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- Design of Machine Components - DMC
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Registration No: Total Number of Pages: 02 B.Tech. PAU5I101 5th Semester Regular Examination 2017-18 Design of Machine Components BRANCH: AUTO Time: 3 Hours Max Marks: 100 Q.CODE: B176 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) c) d) e) f) g) h) i) j) Q3 a) b) Answer the following questions: multiple type or dash fill up type The factor of safety for steel and for steady load is ______________. When a material is subjected to fatigue loading, the ratio of the endurance limit to the ultimate tensile strength is __________. Two shafts A and B are made of the same material. The diameter of the shaft A is twice as that of shaft B. The power transmitted by the shaft A will be ___________ of shaft B. A bolt of M 24 × 2 means that __________________________. The ratio of maximum fluctuation of energy to the ________ is called coefficient of fluctuation of energy. Slenderness ratio is the ratio of ____________________________. If the tearing efficiency of a riveted joint is 50%, then ratio of diameter of rivet hole to pitch of rivets is ___________. When helical compression spring is cut into halves, the stiffness of the resulting spring will be ________________________. The listed life of a roller bearing in a catalogue is ____________. In a full journal bearing the angle of contact of the bearing with the journal is ________________. (2 x 10) Answer the following questions: Short answer type Define stress concentration and notch sensitivity. Define factor of safety. On which factors does it depend? Differentiate between chain and zigzag riveting. Define slenderness ratio and buckling factor. Differentiate axle and spindle. Define and show three lengths of a compression helical spring. Differentiate caulking and fullering. State the differences between hydrostatic and hydrodynamic bearings. Define bearing characteristic number and bearing modulus and write its significance. Why elliptical cross-section is chosen instead of circular cross section for flywheel arms? (2 x 10) Design a double riveted butt joint with two cover plates for the longitudinal seam of a boiler shell 1.5 m in diameter subjected to a steam pressure of 0.95 N/mm2. Assume joint efficiency as 75%, allowable tensile stress in the plate 90 MPa ; compressive stress 140 MPa ; and shear stress in the rivet 56 MPa. Show by neat sketches the various ways in which a riveted joint may fail. (12) (3)

Q4 a) b) Q5 a) b) Q6 a) b) Q7 a) b) Q8 a) b) Q9 a) b) Determine the diameter of the push rod made of mild steel of an I.C. engine if the maximum force exerted by the push rod is 1500N. The length of the push rod is 0.5m. Take FOS as 2.5 and the end fixity coefficient as 2. Write the assumptions of Euler’s column theory. List equivalent lengths of column for different end conditions. (7.5) Write down the steps to design a bolted joint for eccentric loading parallel to the axis of bolts. Also note down the assumptions and considerations for this design. Which factors should be taken into consideration during selection of materials for machine elements. Briefly explain. (10) A shaft is supported on bearings A and B, 800 mm between centres. A 20° straight tooth spur gear having 600 mm pitch diameter, is located 200 mm to the right of the left hand bearing A, and a 700 mm diameter pulley is mounted 250 mm towards the left of bearing B. The gear is driven by a pinion with a downward tangential force while the pulley drives a horizontal belt having 180° angle of wrap. The pulley also serves as a flywheel and weighs 2000 N. The maximum belt tension is 3000 N and the tension ratio is 3:1. Determine the maximum bending moment and the necessary shaft diameter if the allowable shear stress of the material is 40 MPa. A hollow shaft has greater strength and stiffness than solid shaft of equal weight. Explain. (10) In a journal bearing the load on the journal is 3kN, diameter 50 mm, length 75 mm, speed 1600 rpm, diametral clearance 0.001 mm, ambient temperature 15.50C and oil film temperature is 600C. Determine the heat generated and dissipated. Absolute viscosity of oil is 0.014kg/ms. A ball bearing is subjected to a radial load of 5 kN is expected to have a life of 8000 hours at 1450 rpm with a reliability of 99%. Calculate the dynamic load carrying capacity of the bearing so that it can be selected from the manufacturer’s catalogue based on reliability of 90%. (7.5) Design a helical spring for a spring loaded safety valve (Rams bottom safety valve) for the following conditions: Diameter of valve seat = 65 mm ; Operating pressure = 0.7N/mm2; Maximum pressure when the valve blows off freely = 0.75N/mm2; Maximum lift of the valve when the pressure rises from 0.7 to 0.75 N/mm2 = 3.5 mm ; Maximum allowable stress = 550 MPa ; Modulus of rigidity = 84 kN/mm2; Spring index = 6. Draw a neat sketch of the free spring showing the main dimensions. Show individually and superposition of torsional shear stress, direct shear stress and curvature shear stress in the wire of a helical spring (10) A single cylinder double acting steam engine delivers 185 kW at 100 r.p.m. The maximum fluctuation of energy per revolution is 15 percent of energy developed per revolution. The speed variation is limited to 1% either way from the mean. The mean diameter of the rim is 2.4m. Design and draw two views of flywheel. State different stresses developed in flywheel rim and flywheel arm. (12) (7.5) (5) (5) (7.5) (5) (3)

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