B.Tech V(Fifth) Semester Examination 2013-14

Course Code: EME504 Paper ID: 0965219

Design of Machine Elements

Time: 3 Hours Max. Marks: 70 Max Marks: 75

Note: i) Attempt six questions in all. Q. No. 1 is compulsory.

ii) Design hand book is allowed.

1. Answer any five of the following (limit your answer to 50 words). (4x5=20)

a) Preferred numbers

b) Fluctuating stresses

c) Welded joints

d) Square threads

e) Need analysis

f) Pressure angle

g) Goodman criteria

h) ASTM for rubbers

2. What is the role of standards in design? Describe the BIS system of designation of steels and plastic. (10)

3. a) Describe the failure of ductile materials. (4)

b) A machine component is subjected to fluctuating stress that varies from 40.0 to 100.0 N/mm2. The corrected endurance limit stress for the machine component is 270.0 N/mm2. The ultimate tensile strength and yield strength of the material are 600.0 N/mm2 and 450.0 N/mm2 respectively. Find the factor of safety under static condition and dynamic condition using (i) Gerber’s theory (ii) Soderberg line. (6)

4. a) Compare the riveted and screwed joints. (4)

b) A rigid coupling is used to transmit 25 kW power at 700 r.p.m. There are four bolts and the pitch circle diameter of the bolts is 125 mm. The bolts are made of steel having yield strength 350 N/mm2 and factor of safety is 3. Determine the diameter of bolts. (6)

5. a) Describe the nomenclature of gear with the help of diagram. (4)

b) Compare the involute and cycloidal gear tooth profiles. (6)

6. A helical compression spring is used to absorb the shock. The initial compression of the spring is 30 mm and it is further compressed by 50 mm while absorbing the shock. The spring absorbs 250 J of energy during the process. The spring index can be taken as 6. The properties of spring material are as: ultimate tensile strength=1500 N/mm2, modulus of elasticity=9.0 kN/mm2. Design the spring. (10)

7. a) Design the rectangular key for a shaft of 50.0 mm diameter. The shearing and crushing stresses for the key material are 42.0 MPa and 70.0 MPa. Width of key 16.0 mm and thickness of 10.0 mm may be considered. (4)

b) A hollow shaft has greater strength and stiffness than solid shaft of equal weight. Explain. (6)

8. a) Discuss the product developments by evolution and technology. (4)

b) Draw the block diagram of design process and explain it. (6)