Set No. Code No: RR 311802 III B.Tech. I-Semester Regular Examinations, November-2004 MECHANICAL METALLUARGY (Metallurgical and Material Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ---
1
What are partial dislocations. Explain with a sketch and examples. Discuss the movement of dislocations at elevated temperatures as related to creep strain.
2.
Explain the principle and operation involved in Rockwel hardness test. What are the major advantages and limitations of this test over other hardness tests?
3.a) b)
Discuss the effect of transformation temperature on the tensile properties of steel. Explain the limitations encountered in the compression test.
4.a)
Explain the effects of carbon content of steels, grain size and shape, crystal structure in transition temperature. Describe with neat sketches the principles of Izod test.
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1.a) b)
Describe ductile fracture of a material with the aid of a neat sketch. What do you mean by Notch sensitivity? Explain.
6. a)
Define fatigue limit. Explain an experimental set up and the procedure to find endurance limit of a metal. What are the factors which affect the fatigue strength of materials?
7. a) b) 8.
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5. a) b)
What is creep? Draw an ideal creep curve and explain the various stages with the mechanism in operation. Explain the effect of temperature and stress on creep life with the aid of graphs. Sketch and explain X-Ray radiography in NDT. What are its advantages and disadvantages compared to other methods?
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Code No: RR 311802 III B.Tech. I-Semester Regular Examinations, November-2004 MECHANICAL METALLUARGY (Metallurgical and Material Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks --1. a) Explain how dislocation jogs may be formed by interaction of dislocations. Also explain why movement of an edge jog is difficult. b) Explain with neat sketch how the dislocation can be multiplied in a material. Sketch the geometry and comment on their shape for the following: a) Rockwel diamond Indentor b) Vicker’s diamond penetrator c) Tensite test specimen d) Round bars.
3.
Draw engineering stress – strain diagram/curve for mild steel and explain the various properties associated with it.
4.a) b)
Describe a typical notch-bar impact test to determine impact strength. Compare two standard Notched bar impact tests.
5.a)
The half crack length of steel is 2m. Taking E = 200GN/m2 estimate the fracture strength at low temperatures, if the true surface energy is 1.5J/m2. The actual fracture strength is found to be 1200MN/m2. Explain the difference the actual and calculated value. Explain Ductile to Brittle transition temperature.
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2.
Explain crack initiation and propogation failure with the aid of a sketch. What preventive measures can be adopted to avoid fatigue failure?
7. a) b)
Draw an ideal Creep curve and explain the various stages on it. With the sketch of a creep test set up explain how creep rupture tests are conducted.
8.
Explain the following N.D.T Processes. a) Magnetic particle inspection b) Ultrasonic flow detection
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Code No: RR 311802 III B.Tech. I-Semester Regular Examinations, November-2004 MECHANICAL METALLUARGY (Metallurgical and Material Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks --1. a) Explain how the dislocation structure is altered during polyganization. b) Distinguish between dislocation climb and dislocation glide. Explain the factors that affected dislocation climb. Explain the specific advantages of Vicker’s hardness test. What are the units of Rockwell hardness?
3.a) b)
Discuss the relationship between yield strength and hardness for ductile metals. Explain the discrepancy between observed and theoretical yield strengths of single crystals during plastic deformation.
4. a) b)
Explain why does a brittle material not have stable crack growth. Clearly distinguish between COD and CTOD and their lists.
5. a)
What is the significance of Ductile-Brittle transition temperature? Explain with an example. Explain the affect of various metallurgical factors on the transition temperature.
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2. a) b)
Describe cattrel mechanism of fatigue failure. How can we enhance the fatigue life of a component?
7. a) b)
Explain the Naborro mechanism in creep. Explain the role of super alloys and dispersion strengthed alloy in high temperature creep.
8. a) b)
Explain the principle and working of Radiographic NDT. What is the difference between Exgraph and Radiograph?
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Set No. Code No: RR 311802 III B.Tech. I-Semester Regular Examinations, November-2004 MECHANICAL METALLUARGY (Metallurgical and Material Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ---
2. a) b)
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b)
Discuss the effect of dislocation pile up on propagating slip and its relation to grain size. Explain the variation of concentration of vacancies with temperature.
Explain in detail why Brinell’s Hardness test method is preferred for measuring hardness of cast alloys. Among the various hardness test method which method do you think is best and why.
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1. a)
4
Discuss the shear stress – shear strain diagram for FCC single crystals. Explain why the strength of brittle materials is usually larger in compression than in tension.
4. a) b) c)
Explain the significance of equicohesive temperature. Explain clearly the mechanism of brittle fracture in metals. Discuss in detail the significance and test methods for fracture toughness.
5. a)
Under what conditions a ductile material may fail in a brittle manner? Explain about Ductile-Brittle transition temperature. What do you mean by fracture toughness? Explain.
6. a)
b)
What is the effect of the following on fatigue. (i) Stress concentration (ii) Size of the specimen. (iii) Surface condition. Explain the various methods to enhance fatigue life of metals. Explain how long time properties of creep can be predicated by short time tests. Explain Carson-Miller (L-M) parametric method.
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How Eddy current NDT works? Explain one method of this test. In which type of components this test is used. What are its disadvantages?
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