JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III PRINCIPLES OF MACHINE DESIGN Previous Question Paper (August - 2022 - R13)
Answer any five questions. All questions carry equal marks.
Assume suitable data, if necessary.
Main
The piston rod of a steam engine is 50 mm in diameter and 600 mm long. The diameter of the piston is 400 mm and the maximum steam pressure is 0.9 N/mm2. Find the compression of the piston rod if the Young’s modulus for the material of the piston rod is 210 kN/mm2.
Answer
To find the compression of the piston rod, we first calculate the total force acting on the piston rod due to the steam pressure.
The force P is given by the product of the steam pressure and the area of the piston:
Next, we calculate the cross-sectional area of the piston rod (A) with diameter 50 mm:
Using Hooke's Law, the compression (δ) is calculated as:
Given the length L = 600 mm and Young's modulus E = 210,000 N/mm2:
The compression of the piston rod is 0.1645 mm.
What is Endurance limit? Explain.
Answer
The Endurance limit (or fatigue limit) is the maximum stress amplitude that a material can withstand for an infinite number of stress cycles without failure. Below this stress level, the material is theoretically immune to fatigue failure regardless of the number of load repetitions.
In practical engineering, it is often defined based on a specific high number of cycles (typically 106 to 107 cycles). It is a critical design parameter for components subjected to fluctuating or cyclic loads, such as shafts, springs, and connecting rods.
What are steps to increase of fatigue strength?
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Calculate the fatigue strength for the specimen made of 30C8 steel with endurance strength 380 MPa and ultimate strength 500 MPa for a life of 300 000 cycles of stress reversals. What would be the life of a specimen, if the fluctuating reversible stress is taken as 520 MPa.
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A steel plate, connected to a fixed channel using three identical bolts A, B and C carries a load of 6kN as shown in the figure. Considering the effect of direct load and moment, the magnitude of resultant shear force (in kN) on bolt C is.
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Explain the design procedure for socket and spigot joint with neat sketch.
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A belt 200 mm wide and 20 mm thick is transmitting power at 2000 m/min. The net driving tension is 2.4 times the tension on the slack side. If the safe permissible stress on the belt section in 2.6 MPa. Calculate the maximum power that can be transmitted at this speed. Assume density of the leather as 1000 kg/m3.
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Design a flat belt drive to transmit 25 kw at 720 rpm to an Aluminum rolling machine with a speed reduction of 3.0. The distance between the shafts is 3m. Diameter of the rolling machine pulley 1.2m.
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A gear drive consists of two gears, A and B and has a velocity ratio of 1.50. Gear A, the smaller of the two gears, revolves at 126 rpm in the clockwise direction, and has 28 teeth. If the gears have a module of 2 mm, determine,
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A hydrodynamic full journal bearing is to carry a load of 25 kN at a speed of 3000rpm. The journal diameter is 150 mm and the length of bearing is 75 mm. SAE 30 oil is used with an average operating temperature of 55°C. If the radial clearance is 0.075 mm, calculate the power loss, the side leakage and the minimum film thickness?
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