JNTU
JNTU B.Tech II MECHANICAL METALLURGY Previous Question Paper (May - 2019 - R16)
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. Each question carries 10 marks and may have a, b, c as sub questions.
PART- A
What are line defects?
Answer
Line defects, also known as dislocations, are one-dimensional crystalline imperfections where atoms are misaligned along a line. They are primarily categorized into edge dislocations, screw dislocations, and mixed dislocations.
Write about dislocation climb.
Answer
Dislocation climb is a process by which an edge dislocation moves perpendicular to its slip plane. This occurs through the diffusion of vacancies to or from the dislocation core, causing the extra half-plane of atoms to either shorten or lengthen. It is a thermally activated process that allows dislocations to bypass obstacles that would otherwise pin them.
What is the principle of Vickers hardness test?
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What is meant by poldi method?
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A perfectly plastic material is yielding under the stress state σ1, σ2, σ3 where σ1 > σ2 > σ3. Explain what happens if σ1 is increased.
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How strain rate affect the flow stress of a material?
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What is meant by Endurance strength?
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What is meant by stress concentration? Explain.
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What is diffusion creep?
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Explain briefly about Structural changes during Creep of a material?
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PART-B
Derive an equation for critical resolved shear stress (CRSS).
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What is Frank Reed Source? Explain.
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Explain the mechanism of plastic deformation by slip and twinning?
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Define and explain sessile and glissile dislocations.
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Explain Griffith theory of brittle fracture.
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Explain the mechanism of Ductile fracture with necessary sketches.
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Explain relation between hardness and mechanical properties of a material?
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Differentiate between Brinell and Vickers hardness tests?
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What is the effect of temperature and strain rate on tensile properties of a material?
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What is DBTT curve? Give its importance?
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What is necking? Derive the conditions for necking.
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What are the Metallurgical factors affecting ductile-brittle transition temperature? Explain.
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Mention and explain the factors that are to be considered while designing the components to avoid fatigue failure.
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Differentiate between low cycle fatigue and high cycle fatigue.
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Draw S-N curve for mild steel and explain its features?
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Explain the factors effecting fatigue strength of a material.
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Explain the structural changes during creep deformation with necessary sketches.
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What is stress rupture test? Write a brief note on it?
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Explain the Effect of Metallurgical variables on creep.
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