiffness and rigidity considerations of design. What are the parameters on which stiffness and rigidity of a machine part depends ?
2+2
Design and draw a neat sketch (two views) of a cotter joint to connect two mild steel rods to transmit an axial load of 30 kN.
10+2
UNIT - III
Discuss suitability of various cross-sections used for lever arms. How the levers are manufactured ?
3+3
Design completely a bell crank lever to raise a load of 6 kN. The longer and shorter arms of the lever are 500 mm and 150 mm respectively. Support the answer with suitable sketches.
8+2
What is nipping in a leaf spring ? Discuss its role.
2+2
Design and sketch a leaf spring for a four wheeler with the following specification :
Maximum load on springs = 160 kN no. of springs = 4 (all identical) maximum no. of leaves in the spring = 10 (two of them are of full length)
Span = 1m
Permissible deflection = 80 mm
10+2
llllllllllllllllil 2 IContd...
UNIT - IV
Why are line shafts made of constant uniform diameter while the machine shafts are varying diameter even through the power requirements are changing in both ?
7 (a) (b)
A steel shaft ABCD, 9 m long, has four pulleys A, B, C, and D keyed at equal distance apart. Power of 45 kW is being supplied to the shaft through the pulley C while taken off equally from the pulleys A, B and D. The shaft runs at 900 rpm. Calculate the most economical diameters for the various portions of the shaft so that the shear stress does not exceed 40 N/mm2. If shear modulus of the shaft material is 85 GPa, determine the twist of the shaft at pulley D with respect to A.
8+4
Classify shaft couplings mentioning the uses of each type.
8 (a) (b)
4
Design a bushed pipe type flexible coupling for connecting shafts of a motor and pump. The given data are :
Power to be transmitted =15 kW RPM of shaft = 750 Dia of motor shaft = 50 mm Dia of pump shaft : 45 mm
Select suitable materials and allowable stresses for coupling, pins/bolts and bushes. Assume length of rubber bush = 25 mm located at p.c.d. of 3.5 times of the motor shaft diameter. Draw two views of the designed coupling.
10+2
UNIT-V
9 (a)
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A cantilever beam of rectangular cross-section is shown in | |
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PLAN -A |
load W at its free end. If the width 'bx' varies linearly with x, show that the beam is of uniform strength. Also calculate the maximum deflection in the beam and its position.
3+4+1
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(b) A crane runway bracket is shown in Fig. 2. Determine the tensile and compressive stresses produced in the section, x-x when magnitude of wheel load is 10 kN as shown in Fig.2
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25 XX Fig. 2 |
10 (a) The shaft of a rotary machine is subjected to a maximum torque of 2000 N-m alongwith a bending moment of 4500 N-m. The combined shock and fatigue factors in torsion and bending are 1.0 and 1.5, respectively. Determine the shaft diameter for an allowable shear stress of 40 N/mm2.
If the shaft is replaced by a hollow shaft (Do/D,=2)'
what will be % saving in material ? Also compare its rigidity with the solid shaft.
(b) A load of 50 kN is suspended from a plate 'A' which is fastened to a piller by three bolts 1, 2 and 3, Fig. 3. For the given dimensions in the figure, determine the bolt diameter. What will be stresses in the designed bolts 1 and 3 if bolt 2 is removed ? Plate thickness is 12 mm.
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| Earning: Approval pending. |
