Bangalore University 2008-2nd Sem Diploma Mechanical Engineering I - Strength of material Stdte - Question Paper
Code: C-301
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III Semester Diploma Examination, November 2008 CIVIL ENGINEERING BOARD
Time : 3 Hours ] [ Max. Marks : 100
Notes ; (1) Section - I is compulsory.
(2) Answer any two full questions each from Section - II, III and any one full question each from Section IV & V.
SECTION-I s
1. (a) Fill in the blanks with appropriate word/words . 5x1 = 5
(i) The ratio of shear stress to shear strain within the elastic limit is called
(ii) The unbalanced vertical force to the right or left of the cross section of beam is known as____.
(iii) The unit of moment of inertia is_.
(iv)/ The ratio of hoop stress to longitudinal stress in a thin cylinder
(v) The centre to centre distance between two consecutive rivets in a row is called .
(b) Define the following : 5x1 = 5
(i) Youngs Modulus
(ii) Centre of Gravity
(iii) Thin Cylinder
(iv) Bending Moment
(v) Polar Modulus
2. (a) The ultimate shear stress of a mild steel is 400 N/mm . Determine the dia of hole that can be punched through it without exceeding a compressiye stress of 800 N/mm2 in the punch. The thickness of flat is 12:5 mm.
(b) A bar of steel 1500 mm long. For the first 500 mm, it is 20 mm in .dia. for the next 500 mm it is 10 mm in dia. and for remaining length it is 5 mm m
- dia. It is subjected to a pull which produces the maximum tensile stress of
160 N/mm2. find the change in the length of bar. Take E = 210 kN/mm2.
3. (a) A copper rod 25 mm dia. is enclosed in a steel tube of 30 mm internal dia.
and of thickness 5 mm. The edges are rigidity fixed. The composite bar subjected to an axial pull of 40 kN. Find the stress induced in the rod and tube.
Take : E = 2 x 105 N/mm2
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Ec = 1 x 105 N/mm2
Due to sudden onset of summer, the temperature has increased by 60 C. Take E = 2 x 105 N/mm2. a = 12 x 10~6 /C. The length of rail is 15 m. Find the temperature stress when (i) Nuts are rigidly fixed (ii) Supports yield by 2 mm.
A metal bar 50 mm x 50 mm in Section is subjected to an axial compression of 500 kN. The reduction in length is 0.5 mm over a gauge length of 200 mm and increase in thickness is 0.04 mm. Find the values of elastic constants.
4. (a)
At a point in a strained material the principal stress are 200 N/mm (tensile) and 100 N/mm2 (compressive) on two mutually perpendicular planes. Find the normal stress shear stress, resultant stress across a plane inclined at 60 to the axis of major stress.
SECTION-III
(Answer any two full questions)
Draw the S.F.D. and B.M.D. for a cantilever beam of 5 m long which carries a point load of 2 kN at the free end and a u.d.l. of 1 kN/m for a length of 3 m from the fixed end.
(b) A simply supported beam of 6 m carries a u.d.l. of 4 kN/m for a length of
2 m from left support and point loads of 5 kN, 4 kN, and 3 kN at 3 m, 4 m,
5 m from the left support. Draw B.M.D. and S.F.D. 9
6. J&) Locate the centre of gravity of the T section whose flange is 150 mm x 10 mm
and web is 200 mm x 8 mm. - . - " .-I- 6
(b) Find the M.I. of a channel section 100fmm x 50 mm x 10 mm about the
centroidal axis parallel to flange. 9
7. (a) The M.I. of a beam section 50 mm deep is 69.49 x 107 mm4. Find the
longest span over which beam of this section. When simply supported could carry a u.d.l. of 50 kN/m run. The bending stress in the material is not to exceed 110N/mm2. , 6
(b) Design a suitable diameter for a circular shaft required to transmit 100 kW at 180 r.p.m. The shear stress of the shaft not to exceed 70 N/mm2 and the maximum torque exceeds the mean torque by 40%. The shaft is not to twist more than 1 in a length of 3 m. Take C = 80 kN/vh.n2. 9
SECTION - IV
(Answer any one full Question)
(a) Design a double rivetted double cover butt joint to connect two plates
15 mm thick with 23 mm dia. rivets. . ' ' 9
Take ft = 120 N/mm2 f = 95 N/mm2
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fK= 190 N/mm2 b
(b) A 100 mm x 12 mm plate is connected to another plate by fillet welds around the end of bar and also inside a machined slot as shown in Fig. 1. Determine the size of the weld if the joint is subjected to a pull of 140 kN.
Take working stresses for transverse weld and longitudinal weld as 100 N/mm2 and 80 N/mm2 respectively. 9
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All dimension -re in mm |
9. (a) A boiler shell of 2 m dia. is made up of mild steel plates of 20 mm thick.
The efficiency of longitudinal and circumferential joints are 70% and 60% respectively. Determine the safe pressure in the boiler if the permissible tensile stress in the plate section through the rivets is 100 N/mm2, also determine the circumferential stress in the solid plate section and longitudinal stress through the rivets.
(b) A pipe of 400 mm internal dia. and 100 mm thickness contains a fluid at a pressure of 8 N/inm . Find the maximum and minimum hoop stresses across the section.
SECTION - V ; .
(Answer any one question)
A set of concurrent forces acting at O as shown in Fig. 2. Find the forces P and
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Q to keep the point O in equilibrium. 30 kN 25 kN |
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Fig. 2 11. Four forces act on a rigid bar as shown in Fig. 3. Find the value and position of resultant of these forces graphically. 12 |
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Fig. 3 |
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Attachment: |
| Earning: Approval pending. |
