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EndsemMay 20232019 patternTE Mech

Design of Machine Elements (DME) SPPU Endsem Question Paper May 2023

All 8 questions from this SPPU endsem paper, as printed. Read them here or open the PDF.

Open the PDFMost repeated DME questions
Subject code
302043
Pattern
2019 pattern
Exam
Endsem
Session
May 2023
Max. marks
70
Time
2½ Hours
Semester
I
Paper code
[6003]-422

Printed for: T.E. (Mechanical /Mechanical Sandwich)

Instructions to the candidates

  1. Answer Q.1 or Q.2, Q.3 or Q.4, Q.5 or Q.6, Q.7 or Q.8.
  2. Neat diagrams must be drawn wherever necessary.
  3. Figures to the right side indicate full marks.
  4. Assume suitable data, if necessary.

Questions

  1. Q1

    1. a)

      A C-clamp, as shown in Figure, has trapezoidal threads of 12 mm outside diameter and 2 mm pitch. The coefficient of friction for screw threads is 0.12 and for the collar is 0.25. The mean radius of the collar is 6 mm. If the force exerted by the operator at the end of the handle is 80 N, find: i) The length of handle; ii) The maximum shear stress in the body of the screw and where does this exist; and iii) The bearing pressure on the threads.

      [8]
    2. b)

      Derive expression for torque required to lower the loads in case of square threads.

      Also asked:Nov 2025 ·May 2024

      [5]
    3. c)

      What are the different types of screw threads used for power screw? What are the advantages and limitations of power screw? 2

      [4]

  2. Q2

    1. a)

      A vertical two start square threaded screw of 100 mm mean diameter and 20 mm pitch supports a vertical load of 18 kN. The nut of the screw is fitted in the hub of a gear wheel having 80 teeth which meshes with a pinion of 20 teeth. The mechanical efficiency of the pinion and gear wheel drive is 90 percent. The axial thrust on the screw is taken by a collar bearing 250 mm outside diameter and 100 mm inside diameter. Assuming uniform pressure conditions, find, minimum diameter of pinion shaft and height of nut, when coefficient of friction for the vertical screw and nut is 0.15 and that for the collar bearing is 0.20. The permissible shear stress in the shaft material is 56 MPa and allowable bearing pressure is 1.4 N/mm 2 .

      [8]
    2. b)

      Explain self-locking and over-hauling property of screw. Prove the condition for screw to be self-locking.

      [5]
    3. c)

      Prove that efficiency of self-locking square threads is less than 50%.

      Also asked:May 2024

      [4]

  3. Q3

    1. a)

      This part has equations that don’t show as text. Open the PDF to read it.

      [8]
    2. b)

      What is modifying factor to account for stress concentration? Explain Endurance strength modifying factors?

      [5]
    3. c)

      Explain with neat sketch the Gerber curve, Soderberg and godman lines?

      Also asked:Nov 2025

      [5]

  4. Q4

    1. a)

      A cantilever beam made of steel material with S ut =550 N/mm 2 , S yt =320 N/mm 2 as shown in figure is subjected to load which varies from –F to 3F Take surface finish factor 0.89, Size factor 0.85, Theoretical stress concentration factor 1.42, notch sensitivity 0.9, factor of safety 2. Determine miximum value of load F which the cantilever beam can withstand for infinite life. 3

      [8]
    2. b)

      Explain modified Goodman diagram. Draw neat labeled sketches of modified Goodman diagram for axial & Bending stresses.

      Also asked:May 2024

      [5]
    3. c)

      Explain Fatigue Design under Combined Stresses.

      [5]

  5. Q5

    1. a)

      A bracket, subjected to a force of 5 kN inclined at an angle of 60º with the vertical, is shown in figure. The bracket is fastened by means of four identical bolts to the structure. The bolts are made of plain carbon steel 30C8 (S yt = 400 N/mm 2 ) and the factor of safety is 5 based on maximum shear stress. Assume maximum shear stress theory and determine the size of the bolts.

      [8]
    2. b)

      Write a note on: Bolts of uniform strength.

      Also asked:Nov 2025 ·May 2024

      [5]
    3. c)

      Explain the procedure for the design of bolts for eccentrically loaded bolted joints in shear.

      [5]

  6. Q6

    1. a)

      Figure shows a welded joint subjected to a load of 20 kN. Find size of weld if permissible shear stress 80 MPa. 4

      [10]
    2. b)

      Discuss the procedure for designing Axially Loaded Unsymmetrical Welded Sections.

      [5]
    3. c)

      What are the assumptions made in the design of welded joint?

      [3]

  7. Q7

    1. a)

      A helical spring is made from a wire of 6 mm diameter and has outside diameter of 75 mm. If the permissible shear stress is 350 MPa and modulus of rigidity 84 kN/mm 2 , find the axial load which the spring can carry and the deflection per active turn.

      [8]
    2. b)

      What is mean by spring surge and what is its effect?

      Also asked:May 2024

      [5]
    3. c)

      Explain with the neat sketch, nipping of leaf spring.

      Also asked:Nov 2025 ·May 2024

      [4]

  8. Q8

    1. a)

      Design a helical compression spring with following data; Maximum load=4460 N; Mean coil diameter=85 mm; Maximum shear stress 265 N/mm 2 ; Spring stiffness= 67 kN/m; G=81.5 kN/mm 2 ; std wire diameter: 14.5, 15, 15.5, 16, 16.5, 17 (mm).

      [8]
    2. b)

      Derive the expression for the shear stress induced in a helical compression springs.

      [5]
    3. c)

      Explain A.M.Wahl’s factor and state its importance in the design of helical springs. 

      [4]