JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II ELEMENTS OF MECHANICAL ENGINEERING Previous Question Paper (November/December - 2018 - R16)
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. Each question carries 10 marks and may have a, b, c as sub questions.
Part A
Draw the stress strain diagram for brittle materials.
Answer
The stress-strain diagram for a brittle material is a nearly straight line starting from the origin and ending abruptly at the point of fracture without significant plastic deformation. The curve shows a linear elastic region followed by a sudden failure.
What is stress? List out different types of stresses.
Answer
Stress is defined as the internal resistance force offered by a material per unit cross-sectional area when subjected to an external load. It is expressed as force divided by area. The main types of stresses are: 1) Tensile stress, 2) Compressive stress, and 3) Shear stress.
What are the different types of supports?
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Draw the shear force and bending moment diagrams of simply supported beam when it subjected to midpoint load.
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What is Lame’s equation?
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Differentiate the column and Strut.
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How do you classify the IC engines?
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List out the basic engine components.
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What is the difference between belt, rope and chain drives?
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What is the phenomenon of creep in the belts?
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Part B
In a tension test on a steel tube of outer diameter 18 mm and 12 mm bore, an axial load of 1.7 kN produces an elongation of 0.0045 mm on a length of 75 mm, while the outer diameter suffered a reduction of 0.00032 mm. Calculate the values of all the four elastic constants.
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A bar of brass 25 mm diameter is enclosed in a steel tube initially 50 mm external diameter and 25 mm internal diameter. The bar and tube are both initially 1.5 m long and rigidly fastened at both ends using 20 mm diameter pins. Find the stresses in both materials and the increase in length when the temperature rises from 30°C to 100°C. E for steel = 200 GPa, E for brass=100 GPa, α for steel = 11.6×10-6/°C, α for brass = 18.7 × 10-6/°C. Also determine the shear stress induced in the pins.
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A cantilever beam of length 10m carries a uniformly varying load of 10 kN/m run at the fixed end to 3 kN/m run at the mid span and two concentrated loads of 4 kN and 6 kN at 7m and 8m from the fixed end. Draw the SFD and BMD.
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State the assumptions made in the theory of simple bending and derive the relation between the bending stress, moment and radius of curvature.
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Prove that max shear stress in a circular section of a beam is 4/3 times the average shear stress.
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A Cylindrical pipe of diameter 1.5m and thickness 1.5cm is subjected to an internal fluid pressure of 1.2 N/mm2. Determine: a) Longitudinal stress developed in the pipe, and b) Circumferential stress developed in the pipe.
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Define slenderness ratio. State the limitations of Euler's formula.
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A short hollow cylindrical C.I. Column is 240 mm external and 180 mm internal diameter. In casting, the bore got eccentric so that the thickness varies from 20mm at one end to 40 mm at the other. If the column carries a load of 600 KN along the axis of the bore, calculate the extreme intensities of stress induced in the section.
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With neat diagram, explain the working principle of Diesel engine.
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List out advantages and disadvantages of two stroke engines over four stroke engines.
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During the test on single cylinder oil engine working on the four stroke cycle and fitted with a rope brake, the following readings are taken: Effective diameter of brake wheel = 630mm; dead load on brake=200N; spring balance reading=30N; Speed=450rpm; Area of indicator diagram = 420mm2; length of indicator diagram = 60mm; Spring scale = 1.1 bar per mm; diameter of cylinder = 100mm; stroke = 150mm; quantity of oil used = 0.815kg/h; CV of oil = 42,000kJ/kg. Calculate the BP, IP, Mechanical Efficiency, Brake thermal efficiency and brake specific fuel consumption.
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Derive the expression for the length of open belt drive system.
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What is centrifugal tension in a belt? How does it affect the power transmitted?
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Explain briefly the differences between the simple, compound, epicyclic and reverted gear trains. What are the special advantages of epicyclic and reverted gear trains?
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