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Emt 2102 – Material Science Question Paper

Emt 2102 – Material Science

Course:Bachelor Of Science In Mechatronic Engineering

Institution: Dedan Kimathi University Of Technology question papers

Exam Year:2010

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KIMATHI UNIVERSITY COLLEGE OF TECHNOLOGY University Examinations 2010/2011 FIRST YEAR SECOND SEMESTER EXAMINATIONS FOR THE DEGREE OF BACHELOR OF SCIENCE IN MECHATRONIC ENGINEERING EMT 2102: MATERIAL SCIENCE DATE: 8TH DECEMMBER 2010 TIME: 2.00PM – 4.00PM Question one
a) A circular bar of diameter 30mm and length 5m supports a tensile force of 10kN. The Young’s Modulus of the bar material is 200GN/m2. Determine for the bar;
i) The stress (2 marks)
ii) The strain (2 marks)
iii) The change in length (2 marks)
b) Sketch and fully label the expected equilibrium phase diagram between two metals that show complete solubility in the solid state. (4 marks)
c) Give three main factors that affect the accuracy/validity of Brinell hardness test results. (4.5 marks)
d) A certain metal has body centred cubic structure and atomic mass 92.91g/mol. The density of the metal is 8.57x106 g/m3. Given that the Avogadro Number is 6.02x1023 atoms/mol, determine for the metal;
i) The lattice parameter (4 marks) ii) The atomic radius (4 marks)
e) i) Give three main advantages of ceramics as engineering materials. (3 marks)
ii) Briefly explain how direct corrosion takes place. (4.5 marks) Question Two
a) Sketch the directions and planes that are represented by the following Miller indices [101], [221], (111) and (020). (8 marks)
b) Sketch a simplified H2O–Fe Pourbaix diagram and label all the regions. (6 marks)
c) Briefly describe three main methods that can be used to protect a steel pipe from corrosion. (6 marks)
Question Three
a) Define the following material properties;
i) Ultimate tensile strength (2 marks)
ii) Ductility (2 marks)
iii) Proof stress (2 marks)
iv) Brittle-ductile transition (2 marks)
b) Give three main thermal properties of a metal and for each explain its effects when the metal is being welded. (9 marks)
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c) Briefly describe how secondary bonds are formed. (3 marks)
Question Three
a) With the aid of sketches, describe the following crystal defects
i) Grain boundary (2.5 marks)
ii) Vacancy (2.5 marks)
b) Derive an expression for Vickers Hardness Number VHN in terms of applied load P and the diagonal of impression made d. (9 marks)
c) In Vickers hardness test a load of 300kg was applied and the diagonal of impression was found to be 1.5mm. Determine;
i) The minimum thickness of specimen for the results to be valid. (1.5 marks)
ii) The Vickers Hardness Number VHN. (2.5 marks)
d) What is an alloy? (2 marks)
Question Five
a) Draw to scale and fully label the equilibrium phase diagram between two metals A and B given the following information:
Melting point of A = 3100C Melting point of B = 2400C Eutectic temperature = 1830C Maximum solubility of A in B is 2.6% at 1830C Maximum solubility of B in A is 20% at 1830C Eutectic composition = 38% A Solubility of A in B and B in A is negligible at 00C. Use straight lines for all phase boundaries. (11 marks)
b) For 500g of the above alloy containing 20% A;
i) Determine the phases present their chemical composition and quantities at 2000C. (7 marks)
ii) Sketch the expected microstructure at 1000C. (2 marks)

Emt 2102 – Material Science Question Paper

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