III B.Tech I Semester Regular Examinations, November - 2018

DESIGN OF MACHINE MEMBERS - I

(Mechanical Engineering)

Time: 3 hours Max. Marks: 70

Note: 1. Question paper consists of two parts (Part-A and Part-B)

2. Answer ALL the question in Part-A

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3. Answer any FOUR Questions from Part-B

PART-A

(14 Marks)

1. a) Define: i) Endurance limit ii) Notch sensitivity [2M]
2. b) What are the different types of riveted joints? [2M]
3. c) What is the effect of keyway on the strength of the shaft? [2M]

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4. d) List the different types of stresses induced in flywheel rim. [2M]
5. e) What are the different types of spring? [2M]
6. f) State the advantages of hydrodynamic bearings. [2M]
7. g) What are the assumptions made in hydrodynamic lubrication? [2M]

PART-B

(56 Marks)

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1. 2. a) Explain the significance of theories of failure.

   b) A machine component is subjected to the following stresses: sx = 100 MPa; sy = 20 MPa; txy = 30 MPa. Determine the principal stresses, maximum shear stress and the plane on which they act. [7M]

2. 3. Design a triple riveted lap joint for MS plates to connect two plates of thickness 10 mm. Assume st = 75 MPa, t = 60 MPa and sc = 120 MPa. [14M]

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3. 4. A shaft is supported on bearings A and B, 800 mm between centres. A 20° straight tooth spur gear, 600 mm diameter, is located 200 mm to the right of the left hand bearing A, and a 700 mm diameter pulley is mounted 250 mm to 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. [14M]

4. 5. A railway wagon is moving at a velocity of 1.8 kmph. It is brought to rest by two buffer springs. The mass of the wagon is 1800 kg. The maximum deflection of each spring is 180 mm. Determine: i) Maximum force on each spring ii) Stiffness of each spring iii) Number of active turns, if the spring is made of 25 mm diameter steel rod. Take G = 84 x 103 N/mm2 and permissible shear stress as 300 MPa. [14M]

5. 6. Design a cast iron protective flange coupling to connect two shafts in order to transmit 7.5 kW at 720 rpm. The following permissible stresses may be used Shear stress for shaft, bolt and key material = 40 MPa Crushing stress for bolt and key = 80 MPa Shear stress for cast iron = 8 MPa. Draw a neat sketch of the coupling. [14M]

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6. 7. A full journal bearing of 50 mm diameter and 100 mm long has a bearing pressure of 1.4 N/mm2. The speed of the journal is 900 rpm and the ratio of journal diameter to the diametral clearance is 1000. The lubricant used is oil conforming to SAE 20 for which the thermal conductivity is 0.15 W/m°C. The temperature of oil entering the bearing is 40°C. Determine the maximum oil temperature. [14M]

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