Rajasthan Technical University 2010 B.Tech Mechanical Engineering Design of M/c Elements-II - Question Paper
RTU Design of M/c Elements-II
Rajasthan tech. University
B.tech six sem (Main/back)
Year June 2010
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6E3049
B.Tcch. Vlth Semester (Main/Back) Examination, June- 2010 Mechanical Engineering 6MF.1 Design of M/e Elements-11 (Common for Mech., & P.I)
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Time: 3 Hours
Maximum Marks: 80 Min. Passing Marks : 24
Instructions to Candidates:
Attempt any five questions selecting one question from each unit All questions carry equal marks (Schematic diagrams must he shown h'hewer necessary. Any data you feeI missing suitably he assumed and stated clearly Units of quantities med/calculated must be stated clearly.)
Use of following supporting material is permitted during examination (Mentioned in form No. 20S)
I. Design Data Handbook.
Unit -1
). a) Discuss influence of si2c, surface finish and reliability in modifying the Kndurancc limit. (6)
b) A simply supported shaft of C 40 slcei and 1000 mm span carries a ccntral load of 800 kg at the ccntrc of span. The torque varies from 1000 N - m to 2000 N m. Ignoring slrcss concentration, determine diameter of shaft using maximum shear stress theory. Take F. o.S*2. (10)
OR
a) Discuss methods of mitigation of stress concentration. (6)
b) Forarectangularplateofscction70mm* 10mm with a ccntral hole of 5mm, find the value of completely reversed axial toad that can be applied for infinite life and 9S% reliability. The plate is machincd out of Cl 5 steel. Consider the efTect of stress concentration and take notch sensitivity as 0.8 and F.O.S* 2.
(10)
All dimensions arc in mm
6F-3049/W3S0* (I) |C*ntd-
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2. a) Discuss preloading of bolts. Further < |
b) Determine maximum value of stress scuss stresses in bolt due to preloading. (6) n a C-Clamp as shown below. (10) All dimensions are in mm |
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30 kN (Face) |
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OR | |
Draw and describe various thread forms suitable for power screws. (6)
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10-91 *- |
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40 Cross section |
a)
b)
Design a screw jack lo lift 2.5 (onncs by 20 cm. Take C 25 carbon steel for screw, nut and lever. Coefficient of friction for collar and threads is 0.2 Make suitable assumptions wherever needed. (10)
Unit-III
Draw and describe Chordal action in Chain drive. (6)
S.
a)
b)
Determine width of belt and belt length for the following particulars of a flat belt drive: (10)
Centre distance 6000 mm. Power = 100 K W.
Pulley diameters * 420 mm and 1680 mm.
Speed of bigger pulley - 240 rpm Belt thickness " 8 mm of leather Coefficient of friction p=0.3 Material density e*Q92gmlcm'
Allowable stress in belt * 2.0 N/mm.
6E3049 (2)
OR
a) Discuss stresses in a helical spring subjected to axial load. (6)
b) A helical compression spring is made from a wire of 1 mm diameter having yield strength of720N/mnr. It has mean diameter of 12 mm and (here are 14 active coils of spring. Find:
i) Static load corresponding to yield point
ii) Deflection
iii) StifTness
iv) Solid heigh) and
v) free length
Take G * 0.84 * 10s N/mnr Mention end conditions. (10)
Unit - IV
4. a) List out the assumptions made in Lewis equation for gear design. (6)
b) Design a 20' spur gear drive to transmit 10 kW from a shat) running at 1440 r.p.m. to another shaft running at 360 r.p.m. Use C 45 for gear and pinion with suitable FOS. (10)
OR
a) Discuss gear matcrialsandlheir application. (6)
b) A helical pair transmits 20 KW with pinion of 20 teeth and 5 module running at 1200 r.p.m, Pressure angle is 20* and helix angle is 2? Compute
i) The tangent ial fore*
ii) The radial force and
iii) The axial ihnist
Assume suitable positions of gear and pinion and direction of rotation. Accordingly draw a force component diagram. (10)
iE3049 (3) IContd...
Unit - V
5. a) Discuss bearing characteristic number. Wilh bclpofdiagnira discuss different states of hydrodynamic lubrication. (6)
b) Design a journal bearing for supporting a generator shaft of 75 mm dia with a load of 12 KN running at 1440 r.p.m. Suitable data may be picked from design hand book. (10)
OR
a) Discuss the types of antifriction bearings and their application. (5)
b) Draw and discuss pressure distribution diagrams for a hydrodynamic journal bearing. (5)
c) Select a suitable anti friction beanng for a radial load of2000 N with operation at 1200 rp.m. for 2200 hours. Assume the axial load, if any, to be negligible.(6)
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| Earning: Approval pending. |
