Machine Design 1 - May 2012

Mechanical Engineering (Semester 6)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks. 1 (a) Discuss on Aesthetic and Ergonomic considerations in Machine Design.(5 marks) 1 (b) What do you understand by Stress Concentration? Elaborate with various cases.(5 marks) 1 (c) Explain effect of key way on shaft strength. Give equation for "Shaft Strength Factor". (5 marks) 1 (d) Find the size of fillet weld(h) for cantilever circular bar of 50mm diameter (to be welded to plate) subjected to bending moment of 400kN/mm. Take allowable stress for weld material as 60N/mm². (5 marks) 2 (a) Define "Factor of Safety". On which factors its selection depends? Suggest various values for different types of loads and materials.(6 marks) 2 (b) Design cotter joint to transmit load of 40kN which varies from tension to compression. Select suitable Alloy steel and Factor of Safety. Draw sketches of areas involved in various failures.(14 marks) 3 (a) Design flange coupling (Protected type) to transmit 60kW at 1440rpm. Select suitable materials and appropriate Factor of safety with justification.(14 marks) 3 (b) Discuss on various "Fatigue Cycles" and factors affecting "Endurance limit".(6 marks) 4 (a) Explain Chordal Effect of Chain.(4 marks) 4 (b) A circular cross-section bar is subjected to tensile forces varying from 150kN to 450kN. It is to be manufactured by Carbon Steel C35. Determine the size of bar as per Soderberg's equation with n=1.75.(6 marks) 4 (c) Compare the weight, strength and stiffness of a hollow shaft of the same external diameter as that of solid shaft. The inside diameter of hollow shaft being half the external diameter. Both the shafts have same material and length.(10 marks) 5 (a) What do you understand by "Nipping" with reference to leaf springs?(4 marks) 5 (b) Screw press is subjected to load of 80kN. Height of the screw is 500mm, Frame overhang is 400mm. Design:
i) Screw and Nut
ii) Horizontal section of the Frame(16 marks) 6 (a) A helical compression spring is subjected to varying load, maximum up to 1.2kN. Design spring with static approach (Average Service), for a deflection of 40mm. Take ultimate tensile stress for spring material as 1600N/mm². Decide appropriate allowable shear stress (?).(14 marks) 6 (b) Vee belt drive has to transmit 15kW at 1440rpm with velocity ratio of 2.2. Decide optimum centre distance. Use 'C' size belt. Find number of belts required as per 'rating method'.(6 marks) 7 (a) Design flat belt drive to transmit 20kW at 960rpm for centre distance of 2.5m and velocity ratio of 2. Permissible tensile stress for belt material is 2.4MPa. Design both the shafts considering overhang pulleys. Decide all dimensions of C.I. pulleys.(15 marks) 7 (b) Write on Mechanical Properties of Metals.(5 marks)