JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III MECHANICAL WORKING Previous Question Paper (May/June - 2019 - 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.
Part A
Explain the analysis of rolling load and rolling variables.
Answer
Rolling load is the total force exerted by the rolls on the workpiece, calculated based on the contact area and mean yield stress. Rolling variables include roll diameter, reduction in thickness, friction at the roll-strip interface, and material properties, which collectively determine the power requirements and final strip geometry.
What is the role of temperature in extruding the metals?
Answer
Temperature significantly reduces the flow stress of the metal, allowing for higher deformation rates and lower extrusion pressures. It also enhances ductility, preventing cracking during the process, and helps in achieving complex cross-sectional shapes by improving material flow characteristics.
What are the advanced techniques of sheet metal forming process?
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Write short notes on Shear stress.
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What is orange peel effect and how it is minimised?
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What is die-ringing? Show that the maximum die pressure occurs at the die entrance.
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Why are thin sheets are tough than thick sheets?
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Differentiate between cold extrusion and hot extrusion.
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Discuss the strain-rate effects.
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What is impact extrusion and give some examples?
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Part B
Discuss briefly about stress at a point.
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Distinguish between state of a stress in two dimensions and three dimensions.
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Explain about Mohrs circle of stress in two dimensions.
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Differentiate between Stress at a point and strain at a point.
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Draw the flow curve for ductile materials.
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Compare shear stress and shear strain.
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Write short notes on Shear strain.
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Discuss briefly about Von mises distortion energy criterion.
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Distinguish between cold working and hot working.
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Write about forging of a cylinder in plane strain.
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Discuss about the forging defects and their remedial measures.
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Classify the forming processes with examples.
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What is the role of rolling load and rolling variables on rolling processes.
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Discuss about the theories of cold rolling and hot rolling.
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List out the rolling defects and its remedial measures.
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Classify the rolling processes and rolling mills.
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Discuss the different types of extrusion processes.
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Explain with neat sketches of the different type of equipment used in extrusion processes.
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Explain the effect of different factors on residual stresses developed in wire and rod drawing operation.
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Compare the force required to give a 30% reduction in a 0.5" diameter wire in a 100 semi-angle die with the force required to produce the same reduction in a tube blank of 0.4" outside diameter, 0.3" inside diameter using a cylindrical mandrel. Assume that µ = 0.07 for both cases.
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