Design of Machine Elements 2 - Jun 2014
Mechanical Engg. (Semester 6)
TOTAL MARKS: 100
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks. 1 (a) Determine the maximum tensile stress and maximum shear stress of the component shownin'Fig Q1(a) and indicate the location (10 marks) 1 (b) 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 and outer surface(10 marks) 2 (a) A compressor is driven by a motor of 2.5 kw, running at 1200 RPM to a 400 RPM compressor. Select.a suitable V-belt.(10 marks) 2 (b) Explain Hoisting tackle mechanism to raise and lowering load for a rope(10 marks) 3 (a) Derive an expression for the stres induced in a helical spring with usual notations.(10 marks) 3 (b) Design a leaf spring for the following specification for a truck total load=120 KN, number of springs= 4, material for the spring is chrome-vanadium steel permissible stress in 0.55 GPa. Span of spring=1100 mm, width of central band= 100 mm.and allowable deflection =80 mm, number of fulI length leaves are 2 and, graduated leaves 6(10 marks) 4 (a) Design a pair of spur gear to transmit a power of 18 kW from a shaft running at 1000 RPM toa parallel shaft to be run at 250 rprn maintaining a distance of 160 mm between the shaft centres. Suggest suitable surface hardness for the gear pair.(20 marks) 5 A pair of bevel gear wheels with 20° pressure angle consists of 20 teeth pinion meshing with 30 teeth gear is 400 BHN. The pinion rotates at 500 RPM and recives power from an electric motor. The starting torque of the motor is 150 percent of the rated torque. Determine the safe power that can be transmitted considering the dynamics load wear strength and endurance strength. The allowable bending stress may be taken as 240 Mpa.(20 marks) 6 (a) A plate clutch with a maximum diameter of 600 mm has maximum lining pressure of 0.35 MPa. The power to be transmitted at 400 RPM is 135 kw and μ =0.3. . find inside diameter and spring force required to engage the clutch, if the spring with spring index 6 and material of spring the wire diameter if 6 springs are used(10 marks) 6 (b) The torque absorbed in the band break shown in Fig Q6 (b) is 440×103 Nmm. Design the band and lever taking μ=0.27 and diameters of drum as 400mm. The allowable stress in band may be taken as 70 N/mm2. (10 marks) 7 (a) Derive Petroff's equation for co-efficient of friction in journal bearings.(8 marks) 7 (b) Design the main bearing of a steam turbine that runs at 1800 RPM and 70°C. The load on the bearing estimated to be 2500N.(12 marks) 8 Design a cast iron piston for a single acting four stoke diesel engine from the following data:
Length of stroke=125 mm
Brake mean effective pressure=0.5MPa,
Maximum gas pressure=5MPa,
Fuel consumption =0.25 kh/Break power in kW/hour
Assume any further data required for the design.(20 marks)