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 April/May 2008 CIVIL ENGINEERING BOARD STRENGTKLOF MATERIALS
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[ Max. Marks : 100
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Time : 3 Hours ] 2, o
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Instructions: (1) Section - I is compulsory.
(2) Answer any two full questions each from Section II, III and IV.
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SECTION -1
Fill in the blanks with appropriate word/words : 1x5 = 5
i:
(i) The maximum strain energy per unit volume is known as_.
(ii) Inverse of Poissons ratio is always_than one. .
(iii) Bending stress is zero at_.
(iv) The line of intersection of the neutral layer with any normal section of the beam is called the of that section.
stress in the shaft.
(v) Torsion induces
/\b)J Explain the stress-strain diagram for a M.S. material, subjected to a gradually applied tensile load. 5
SECTION - II
(a) A load of 2500 N is to be lifted by a steel wire. Determine the diameter of the wire so that the stress may not exceed 100 N/mm2. Also determine the elongation over a length of 5 m. Take E = 2 x 105 N/mm2. 7
(b) A square bar of steel of hollow cross section has internal dimension
20 mm x 20 mm and of uniform thickness 5 mm is subjected to a tensile load of 50 kN. If the length of the bar is 1 m long and modulus of elasticity of steel is
2 x 105 N/mm2. , 8
Calculate :
(iii) Elongation
(ii) Strain
(i) Stress
A steel rod is 20 m long at 20 C. Find the expansion of the rod when the temperature is raised to 70 C. Find the temperature stress in the rod 6
When the rod is permitted to expand 6 mm
3- (a)
Take as = 12 x lO6 /C
Es = 200 kN/mm2
A bar is 20 mm in diameter and 1 m. long. Calculate the modulus of rigidity and bulk modulus if modulus of elasticity of the material is 1 x 105 N/mm2. Also find the change in volume when the bar is subjected to an intensity of pressure of 100 N/mm2. Longitudinal strain is 4 times the lateral strain. 9
(b)
*
At a point in a strained material the principal stresses are 120 MPa (tensile) and 80 MPa (compressive). Determine the normal stress, shear stress and resultant stress on a plane inclined at 45 to the axis of major principal stress. Also determine the maximum shear stress at the point. 7
>(a)
(b)
5/00
(b)
An axial pull of 40000 N is suddenly applied to a steel rod 2 m long 1000 mm2 in cross section. Calculate the strain energy stored. Take E is 2 x 105 N/mm2, 8
An I section consists of top flange 50 mm x 20 - mm, bottom flange 100 mm x 15 mm and web 10 mm x 240 mm. Find the M.I. of the section about their centroidal axes. v . 10
What are the assumptions made in the theory of simple bending ? 5
A simply supported beam of gm span carries point loads of 10 kN and 20 kN at
2 m & 5 m respectively from the left'support. In addition it also carries a u.d.l. of 10 kN/m for 3 m starting from the right support. Draw SFD & BMD. 10
A rectangular beam 300 mm deep is simply supported over a span of 4 m. What uniformly distributed load per metre the beam may carry if.the bending stress is notto exceed 120 N/mm2 ? . 5
Take 1 = 8 x 106 mm4
7. (a) A cantilever beam of span 5 m carries point loads of 3 kN at its free end and
6 kN at 1 m from free end. Draw BMD & SFD. . 7
A timber cantilever beam 200 mm wide & 300 mm deep 3 m long is loaded s with a u.d.l. of 3000 N/m over the entire span. What concentrated load is to be placed at the free end of the cantilever of the stress is not to exceed 7.2 N/mm2. 8
SECTION-IV -
State the assumptions made in the theory of pure Torsion. " -
(a)
(b)
8.
Design a suitable dia. for a circular shaft required to transmit 90 kN at 180 rpm. The_shear stress in the shaft is limited to 70 N/mm2 and max. torque exceed the mean by 40%. Also calculate the angleof twist in a length of 2 m. Take C = 0.9 x 105 N/mm2. ~ 10
5
9.
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10
Define welded joint and write three advantages. _
A single riveted double cover butt joint in a structure it is used for connecting two plates 12 mm thick. The diameter of the rivets is 24 mm. The permissible stresses are 120 N/mm2 in tension, 100 N/mm2 in single shear, 200 N/mm2 in double shear and in bearing. Calculate the necessary pitch and efficiency of the joint.
10. Six strings are tied at a point are pulled in directions equally spaces from one
Kjy another as shown in fig. Find the magnitude of the pulls Pj & P2 so that th'ey are in equilibrium.
5
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10 kN |  |
30 kN |
60 kN 50 kN
Find the reactions of supports of the beam as shown in Fig.
. 2 kN/M
20kN 10kN
5 kN
12 kN
<r- 2 2 -H- 2 ->K- 2
1M
10
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