Karnatak University 2007 Diploma Mechanical Engineering Strength of material Annual - Question Paper
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Third Semester Diploma (Annual) Examination, 2007 CIVIL ENGINEERING BOARD
Time : 3 Hours ]
Note: (1) Section-I is compulsory.
[ Max. Marks : 100
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(2) Answer any two full questions each from Section-II and Section-Ill and any one full question each from Section-IV and Section -V.
SECTION - I
(a) Fill in the blanks with appropriate word /words.
5x1 = 5
(i) The ratio of shear stress to shear strain is known as
(ii) The point through which the whole weight of the body acts is known as_.
(iii) A beam fixed at one end and free at the other end is known as __beam.
(iv) At the neutral axis the value of compressive stress and tensile stress is _, ,
(v) Due to the torque every cross section of the shaft is subjected to some_stress.
(b) What are the assumptions made in the theory of simple bending.
SECTION - II
(a)
A steel rod 500mm long 20mm dia is subjected to an axial tensile load of 50 kN. Detennine (1) Stress (2) Strain (3) Elongation (4) Lateral strain. (5) Change in diameter. Es
2 x 105 N/mm2; l/m=0.25.
A bar 300mm is made of two portions. The top having a dia of 50mm. It is subjected to a tensile load of 152 kN. Find the diameter of the bottom portion if the stress there should not exceed 140 N/mm2 Find also the length of the bottom portion if the total elongation of the bar is 0.16mm. E ~2 x 10" N/mm2.
(b)
(a) A bar 30 mm dia is subjected to a pull of 60 kN. The measured extension on a gauge length of 200 mm is 0.09mm and the change in dia is 0.0039 mm. Calculate the poisons ratio 'and the values of three moduili. 8
(b) Steel rod 20 mm dia and 6 m long is connected to two grips at each end at a temperature of 120. Find the pull exerted when the temperature falls to 40 C. (i) if the ends do not yield (ii) if the ends yield by 1.1 mm. E 2 xlO N/mm2. oc=12 x 10_6 /C. \. 7
(a) An axial pull of 50 kN is suddenly applied to a steel rod of 2m long 40 mm dia. Calculate the stress produced & strain energy that can be stored if
E = 200 kN/miri2 _ i: s ; - 4
(b) A steel punch can be worked to a compressive stress of 800 kN/mm2 Find the least diameter of the hole which can be punched through a steel plate of 10 mm thick if its ultimate shear strength is 350 kN/mm2 4
(e) ' At a point in a strained material the principal stresses are 100 N/mm2 (tensile) and 60 N/mm2 (compressive). Calculate the normal stress, tangential stress and resultant stress on a plane inclined at 30 with the axis of minor principal stress. 7
(a) The moment of inertia of a rectangular section about x-x and y-y axis passing through centre of gravity are 27 xlO7 and 432 x 105 mm4. Find the size of the section. 7
(b) A simply supported beam 6m span is carrying a udl of 20 kN/m over a length of 3m from the right support. Draw S.F.D and B.M.D. Also calculate' the maximum BM. 8
(a) A 10 m long beam having a span of 8 m is overhanging on the right side by 2m.
A point load of 200 N is acting at 2 m and another point load of 200N at 6 m from the left end. In addition another point load of 200 N is acting at the free end of overhang. Draw B.M. & S.F. Also find the point of centraflexure. Indicate the values of max. B.M. & S. F. c 10
ib) Locate tliL centre of gravity of an equal angle section 100mm x 100mm x 10mm. 5
(a) Kind the dimensions of timber foist. Span 6m to carry a brick wall 225mm.
3 m high. The weight of the brick is 20 kN/mJ and the maximum permissible stress is limited to 8 N/ m2, The depth of the foist is to be twice its width.
(b) A shaft has to transmit 105 kN at 160 rpm. If the shear stress is not to exceed 65 N/mm2 and the twist is a length of 7.35'm must not exceed 1. Find the suitable dia. C = 8 xlO4 N/mm2
8. (a) Two plates 10mm thickness are to be connected in a double riveted butt joint 20 mm rivet at a pitch of 75mm of the ultimate tensile, shearing and bearing stress are 460 N/mm2 320 N/mm2 and 640 N/mm2 respectively. Find the pull per pitch length the joint will fail. Find also the efficiency of the joint.
* (b) A welded joint is provided to conncci two tie bars 150 mm xlO mm as shown in
-. . *) the figure. The working stress iir the bar is 150 N/mm Size of the fiUet weld is
8 mm. Safe stress for the weld is 102.5 N/mm2 Investigate the design.
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(c) Discuss the failure of riveted joints.
9. (a) A thick metallic cylindrical shell of 150 mm internal dia is required to withstand an internal pressure of 8N/mm . Find the necessaiy thickness of the shell if the permissible tensile stress is 20 N/mm2. 7
(b) A vertical thin walled stand pipe is 4.8 m in dia and stands 30 m high. If the allowable working stress in tension is 120 N/mm . What is the required wall thickness of the pipe ? Assume that the pipe is filled with water of specific weight 10 kN/m3. 7
(c) Differentiate between circumferential stress and longitudinal stress. 4
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!0 (a) Find graphically the resultant of the coplanar concurrent foixe system shown in the figure. What is the value of the resultant ? 12 |
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Simply supported beam of span 6 m has udl of 10 kN/m run over 2 m from the left support. In addition there are two point loads of 20 kN each at 2m and 3.5 m from the right support. Determine graphically the support reactions. 12
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| Earning: Approval pending. |
