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Registration No: Total Number of Pages: 02 B.Tech. PCAT4301 5th Semester Back Examination 2017-18 Design of Machine Components BRANCH: AUTO Time: 3 Hours Max Marks: 70 Q.CODE: B199 Answer Question No.1 and 2 which are compulsory and any four from the rest. The figures in the right hand margin indicate marks. Q1 a) b) c) d) e) f) g) h) i) j) Q2 a) b) Q3 a) b) Q4 a) Answer the following questions: Short answer type What is meant by endurance strength of a material? What is Euler’s formula? What do you understand by the single start and double start threads ? Define the following terms : (a )Pitch, and (b) Lead. What type of stresses are induced in shafts ? What do you understand by torsional rigidity and lateral rigidity. What is meant by hydrodynamic lubrication? Define ‘coefficient of fluctuation of energy’. What is the resultant stiffness of the spring when two springs are connected in series? What is meant by eccentric loading and eccentricity? (2 x 10) A circular bar of 500 mm length is supported freely at its two ends. It is acted upon by a central concentrated cyclic load having a minimum value of 20 kN and a maximum value of 50 kN. Determine the diameter of bar by taking a factor of safety of 1.5, size effect of 0.85, surface finish factor of 0.9. The material properties of bar are given by : ultimate strength of 650 MPa, yield strength of 500 MPa and endurance strength of 350 MPa. What is meant by `stress concentration'? How do you take it into consideration in case of a component subjected to dynamic loading? (5) A steam engine of effective diameter 300 mm is subjected to a steam pressure of 1.5 N/mm2. The cylinder head is connected by 8 bolts having yield point 330 MPa and endurance limit at 240 MPa. The bolts are tightened with an initial preload of 1.5 times the steam load. A soft copper gasket is used to make the joint leak-proof. Assuming a factor of safety 2, find the size of bolt required. The stiffness factor for copper gasket may be taken as 0.5. Define equivalent twisting moment and equivalent bending moment. State when these two terms are used in design of shafts. (5) A steel spindle transmits 4 kW at 800 r.p.m. The angular deflection should not exceed 0.25° per metre of the spindle. If the modulus of rigidity for the material of the spindle is 84GPa, find the diameter of the spindle and the shear stress induced in the spindle. (5) (5) (5)

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Q5 b) A hollow shaft has greater strength and stiffness than solid shaft of equal weight. Explain. (5) a) Design a journal bearing for a centrifugal pump from the following data : Load on the journal = 20 000 N; Speed of the journal = 900 r.p.m.; Type of oil is SAE 10, for which the absolute viscosity at 55°C = 0.017 kg / m-s; Ambient temperature of oil = 15.5°C ; Maximum bearing pressure for the pump = 1.5 N / mm2. Calculate also mass of the lubricating oil required for artificial cooling, if rise of temperature of oil be limited to 10°C. Heat dissipation coefficient = 1232 W/m2/°C. Write short note on classifications and different types of antifriction bearings. (5) A single cylinder double acting steam engine delivers 185 kW at 100 r.p.m.The maximum fluctuation of energy per revolution is 15 per cent of the energy developed per revolution. The speed variation is limited to 1 per cent either way from the mean. The mean diameter of the rim is 2.4 m. Design and draw two views of the flywheel. Explain ‘coefficient of fluctuation of speed’ and ‘coefficient of steadinesses. (5) Design a close coiled helical compression spring for a service load ranging from 2250 N to 2750 N. The axial deflection of the spring for the load range is 6 mm. Assume a spring index of 5. The permissible shear stress intensity is 420 MPa and modulus of rigidity, G = 84 kN/mm2. Neglect the effect of stress concentration. Draw a fully dimensioned sketch of the spring, showing details of the finish of the end coils. Explain what you understand by. Wahl’s factor and state its importance in the design of helical springs? (5) A shaft rotating at constant speed is subjected to variable load. The bearings supporting the shaft are subjected to stationary equivalent radial load of 3 kN for 10 per cent of time, 2 kN for 20 per cent of time, 1 kN for 30 per cent of time and no load for remaining time of cycle. If the total life expected for the bearing is 20 × 106 revolutions at 95 per cent reliability, calculate dynamic load rating of the ball bearing. Explain wedge film and squeeze film journal bearings. (5) b) Q6 a) b) Q7 a) b) Q8 a) b) (5) (5) (5) (5)

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