GTU B.Tech 2020 Winter Question Papers || Gujarat Technological University
GUJARAT TECHNOLOGICAL UNIVERSITY
BE- SEMESTER-V (NEW) EXAMINATION - WINTER 2020
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Subject Code: 2152508 Date: 03/02/2021
Subject Name: Design of Machine Elements
Time: 10:30 AM TO 12:30 PM Total Marks: 56
Instructions:
- Attempt any FOUR questions out of EIGHT questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
- Use of PSG design data book permitted.
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| MARKS | ||
|---|---|---|
| Q.1 (a) | Explain completely reversed or cyclic stresses. | 03 |
| (b) | Discuss Gerber method for combination of stresses. | 04 |
| (c) | Determine the thickness of a 120 mm wide uniform plate for safe continuous operation if the plate is to be subjected to a tensile load that has a maximum value of 250 kN and a minimum value of 100 kN. The properties of the plate material are as follows: Endurance limit stress = 225 MPa, and Yield point stress = 300 MPa. The factor of safety based on yield point may be taken as 1.5. | 07 |
| Q.2 (a) | Give characteristics of material for friction surfaces. | 03 |
| (b) | Explain positive clutch and friction clutch. | 04 |
| (c) | Discuss design procedure of simple band brake. | 07 |
| Q.3 (a) | Draw stress distribution diagram of thick cylinder subjected to an internal pressure. | 03 |
| (b) | Give classification of pressure vessels. | 04 |
| (c) | A cast iron cylinder of internal diameter 200 mm and thickness 50 mm is subjected to a pressure of 5 N/mm². Calculate the tangential and radial stresses at the inner, middle (radius = 125 mm) and outer surfaces. | 07 |
| Q.4 (a) | Give classification of bevel gear. | 03 |
| (b) | Explain any four terms of worm gear. | 04 |
| (c) | Discuss step by step design procedure of C- clamp. | 07 |
| Q.5 (a) | Explain coefficient of fluctuation of speed. | 03 |
| (b) | Prove that fluctuation of energy in flywheel ?E = m R² ?²Cs. | 04 |
| (c) | The intercepted areas between the output torque curve and the mean resistance line of a turning moment diagram for a multicylinder engine, taken in order from one end are as follows: —35,+410, - 285, + 325, — 335, + 260, — 365, + 285, — 260 mm². The diagram has been drawn to a scale of 1 mm =70 N-m and 1 mm = 4.5°. The engine speed is 900 r.p.m. and the fluctuation in speed is not to exceed 2% of the mean speed. Find the mass and cross-section of the flywheel rim having 650 mm mean diameter. The density of the material of the flywheel may be taken as 7200 kg / m3. The rim is rectangular with the width 2 times the thickness. | 07 |
| Q.6 (a) | Explain terms used in helical gears. | 03 |
| (b) | Give advantages and disadvantages of gear drive. | 04 |
| (c) | A bronze spur pinion rotating at 600 r.p.m. drives a cast iron spur gear at a transmission ratio of 4 : 1. The allowable static stresses for the pinion and gear are 120 MPa and 105 MPa respectively. The pinion has 16 standard 20° full depth in volutes teeth of module 8 mm. The face width of both the gears is 90 mm. Find the power that can be transmitted from the standpoint of strength. | 07 |
| Q.7 (a) | Explain conical and volute springs. | 03 |
| (b) | Discuss surge in springs. | 04 |
| (c) | 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/mm², find the axial load which the spring can carry and the deflection per active turn. | 07 |
| Q.8 (a) | Derive equations for maximum efficiency of a square threaded screw. | 03 |
| (b) | Explain types of screw threads used for power screws. | 04 |
| (c) | Discuss complete design procedure of Screw jack. | 07 |
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