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GUJARAT TECHNOLOGICAL UNIVERSITY
Diploma Engineering - SEMESTER–V • Examination – WINTER • 2014
Subject Code: 3351902 Date: 28-11-2014
Subject Name: Design of Machine Elements
Time: 10:30 am - 01:00 pm Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
4. English version is considered to be Authentic.
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Q.1 Answer any seven out of ten. 14
1. Distinguish between Contact stress & Bearing Stress.
2. List applications of Cotter Joint.
3. Sketch Single Riveted Lap Joint.(Two Views)
4. State at least four uses of Pressure Vessels.
5. Give names of different types of Antifriction Bearings.
6. Write the equation by which angle of twist for a shaft is calculated.
7. Define Bearing Life.
8. State the assumptions made in the design of thick cylinder.
9. Name four possible cases in which bolts are carrying eccentric loading.
10. State functions of Leaf Spring.
Q.2 (a) Define (1) Plasticity (2) Toughness & (3) Hardenability 03
OR
(a) Explain the following designation of materials. (1) 40 C 8 (2) 49 Cr 1 Mo 28 (3) T 50 03
(b) A 20 mm side equilateral triangle hole is to be punched in 8 mm thick plate. Calculate the capacity of punch, if shear stress of plate is 100 N/mm2. 03
OR
(b) An eye bolt has to lift 30 KN load. If permissible tensile stress is 60 N/mm2, find bolt size. 03
(c) Standardize six speeds between 200 RPM and 1000 RPM. 04
OR
(c) Write R10/3 series for numbers between 10 and 100. 04
(d) Two rods are connected by a Knuckle Joint to sustain a maximum load of 50 KN. Calculate diameter of the rod and knuckle pin diameter using following stresses. f t = 80 N/mm2and f s = 50 N/mm2. 04
OR
(d) Write the area resisting for each failure with the help of sketch for Spigot End of Cotter Joint. 04
Q.3 (a) A double riveted double cover Butt Joint is used to connect two plates of 10 mm thick using 18 mm diameter rivets. If permissible stresses are 80 N/mm2in tension for plates, 65 N/mm2in shear and 130 N/mm2i n crushing for rivets, find pitch. What is the efficiency of the joint?06
OR
(a) The compressive load on the nut and screw clamp is 70 KN. Calculate the diameter of the screw and height of nut. Neglect buckling. Assume single start square threads of 2 threads/cm. Take for screw fc = 100 N/mm2and bearing pressure f bearing = 20 N/mm2 06
(b) Draw neat sketch of a Semi Elliptical Leaf Spring. Label its various parts. 03
OR
(b) State the modulus of section with neat sketch for the following cross sections.
(a) Hollow Rectangular Cross Section (b)Elliptical Cross Section (c.) Hollow Circular Cross Section 03
(c) Design a fulcrum pin of a right angled bell crank lever to raise a vertical load of6 KN at longer arm. The arm lengths are 600 mm & 200 mm. The stresses are f t = 100 N/mm2, f bearing = 15 N/mm2& fs = 50 N/mm2 Neglect bending. (Assume l/d = 1.25) 05
OR
(c) Determine bending stress induced in a semi elliptical leaf spring from following data.
(i) Central Load = 10 KN
(ii)Effective span = 1000 mm
(iii) Width of leaves = 50 mm
(iv) Thickness of leaves = 5 mm
(v) Total Numbers of leaves = 10 ( including 2 extra full length leaves)Also find deflection of spring if E = 2 X 105MPa 05
Q.4 (a) Explain with the help of neat sketch the difference between solid length & free length for a compression spring. 03
OR
(a) State at least three requisites for a good coupling. 03
(b) A hollow shaft 200 mm inside diameter and 300 mm outside diameter transmits 2500 KW at 200 RPM. Calculate the stress induced in shaft. 04
OR
(b) For Closed coil helical spring, find spring wire diameter & no. of active turns of coil from following data.
(i) Load Range = 2.25 KN to 2.75 KN
(ii) Spring Deflection for above load range = 6 mm
(iii) Spring Index = 5
(iv) Shear Stress for spring = 420 N/mm2
(v) Modulus of Rigidity, G = 84 KN/mm2 04
(c) A simple flange coupling has to transmit 50 KW at 250 RPM. . Assume torque to be 20 % more than the full load. Calculate (a) Shaft diameter (b) Key Dimensions and (c) number & size of Bolts. The stresses are as under,For Shaft & Key fc = 100 N/mm2, f s = 50 N/mm2& f\t = 75 N/mm2For Bolt fs = 40 N/mm2 07
Q.5 (a) The vertical load on a “C” clamp is 30 KN. The distance between load line and neutral axis is 200 mm. The frame is made up of Cast iron having rectangular cross section. The height of cross section is twice the width. For “C” clamp, the maximum safe stress is 100 N/mm2. Find the dimensions of rectangular cross section.06
(b) Calculate the thickness of cylinder from the following data using Lame’s theory.
(1) Hoop stress = 80 N/mm2
(2) The Internal dia. Of cylinder = 250 mm
(3) The maximum pressure of the fluid inside the cylinder is 40 N/mm2 04
(c) Differentiate between Journal Bearing and Antifriction Bearing only for load, speed, noise & maintenance 04
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