JNTU
JNTU B.Tech II MECHANICAL METALLURGY Previous Question Paper (December - 2018 - 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 is mean by Jogs?
Answer
A jog is a short segment of a dislocation line that lies on a slip plane different from the main slip plane of the dislocation. It is formed when two non-parallel dislocations intersect, causing the dislocation line to climb or cross-slip locally.
Differentiate between slip and twinning deformation in materials.
Answer
Slip involves the movement of dislocations along specific crystallographic planes and directions, resulting in a permanent displacement of crystal blocks where the orientation remains unchanged. In contrast, twinning involves a homogeneous shear of the crystal lattice, resulting in a mirror-image orientation of the twinned region relative to the parent crystal.
List the different types of fractures.
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What is Griffith’s theory of brittle fracture?
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Define Fracture toughness.
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Define True stress and True Strain.
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List the factors affecting the fatigue failure.
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Write short note on S-N Curve.
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What is stress rupture?
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What are the creep resistant materials? List them.
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Part B
Explain the concept of critical revolved shear stress with suitable examples.
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Explain briefly glissile and sessile dislocations with an example.
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What is fracture? Sketch the basic modes of fractures. State the differences between ductile and brittle fractures.
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With an example explain the different methods to test the hardness.
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Establish the relationship between engineering stress and true stress also show the relationship of engineering strain and true strain.
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What do you mean by linear and nonlinear elastic properties of a material? Explain any two properties briefly?
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What is the importance of DBTT curve? Explain.
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What is stress cycle? Explain different types stress cycles.
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A fatigue test is made with mean stress, σm = 120MPa and stress-amplitude σa = 165MPa, find σmax, σmin, σrange and σratio.
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Write a short note on:
Low cycle fatigue
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High cycle fatigue.
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Define creep with a typical creep curves. Explain the structural changes during creep.
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Explain with sketch the different stages of creep deformation. What is the effect of stress and temperature on creep curve?
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