JNTU B.Tech II ELEMENTS OF MECHANICAL ENGINEERING Previous Question Paper (May/June - 2019 - R13)

What do you mean by complementary shear stress?

State the Saint Venant’s Principle.

How are beams classified?

State the theory of simple bending.

How do you reinforce the thin cylinders?

What do you mean by volume change in shells due to internal pressure?

Give the classification of IC engines.

Draw a simple sketch of an IC engine, showing its constructional features.

What are different modes of transmitting power from one shaft to another?

Deduce an expression for the ratio of tight and slack side tensions in case of a V-belt drive.

Composite bar stress problem.

A flat steel plate is of trapezoidal form. The thickness of the plate is 15 mm and it tapers uniformly form a width of 60 mm to 10 mm in a length of 30 cm. If an axial force of 100 kN is applied at each end, determine the elongation of the plate. Take E = 204 kN/mm².

If a bar is stretched in such a manner that all the lateral strain is prevented, what is the value of the modified modulus of elasticity and modified Poisson's ratio? Take μ as the Poisson's ratio.

Determine the percentage change in volume of a steel bar 50 mm square and 1m long when subjected to an axial compressive load of 20 kN. What change in volume would a 100 mm cube of steel at a depth of 5 km in a sea water have? Take E = 2.05 × 10⁵ N/mm² and N = 0.82 × 10⁵ N/mm².

A horizontal beam is simply supported at the ends and carries a distributed load of 30 kN/m between the supports placed 10 m apart. Counter-clockwise moments of 300 kN-m and 200 kN-m are applied to the beam at the supports. Draw the B.M. and S.F. diagrams showing the principal values. Find the position and value of maximum B.M.

A beam AB of 6 m span carries a distributed load with an intensity increasing from zero at A to 30 kN/m at B. Find the reactions, the location and value of maximum bending moment. Plot the B.M. and S.F. diagrams.

A beam of length L carries an evenly distributed load and rests on two supports. How far from the ends must the support be placed if the greatest bending moment to which the beam is subjected is to be small as possible? Where are the points of contraflexure?

A beam ABCD, 10 m long, is simply supported at B and C which are 4 m apart, and overhangs the support B by 3 m. The overhanging part AB carries U.D.L. of 20 kN/m and the part BD carries U.D.L. of 10 kN/m. Calculate the position and magnitude of the least value of the bending moment between the supports. Plot B.M. and S.F. diagrams.

Derive an expression for the proportional increase in the capacity of a thin cylindrical shell subjected to an internal fluid pressure. Calculate the increase in the volume of a boiler shell, 3 m long and 1 m in diameter, when it is subjected to an internal pressure of 1.6 N/mm². The wall thickness is such that the maximum tensile stress in the shell is 20 N/mm² under this pressure. Take Poisson’s ratio = 0.28 and E = 2.05 × 10⁵ N/mm².

A spherical shell of 80 mm internal diameter has to withstand an internal pressure of 30 N/mm². Calculate the thickness of the shell if the maximum permissible tensile strength is 80 N/mm².

A spherical shell of 1 m diameter is subjected to an internal pressure of 1.2 N/mm². Taking the maximum allowable stress as 100 N/mm², find the necessary thickness of plate. Take the joint efficiency at 75%.

Find the ratio of thickness to internal diameter for a tube subjected to internal pressure when the ratio of the internal pressure to the greatest circumferential stress is 0.5. Find the alteration of thickness of metal in such a tube, 250 mm internal diameter, when the internal pressure is 75 N/mm². Take Poisson’s ratio = 0.304 and E = 2.05 × 10⁵ N/mm².

Distinguish between 4-stroke cycle and 2-stroke cycle engines.

The following observations were made during a trial on 2-stroke engine for half an hour when it was running at 300 RPM. Stroke: 300 mm, Bore: 200 mm, m.e.p: 6 bar, Reading of spring balances: 139 kg and 9 kg, Mean circumference of brake drum: 3600 mm, Fuel consumed: 4.35 kg, C.V. of fuel: 44,000 kJ/kg. Determine mechanical and thermal efficiencies of the engine.

Compare the S.I. engines with Diesel engines.

A petrol engine uses 0.270 kg of fuel per B.P. hour. Calorific value of fuel is 44,000 kJ/kg. Mechanical efficiency is 80% and compression ratio is 5.6. Calculate (i) Brake thermal efficiency (ii) Indicated thermal efficiency (iii) Ideal air standard efficiency (iv) Relative efficiency. Take γ = 1.4 for air.

How does the velocity ratio of a belt drive effect, when some slip is taking place between the belt and the two pulleys?

A chain drive is used for reduction of speed from 240 r.p.m. to 120 r.p.m. The number of teeth on the driving sprocket is 20. Find the number of teeth on the driven sprocket. If the pitch circle diameter of the driven sprocket is 600 mm and centre to centre distance between the two sprockets is 800 mm, determine the pitch and length of the chain.

Derive the condition for transmitting the maximum power in a flat belt drive.

A rope drive transmits 600 kW from a pulley of effective diameter 4 m, which runs at a speed of 90 r.p.m. The angle of lap is 160°; the angle of groove 45°; the coefficient of friction 0.28; the mass of rope 1.5 kg / m and the allowable tension in each rope 2400 N. Find the number of ropes required.