JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II Year ELEMENTS OF MECHANICAL ENGINEERING Previous Question Paper (November/December - 2017 - R13)
Note: This question paper contains two parts A and B. Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit.
PART- A
Answer
Hooke's law states that within the elastic limit, the stress applied to a material is directly proportional to the strain produced in it. Mathematically, it is expressed as:
where σ is stress, ε is strain, and E is Young's modulus of elasticity.
Answer
The stress-strain diagram for a ductile material (like mild steel) shows the following key points: Proportional limit, Elastic limit, Upper yield point, Lower yield point, Ultimate stress point, and the Fracture point.
The curve starts linearly from the origin (proportional limit), followed by a slight curve to the elastic limit. It then shows a yield region, a strain-hardening region reaching the ultimate stress, and finally a necking region leading to the fracture point.
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PART-B
A steel plate of constant thickness 12 mm is having a breadth of 120 mm at one end and uniformly varies to a breadth of 70 mm at the other end. Find the total extension due to an axial pull of 86 kN at the ends. Take E = 206 kN/mm2 and length of the plate as 850mm. Derive the formula involved from first principles.
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A simply supported beam of 9m span is loaded as shown in Figure. Draw the B.M and S.F diagrams indicating maximum and minimum principal values.
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Differentiate between a thin cylinder and a thick cylinder. Find an expression for the radial pressure and hoop stress at any point in case of a thick cylinder.
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A spherical shell of internal diameter 0.9 m and of thickness 10 mm is subjected to an internal pressure of 1.4 N/mm2. Determine the increase in diameter and increase in volume. Take E = 2×105 N/mm2 and Poisson’s ratio is 1/3.
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An engines uses 6.5kg of oil per hour of Calorific value 30000KJ/Kg. If the BP of the engine is 22kW and Mechanical efficiency 85%, calculate:
a) Indicated thermal efficiency
b) Break thermal Efficiency and
c) Specific fuel consumption in kg/BP/h.
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Two pulleys, one diameter 450mm and the other 200mm diameter are on parallel shafts 1.95m apart and are connected by a crossed belt. Find the length of the belt required and the angle of contact between the belt and each pulley. What power can be transmitted by the belt when the larger pulley rotates at 200rev/min, If the maximum permissible tension in the belt is 1kN, and the coefficient of friction between the belt and pulley is 0.25?
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What do you understand by the term Gear train? Discuss the various types of Gear Trains.
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