Anna
University,Chennai Nov/Dec 2012 Examinations

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Important Questions

ME2303– DESIGN
OF MACHINE ELEMENTS

UNIT
I-V

1.
Explain with mathematical expressions. Maximum
principal stress theory and Von-Mises-Henky theory

2.
A transmission of shaft made C45 steel subjected
to a fluctuating torque varying from -100N-m to +500N-m.Also a fluctuating
bending moment acts on the shaft which varies from +500N-m to -500Nm. Let the
stress concentration factor be 2. The shaft is machined for a factor of safety
1.5.Determine the required diameter of the shaft

3.
A circular bar is simply supported with a span of
0.5mand is subjected to a concentrated cyclic load at its midspan. The load
varies from a minimum value of20KN to maximum value of 45 KN. The load 3
direction is transverse to the shaft axis. Decide upon the diameter of the bar
taking a factor of safety of 1.5 and factor of 0.85 and 0.89 respectively for
size effect and surface finish. Take often following values for material
properties. Ultimate strength = 650N/mm2, Yield strength = 450N/mm2 Endurance
strength =350N/mm2

4.
A steel member is subjected to a 3-D stress
system and resulting principal stress are 120N/mm2 tension, 80N/mm2and 40N/mm2
co.mpression. If the proportional limit of the material in simple tension is
280N/mm2 and its poison's ratio is O.3.Determine the factor of safety according
to (a) Maximum principal stress theory (b) Maximum principal strain theory (c) Maximum
shear stress theory.

5.
An electric generator rotates at 200rpm and
receives 300KW from the driving engine. The armature of the generator is 60cm
long and located between bearing 120cm center to center. Owing to the combined
weight of armature and magnetic pull, the shaft is subjected to 9000kg acting
at right angles to the shaft. The ultimate stress for the shaft is 4480kg/cm2
and shear stress is 3920kg/cm2.Find the diameter of the shaft for a factor of
safety of 6

6.
Design a cast iron protective type flange
coupling to transmit 15KW at 900rpm from an electric motor to a compressor. The
service factor may be assumed as 1.35. The following permissible stress may be
used: Shear stress for the shaft, bolt and key material=40MPa Crushing stress
for bolt and key=80Mpa Shear stress for cast iron=8Mpa

7.
Design and sketch protective type C.I flange
coupling to transmit 10KW at 250rpm. The permissible shear stress for key,
shaft, and bolt as 50N/mm2.Take crushing stress of key as 90N/mm2 and shear
stress for C.I as 14N/mm2.Assume maximum torque is 30% higher than mean torque.

8.
A line shaft rotating at 200rpm is to transmit
20KW power. the allowable shear stress for the shaft material is 42N/mm2.If the
shaft carries a central load of 900N and is simply supported between bearing
3meters apart determine the diameter of the shaft. The maximum tensile or
compressive stress is not to exceed 56N/mm2

9.
A steam of effective diameter 300mm is subjected
to a steam pressure of 1.5N/mm2.The cylinder head is connected by 8 bolts
having yield point 330MPa and endurance limit at 240MPa.The bolts are tightened
with an initial per load 1.5 times the steam load. A soft copper gasket is used
to make the joint leak proof. Assuming a factor of safety 2, find engine size
of bolt required. The stiffness factor for copper gasket may be taken as 0.5.

10.A plate 75mm wide and 10mm thick is jointed with another plate by a single
transverse weld and double parallel fillet as shown in fig. The joint is subjected
to a maximum tensile force of 55KN. The permissible tensile and shear stress
are 70MPa and 50MPa respectively. Find the length of each parallel fillet weld

11.
A plate 100m wide and 12.5mm thick is to be
welded to another plate by means of two parallel fillet welds. The plates are
subjected to a load of 50KN.Find the length of the weld so that the maximum
stress does not exceed 56N/mm2. (Do the calculations under static loading).

12. A gas engine valve spring is to have a mean diameter 37.5mm.The maximum
load will have to sustain is 450N with a corresponding deflection of 12.5mm.The
spring is to be subjected to repeated loading and fatigue must be considered a
low working stress of 300N/mm2 will be used. Find the sizefor the wire and
number of coil used. Take rigidity of modulus as 0.8XI05 N/mm2

13.
A closely coil helical spring is made of 10mm
diameter steel wire, the coil consisting of 10 complete turns with a mean
diameter of 120mm.The springs carries an axial pull of 200N.Determine also
deflection in the spring, its stiffness and strain energy stored by it if the
modulus of rigidity of the material is 80KN/mm2

14.A semi-elliptical leaf spring of 1m long and is required to resist a
load of 50KN.The spring has 15 leaves of which three are full length leaves.
The width of central band is 100mm. All the leaves are to be stressed to 420MPa.The
ratio of total depth to width is 3.Take, =2.1Xl05MPa.Determine, (i) The
thickness and width of the leaves. (ii)The initial gap that should be provided
between the full lengths and graduated leaves before assembly. (iii)The load
exerted on the band for the assembly

15.
Design of leaf spring for a truck to the
following specifications: Maximum load on the spring = 140KN No of spring = 4
Material for spring chromium vanadium steel Permissible tensile stress =
600N/mm2 Maximum number of leaves =10 Span of spring = 1000mm Permissible
deflection = 80mm Young's modulus of the spring = 200N/mm2

16.Design a journal bearing for a centrifugal pump from the following
data: Load on the journal=20000N, Speed of the journal=900rpm, Type of oil is SAElO,
for which the absolute viscosity at 55°C=0.017kg/m-s, Ambient temperature of
oil = 15.50C, Maximum bearing pressure for the pump=1.5N/mm2.Calculate also
mass of the lubricating oil required for artificial cooling, If the rise of
temperature, if the rise of temperature of oil be limited to lOoC heat
dissipation coefficient=1232W/m2/oC

17.
A 150mm diameter shaft supporting a load of 10KN
has a speed of 1500rpm.The shaft run in whose bearing length is 1.5 times the
shaft diameter. If the diametric clearance of bearing is 0.15mm and the
absolute viscosity of the oil at the operating temperature is 0.011 Kg/m-s.
Find the power wasted in friction

18.A full journal bearing of 50mm diameter and 100mm long has a bearing pressure
of l.4N/mm2• The speed of the journal is 900rpm and the ratio of journal
diameter to the diametric clearance is 1000. The bearing is lubricated with
oil, whose absolute viscosity at the operating temperature of 75°C may be taken
as 0.011 kg/m-s. The room temperature is 350C.Find, (1) The amount of
artificial cooling required. (2)The mass of lubricating oil required, if the
difference between the outlet and inlet temperature of the oil is 10°C. Take
specific heat of oil as 1850J/Kg/0C.

19.The turning moment diagram of a multi-cylinder engine is drawn with a scale
of (1 mm = 1°) on the abscissa and (1 mm = 250 Nm)on the ordinate. The
intercepted between the torque developed by the engine and the mean resisting
torque of the machine, taken in order from one are -350,+800,- 600,+900,
11-550,+450,-650 mm2.The engine is running at a mean speed fluctuations is
limited to 0.02.A rimmed flywheel made of grey cast iron FG 200
(Density=7100Kg/m3) is provided. The spokes, shaft and hub are assumed to
contribute 10% of the required moment of inertia. The rim has rectangular cross
section and the ratio of width to thickness is 1.5.Determine the dimensions of
the rim.

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