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Cork Institute of Technology
Bachelor of Engineering in Mechanical Engineering – Stage 2
(EMECH_7_Y2)
Summer 2008
Manufacturing Technology – (Machineshop/Materials)
(Time: 3 Hours)
Instructions Answer FIVE questions. All questions carry equal marks. Question 1 must be answered. Use separate answer books for each Section.. Use annotated diagrams where applicable.
Examiners: Mr. R. Kennedy Dr. G. Kelly Mr. A. Bateman Dr. P. Delassus
Section A
Q1.(a) You are supplied with a shaft measuring 50mm in diameter. You are required to machine the largest square possible (four flats at right angles to each other) on a section 43mm long. List the following:- (i) equipment including specifically the type of machine you would use, (5 marks) (ii) calculations, (5 marks) (iii) the procedure to complete the task. (6 marks)
(b) Name two form relieved cutters used on a horizontal milling machine and state their uses (4 marks)
Section B
Q2.
(a) Describe the solidification of a 15% Sn 85% Pb solution when it is cooled from a temperature of 330°C to 120°C with the aid of the attached equilibrium diagram. Identify the phases present and estimate their composition at the points d to h indicated on the Pb Sn diagram. (10 marks)
(Note Please return the equilibrium diagram with your answer book)
(b) Determine the variation in the composition of the α and β phases for Sn Pb solid solutions with overall compositions of 15% Sn 85% Pb, 50% Sn 50% Pb, 85% Sn 15% Pb at a temperature of 120°C. Comment on the result. (10 marks)
Q3.
(a) Sketch the different stages of crystalline development from the nucleation stage to formation of grain boundaries in a metal. (6 marks)
(b) Explain what happens when a ductile material is subject to an externally applied force in a given direction. Why are fine grained materials less ductile than large grained materials? (6 marks)
(c) Describe the relationship between plastic deformation and dislocation movement in ductile materials. Is plastic deformation due to block slip? Justify your answer. (8 marks)
Q4. (a) Describe the 4 differences between extrusion and injection molding of thermoplastic materials (4 marks)
(b) Describe (with the help of annotated diagrams) the features and operation of rotational moulding. (8 marks)
(c) List 4 significant advantages and 4 significant disadvantage of rotational molding compared with other molding processes. (8 marks)
Q5.
Section B
Q2 Pb Sn Equilibrium diagram
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