RTU 2016 Question Paper Semester VI Mechanical Engineering Design of Machine Elements II

>-q lq
I B*rs

RollNo.
!.{
Total No of Pages:
tr
F{ 6E7OLL
o
f-
B. Tech. VI-Sem. (MainlBack) Exam., ApriUM ay-2016
Mechanical Engineering
E]
\0 6ME1A Design of Machine Elements-Il
Common with AE, ME, pI
Time: 3 Hours
Min. Passing *,.ff?ilHtT::fi ; ::
I nstructions to Candidate s : -

Attempt any live questions, selecting one question .from each unit. All
Questions carry equal marks. schematic diagrams must be shown
wherever necessary. Any data you feel missing may suitably be assumed
and stated clearly.
units of quantities used/ calculated must be stated clearly.
Use of foltowing supporting material is permitted during examination.
(Mentioned inform No. 205)
l. Design Data Book 2. NIL

UNIT-I
Q.1 (a) What is physical significance of notch sensitivity factor being one and zero. t4l
O) What is fluctuating stress? Draw stress - time curve for fluctuating stress.12+2=4)
(c) A bolted assembly is subjected to an external force, that varies from 0 to 10 KN.
The combined stiffness of the parts, held together by the bolt, is three times the
stiffness of the bolt. The bolt is initially so tightened that at 50To overload
condition the parts held together by the bolt are just about to separate. The bolt is
made of plain carbon steel 50 C4. The fatigue stress concentration factor is 2.2

and the expected reliability is 90Vo. The factor of safety is 2. Determine the size

of the bolt with fine threads.
t8l

[687011] Page 1 of 4
[12080]

Q.1 (a) Explain modified Goodman diagram for bending stresses? t6l
(b) What is the difference between failure due to static load and fatigue failure? l2l
(c) A transmission shaft carries a pulley midway between the two bearings. The
bending moment at the pulley varies from 200N - M to 600 N - M, as the tore
zonalmoment in the shaft varies from 70 N - M to 200 N - M. The frequencies
of variation of bending and tore zonal moments are equal to the shaft speed. The
shaft is made of steel FeE 400. The corrected endurance limit of the shaft is 200
N/mm2. Determine the diameter of the shaft using a factor of safety of 2. t8l
UNIT.II
Q) Design a plain carbon steel crank shaft for a 0.40m by 0.60m single acting 4 stroke
single cylinder engine to operate at 2O0 r. p. m. The mean effective pressure is 0.49
MPa, and the maximum combustion pressure is 2.625 Mpa. At maximum tensional
moment, when the crank angle is 36o, the gas pressure. is 0.975 MPa. The ratio of the
. connecting rod length to the crank radius is 4.8. The flywheel is used as a pulley. The
weight of the flywheel is 54.50 KN and the total belt pull is 6.75 KN. Assume suitable
values for the missing data. t16l
OR

Q.2 (a) What are the desirable properties of a piston in I.C. engine? [4]
(b) Determine the thickness of a cost iron cylinder wall and the stresses for a 300mm
petrol engine, with a maximum gas pressure of 3.5 N/mm2 t6l
(c) A vertical4 - stroke C.I. engine has the following specifications :-
Break Power = 4.5 kw, speed = 1200rpm.
Indicated mean effective pressure = 0.35 N/mm2 & ,-l- = 0.80 Determine the
dimensions of the cylinder. t6l

Q.3 (a) It is required to design a helical torsion spring for a window shade. The spring is
made of patented and cold - drawn steel wire of grade - 4. The yield strength of
the material is 607o of the ultimate tensile strength and the factor of safety is 2.
From space considerations, the mean coil diameter is kept as 18mm. The
Maximum bending moment acting on the spring is 250 N - mm. Determine the
wire diameter and the number of active coils.
TakeE =207 x 103N/mm2 & K(stiffness of spring)= 3N-mm/rad. t8l

[6E7011] Page2 of4 [12080]

(b) A helical tension spring is used in the spring balance to rneasure the weights. One
end of the spring is attached to the rigid support while the other end, which is
free, carries the weights to be measured. The maximum weight attached to the
spring balance is 1500 N and the length of the scale should be approximately 100

mm. The spring index can be taken as 6. The spring is made of oil - hardened
and tempered steel wire with ultimate tensile strength of 1360 N/mm2 and
modules of rigidity of 81370 N/mm2. The permissible shear stress in the spring
wire should be taken as 50Vo of the ultimate tensile strength. Design the spring
and calculate : l8l
(i) Wire diaineter
(ii) No. of active coils
(iii) Required spring rate: and
(iv) Actual spring rate.
OR
Q.3 Design an open flat belt drive to connect horizontal shaft at 4.5m centre distance
velocity ratio of deriver / driven pulleys is 2.5. Speed of smaller pulley is 960 rpm.
Nominal power transmission is 20kw under very light shock. t15l

UNIT.IV
Q.4 (a) A pair of worm and worm wheel is designated as 316011016. The worm is
transmitting 5kw power at l44O rpm to the worm wheel. The co - efficient of
function is 0.1 and the normal pressure angle is 20. Determine the components of
the gear tooth force acting on the worm and worm wheel. t10l
(b) Derive the expression for beam strength of a gear tooth. t61

OR
Q.4 (a) Design a pair of equal diameter, 20o stud tooth helical gears to transmit 37.5 kw
with moderate shock at 1200rpm. The two shafts are parallel and 0.45m a pofi.
Each gear is to be of steel. Find the module and face width of the teeth. t10l

l6E70ttl Page 3 of4 [12080]

(b) A C' I' bevel gear has a module
of 2.5mrn and its pitch diameter
is 0.60m. The
rhe teeth are 20o fulr depth.
:ffiI#.il.o*o Derermine rhe permissible

t6l

UNTT.V
Q'5 (a) A single deep - groove ball bearing
is subjected to a radiar force
thrust force of 3KN' The of gKN and a
shaft rotates at tioorpm.
bearing is 20000hr. The The expected rife L166 of the
minimum u.."ptuui" diameter
Select a suitable ball bearing of the shaft is 75mm.
for this application.
(b) Explain the method of lubrication r' tSl
in detail.
t8l
OR
Q'5 (a) A taper roller bearing has a dynamic
has a dynamic load capacity
of 26KN. The
desired life for 90vo of the
bearings is 8000hr and the
speed is 300rpm. calculate
the equivalent radial load
that the bearing can carry.
(b) Forowing data is given for a 360o L4l
hydrodynamic bearing : Radial
road = 10KN,
Journal speed
= 1440 rpm, unit bearing pressure
= 1000kpa, crearance ratio (r/c)
= 800; viscosity of lubricant = 30mpas. Assuming that the total heat
generated in
the bearing is carried by
the total oil flow in the bearing.
Calculate:_
(i) Dimensions of bearing; l6x2=121

(ii) Co - efficient of fricrion;
(iii) Power lost in friction;ss
(iv) Total flow of oil;
(v) Side leakage; and
(vi) Temperature rise.

[687011]
Page 4 of 4
[120801