JNTU B.Tech III PRINCIPLES OF MACHINE DESIGN Previous Question Paper (May/June - 2019 - R15)

A section of a shaft of diameter d is joined to another section of a shaft of diameter 1.5 d with a fillet which produces an actual stress concentration factor of 1.2 for the shaft in torsion. The material has a yield point in tension of 560 MPa and endurance limit of 288 MPa in reversed torsion. Using a size factor of 0.85, surface finish factor of 0.85, and A (correction factor for type of loading other than reversed bending) as 0.6, determine the size of the shaft required for a torque which varies from zero to 2400 Nm on the shaft at the smaller diameter. Use a design factor N = 2.

A bronze disc 50 mm thick is to be pressed on to a steel shaft which has a diameter of 100 mm. The outside diameter of the disc is 300 mm. When assembled, the fit must be able to withstand a torque of 8.1 kN-m. Determine the allowance which must be made to obtain this force fit. The coefficient of friction for the two surfaces is 0.3. Take E for steel = 0.21 × 10

A horizontal steel flat, rectangular in cross section, is connected to a vertical member by four rivets placed on the corners of a square of side 120 mm, where one of the diagonals is parallel to the load line. The steel flat carries a load of 20 kN acting verticall downwards at a distance of 300 mm from the C.G. of the rivets. Determine the rivet diameter, if the permissible shear stress is limited to 50 MPa.

Design a knuckle joint to connect two rods of 80 mm diameter. The safe allowable stresses for the material in tension, shear, and bearing may be assumed as 80 MPa, 60 MPa, and 100 MPa respectively. Draw a neat dimensioned sketch of the joint.

The driving pulley on a main shaft running at 120 rpm is of 50 cm diameter, and drives by means of a belt a countershaft which rotates at 300 rpm. The minimum angle of lap is 170°, the coefficient of friction between the belt and pulley surfaces is 0.25, the weight per cubic cm of belt material is 9 N, and the safe stress in the belt material is 300 N / cm

A rope drive is to transmit 250 kW from a pulley of 1.2 m diameter running at a speed of 320 rpm. The angle of lap is π radians, and the half – angle of groove is 22.5°. The ropes to be used are 45 mm in diameter. The weight of rope is 1.25 kg per meter length, and each rope has a safe maximum pull of 2.2 kN. If the coefficient of friction between the rope and pulley is 0.25, find the number of ropes required.

A pair of parallel helical gears consists of an 18 – teeth pinion meshing with a 45 – teeth gear. A 7.5 kW power at 2000 rpm is supplied to the pinion through its shaft. The normal module is 6 mm, while the normal pressure angle is 20°. The helix angle is 23°. Determine the tangential, radial, and axial components of the resultant tooth force between the mating teeth.

It is required to design a pair of spur gears with 20° full – depth involute teeth based on the Lewis equation. The velocity factor is to be used to account for dynamic load. The pinion shaft is connected to a 9 kW, 1400 rpm motor. The starting torque of the motor is 150% of the rated torque, and the speed reduction is 4 : 1. The pinion and gear are made of plain carbon steel 40C8 (Sut = 600 N/mm

A shaft running at 900 rpm is supported by a bearing having (l / d) ratio of 1.5. The bearing operates in still air at a room temperature of 30°C. The oil used has absolute viscosity of 0.013 kg/m-s at the oil operating temperature of 130°C. Diameter of the journal is 50 mm, and the (d / c) ratio is 1000. Determine the permissible load for the bearing and the power lost at the bearing. Assume that the heat generated equals the heat dissipated.