Engineering Design Question Paper
Engineering Design
Course:Bachelor Of Science In Engineering
Institution: Kenyatta University question papers
Exam Year:2009
KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2009/2010
FIRST SEMESTER EXAMINATION FOR THE DEGREE OF BACHELOR OF
SCIENCE
SET 408: ENGINEERING DESIGN
DATE: Wednesday 30th December, 2009 TIME: 11.00 a.m. – 1.00 p.m.
INSTRUCTIONS
Attempt any THREE questions.
Question 1
(a)
(i)
Discuss three factors which govern the selection of a material for a
machine
component.
[6
marks]
(ii)
Describe the four steps followed in the weighted point method for material
selection.
[2 marks]
(iii)
State the limitation of the ‘weighted point method’.
[2½ marks]
(b)
(i)
State three advantages and two disadvantages of cast iron as an
engineering material from design stand point.
[2½ marks]
(ii)
Why are the properties of cast iron section sensitive?
[1 mark]
(c)
(i)
What
are
alloy
steels?
[½
mark]
(ii)
What are the effects of the following alloying elements in steel Nickel,
manganese,
silicon)
[1½
mark]
(d)
(i)
Name two ways through which case hardening can be achieved.
(ii)
Why is it sometimes necessary to case-harden steel?
Page 1 of 8
Question 2
(a)
(i)
Distinguish the ultimate Tensile strength from yield point of a material.
[1 mark]
(ii)
Define the terms:
-
Safety factor
[1 mark
-
The stress concentration factor Kt.
[1
mark]
(b)
A flat plate subjected to a tensile force 6.2 KN is shown at Fig.1. The plate
material is grey cast iron FG200 and the factor of safety is 2.65.
Calculate
the
thickness
of
the
plate.
[7
marks]
(c)
A non-rotating shaft supports a load of 2.5KN (see fig. 2). The material is brittle
with an ultimate tensile strength of 300N/mm2.
Calculate the safety factor and d = 41.55mm. Assume the Kf for the fillet = 1.61.
[7 marks]
(d)
Name three regions on a machine component where fatigue failure is likely to
occur.
[3 marks]
Question 3
(a)
(i)
Define
design
synthesis.
[1
mark]
(ii)
Compare design synthesis with design analysis.
[1 mark]
(iii)
What is the importance of aesthetic consideration in machine design?
[2 marks]
(b)
(i)
Define
standardization. [1
mark]
(ii)
What are international, national and company standards? [3 marks]
(iii)
Name three advantages of standards in machine design?
[3 marks]
(c)
(i)
Explain the meaning of the term “Breakeven Point”.
(ii)
An automatic screw machine can manufacture 50 machine components
per hour. A hand screw machine can produce 20 machine components per
hour. The set up time for the automatic machine is 3 hours, and labour
cost for either machine is ksh 2000/- per hour. If the required production
is greater than 100 components, which machine is economically advisable
to use.
[5 marks]
Page 2 of 8
Question 4
(a)
Name three modes of fabrication in mechanical engineering practice.
[3 marks]
(b)
Two circular plates with (2d) and (d) as outer and inner diameters respectively are
clamped together by means of a bolt (see fig 3). The bolt is made of plain carbon
steel 45C8 with sy = 380N/mm2 and E = 207000N/mm2. The plates are made of
aluminium with E = 71000N/mm2. The initial pre-load in the bolt is 5KN and the
extend force acting on the bolted joint is 10KN.
Calculate the diameter of the bolt, if the factor of safety is 2.5.
[8 marks]
(c)
(i)
Sketch 5 types of welded joints.
[2½ marks]
(ii)
A welded construction is shown at fig. 4 is subjected to an eccentric force
8.0KN
Determine the size of welds if the permissible shear stress for the weld is
120 N/mm2. Assume static loading conditions.
[6½ marks]
Question 5
(a)
Specify using “BIS System of Designation of Steels’ the alloys suitable for
making:-
(i)
high
strength
gear
[1
mark]
(ii)
Transmission
shaft
and
axle
[1
mark]
(iii)
leaf
and
coil
springs
[1
mark]
(iv)
Welded
parts
spindle
and
shaft [1
mark]
(b)
A line shaft supporting two pulleys A and B is shown in fig (5). Power is
supplied to the shaft by a vertical belt on pulley A, which is then transmitted to
pulley B carrying a horizontal belt.
The ratio of belt tension on tight and slack sides are 3: 1 and maximum tension in
either but is limited to 2.7KN. The shaft is made of plain carbon steel 40C8
(suts=650Mmm2 and sYP = 380Mmm2) the pulleys and keyed to the shaft.
Determine the shaft diameter if Kt = 1.5 Kf = 1.0
[15 marks]
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