JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II Year PRODUCTION TECHNOLOGY Previous Question Paper (August/September - 2022 - R18)
Answer any five questions. All questions carry equal marks.
Main
Define gating ratio. Explain the steps involved in designing a gating system.
Answer
The gating ratio is defined as the ratio of the cross-sectional areas of the components in the gating system, expressed as: Sprue area : Runner area : Ingate area. It is a critical parameter for controlling the flow rate and minimizing turbulence during mold filling.
The steps involved in designing a gating system are:
- Determine the total volume of the casting and the required pouring time based on the material properties and casting weight.
- Calculate the choke area, which is the smallest cross-section in the system that controls the flow rate, using the continuity equation and Bernoulli's theorem.
- Select an appropriate gating ratio (e.g., pressurized or unpressurized) to ensure a smooth, non-turbulent flow and to prevent aspiration of air.
- Design the sprue, runner, and ingate dimensions based on the chosen ratio and the calculated choke area.
- Incorporate features like sprue wells, runner extensions, and tapered sprues to minimize turbulence and trap dross or slag before it enters the mold cavity.
Calculate the sizes of riser for casting steel bar of 75 × 12.5 × 12.5 cm with top riser placed at the center of the bar. Use modulus method.
Answer
To ensure directional solidification, the modulus of the riser (Mr) must be greater than the modulus of the casting (Mc). For steel, a common design criterion is Mr = 1.2 × Mc.
1. Calculate the Modulus of the casting (Mc):
2. Determine the Riser Modulus (Mr):
3. Calculate riser dimensions (assuming a cylindrical riser where height H = Diameter D):
Substituting H = D:
The riser should have a diameter of approximately 17.31 cm and a height of 17.31 cm.
With neat sketch, explain the principle and working of cupola furnace.
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Calculate the optimum pouring time for a casting whose mass is 20 kg and having an average section thickness of 15 mm. The materials of the casting are grey cast iron and steel. Take the fluidity of iron as 711.2 mm.
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Explain the principle, limitations and applications of explosive welding.
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What types of structure and property modifications can occur in welding heat zones?
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Explain the method and application of friction stir welding.
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Determine the melting efficiency in the case of arc welding of steel with a potential of 22V and current of 230 A. The cross-sectional area of the joint is 22 mm2 and the travel speed is 5 mm/s. Heat required to melt steel may be taken as 12 J/mm3 and the heat transfer efficiency as 85%.
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Explain the forces and power calculations required for drawing operation.
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Explain the cold work - annealing cycle.
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Explain about bending process. What is spring back and what are its remedies?
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Calculate the bite angle when rolling plates of 15 mm thickness, using work rolls of 400 mm diameter and reducing the thickness by 3 mm.
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Explain the role of container and die in the analysis of forward extrusion process.
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Explain the terms of lapping and backing as related to forging practice.
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Explain the differences between open die forging and impression die forging.
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Distinguish between electro-hydraulic forming and electro-magnetic forming.
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